md: add ->takeover method for raid5 to be able to take over raid1
[safe/jmp/linux-2.6] / drivers / md / raid5.c
index d89a25e..611ea7b 100644 (file)
  * miss any bits.
  */
 
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/highmem.h>
-#include <linux/bitops.h>
+#include <linux/blkdev.h>
 #include <linux/kthread.h>
-#include <asm/atomic.h>
-#include "raid6.h"
-
-#include <linux/raid/bitmap.h>
 #include <linux/async_tx.h>
+#include <linux/seq_file.h>
+#include "md.h"
+#include "raid5.h"
+#include "raid6.h"
+#include "bitmap.h"
 
 /*
  * Stripe cache
@@ -63,6 +61,7 @@
 #define STRIPE_SHIFT           (PAGE_SHIFT - 9)
 #define STRIPE_SECTORS         (STRIPE_SIZE>>9)
 #define        IO_THRESHOLD            1
+#define BYPASS_THRESHOLD       1
 #define NR_HASH                        (PAGE_SIZE / sizeof(struct hlist_head))
 #define HASH_MASK              (NR_HASH - 1)
 
 #define __inline__
 #endif
 
+#define printk_rl(args...) ((void) (printk_ratelimit() && printk(args)))
+
 #if !RAID6_USE_EMPTY_ZERO_PAGE
 /* In .bss so it's zeroed */
 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
 #endif
 
+/*
+ * We maintain a biased count of active stripes in the bottom 16 bits of
+ * bi_phys_segments, and a count of processed stripes in the upper 16 bits
+ */
+static inline int raid5_bi_phys_segments(struct bio *bio)
+{
+       return bio->bi_phys_segments & 0xffff;
+}
+
+static inline int raid5_bi_hw_segments(struct bio *bio)
+{
+       return (bio->bi_phys_segments >> 16) & 0xffff;
+}
+
+static inline int raid5_dec_bi_phys_segments(struct bio *bio)
+{
+       --bio->bi_phys_segments;
+       return raid5_bi_phys_segments(bio);
+}
+
+static inline int raid5_dec_bi_hw_segments(struct bio *bio)
+{
+       unsigned short val = raid5_bi_hw_segments(bio);
+
+       --val;
+       bio->bi_phys_segments = (val << 16) | raid5_bi_phys_segments(bio);
+       return val;
+}
+
+static inline void raid5_set_bi_hw_segments(struct bio *bio, unsigned int cnt)
+{
+       bio->bi_phys_segments = raid5_bi_phys_segments(bio) || (cnt << 16);
+}
+
+/* Find first data disk in a raid6 stripe */
+static inline int raid6_d0(struct stripe_head *sh)
+{
+       if (sh->ddf_layout)
+               /* ddf always start from first device */
+               return 0;
+       /* md starts just after Q block */
+       if (sh->qd_idx == sh->disks - 1)
+               return 0;
+       else
+               return sh->qd_idx + 1;
+}
 static inline int raid6_next_disk(int disk, int raid_disks)
 {
        disk++;
        return (disk < raid_disks) ? disk : 0;
 }
 
+/* When walking through the disks in a raid5, starting at raid6_d0,
+ * We need to map each disk to a 'slot', where the data disks are slot
+ * 0 .. raid_disks-3, the parity disk is raid_disks-2 and the Q disk
+ * is raid_disks-1.  This help does that mapping.
+ */
+static int raid6_idx_to_slot(int idx, struct stripe_head *sh,
+                            int *count, int syndrome_disks)
+{
+       int slot;
+
+       if (idx == sh->pd_idx)
+               return syndrome_disks;
+       if (idx == sh->qd_idx)
+               return syndrome_disks + 1;
+       slot = (*count)++;
+       return slot;
+}
+
 static void return_io(struct bio *return_bi)
 {
        struct bio *bi = return_bi;
        while (bi) {
-               int bytes = bi->bi_size;
 
                return_bi = bi->bi_next;
                bi->bi_next = NULL;
                bi->bi_size = 0;
-               bi->bi_end_io(bi, bytes,
-                             test_bit(BIO_UPTODATE, &bi->bi_flags)
-                               ? 0 : -EIO);
+               bio_endio(bi, 0);
                bi = return_bi;
        }
 }
 
 static void print_raid5_conf (raid5_conf_t *conf);
 
+static int stripe_operations_active(struct stripe_head *sh)
+{
+       return sh->check_state || sh->reconstruct_state ||
+              test_bit(STRIPE_BIOFILL_RUN, &sh->state) ||
+              test_bit(STRIPE_COMPUTE_RUN, &sh->state);
+}
+
 static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
 {
        if (atomic_dec_and_test(&sh->count)) {
@@ -141,7 +210,7 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
                        }
                        md_wakeup_thread(conf->mddev->thread);
                } else {
-                       BUG_ON(sh->ops.pending);
+                       BUG_ON(stripe_operations_active(sh));
                        if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
                                atomic_dec(&conf->preread_active_stripes);
                                if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
@@ -157,6 +226,7 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
                }
        }
 }
+
 static void release_stripe(struct stripe_head *sh)
 {
        raid5_conf_t *conf = sh->raid_conf;
@@ -234,16 +304,18 @@ static int grow_buffers(struct stripe_head *sh, int num)
        return 0;
 }
 
-static void raid5_build_block (struct stripe_head *sh, int i);
+static void raid5_build_block(struct stripe_head *sh, int i);
+static void stripe_set_idx(sector_t stripe, raid5_conf_t *conf, int previous,
+                           struct stripe_head *sh);
 
-static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx, int disks)
+static void init_stripe(struct stripe_head *sh, sector_t sector, int previous)
 {
        raid5_conf_t *conf = sh->raid_conf;
        int i;
 
        BUG_ON(atomic_read(&sh->count) != 0);
        BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
-       BUG_ON(sh->ops.pending || sh->ops.ack || sh->ops.complete);
+       BUG_ON(stripe_operations_active(sh));
 
        CHECK_DEVLOCK();
        pr_debug("init_stripe called, stripe %llu\n",
@@ -251,11 +323,11 @@ static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx, int
 
        remove_hash(sh);
 
+       sh->disks = previous ? conf->previous_raid_disks : conf->raid_disks;
        sh->sector = sector;
-       sh->pd_idx = pd_idx;
+       stripe_set_idx(sector, conf, previous, sh);
        sh->state = 0;
 
-       sh->disks = disks;
 
        for (i = sh->disks; i--; ) {
                struct r5dev *dev = &sh->dev[i];
@@ -289,12 +361,14 @@ static struct stripe_head *__find_stripe(raid5_conf_t *conf, sector_t sector, in
 }
 
 static void unplug_slaves(mddev_t *mddev);
-static void raid5_unplug_device(request_queue_t *q);
+static void raid5_unplug_device(struct request_queue *q);
 
-static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector, int disks,
-                                            int pd_idx, int noblock)
+static struct stripe_head *
+get_active_stripe(raid5_conf_t *conf, sector_t sector,
+                 int previous, int noblock)
 {
        struct stripe_head *sh;
+       int disks = previous ? conf->previous_raid_disks : conf->raid_disks;
 
        pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
 
@@ -322,7 +396,7 @@ static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector
                                        );
                                conf->inactive_blocked = 0;
                        } else
-                               init_stripe(sh, sector, pd_idx, disks);
+                               init_stripe(sh, sector, previous);
                } else {
                        if (atomic_read(&sh->count)) {
                          BUG_ON(!list_empty(&sh->lru));
@@ -344,50 +418,12 @@ static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector
        return sh;
 }
 
-/* test_and_ack_op() ensures that we only dequeue an operation once */
-#define test_and_ack_op(op, pend) \
-do {                                                   \
-       if (test_bit(op, &sh->ops.pending) &&           \
-               !test_bit(op, &sh->ops.complete)) {     \
-               if (test_and_set_bit(op, &sh->ops.ack)) \
-                       clear_bit(op, &pend);           \
-               else                                    \
-                       ack++;                          \
-       } else                                          \
-               clear_bit(op, &pend);                   \
-} while (0)
-
-/* find new work to run, do not resubmit work that is already
- * in flight
- */
-static unsigned long get_stripe_work(struct stripe_head *sh)
-{
-       unsigned long pending;
-       int ack = 0;
-
-       pending = sh->ops.pending;
-
-       test_and_ack_op(STRIPE_OP_BIOFILL, pending);
-       test_and_ack_op(STRIPE_OP_COMPUTE_BLK, pending);
-       test_and_ack_op(STRIPE_OP_PREXOR, pending);
-       test_and_ack_op(STRIPE_OP_BIODRAIN, pending);
-       test_and_ack_op(STRIPE_OP_POSTXOR, pending);
-       test_and_ack_op(STRIPE_OP_CHECK, pending);
-       if (test_and_clear_bit(STRIPE_OP_IO, &sh->ops.pending))
-               ack++;
-
-       sh->ops.count -= ack;
-       BUG_ON(sh->ops.count < 0);
-
-       return pending;
-}
-
-static int
-raid5_end_read_request(struct bio *bi, unsigned int bytes_done, int error);
-static int
-raid5_end_write_request (struct bio *bi, unsigned int bytes_done, int error);
+static void
+raid5_end_read_request(struct bio *bi, int error);
+static void
+raid5_end_write_request(struct bio *bi, int error);
 
-static void ops_run_io(struct stripe_head *sh)
+static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 {
        raid5_conf_t *conf = sh->raid_conf;
        int i, disks = sh->disks;
@@ -422,14 +458,14 @@ static void ops_run_io(struct stripe_head *sh)
                rcu_read_unlock();
 
                if (rdev) {
-                       if (test_bit(STRIPE_SYNCING, &sh->state) ||
-                               test_bit(STRIPE_EXPAND_SOURCE, &sh->state) ||
-                               test_bit(STRIPE_EXPAND_READY, &sh->state))
+                       if (s->syncing || s->expanding || s->expanded)
                                md_sync_acct(rdev->bdev, STRIPE_SECTORS);
 
+                       set_bit(STRIPE_IO_STARTED, &sh->state);
+
                        bi->bi_bdev = rdev->bdev;
                        pr_debug("%s: for %llu schedule op %ld on disc %d\n",
-                               __FUNCTION__, (unsigned long long)sh->sector,
+                               __func__, (unsigned long long)sh->sector,
                                bi->bi_rw, i);
                        atomic_inc(&sh->count);
                        bi->bi_sector = sh->sector + rdev->data_offset;
@@ -493,12 +529,12 @@ async_copy_data(int frombio, struct bio *bio, struct page *page,
                        if (frombio)
                                tx = async_memcpy(page, bio_page, page_offset,
                                        b_offset, clen,
-                                       ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_SRC,
+                                       ASYNC_TX_DEP_ACK,
                                        tx, NULL, NULL);
                        else
                                tx = async_memcpy(bio_page, page, b_offset,
                                        page_offset, clen,
-                                       ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_DST,
+                                       ASYNC_TX_DEP_ACK,
                                        tx, NULL, NULL);
                }
                if (clen < len) /* hit end of page */
@@ -514,52 +550,44 @@ static void ops_complete_biofill(void *stripe_head_ref)
        struct stripe_head *sh = stripe_head_ref;
        struct bio *return_bi = NULL;
        raid5_conf_t *conf = sh->raid_conf;
-       int i, more_to_read = 0;
+       int i;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        /* clear completed biofills */
+       spin_lock_irq(&conf->device_lock);
        for (i = sh->disks; i--; ) {
                struct r5dev *dev = &sh->dev[i];
-               /* check if this stripe has new incoming reads */
-               if (dev->toread)
-                       more_to_read++;
 
                /* acknowledge completion of a biofill operation */
-               /* and check if we need to reply to a read request
-               */
-               if (test_bit(R5_Wantfill, &dev->flags) && !dev->toread) {
+               /* and check if we need to reply to a read request,
+                * new R5_Wantfill requests are held off until
+                * !STRIPE_BIOFILL_RUN
+                */
+               if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
                        struct bio *rbi, *rbi2;
-                       clear_bit(R5_Wantfill, &dev->flags);
 
-                       /* The access to dev->read is outside of the
-                        * spin_lock_irq(&conf->device_lock), but is protected
-                        * by the STRIPE_OP_BIOFILL pending bit
-                        */
                        BUG_ON(!dev->read);
                        rbi = dev->read;
                        dev->read = NULL;
                        while (rbi && rbi->bi_sector <
                                dev->sector + STRIPE_SECTORS) {
                                rbi2 = r5_next_bio(rbi, dev->sector);
-                               spin_lock_irq(&conf->device_lock);
-                               if (--rbi->bi_phys_segments == 0) {
+                               if (!raid5_dec_bi_phys_segments(rbi)) {
                                        rbi->bi_next = return_bi;
                                        return_bi = rbi;
                                }
-                               spin_unlock_irq(&conf->device_lock);
                                rbi = rbi2;
                        }
                }
        }
-       clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
-       clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
+       spin_unlock_irq(&conf->device_lock);
+       clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
 
        return_io(return_bi);
 
-       if (more_to_read)
-               set_bit(STRIPE_HANDLE, &sh->state);
+       set_bit(STRIPE_HANDLE, &sh->state);
        release_stripe(sh);
 }
 
@@ -569,7 +597,7 @@ static void ops_run_biofill(struct stripe_head *sh)
        raid5_conf_t *conf = sh->raid_conf;
        int i;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        for (i = sh->disks; i--; ) {
@@ -600,19 +628,20 @@ static void ops_complete_compute5(void *stripe_head_ref)
        int target = sh->ops.target;
        struct r5dev *tgt = &sh->dev[target];
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        set_bit(R5_UPTODATE, &tgt->flags);
        BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
        clear_bit(R5_Wantcompute, &tgt->flags);
-       set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
+       clear_bit(STRIPE_COMPUTE_RUN, &sh->state);
+       if (sh->check_state == check_state_compute_run)
+               sh->check_state = check_state_compute_result;
        set_bit(STRIPE_HANDLE, &sh->state);
        release_stripe(sh);
 }
 
-static struct dma_async_tx_descriptor *
-ops_run_compute5(struct stripe_head *sh, unsigned long pending)
+static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
 {
        /* kernel stack size limits the total number of disks */
        int disks = sh->disks;
@@ -625,7 +654,7 @@ ops_run_compute5(struct stripe_head *sh, unsigned long pending)
        int i;
 
        pr_debug("%s: stripe %llu block: %d\n",
-               __FUNCTION__, (unsigned long long)sh->sector, target);
+               __func__, (unsigned long long)sh->sector, target);
        BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
 
        for (i = disks; i--; )
@@ -642,10 +671,6 @@ ops_run_compute5(struct stripe_head *sh, unsigned long pending)
                        ASYNC_TX_XOR_ZERO_DST, NULL,
                        ops_complete_compute5, sh);
 
-       /* ack now if postxor is not set to be run */
-       if (tx && !test_bit(STRIPE_OP_POSTXOR, &pending))
-               async_tx_ack(tx);
-
        return tx;
 }
 
@@ -653,10 +678,8 @@ static void ops_complete_prexor(void *stripe_head_ref)
 {
        struct stripe_head *sh = stripe_head_ref;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
-
-       set_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
 }
 
 static struct dma_async_tx_descriptor *
@@ -670,13 +693,13 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
        /* existing parity data subtracted */
        struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        for (i = disks; i--; ) {
                struct r5dev *dev = &sh->dev[i];
                /* Only process blocks that are known to be uptodate */
-               if (dev->towrite && test_bit(R5_Wantprexor, &dev->flags))
+               if (test_bit(R5_Wantdrain, &dev->flags))
                        xor_srcs[count++] = dev->page;
        }
 
@@ -691,33 +714,16 @@ static struct dma_async_tx_descriptor *
 ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 {
        int disks = sh->disks;
-       int pd_idx = sh->pd_idx, i;
-
-       /* check if prexor is active which means only process blocks
-        * that are part of a read-modify-write (Wantprexor)
-        */
-       int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+       int i;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        for (i = disks; i--; ) {
                struct r5dev *dev = &sh->dev[i];
                struct bio *chosen;
-               int towrite;
 
-               towrite = 0;
-               if (prexor) { /* rmw */
-                       if (dev->towrite &&
-                           test_bit(R5_Wantprexor, &dev->flags))
-                               towrite = 1;
-               } else { /* rcw */
-                       if (i != pd_idx && dev->towrite &&
-                               test_bit(R5_LOCKED, &dev->flags))
-                               towrite = 1;
-               }
-
-               if (towrite) {
+               if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
                        struct bio *wbi;
 
                        spin_lock(&sh->lock);
@@ -742,21 +748,9 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 static void ops_complete_postxor(void *stripe_head_ref)
 {
        struct stripe_head *sh = stripe_head_ref;
-
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
-               (unsigned long long)sh->sector);
-
-       set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
-       set_bit(STRIPE_HANDLE, &sh->state);
-       release_stripe(sh);
-}
-
-static void ops_complete_write(void *stripe_head_ref)
-{
-       struct stripe_head *sh = stripe_head_ref;
        int disks = sh->disks, i, pd_idx = sh->pd_idx;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        for (i = disks; i--; ) {
@@ -765,8 +759,14 @@ static void ops_complete_write(void *stripe_head_ref)
                        set_bit(R5_UPTODATE, &dev->flags);
        }
 
-       set_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
-       set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
+       if (sh->reconstruct_state == reconstruct_state_drain_run)
+               sh->reconstruct_state = reconstruct_state_drain_result;
+       else if (sh->reconstruct_state == reconstruct_state_prexor_drain_run)
+               sh->reconstruct_state = reconstruct_state_prexor_drain_result;
+       else {
+               BUG_ON(sh->reconstruct_state != reconstruct_state_run);
+               sh->reconstruct_state = reconstruct_state_result;
+       }
 
        set_bit(STRIPE_HANDLE, &sh->state);
        release_stripe(sh);
@@ -781,17 +781,17 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 
        int count = 0, pd_idx = sh->pd_idx, i;
        struct page *xor_dest;
-       int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+       int prexor = 0;
        unsigned long flags;
-       dma_async_tx_callback callback;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        /* check if prexor is active which means only process blocks
         * that are part of a read-modify-write (written)
         */
-       if (prexor) {
+       if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+               prexor = 1;
                xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
                for (i = disks; i--; ) {
                        struct r5dev *dev = &sh->dev[i];
@@ -807,10 +807,6 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
                }
        }
 
-       /* check whether this postxor is part of a write */
-       callback = test_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending) ?
-               ops_complete_write : ops_complete_postxor;
-
        /* 1/ if we prexor'd then the dest is reused as a source
         * 2/ if we did not prexor then we are redoing the parity
         * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
@@ -824,25 +820,20 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
        if (unlikely(count == 1)) {
                flags &= ~(ASYNC_TX_XOR_DROP_DST | ASYNC_TX_XOR_ZERO_DST);
                tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
-                       flags, tx, callback, sh);
+                       flags, tx, ops_complete_postxor, sh);
        } else
                tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
-                       flags, tx, callback, sh);
+                       flags, tx, ops_complete_postxor, sh);
 }
 
 static void ops_complete_check(void *stripe_head_ref)
 {
        struct stripe_head *sh = stripe_head_ref;
-       int pd_idx = sh->pd_idx;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
-       if (test_and_clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending) &&
-               sh->ops.zero_sum_result == 0)
-               set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-
-       set_bit(STRIPE_OP_CHECK, &sh->ops.complete);
+       sh->check_state = check_state_check_result;
        set_bit(STRIPE_HANDLE, &sh->state);
        release_stripe(sh);
 }
@@ -857,7 +848,7 @@ static void ops_run_check(struct stripe_head *sh)
        int count = 0, pd_idx = sh->pd_idx, i;
        struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
 
-       pr_debug("%s: stripe %llu\n", __FUNCTION__,
+       pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
 
        for (i = disks; i--; ) {
@@ -869,46 +860,42 @@ static void ops_run_check(struct stripe_head *sh)
        tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
                &sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
 
-       if (tx)
-               set_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
-       else
-               clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
-
        atomic_inc(&sh->count);
        tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
                ops_complete_check, sh);
 }
 
-static void raid5_run_ops(struct stripe_head *sh, unsigned long pending)
+static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
 {
        int overlap_clear = 0, i, disks = sh->disks;
        struct dma_async_tx_descriptor *tx = NULL;
 
-       if (test_bit(STRIPE_OP_BIOFILL, &pending)) {
+       if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
                ops_run_biofill(sh);
                overlap_clear++;
        }
 
-       if (test_bit(STRIPE_OP_COMPUTE_BLK, &pending))
-               tx = ops_run_compute5(sh, pending);
+       if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
+               tx = ops_run_compute5(sh);
+               /* terminate the chain if postxor is not set to be run */
+               if (tx && !test_bit(STRIPE_OP_POSTXOR, &ops_request))
+                       async_tx_ack(tx);
+       }
 
-       if (test_bit(STRIPE_OP_PREXOR, &pending))
+       if (test_bit(STRIPE_OP_PREXOR, &ops_request))
                tx = ops_run_prexor(sh, tx);
 
-       if (test_bit(STRIPE_OP_BIODRAIN, &pending)) {
+       if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
                tx = ops_run_biodrain(sh, tx);
                overlap_clear++;
        }
 
-       if (test_bit(STRIPE_OP_POSTXOR, &pending))
+       if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
                ops_run_postxor(sh, tx);
 
-       if (test_bit(STRIPE_OP_CHECK, &pending))
+       if (test_bit(STRIPE_OP_CHECK, &ops_request))
                ops_run_check(sh);
 
-       if (test_bit(STRIPE_OP_IO, &pending))
-               ops_run_io(sh);
-
        if (overlap_clear)
                for (i = disks; i--; ) {
                        struct r5dev *dev = &sh->dev[i];
@@ -946,12 +933,14 @@ static int grow_stripes(raid5_conf_t *conf, int num)
        struct kmem_cache *sc;
        int devs = conf->raid_disks;
 
-       sprintf(conf->cache_name[0], "raid5-%s", mdname(conf->mddev));
-       sprintf(conf->cache_name[1], "raid5-%s-alt", mdname(conf->mddev));
+       sprintf(conf->cache_name[0],
+               "raid%d-%s", conf->level, mdname(conf->mddev));
+       sprintf(conf->cache_name[1],
+               "raid%d-%s-alt", conf->level, mdname(conf->mddev));
        conf->active_name = 0;
        sc = kmem_cache_create(conf->cache_name[conf->active_name],
                               sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
-                              0, 0, NULL, NULL);
+                              0, 0, NULL);
        if (!sc)
                return 1;
        conf->slab_cache = sc;
@@ -991,19 +980,21 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
        struct stripe_head *osh, *nsh;
        LIST_HEAD(newstripes);
        struct disk_info *ndisks;
-       int err = 0;
+       int err;
        struct kmem_cache *sc;
        int i;
 
        if (newsize <= conf->pool_size)
                return 0; /* never bother to shrink */
 
-       md_allow_write(conf->mddev);
+       err = md_allow_write(conf->mddev);
+       if (err)
+               return err;
 
        /* Step 1 */
        sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
                               sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
-                              0, 0, NULL, NULL);
+                              0, 0, NULL);
        if (!sc)
                return -ENOMEM;
 
@@ -1113,18 +1104,15 @@ static void shrink_stripes(raid5_conf_t *conf)
        conf->slab_cache = NULL;
 }
 
-static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
-                                  int error)
+static void raid5_end_read_request(struct bio * bi, int error)
 {
-       struct stripe_head *sh = bi->bi_private;
+       struct stripe_head *sh = bi->bi_private;
        raid5_conf_t *conf = sh->raid_conf;
        int disks = sh->disks, i;
        int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
        char b[BDEVNAME_SIZE];
        mdk_rdev_t *rdev;
 
-       if (bi->bi_size)
-               return 1;
 
        for (i=0 ; i<disks; i++)
                if (bi == &sh->dev[i].req)
@@ -1135,17 +1123,19 @@ static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
                uptodate);
        if (i == disks) {
                BUG();
-               return 0;
+               return;
        }
 
        if (uptodate) {
                set_bit(R5_UPTODATE, &sh->dev[i].flags);
                if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
                        rdev = conf->disks[i].rdev;
-                       printk(KERN_INFO "raid5:%s: read error corrected (%lu sectors at %llu on %s)\n",
-                              mdname(conf->mddev), STRIPE_SECTORS,
-                              (unsigned long long)sh->sector + rdev->data_offset,
-                              bdevname(rdev->bdev, b));
+                       printk_rl(KERN_INFO "raid5:%s: read error corrected"
+                                 " (%lu sectors at %llu on %s)\n",
+                                 mdname(conf->mddev), STRIPE_SECTORS,
+                                 (unsigned long long)(sh->sector
+                                                      + rdev->data_offset),
+                                 bdevname(rdev->bdev, b));
                        clear_bit(R5_ReadError, &sh->dev[i].flags);
                        clear_bit(R5_ReWrite, &sh->dev[i].flags);
                }
@@ -1159,16 +1149,22 @@ static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
                clear_bit(R5_UPTODATE, &sh->dev[i].flags);
                atomic_inc(&rdev->read_errors);
                if (conf->mddev->degraded)
-                       printk(KERN_WARNING "raid5:%s: read error not correctable (sector %llu on %s).\n",
-                              mdname(conf->mddev),
-                              (unsigned long long)sh->sector + rdev->data_offset,
-                              bdn);
+                       printk_rl(KERN_WARNING
+                                 "raid5:%s: read error not correctable "
+                                 "(sector %llu on %s).\n",
+                                 mdname(conf->mddev),
+                                 (unsigned long long)(sh->sector
+                                                      + rdev->data_offset),
+                                 bdn);
                else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
                        /* Oh, no!!! */
-                       printk(KERN_WARNING "raid5:%s: read error NOT corrected!! (sector %llu on %s).\n",
-                              mdname(conf->mddev),
-                              (unsigned long long)sh->sector + rdev->data_offset,
-                              bdn);
+                       printk_rl(KERN_WARNING
+                                 "raid5:%s: read error NOT corrected!! "
+                                 "(sector %llu on %s).\n",
+                                 mdname(conf->mddev),
+                                 (unsigned long long)(sh->sector
+                                                      + rdev->data_offset),
+                                 bdn);
                else if (atomic_read(&rdev->read_errors)
                         > conf->max_nr_stripes)
                        printk(KERN_WARNING
@@ -1188,20 +1184,15 @@ static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
        clear_bit(R5_LOCKED, &sh->dev[i].flags);
        set_bit(STRIPE_HANDLE, &sh->state);
        release_stripe(sh);
-       return 0;
 }
 
-static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
-                                   int error)
+static void raid5_end_write_request(struct bio *bi, int error)
 {
-       struct stripe_head *sh = bi->bi_private;
+       struct stripe_head *sh = bi->bi_private;
        raid5_conf_t *conf = sh->raid_conf;
        int disks = sh->disks, i;
        int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
 
-       if (bi->bi_size)
-               return 1;
-
        for (i=0 ; i<disks; i++)
                if (bi == &sh->dev[i].req)
                        break;
@@ -1211,7 +1202,7 @@ static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
                uptodate);
        if (i == disks) {
                BUG();
-               return 0;
+               return;
        }
 
        if (!uptodate)
@@ -1222,13 +1213,12 @@ static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
        clear_bit(R5_LOCKED, &sh->dev[i].flags);
        set_bit(STRIPE_HANDLE, &sh->state);
        release_stripe(sh);
-       return 0;
 }
 
 
 static sector_t compute_blocknr(struct stripe_head *sh, int i);
        
-static void raid5_build_block (struct stripe_head *sh, int i)
+static void raid5_build_block(struct stripe_head *sh, int i)
 {
        struct r5dev *dev = &sh->dev[i];
 
@@ -1263,13 +1253,13 @@ static void error(mddev_t *mddev, mdk_rdev_t *rdev)
                        /*
                         * if recovery was running, make sure it aborts.
                         */
-                       set_bit(MD_RECOVERY_ERR, &mddev->recovery);
+                       set_bit(MD_RECOVERY_INTR, &mddev->recovery);
                }
                set_bit(Faulty, &rdev->flags);
-               printk (KERN_ALERT
-                       "raid5: Disk failure on %s, disabling device."
-                       " Operation continuing on %d devices\n",
-                       bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
+               printk(KERN_ALERT
+                      "raid5: Disk failure on %s, disabling device.\n"
+                      "raid5: Operation continuing on %d devices.\n",
+                      bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
        }
 }
 
@@ -1277,15 +1267,20 @@ static void error(mddev_t *mddev, mdk_rdev_t *rdev)
  * Input: a 'big' sector number,
  * Output: index of the data and parity disk, and the sector # in them.
  */
-static sector_t raid5_compute_sector(sector_t r_sector, unsigned int raid_disks,
-                       unsigned int data_disks, unsigned int * dd_idx,
-                       unsigned int * pd_idx, raid5_conf_t *conf)
+static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector,
+                                    int previous, int *dd_idx,
+                                    struct stripe_head *sh)
 {
        long stripe;
        unsigned long chunk_number;
        unsigned int chunk_offset;
+       int pd_idx, qd_idx;
+       int ddf_layout = 0;
        sector_t new_sector;
        int sectors_per_chunk = conf->chunk_size >> 9;
+       int raid_disks = previous ? conf->previous_raid_disks
+                                 : conf->raid_disks;
+       int data_disks = raid_disks - conf->max_degraded;
 
        /* First compute the information on this sector */
 
@@ -1309,68 +1304,170 @@ static sector_t raid5_compute_sector(sector_t r_sector, unsigned int raid_disks,
        /*
         * Select the parity disk based on the user selected algorithm.
         */
+       pd_idx = qd_idx = ~0;
        switch(conf->level) {
        case 4:
-               *pd_idx = data_disks;
+               pd_idx = data_disks;
                break;
        case 5:
                switch (conf->algorithm) {
                case ALGORITHM_LEFT_ASYMMETRIC:
-                       *pd_idx = data_disks - stripe % raid_disks;
-                       if (*dd_idx >= *pd_idx)
+                       pd_idx = data_disks - stripe % raid_disks;
+                       if (*dd_idx >= pd_idx)
                                (*dd_idx)++;
                        break;
                case ALGORITHM_RIGHT_ASYMMETRIC:
-                       *pd_idx = stripe % raid_disks;
-                       if (*dd_idx >= *pd_idx)
+                       pd_idx = stripe % raid_disks;
+                       if (*dd_idx >= pd_idx)
                                (*dd_idx)++;
                        break;
                case ALGORITHM_LEFT_SYMMETRIC:
-                       *pd_idx = data_disks - stripe % raid_disks;
-                       *dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
+                       pd_idx = data_disks - stripe % raid_disks;
+                       *dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
                        break;
                case ALGORITHM_RIGHT_SYMMETRIC:
-                       *pd_idx = stripe % raid_disks;
-                       *dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
+                       pd_idx = stripe % raid_disks;
+                       *dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
+                       break;
+               case ALGORITHM_PARITY_0:
+                       pd_idx = 0;
+                       (*dd_idx)++;
+                       break;
+               case ALGORITHM_PARITY_N:
+                       pd_idx = data_disks;
                        break;
                default:
                        printk(KERN_ERR "raid5: unsupported algorithm %d\n",
                                conf->algorithm);
+                       BUG();
                }
                break;
        case 6:
 
-               /**** FIX THIS ****/
                switch (conf->algorithm) {
                case ALGORITHM_LEFT_ASYMMETRIC:
-                       *pd_idx = raid_disks - 1 - (stripe % raid_disks);
-                       if (*pd_idx == raid_disks-1)
-                               (*dd_idx)++;    /* Q D D D P */
-                       else if (*dd_idx >= *pd_idx)
+                       pd_idx = raid_disks - 1 - (stripe % raid_disks);
+                       qd_idx = pd_idx + 1;
+                       if (pd_idx == raid_disks-1) {
+                               (*dd_idx)++;    /* Q D D D P */
+                               qd_idx = 0;
+                       } else if (*dd_idx >= pd_idx)
                                (*dd_idx) += 2; /* D D P Q D */
                        break;
                case ALGORITHM_RIGHT_ASYMMETRIC:
-                       *pd_idx = stripe % raid_disks;
-                       if (*pd_idx == raid_disks-1)
-                               (*dd_idx)++;    /* Q D D D P */
-                       else if (*dd_idx >= *pd_idx)
+                       pd_idx = stripe % raid_disks;
+                       qd_idx = pd_idx + 1;
+                       if (pd_idx == raid_disks-1) {
+                               (*dd_idx)++;    /* Q D D D P */
+                               qd_idx = 0;
+                       } else if (*dd_idx >= pd_idx)
                                (*dd_idx) += 2; /* D D P Q D */
                        break;
                case ALGORITHM_LEFT_SYMMETRIC:
-                       *pd_idx = raid_disks - 1 - (stripe % raid_disks);
-                       *dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
+                       pd_idx = raid_disks - 1 - (stripe % raid_disks);
+                       qd_idx = (pd_idx + 1) % raid_disks;
+                       *dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
                        break;
                case ALGORITHM_RIGHT_SYMMETRIC:
-                       *pd_idx = stripe % raid_disks;
-                       *dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
+                       pd_idx = stripe % raid_disks;
+                       qd_idx = (pd_idx + 1) % raid_disks;
+                       *dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
+                       break;
+
+               case ALGORITHM_PARITY_0:
+                       pd_idx = 0;
+                       qd_idx = 1;
+                       (*dd_idx) += 2;
+                       break;
+               case ALGORITHM_PARITY_N:
+                       pd_idx = data_disks;
+                       qd_idx = data_disks + 1;
+                       break;
+
+               case ALGORITHM_ROTATING_ZERO_RESTART:
+                       /* Exactly the same as RIGHT_ASYMMETRIC, but or
+                        * of blocks for computing Q is different.
+                        */
+                       pd_idx = stripe % raid_disks;
+                       qd_idx = pd_idx + 1;
+                       if (pd_idx == raid_disks-1) {
+                               (*dd_idx)++;    /* Q D D D P */
+                               qd_idx = 0;
+                       } else if (*dd_idx >= pd_idx)
+                               (*dd_idx) += 2; /* D D P Q D */
+                       ddf_layout = 1;
+                       break;
+
+               case ALGORITHM_ROTATING_N_RESTART:
+                       /* Same a left_asymmetric, by first stripe is
+                        * D D D P Q  rather than
+                        * Q D D D P
+                        */
+                       pd_idx = raid_disks - 1 - ((stripe + 1) % raid_disks);
+                       qd_idx = pd_idx + 1;
+                       if (pd_idx == raid_disks-1) {
+                               (*dd_idx)++;    /* Q D D D P */
+                               qd_idx = 0;
+                       } else if (*dd_idx >= pd_idx)
+                               (*dd_idx) += 2; /* D D P Q D */
+                       ddf_layout = 1;
+                       break;
+
+               case ALGORITHM_ROTATING_N_CONTINUE:
+                       /* Same as left_symmetric but Q is before P */
+                       pd_idx = raid_disks - 1 - (stripe % raid_disks);
+                       qd_idx = (pd_idx + raid_disks - 1) % raid_disks;
+                       *dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
+                       ddf_layout = 1;
+                       break;
+
+               case ALGORITHM_LEFT_ASYMMETRIC_6:
+                       /* RAID5 left_asymmetric, with Q on last device */
+                       pd_idx = data_disks - stripe % (raid_disks-1);
+                       if (*dd_idx >= pd_idx)
+                               (*dd_idx)++;
+                       qd_idx = raid_disks - 1;
+                       break;
+
+               case ALGORITHM_RIGHT_ASYMMETRIC_6:
+                       pd_idx = stripe % (raid_disks-1);
+                       if (*dd_idx >= pd_idx)
+                               (*dd_idx)++;
+                       qd_idx = raid_disks - 1;
+                       break;
+
+               case ALGORITHM_LEFT_SYMMETRIC_6:
+                       pd_idx = data_disks - stripe % (raid_disks-1);
+                       *dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
+                       qd_idx = raid_disks - 1;
+                       break;
+
+               case ALGORITHM_RIGHT_SYMMETRIC_6:
+                       pd_idx = stripe % (raid_disks-1);
+                       *dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
+                       qd_idx = raid_disks - 1;
+                       break;
+
+               case ALGORITHM_PARITY_0_6:
+                       pd_idx = 0;
+                       (*dd_idx)++;
+                       qd_idx = raid_disks - 1;
                        break;
+
+
                default:
-                       printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
-                               conf->algorithm);
+                       printk(KERN_CRIT "raid6: unsupported algorithm %d\n",
+                              conf->algorithm);
+                       BUG();
                }
                break;
        }
 
+       if (sh) {
+               sh->pd_idx = pd_idx;
+               sh->qd_idx = qd_idx;
+               sh->ddf_layout = ddf_layout;
+       }
        /*
         * Finally, compute the new sector number
         */
@@ -1388,8 +1485,9 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i)
        int sectors_per_chunk = conf->chunk_size >> 9;
        sector_t stripe;
        int chunk_offset;
-       int chunk_number, dummy1, dummy2, dd_idx = i;
+       int chunk_number, dummy1, dd_idx = i;
        sector_t r_sector;
+       struct stripe_head sh2;
 
 
        chunk_offset = sector_div(new_sector, sectors_per_chunk);
@@ -1413,19 +1511,27 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i)
                                i += raid_disks;
                        i -= (sh->pd_idx + 1);
                        break;
+               case ALGORITHM_PARITY_0:
+                       i -= 1;
+                       break;
+               case ALGORITHM_PARITY_N:
+                       break;
                default:
                        printk(KERN_ERR "raid5: unsupported algorithm %d\n",
                               conf->algorithm);
+                       BUG();
                }
                break;
        case 6:
-               if (i == raid6_next_disk(sh->pd_idx, raid_disks))
+               if (i == sh->qd_idx)
                        return 0; /* It is the Q disk */
                switch (conf->algorithm) {
                case ALGORITHM_LEFT_ASYMMETRIC:
                case ALGORITHM_RIGHT_ASYMMETRIC:
-                       if (sh->pd_idx == raid_disks-1)
-                               i--;    /* Q D D D P */
+               case ALGORITHM_ROTATING_ZERO_RESTART:
+               case ALGORITHM_ROTATING_N_RESTART:
+                       if (sh->pd_idx == raid_disks-1)
+                               i--;    /* Q D D D P */
                        else if (i > sh->pd_idx)
                                i -= 2; /* D D P Q D */
                        break;
@@ -1440,9 +1546,35 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i)
                                i -= (sh->pd_idx + 2);
                        }
                        break;
+               case ALGORITHM_PARITY_0:
+                       i -= 2;
+                       break;
+               case ALGORITHM_PARITY_N:
+                       break;
+               case ALGORITHM_ROTATING_N_CONTINUE:
+                       if (sh->pd_idx == 0)
+                               i--;    /* P D D D Q */
+                       else if (i > sh->pd_idx)
+                               i -= 2; /* D D Q P D */
+                       break;
+               case ALGORITHM_LEFT_ASYMMETRIC_6:
+               case ALGORITHM_RIGHT_ASYMMETRIC_6:
+                       if (i > sh->pd_idx)
+                               i--;
+                       break;
+               case ALGORITHM_LEFT_SYMMETRIC_6:
+               case ALGORITHM_RIGHT_SYMMETRIC_6:
+                       if (i < sh->pd_idx)
+                               i += data_disks + 1;
+                       i -= (sh->pd_idx + 1);
+                       break;
+               case ALGORITHM_PARITY_0_6:
+                       i -= 1;
+                       break;
                default:
-                       printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
-                               conf->algorithm);
+                       printk(KERN_CRIT "raid6: unsupported algorithm %d\n",
+                              conf->algorithm);
+                       BUG();
                }
                break;
        }
@@ -1450,8 +1582,11 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i)
        chunk_number = stripe * data_disks + i;
        r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
 
-       check = raid5_compute_sector (r_sector, raid_disks, data_disks, &dummy1, &dummy2, conf);
-       if (check != sh->sector || dummy1 != dd_idx || dummy2 != sh->pd_idx) {
+       check = raid5_compute_sector(conf, r_sector,
+                                    (raid_disks != conf->raid_disks),
+                                    &dummy1, &sh2);
+       if (check != sh->sector || dummy1 != dd_idx || sh2.pd_idx != sh->pd_idx
+               || sh2.qd_idx != sh->qd_idx) {
                printk(KERN_ERR "compute_blocknr: map not correct\n");
                return 0;
        }
@@ -1516,140 +1651,18 @@ static void copy_data(int frombio, struct bio *bio,
                           }                                              \
                        } while(0)
 
-
-static void compute_block(struct stripe_head *sh, int dd_idx)
-{
-       int i, count, disks = sh->disks;
-       void *ptr[MAX_XOR_BLOCKS], *dest, *p;
-
-       pr_debug("compute_block, stripe %llu, idx %d\n",
-               (unsigned long long)sh->sector, dd_idx);
-
-       dest = page_address(sh->dev[dd_idx].page);
-       memset(dest, 0, STRIPE_SIZE);
-       count = 0;
-       for (i = disks ; i--; ) {
-               if (i == dd_idx)
-                       continue;
-               p = page_address(sh->dev[i].page);
-               if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
-                       ptr[count++] = p;
-               else
-                       printk(KERN_ERR "compute_block() %d, stripe %llu, %d"
-                               " not present\n", dd_idx,
-                               (unsigned long long)sh->sector, i);
-
-               check_xor();
-       }
-       if (count)
-               xor_blocks(count, STRIPE_SIZE, dest, ptr);
-       set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
-}
-
-static void compute_parity5(struct stripe_head *sh, int method)
-{
-       raid5_conf_t *conf = sh->raid_conf;
-       int i, pd_idx = sh->pd_idx, disks = sh->disks, count;
-       void *ptr[MAX_XOR_BLOCKS], *dest;
-       struct bio *chosen;
-
-       pr_debug("compute_parity5, stripe %llu, method %d\n",
-               (unsigned long long)sh->sector, method);
-
-       count = 0;
-       dest = page_address(sh->dev[pd_idx].page);
-       switch(method) {
-       case READ_MODIFY_WRITE:
-               BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags));
-               for (i=disks ; i-- ;) {
-                       if (i==pd_idx)
-                               continue;
-                       if (sh->dev[i].towrite &&
-                           test_bit(R5_UPTODATE, &sh->dev[i].flags)) {
-                               ptr[count++] = page_address(sh->dev[i].page);
-                               chosen = sh->dev[i].towrite;
-                               sh->dev[i].towrite = NULL;
-
-                               if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-                                       wake_up(&conf->wait_for_overlap);
-
-                               BUG_ON(sh->dev[i].written);
-                               sh->dev[i].written = chosen;
-                               check_xor();
-                       }
-               }
-               break;
-       case RECONSTRUCT_WRITE:
-               memset(dest, 0, STRIPE_SIZE);
-               for (i= disks; i-- ;)
-                       if (i!=pd_idx && sh->dev[i].towrite) {
-                               chosen = sh->dev[i].towrite;
-                               sh->dev[i].towrite = NULL;
-
-                               if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-                                       wake_up(&conf->wait_for_overlap);
-
-                               BUG_ON(sh->dev[i].written);
-                               sh->dev[i].written = chosen;
-                       }
-               break;
-       case CHECK_PARITY:
-               break;
-       }
-       if (count) {
-               xor_blocks(count, STRIPE_SIZE, dest, ptr);
-               count = 0;
-       }
-       
-       for (i = disks; i--;)
-               if (sh->dev[i].written) {
-                       sector_t sector = sh->dev[i].sector;
-                       struct bio *wbi = sh->dev[i].written;
-                       while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
-                               copy_data(1, wbi, sh->dev[i].page, sector);
-                               wbi = r5_next_bio(wbi, sector);
-                       }
-
-                       set_bit(R5_LOCKED, &sh->dev[i].flags);
-                       set_bit(R5_UPTODATE, &sh->dev[i].flags);
-               }
-
-       switch(method) {
-       case RECONSTRUCT_WRITE:
-       case CHECK_PARITY:
-               for (i=disks; i--;)
-                       if (i != pd_idx) {
-                               ptr[count++] = page_address(sh->dev[i].page);
-                               check_xor();
-                       }
-               break;
-       case READ_MODIFY_WRITE:
-               for (i = disks; i--;)
-                       if (sh->dev[i].written) {
-                               ptr[count++] = page_address(sh->dev[i].page);
-                               check_xor();
-                       }
-       }
-       if (count)
-               xor_blocks(count, STRIPE_SIZE, dest, ptr);
-
-       if (method != CHECK_PARITY) {
-               set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-               set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
-       } else
-               clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-}
-
 static void compute_parity6(struct stripe_head *sh, int method)
 {
-       raid6_conf_t *conf = sh->raid_conf;
-       int i, pd_idx = sh->pd_idx, qd_idx, d0_idx, disks = sh->disks, count;
+       raid5_conf_t *conf = sh->raid_conf;
+       int i, pd_idx, qd_idx, d0_idx, disks = sh->disks, count;
+       int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);
        struct bio *chosen;
        /**** FIX THIS: This could be very bad if disks is close to 256 ****/
-       void *ptrs[disks];
+       void *ptrs[syndrome_disks+2];
 
-       qd_idx = raid6_next_disk(pd_idx, disks);
-       d0_idx = raid6_next_disk(qd_idx, disks);
+       pd_idx = sh->pd_idx;
+       qd_idx = sh->qd_idx;
+       d0_idx = raid6_d0(sh);
 
        pr_debug("compute_parity, stripe %llu, method %d\n",
                (unsigned long long)sh->sector, method);
@@ -1687,24 +1700,29 @@ static void compute_parity6(struct stripe_head *sh, int method)
                        set_bit(R5_UPTODATE, &sh->dev[i].flags);
                }
 
-//     switch(method) {
-//     case RECONSTRUCT_WRITE:
-//     case CHECK_PARITY:
-//     case UPDATE_PARITY:
-               /* Note that unlike RAID-5, the ordering of the disks matters greatly. */
-               /* FIX: Is this ordering of drives even remotely optimal? */
-               count = 0;
-               i = d0_idx;
-               do {
-                       ptrs[count++] = page_address(sh->dev[i].page);
-                       if (count <= disks-2 && !test_bit(R5_UPTODATE, &sh->dev[i].flags))
-                               printk("block %d/%d not uptodate on parity calc\n", i,count);
-                       i = raid6_next_disk(i, disks);
-               } while ( i != d0_idx );
-//             break;
-//     }
-
-       raid6_call.gen_syndrome(disks, STRIPE_SIZE, ptrs);
+       /* Note that unlike RAID-5, the ordering of the disks matters greatly.*/
+
+       for (i = 0; i < disks; i++)
+               ptrs[i] = (void *)raid6_empty_zero_page;
+
+       count = 0;
+       i = d0_idx;
+       do {
+               int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
+
+               ptrs[slot] = page_address(sh->dev[i].page);
+               if (slot < syndrome_disks &&
+                   !test_bit(R5_UPTODATE, &sh->dev[i].flags)) {
+                       printk(KERN_ERR "block %d/%d not uptodate "
+                              "on parity calc\n", i, count);
+                       BUG();
+               }
+
+               i = raid6_next_disk(i, disks);
+       } while (i != d0_idx);
+       BUG_ON(count != syndrome_disks);
+
+       raid6_call.gen_syndrome(syndrome_disks+2, STRIPE_SIZE, ptrs);
 
        switch(method) {
        case RECONSTRUCT_WRITE:
@@ -1726,8 +1744,7 @@ static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
 {
        int i, count, disks = sh->disks;
        void *ptr[MAX_XOR_BLOCKS], *dest, *p;
-       int pd_idx = sh->pd_idx;
-       int qd_idx = raid6_next_disk(pd_idx, disks);
+       int qd_idx = sh->qd_idx;
 
        pr_debug("compute_block_1, stripe %llu, idx %d\n",
                (unsigned long long)sh->sector, dd_idx);
@@ -1763,66 +1780,136 @@ static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
 static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
 {
        int i, count, disks = sh->disks;
-       int pd_idx = sh->pd_idx;
-       int qd_idx = raid6_next_disk(pd_idx, disks);
-       int d0_idx = raid6_next_disk(qd_idx, disks);
-       int faila, failb;
+       int syndrome_disks = sh->ddf_layout ? disks : disks-2;
+       int d0_idx = raid6_d0(sh);
+       int faila = -1, failb = -1;
+       /**** FIX THIS: This could be very bad if disks is close to 256 ****/
+       void *ptrs[syndrome_disks+2];
+
+       for (i = 0; i < disks ; i++)
+               ptrs[i] = (void *)raid6_empty_zero_page;
+       count = 0;
+       i = d0_idx;
+       do {
+               int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
 
-       /* faila and failb are disk numbers relative to d0_idx */
-       /* pd_idx become disks-2 and qd_idx become disks-1 */
-       faila = (dd_idx1 < d0_idx) ? dd_idx1+(disks-d0_idx) : dd_idx1-d0_idx;
-       failb = (dd_idx2 < d0_idx) ? dd_idx2+(disks-d0_idx) : dd_idx2-d0_idx;
+               ptrs[slot] = page_address(sh->dev[i].page);
+
+               if (i == dd_idx1)
+                       faila = slot;
+               if (i == dd_idx2)
+                       failb = slot;
+               i = raid6_next_disk(i, disks);
+       } while (i != d0_idx);
+       BUG_ON(count != syndrome_disks);
 
        BUG_ON(faila == failb);
        if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
 
        pr_debug("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
-              (unsigned long long)sh->sector, dd_idx1, dd_idx2, faila, failb);
+                (unsigned long long)sh->sector, dd_idx1, dd_idx2,
+                faila, failb);
 
-       if ( failb == disks-1 ) {
+       if (failb == syndrome_disks+1) {
                /* Q disk is one of the missing disks */
-               if ( faila == disks-2 ) {
+               if (faila == syndrome_disks) {
                        /* Missing P+Q, just recompute */
                        compute_parity6(sh, UPDATE_PARITY);
                        return;
                } else {
                        /* We're missing D+Q; recompute D from P */
-                       compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1, 0);
+                       compute_block_1(sh, ((dd_idx1 == sh->qd_idx) ?
+                                            dd_idx2 : dd_idx1),
+                                       0);
                        compute_parity6(sh, UPDATE_PARITY); /* Is this necessary? */
                        return;
                }
        }
 
-       /* We're missing D+P or D+D; build pointer table */
-       {
-               /**** FIX THIS: This could be very bad if disks is close to 256 ****/
-               void *ptrs[disks];
+       /* We're missing D+P or D+D; */
+       if (failb == syndrome_disks) {
+               /* We're missing D+P. */
+               raid6_datap_recov(syndrome_disks+2, STRIPE_SIZE, faila, ptrs);
+       } else {
+               /* We're missing D+D. */
+               raid6_2data_recov(syndrome_disks+2, STRIPE_SIZE, faila, failb,
+                                 ptrs);
+       }
 
-               count = 0;
-               i = d0_idx;
-               do {
-                       ptrs[count++] = page_address(sh->dev[i].page);
-                       i = raid6_next_disk(i, disks);
-                       if (i != dd_idx1 && i != dd_idx2 &&
-                           !test_bit(R5_UPTODATE, &sh->dev[i].flags))
-                               printk("compute_2 with missing block %d/%d\n", count, i);
-               } while ( i != d0_idx );
-
-               if ( failb == disks-2 ) {
-                       /* We're missing D+P. */
-                       raid6_datap_recov(disks, STRIPE_SIZE, faila, ptrs);
-               } else {
-                       /* We're missing D+D. */
-                       raid6_2data_recov(disks, STRIPE_SIZE, faila, failb, ptrs);
-               }
+       /* Both the above update both missing blocks */
+       set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
+       set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
+}
 
-               /* Both the above update both missing blocks */
-               set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
-               set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
+static void
+schedule_reconstruction5(struct stripe_head *sh, struct stripe_head_state *s,
+                        int rcw, int expand)
+{
+       int i, pd_idx = sh->pd_idx, disks = sh->disks;
+
+       if (rcw) {
+               /* if we are not expanding this is a proper write request, and
+                * there will be bios with new data to be drained into the
+                * stripe cache
+                */
+               if (!expand) {
+                       sh->reconstruct_state = reconstruct_state_drain_run;
+                       set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
+               } else
+                       sh->reconstruct_state = reconstruct_state_run;
+
+               set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
+
+               for (i = disks; i--; ) {
+                       struct r5dev *dev = &sh->dev[i];
+
+                       if (dev->towrite) {
+                               set_bit(R5_LOCKED, &dev->flags);
+                               set_bit(R5_Wantdrain, &dev->flags);
+                               if (!expand)
+                                       clear_bit(R5_UPTODATE, &dev->flags);
+                               s->locked++;
+                       }
+               }
+               if (s->locked + 1 == disks)
+                       if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
+                               atomic_inc(&sh->raid_conf->pending_full_writes);
+       } else {
+               BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
+                       test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
+
+               sh->reconstruct_state = reconstruct_state_prexor_drain_run;
+               set_bit(STRIPE_OP_PREXOR, &s->ops_request);
+               set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
+               set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
+
+               for (i = disks; i--; ) {
+                       struct r5dev *dev = &sh->dev[i];
+                       if (i == pd_idx)
+                               continue;
+
+                       if (dev->towrite &&
+                           (test_bit(R5_UPTODATE, &dev->flags) ||
+                            test_bit(R5_Wantcompute, &dev->flags))) {
+                               set_bit(R5_Wantdrain, &dev->flags);
+                               set_bit(R5_LOCKED, &dev->flags);
+                               clear_bit(R5_UPTODATE, &dev->flags);
+                               s->locked++;
+                       }
+               }
        }
-}
 
+       /* keep the parity disk locked while asynchronous operations
+        * are in flight
+        */
+       set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
+       clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+       s->locked++;
 
+       pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
+               __func__, (unsigned long long)sh->sector,
+               s->locked, s->ops_request);
+}
 
 /*
  * Each stripe/dev can have one or more bion attached.
@@ -1860,7 +1947,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
        if (*bip)
                bi->bi_next = *bip;
        *bip = bi;
-       bi->bi_phys_segments ++;
+       bi->bi_phys_segments++;
        spin_unlock_irq(&conf->device_lock);
        spin_unlock(&sh->lock);
 
@@ -1906,21 +1993,23 @@ static int page_is_zero(struct page *p)
                memcmp(a, a+4, STRIPE_SIZE-4)==0);
 }
 
-static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks)
+static void stripe_set_idx(sector_t stripe, raid5_conf_t *conf, int previous,
+                           struct stripe_head *sh)
 {
        int sectors_per_chunk = conf->chunk_size >> 9;
-       int pd_idx, dd_idx;
+       int dd_idx;
        int chunk_offset = sector_div(stripe, sectors_per_chunk);
+       int disks = previous ? conf->previous_raid_disks : conf->raid_disks;
 
-       raid5_compute_sector(stripe * (disks - conf->max_degraded)
+       raid5_compute_sector(conf,
+                            stripe * (disks - conf->max_degraded)
                             *sectors_per_chunk + chunk_offset,
-                            disks, disks - conf->max_degraded,
-                            &dd_idx, &pd_idx, conf);
-       return pd_idx;
+                            previous,
+                            &dd_idx, sh);
 }
 
 static void
-handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
+handle_failed_stripe(raid5_conf_t *conf, struct stripe_head *sh,
                                struct stripe_head_state *s, int disks,
                                struct bio **return_bi)
 {
@@ -1954,7 +2043,7 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
                        sh->dev[i].sector + STRIPE_SECTORS) {
                        struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
                        clear_bit(BIO_UPTODATE, &bi->bi_flags);
-                       if (--bi->bi_phys_segments == 0) {
+                       if (!raid5_dec_bi_phys_segments(bi)) {
                                md_write_end(conf->mddev);
                                bi->bi_next = *return_bi;
                                *return_bi = bi;
@@ -1969,7 +2058,7 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
                       sh->dev[i].sector + STRIPE_SECTORS) {
                        struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
                        clear_bit(BIO_UPTODATE, &bi->bi_flags);
-                       if (--bi->bi_phys_segments == 0) {
+                       if (!raid5_dec_bi_phys_segments(bi)) {
                                md_write_end(conf->mddev);
                                bi->bi_next = *return_bi;
                                *return_bi = bi;
@@ -1977,9 +2066,12 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
                        bi = bi2;
                }
 
-               /* fail any reads if this device is non-operational */
-               if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
-                   test_bit(R5_ReadError, &sh->dev[i].flags)) {
+               /* fail any reads if this device is non-operational and
+                * the data has not reached the cache yet.
+                */
+               if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
+                   (!test_bit(R5_Insync, &sh->dev[i].flags) ||
+                     test_bit(R5_ReadError, &sh->dev[i].flags))) {
                        bi = sh->dev[i].toread;
                        sh->dev[i].toread = NULL;
                        if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
@@ -1990,7 +2082,7 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
                                struct bio *nextbi =
                                        r5_next_bio(bi, sh->dev[i].sector);
                                clear_bit(BIO_UPTODATE, &bi->bi_flags);
-                               if (--bi->bi_phys_segments == 0) {
+                               if (!raid5_dec_bi_phys_segments(bi)) {
                                        bi->bi_next = *return_bi;
                                        *return_bi = bi;
                                }
@@ -2003,43 +2095,84 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
                                        STRIPE_SECTORS, 0, 0);
        }
 
+       if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
+               if (atomic_dec_and_test(&conf->pending_full_writes))
+                       md_wakeup_thread(conf->mddev->thread);
 }
 
-static void handle_issuing_new_read_requests5(struct stripe_head *sh,
-                       struct stripe_head_state *s, int disks)
+/* fetch_block5 - checks the given member device to see if its data needs
+ * to be read or computed to satisfy a request.
+ *
+ * Returns 1 when no more member devices need to be checked, otherwise returns
+ * 0 to tell the loop in handle_stripe_fill5 to continue
+ */
+static int fetch_block5(struct stripe_head *sh, struct stripe_head_state *s,
+                       int disk_idx, int disks)
 {
-       int i;
-       for (i = disks; i--; ) {
-               struct r5dev *dev = &sh->dev[i];
-               if (!test_bit(R5_LOCKED, &dev->flags) &&
-                   !test_bit(R5_UPTODATE, &dev->flags) &&
-                   (dev->toread ||
-                    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
-                    s->syncing || s->expanding ||
-                    (s->failed && (sh->dev[s->failed_num].toread ||
-                       (sh->dev[s->failed_num].towrite &&
-                       !test_bit(R5_OVERWRITE, &sh->dev[s->failed_num].flags))
-                     )))) {
-                       /* we would like to get this block, possibly
-                        * by computing it, but we might not be able to
+       struct r5dev *dev = &sh->dev[disk_idx];
+       struct r5dev *failed_dev = &sh->dev[s->failed_num];
+
+       /* is the data in this block needed, and can we get it? */
+       if (!test_bit(R5_LOCKED, &dev->flags) &&
+           !test_bit(R5_UPTODATE, &dev->flags) &&
+           (dev->toread ||
+            (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
+            s->syncing || s->expanding ||
+            (s->failed &&
+             (failed_dev->toread ||
+              (failed_dev->towrite &&
+               !test_bit(R5_OVERWRITE, &failed_dev->flags)))))) {
+               /* We would like to get this block, possibly by computing it,
+                * otherwise read it if the backing disk is insync
+                */
+               if ((s->uptodate == disks - 1) &&
+                   (s->failed && disk_idx == s->failed_num)) {
+                       set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+                       set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+                       set_bit(R5_Wantcompute, &dev->flags);
+                       sh->ops.target = disk_idx;
+                       s->req_compute = 1;
+                       /* Careful: from this point on 'uptodate' is in the eye
+                        * of raid5_run_ops which services 'compute' operations
+                        * before writes. R5_Wantcompute flags a block that will
+                        * be R5_UPTODATE by the time it is needed for a
+                        * subsequent operation.
                         */
-                       if (s->uptodate == disks-1) {
-                               pr_debug("Computing block %d\n", i);
-                               compute_block(sh, i);
-                               s->uptodate++;
-                       } else if (test_bit(R5_Insync, &dev->flags)) {
-                               set_bit(R5_LOCKED, &dev->flags);
-                               set_bit(R5_Wantread, &dev->flags);
-                               s->locked++;
-                               pr_debug("Reading block %d (sync=%d)\n",
-                                       i, s->syncing);
-                       }
+                       s->uptodate++;
+                       return 1; /* uptodate + compute == disks */
+               } else if (test_bit(R5_Insync, &dev->flags)) {
+                       set_bit(R5_LOCKED, &dev->flags);
+                       set_bit(R5_Wantread, &dev->flags);
+                       s->locked++;
+                       pr_debug("Reading block %d (sync=%d)\n", disk_idx,
+                               s->syncing);
                }
        }
+
+       return 0;
+}
+
+/**
+ * handle_stripe_fill5 - read or compute data to satisfy pending requests.
+ */
+static void handle_stripe_fill5(struct stripe_head *sh,
+                       struct stripe_head_state *s, int disks)
+{
+       int i;
+
+       /* look for blocks to read/compute, skip this if a compute
+        * is already in flight, or if the stripe contents are in the
+        * midst of changing due to a write
+        */
+       if (!test_bit(STRIPE_COMPUTE_RUN, &sh->state) && !sh->check_state &&
+           !sh->reconstruct_state)
+               for (i = disks; i--; )
+                       if (fetch_block5(sh, s, i, disks))
+                               break;
        set_bit(STRIPE_HANDLE, &sh->state);
 }
 
-static void handle_issuing_new_read_requests6(struct stripe_head *sh,
+static void handle_stripe_fill6(struct stripe_head *sh,
                        struct stripe_head_state *s, struct r6_state *r6s,
                        int disks)
 {
@@ -2060,7 +2193,9 @@ static void handle_issuing_new_read_requests6(struct stripe_head *sh,
                        /* we would like to get this block, possibly
                         * by computing it, but we might not be able to
                         */
-                       if (s->uptodate == disks-1) {
+                       if ((s->uptodate == disks - 1) &&
+                           (s->failed && (i == r6s->failed_num[0] ||
+                                          i == r6s->failed_num[1]))) {
                                pr_debug("Computing stripe %llu block %d\n",
                                       (unsigned long long)sh->sector, i);
                                compute_block_1(sh, i, 0);
@@ -2096,12 +2231,12 @@ static void handle_issuing_new_read_requests6(struct stripe_head *sh,
 }
 
 
-/* handle_completed_write_requests
+/* handle_stripe_clean_event
  * any written block on an uptodate or failed drive can be returned.
  * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
  * never LOCKED, so we don't need to test 'failed' directly.
  */
-static void handle_completed_write_requests(raid5_conf_t *conf,
+static void handle_stripe_clean_event(raid5_conf_t *conf,
        struct stripe_head *sh, int disks, struct bio **return_bi)
 {
        int i;
@@ -2122,7 +2257,7 @@ static void handle_completed_write_requests(raid5_conf_t *conf,
                                while (wbi && wbi->bi_sector <
                                        dev->sector + STRIPE_SECTORS) {
                                        wbi2 = r5_next_bio(wbi, dev->sector);
-                                       if (--wbi->bi_phys_segments == 0) {
+                                       if (!raid5_dec_bi_phys_segments(wbi)) {
                                                md_write_end(conf->mddev);
                                                wbi->bi_next = *return_bi;
                                                *return_bi = wbi;
@@ -2140,9 +2275,13 @@ static void handle_completed_write_requests(raid5_conf_t *conf,
                                                        0);
                        }
                }
+
+       if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
+               if (atomic_dec_and_test(&conf->pending_full_writes))
+                       md_wakeup_thread(conf->mddev->thread);
 }
 
-static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
+static void handle_stripe_dirtying5(raid5_conf_t *conf,
                struct stripe_head *sh, struct stripe_head_state *s, int disks)
 {
        int rmw = 0, rcw = 0, i;
@@ -2151,7 +2290,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                struct r5dev *dev = &sh->dev[i];
                if ((dev->towrite || i == sh->pd_idx) &&
                    !test_bit(R5_LOCKED, &dev->flags) &&
-                   !test_bit(R5_UPTODATE, &dev->flags)) {
+                   !(test_bit(R5_UPTODATE, &dev->flags) ||
+                     test_bit(R5_Wantcompute, &dev->flags))) {
                        if (test_bit(R5_Insync, &dev->flags))
                                rmw++;
                        else
@@ -2160,9 +2300,9 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                /* Would I have to read this buffer for reconstruct_write */
                if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
                    !test_bit(R5_LOCKED, &dev->flags) &&
-                   !test_bit(R5_UPTODATE, &dev->flags)) {
-                       if (test_bit(R5_Insync, &dev->flags))
-                               rcw++;
+                   !(test_bit(R5_UPTODATE, &dev->flags) ||
+                   test_bit(R5_Wantcompute, &dev->flags))) {
+                       if (test_bit(R5_Insync, &dev->flags)) rcw++;
                        else
                                rcw += 2*disks;
                }
@@ -2176,7 +2316,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                        struct r5dev *dev = &sh->dev[i];
                        if ((dev->towrite || i == sh->pd_idx) &&
                            !test_bit(R5_LOCKED, &dev->flags) &&
-                           !test_bit(R5_UPTODATE, &dev->flags) &&
+                           !(test_bit(R5_UPTODATE, &dev->flags) ||
+                           test_bit(R5_Wantcompute, &dev->flags)) &&
                            test_bit(R5_Insync, &dev->flags)) {
                                if (
                                  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
@@ -2198,7 +2339,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                        if (!test_bit(R5_OVERWRITE, &dev->flags) &&
                            i != sh->pd_idx &&
                            !test_bit(R5_LOCKED, &dev->flags) &&
-                           !test_bit(R5_UPTODATE, &dev->flags) &&
+                           !(test_bit(R5_UPTODATE, &dev->flags) ||
+                           test_bit(R5_Wantcompute, &dev->flags)) &&
                            test_bit(R5_Insync, &dev->flags)) {
                                if (
                                  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
@@ -2216,31 +2358,20 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
        /* now if nothing is locked, and if we have enough data,
         * we can start a write request
         */
-       if (s->locked == 0 && (rcw == 0 || rmw == 0) &&
-           !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
-               pr_debug("Computing parity...\n");
-               compute_parity5(sh, rcw == 0 ?
-                       RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
-               /* now every locked buffer is ready to be written */
-               for (i = disks; i--; )
-                       if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
-                               pr_debug("Writing block %d\n", i);
-                               s->locked++;
-                               set_bit(R5_Wantwrite, &sh->dev[i].flags);
-                               if (!test_bit(R5_Insync, &sh->dev[i].flags)
-                                   || (i == sh->pd_idx && s->failed == 0))
-                                       set_bit(STRIPE_INSYNC, &sh->state);
-                       }
-               if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
-                       atomic_dec(&conf->preread_active_stripes);
-                       if (atomic_read(&conf->preread_active_stripes) <
-                           IO_THRESHOLD)
-                               md_wakeup_thread(conf->mddev->thread);
-               }
-       }
+       /* since handle_stripe can be called at any time we need to handle the
+        * case where a compute block operation has been submitted and then a
+        * subsequent call wants to start a write request.  raid5_run_ops only
+        * handles the case where compute block and postxor are requested
+        * simultaneously.  If this is not the case then new writes need to be
+        * held off until the compute completes.
+        */
+       if ((s->req_compute || !test_bit(STRIPE_COMPUTE_RUN, &sh->state)) &&
+           (s->locked == 0 && (rcw == 0 || rmw == 0) &&
+           !test_bit(STRIPE_BIT_DELAY, &sh->state)))
+               schedule_reconstruction5(sh, s, rcw == 0, 0);
 }
 
-static void handle_issuing_new_write_requests6(raid5_conf_t *conf,
+static void handle_stripe_dirtying6(raid5_conf_t *conf,
                struct stripe_head *sh, struct stripe_head_state *s,
                struct r6_state *r6s, int disks)
 {
@@ -2325,6 +2456,9 @@ static void handle_issuing_new_write_requests6(raid5_conf_t *conf,
                                s->locked++;
                                set_bit(R5_Wantwrite, &sh->dev[i].flags);
                        }
+               if (s->locked == disks)
+                       if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
+                               atomic_inc(&conf->pending_full_writes);
                /* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
                set_bit(STRIPE_INSYNC, &sh->state);
 
@@ -2340,40 +2474,86 @@ static void handle_issuing_new_write_requests6(raid5_conf_t *conf,
 static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
                                struct stripe_head_state *s, int disks)
 {
+       struct r5dev *dev = NULL;
+
        set_bit(STRIPE_HANDLE, &sh->state);
-       if (s->failed == 0) {
+
+       switch (sh->check_state) {
+       case check_state_idle:
+               /* start a new check operation if there are no failures */
+               if (s->failed == 0) {
+                       BUG_ON(s->uptodate != disks);
+                       sh->check_state = check_state_run;
+                       set_bit(STRIPE_OP_CHECK, &s->ops_request);
+                       clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
+                       s->uptodate--;
+                       break;
+               }
+               dev = &sh->dev[s->failed_num];
+               /* fall through */
+       case check_state_compute_result:
+               sh->check_state = check_state_idle;
+               if (!dev)
+                       dev = &sh->dev[sh->pd_idx];
+
+               /* check that a write has not made the stripe insync */
+               if (test_bit(STRIPE_INSYNC, &sh->state))
+                       break;
+
+               /* either failed parity check, or recovery is happening */
+               BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
                BUG_ON(s->uptodate != disks);
-               compute_parity5(sh, CHECK_PARITY);
-               s->uptodate--;
-               if (page_is_zero(sh->dev[sh->pd_idx].page)) {
-                       /* parity is correct (on disc, not in buffer any more)
+
+               set_bit(R5_LOCKED, &dev->flags);
+               s->locked++;
+               set_bit(R5_Wantwrite, &dev->flags);
+
+               clear_bit(STRIPE_DEGRADED, &sh->state);
+               set_bit(STRIPE_INSYNC, &sh->state);
+               break;
+       case check_state_run:
+               break; /* we will be called again upon completion */
+       case check_state_check_result:
+               sh->check_state = check_state_idle;
+
+               /* if a failure occurred during the check operation, leave
+                * STRIPE_INSYNC not set and let the stripe be handled again
+                */
+               if (s->failed)
+                       break;
+
+               /* handle a successful check operation, if parity is correct
+                * we are done.  Otherwise update the mismatch count and repair
+                * parity if !MD_RECOVERY_CHECK
+                */
+               if (sh->ops.zero_sum_result == 0)
+                       /* parity is correct (on disc,
+                        * not in buffer any more)
                         */
                        set_bit(STRIPE_INSYNC, &sh->state);
-               else {
+               else {
                        conf->mddev->resync_mismatches += STRIPE_SECTORS;
                        if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
                                /* don't try to repair!! */
                                set_bit(STRIPE_INSYNC, &sh->state);
                        else {
-                               compute_block(sh, sh->pd_idx);
+                               sh->check_state = check_state_compute_run;
+                               set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+                               set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+                               set_bit(R5_Wantcompute,
+                                       &sh->dev[sh->pd_idx].flags);
+                               sh->ops.target = sh->pd_idx;
                                s->uptodate++;
                        }
                }
-       }
-       if (!test_bit(STRIPE_INSYNC, &sh->state)) {
-               struct r5dev *dev;
-               /* either failed parity check, or recovery is happening */
-               if (s->failed == 0)
-                       s->failed_num = sh->pd_idx;
-               dev = &sh->dev[s->failed_num];
-               BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
-               BUG_ON(s->uptodate != disks);
-
-               set_bit(R5_LOCKED, &dev->flags);
-               set_bit(R5_Wantwrite, &dev->flags);
-               clear_bit(STRIPE_DEGRADED, &sh->state);
-               s->locked++;
-               set_bit(STRIPE_INSYNC, &sh->state);
+               break;
+       case check_state_compute_run:
+               break;
+       default:
+               printk(KERN_ERR "%s: unknown check_state: %d sector: %llu\n",
+                      __func__, sh->check_state,
+                      (unsigned long long) sh->sector);
+               BUG();
        }
 }
 
@@ -2479,19 +2659,17 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
        /* We have read all the blocks in this stripe and now we need to
         * copy some of them into a target stripe for expand.
         */
+       struct dma_async_tx_descriptor *tx = NULL;
        clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
        for (i = 0; i < sh->disks; i++)
-               if (i != sh->pd_idx && (r6s && i != r6s->qd_idx)) {
-                       int dd_idx, pd_idx, j;
+               if (i != sh->pd_idx && (!r6s || i != r6s->qd_idx)) {
+                       int dd_idx, j;
                        struct stripe_head *sh2;
 
                        sector_t bn = compute_blocknr(sh, i);
-                       sector_t s = raid5_compute_sector(bn, conf->raid_disks,
-                                               conf->raid_disks -
-                                               conf->max_degraded, &dd_idx,
-                                               &pd_idx, conf);
-                       sh2 = get_active_stripe(conf, s, conf->raid_disks,
-                                               pd_idx, 1);
+                       sector_t s = raid5_compute_sector(conf, bn, 0,
+                                                         &dd_idx, NULL);
+                       sh2 = get_active_stripe(conf, s, 0, 1);
                        if (sh2 == NULL)
                                /* so far only the early blocks of this stripe
                                 * have been requested.  When later blocks
@@ -2504,14 +2682,17 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
                                release_stripe(sh2);
                                continue;
                        }
-                       memcpy(page_address(sh2->dev[dd_idx].page),
-                              page_address(sh->dev[i].page),
-                              STRIPE_SIZE);
+
+                       /* place all the copies on one channel */
+                       tx = async_memcpy(sh2->dev[dd_idx].page,
+                               sh->dev[i].page, 0, 0, STRIPE_SIZE,
+                               ASYNC_TX_DEP_ACK, tx, NULL, NULL);
+
                        set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
                        set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
                        for (j = 0; j < conf->raid_disks; j++)
                                if (j != sh2->pd_idx &&
-                                   (r6s && j != r6s->qd_idx) &&
+                                   (!r6s || j != sh2->qd_idx) &&
                                    !test_bit(R5_Expanded, &sh2->dev[j].flags))
                                        break;
                        if (j == conf->raid_disks) {
@@ -2519,9 +2700,16 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
                                set_bit(STRIPE_HANDLE, &sh2->state);
                        }
                        release_stripe(sh2);
+
                }
+       /* done submitting copies, wait for them to complete */
+       if (tx) {
+               async_tx_ack(tx);
+               dma_wait_for_async_tx(tx);
+       }
 }
 
+
 /*
  * handle_stripe - do things to a stripe.
  *
@@ -2539,20 +2727,21 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
  *
  */
 
-static void handle_stripe5(struct stripe_head *sh)
+static bool handle_stripe5(struct stripe_head *sh)
 {
        raid5_conf_t *conf = sh->raid_conf;
        int disks = sh->disks, i;
        struct bio *return_bi = NULL;
        struct stripe_head_state s;
        struct r5dev *dev;
-       unsigned long pending = 0;
+       mdk_rdev_t *blocked_rdev = NULL;
+       int prexor;
 
        memset(&s, 0, sizeof(s));
-       pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d "
-               "ops=%lx:%lx:%lx\n", (unsigned long long)sh->sector, sh->state,
-               atomic_read(&sh->count), sh->pd_idx,
-               sh->ops.pending, sh->ops.ack, sh->ops.complete);
+       pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d check:%d "
+                "reconstruct:%d\n", (unsigned long long)sh->sector, sh->state,
+                atomic_read(&sh->count), sh->pd_idx, sh->check_state,
+                sh->reconstruct_state);
 
        spin_lock(&sh->lock);
        clear_bit(STRIPE_HANDLE, &sh->state);
@@ -2561,44 +2750,35 @@ static void handle_stripe5(struct stripe_head *sh)
        s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
        s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
        s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
-       /* Now to look around and see what can be done */
 
+       /* Now to look around and see what can be done */
        rcu_read_lock();
        for (i=disks; i--; ) {
                mdk_rdev_t *rdev;
                struct r5dev *dev = &sh->dev[i];
                clear_bit(R5_Insync, &dev->flags);
 
-               pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
-                       i, dev->flags, dev->toread, dev->towrite, dev->written);
-               /* maybe we can reply to a read */
-               if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
-                       struct bio *rbi, *rbi2;
-                       pr_debug("Return read for disc %d\n", i);
-                       spin_lock_irq(&conf->device_lock);
-                       rbi = dev->toread;
-                       dev->toread = NULL;
-                       if (test_and_clear_bit(R5_Overlap, &dev->flags))
-                               wake_up(&conf->wait_for_overlap);
-                       spin_unlock_irq(&conf->device_lock);
-                       while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
-                               copy_data(0, rbi, dev->page, dev->sector);
-                               rbi2 = r5_next_bio(rbi, dev->sector);
-                               spin_lock_irq(&conf->device_lock);
-                               if (--rbi->bi_phys_segments == 0) {
-                                       rbi->bi_next = return_bi;
-                                       return_bi = rbi;
-                               }
-                               spin_unlock_irq(&conf->device_lock);
-                               rbi = rbi2;
-                       }
-               }
+               pr_debug("check %d: state 0x%lx toread %p read %p write %p "
+                       "written %p\n", i, dev->flags, dev->toread, dev->read,
+                       dev->towrite, dev->written);
+
+               /* maybe we can request a biofill operation
+                *
+                * new wantfill requests are only permitted while
+                * ops_complete_biofill is guaranteed to be inactive
+                */
+               if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
+                   !test_bit(STRIPE_BIOFILL_RUN, &sh->state))
+                       set_bit(R5_Wantfill, &dev->flags);
 
                /* now count some things */
                if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
                if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
+               if (test_bit(R5_Wantcompute, &dev->flags)) s.compute++;
 
-               if (dev->toread)
+               if (test_bit(R5_Wantfill, &dev->flags))
+                       s.to_fill++;
+               else if (dev->toread)
                        s.to_read++;
                if (dev->towrite) {
                        s.to_write++;
@@ -2608,6 +2788,11 @@ static void handle_stripe5(struct stripe_head *sh)
                if (dev->written)
                        s.written++;
                rdev = rcu_dereference(conf->disks[i].rdev);
+               if (blocked_rdev == NULL &&
+                   rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                       blocked_rdev = rdev;
+                       atomic_inc(&rdev->nr_pending);
+               }
                if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                        /* The ReadError flag will just be confusing now */
                        clear_bit(R5_ReadError, &dev->flags);
@@ -2621,6 +2806,23 @@ static void handle_stripe5(struct stripe_head *sh)
                        set_bit(R5_Insync, &dev->flags);
        }
        rcu_read_unlock();
+
+       if (unlikely(blocked_rdev)) {
+               if (s.syncing || s.expanding || s.expanded ||
+                   s.to_write || s.written) {
+                       set_bit(STRIPE_HANDLE, &sh->state);
+                       goto unlock;
+               }
+               /* There is nothing for the blocked_rdev to block */
+               rdev_dec_pending(blocked_rdev, conf->mddev);
+               blocked_rdev = NULL;
+       }
+
+       if (s.to_fill && !test_bit(STRIPE_BIOFILL_RUN, &sh->state)) {
+               set_bit(STRIPE_OP_BIOFILL, &s.ops_request);
+               set_bit(STRIPE_BIOFILL_RUN, &sh->state);
+       }
+
        pr_debug("locked=%d uptodate=%d to_read=%d"
                " to_write=%d failed=%d failed_num=%d\n",
                s.locked, s.uptodate, s.to_read, s.to_write,
@@ -2629,8 +2831,7 @@ static void handle_stripe5(struct stripe_head *sh)
         * need to be failed
         */
        if (s.failed > 1 && s.to_read+s.to_write+s.written)
-               handle_requests_to_failed_array(conf, sh, &s, disks,
-                                               &return_bi);
+               handle_failed_stripe(conf, sh, &s, disks, &return_bi);
        if (s.failed > 1 && s.syncing) {
                md_done_sync(conf->mddev, STRIPE_SECTORS,0);
                clear_bit(STRIPE_SYNCING, &sh->state);
@@ -2646,27 +2847,71 @@ static void handle_stripe5(struct stripe_head *sh)
               !test_bit(R5_LOCKED, &dev->flags) &&
               test_bit(R5_UPTODATE, &dev->flags)) ||
               (s.failed == 1 && s.failed_num == sh->pd_idx)))
-               handle_completed_write_requests(conf, sh, disks, &return_bi);
+               handle_stripe_clean_event(conf, sh, disks, &return_bi);
 
        /* Now we might consider reading some blocks, either to check/generate
         * parity, or to satisfy requests
         * or to load a block that is being partially written.
         */
        if (s.to_read || s.non_overwrite ||
-               (s.syncing && (s.uptodate < disks)) || s.expanding)
-               handle_issuing_new_read_requests5(sh, &s, disks);
+           (s.syncing && (s.uptodate + s.compute < disks)) || s.expanding)
+               handle_stripe_fill5(sh, &s, disks);
 
-       /* now to consider writing and what else, if anything should be read */
-       if (s.to_write)
-               handle_issuing_new_write_requests5(conf, sh, &s, disks);
+       /* Now we check to see if any write operations have recently
+        * completed
+        */
+       prexor = 0;
+       if (sh->reconstruct_state == reconstruct_state_prexor_drain_result)
+               prexor = 1;
+       if (sh->reconstruct_state == reconstruct_state_drain_result ||
+           sh->reconstruct_state == reconstruct_state_prexor_drain_result) {
+               sh->reconstruct_state = reconstruct_state_idle;
+
+               /* All the 'written' buffers and the parity block are ready to
+                * be written back to disk
+                */
+               BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
+               for (i = disks; i--; ) {
+                       dev = &sh->dev[i];
+                       if (test_bit(R5_LOCKED, &dev->flags) &&
+                               (i == sh->pd_idx || dev->written)) {
+                               pr_debug("Writing block %d\n", i);
+                               set_bit(R5_Wantwrite, &dev->flags);
+                               if (prexor)
+                                       continue;
+                               if (!test_bit(R5_Insync, &dev->flags) ||
+                                   (i == sh->pd_idx && s.failed == 0))
+                                       set_bit(STRIPE_INSYNC, &sh->state);
+                       }
+               }
+               if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+                       atomic_dec(&conf->preread_active_stripes);
+                       if (atomic_read(&conf->preread_active_stripes) <
+                               IO_THRESHOLD)
+                               md_wakeup_thread(conf->mddev->thread);
+               }
+       }
+
+       /* Now to consider new write requests and what else, if anything
+        * should be read.  We do not handle new writes when:
+        * 1/ A 'write' operation (copy+xor) is already in flight.
+        * 2/ A 'check' operation is in flight, as it may clobber the parity
+        *    block.
+        */
+       if (s.to_write && !sh->reconstruct_state && !sh->check_state)
+               handle_stripe_dirtying5(conf, sh, &s, disks);
 
        /* maybe we need to check and possibly fix the parity for this stripe
-        * Any reads will already have been scheduled, so we just see if enough data
-        * is available
+        * Any reads will already have been scheduled, so we just see if enough
+        * data is available.  The parity check is held off while parity
+        * dependent operations are in flight.
         */
-       if (s.syncing && s.locked == 0 &&
-           !test_bit(STRIPE_INSYNC, &sh->state))
+       if (sh->check_state ||
+           (s.syncing && s.locked == 0 &&
+            !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
+            !test_bit(STRIPE_INSYNC, &sh->state)))
                handle_parity_checks5(conf, sh, &s, disks);
+
        if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
                md_done_sync(conf->mddev, STRIPE_SECTORS,1);
                clear_bit(STRIPE_SYNCING, &sh->state);
@@ -2694,108 +2939,63 @@ static void handle_stripe5(struct stripe_head *sh)
                }
        }
 
-       if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
-               /* Need to write out all blocks after computing parity */
-               sh->disks = conf->raid_disks;
-               sh->pd_idx = stripe_to_pdidx(sh->sector, conf, conf->raid_disks);
-               compute_parity5(sh, RECONSTRUCT_WRITE);
+       /* Finish reconstruct operations initiated by the expansion process */
+       if (sh->reconstruct_state == reconstruct_state_result) {
+               sh->reconstruct_state = reconstruct_state_idle;
+               clear_bit(STRIPE_EXPANDING, &sh->state);
                for (i = conf->raid_disks; i--; ) {
+                       set_bit(R5_Wantwrite, &sh->dev[i].flags);
                        set_bit(R5_LOCKED, &sh->dev[i].flags);
                        s.locked++;
-                       set_bit(R5_Wantwrite, &sh->dev[i].flags);
                }
-               clear_bit(STRIPE_EXPANDING, &sh->state);
-       } else if (s.expanded) {
+       }
+
+       if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
+           !sh->reconstruct_state) {
+               /* Need to write out all blocks after computing parity */
+               sh->disks = conf->raid_disks;
+               stripe_set_idx(sh->sector, conf, 0, sh);
+               schedule_reconstruction5(sh, &s, 1, 1);
+       } else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
                clear_bit(STRIPE_EXPAND_READY, &sh->state);
                atomic_dec(&conf->reshape_stripes);
                wake_up(&conf->wait_for_overlap);
                md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
        }
 
-       if (s.expanding && s.locked == 0)
+       if (s.expanding && s.locked == 0 &&
+           !test_bit(STRIPE_COMPUTE_RUN, &sh->state))
                handle_stripe_expansion(conf, sh, NULL);
 
-       if (sh->ops.count)
-               pending = get_stripe_work(sh);
-
+ unlock:
        spin_unlock(&sh->lock);
 
-       if (pending)
-               raid5_run_ops(sh, pending);
+       /* wait for this device to become unblocked */
+       if (unlikely(blocked_rdev))
+               md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
+
+       if (s.ops_request)
+               raid5_run_ops(sh, s.ops_request);
+
+       ops_run_io(sh, &s);
 
        return_io(return_bi);
 
-       for (i=disks; i-- ;) {
-               int rw;
-               struct bio *bi;
-               mdk_rdev_t *rdev;
-               if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
-                       rw = WRITE;
-               else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
-                       rw = READ;
-               else
-                       continue;
-               bi = &sh->dev[i].req;
-               bi->bi_rw = rw;
-               if (rw == WRITE)
-                       bi->bi_end_io = raid5_end_write_request;
-               else
-                       bi->bi_end_io = raid5_end_read_request;
-               rcu_read_lock();
-               rdev = rcu_dereference(conf->disks[i].rdev);
-               if (rdev && test_bit(Faulty, &rdev->flags))
-                       rdev = NULL;
-               if (rdev)
-                       atomic_inc(&rdev->nr_pending);
-               rcu_read_unlock();
-               if (rdev) {
-                       if (s.syncing || s.expanding || s.expanded)
-                               md_sync_acct(rdev->bdev, STRIPE_SECTORS);
+       return blocked_rdev == NULL;
+}
 
-                       bi->bi_bdev = rdev->bdev;
-                       pr_debug("for %llu schedule op %ld on disc %d\n",
-                               (unsigned long long)sh->sector, bi->bi_rw, i);
-                       atomic_inc(&sh->count);
-                       bi->bi_sector = sh->sector + rdev->data_offset;
-                       bi->bi_flags = 1 << BIO_UPTODATE;
-                       bi->bi_vcnt = 1;        
-                       bi->bi_max_vecs = 1;
-                       bi->bi_idx = 0;
-                       bi->bi_io_vec = &sh->dev[i].vec;
-                       bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
-                       bi->bi_io_vec[0].bv_offset = 0;
-                       bi->bi_size = STRIPE_SIZE;
-                       bi->bi_next = NULL;
-                       if (rw == WRITE &&
-                           test_bit(R5_ReWrite, &sh->dev[i].flags))
-                               atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
-                       generic_make_request(bi);
-               } else {
-                       if (rw == WRITE)
-                               set_bit(STRIPE_DEGRADED, &sh->state);
-                       pr_debug("skip op %ld on disc %d for sector %llu\n",
-                               bi->bi_rw, i, (unsigned long long)sh->sector);
-                       clear_bit(R5_LOCKED, &sh->dev[i].flags);
-                       set_bit(STRIPE_HANDLE, &sh->state);
-               }
-       }
-}
-
-static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
+static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 {
-       raid6_conf_t *conf = sh->raid_conf;
+       raid5_conf_t *conf = sh->raid_conf;
        int disks = sh->disks;
        struct bio *return_bi = NULL;
        int i, pd_idx = sh->pd_idx;
        struct stripe_head_state s;
        struct r6_state r6s;
        struct r5dev *dev, *pdev, *qdev;
+       mdk_rdev_t *blocked_rdev = NULL;
 
-       r6s.qd_idx = raid6_next_disk(pd_idx, disks);
+       r6s.qd_idx = sh->qd_idx;
        pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
                "pd_idx=%d, qd_idx=%d\n",
               (unsigned long long)sh->sector, sh->state,
@@ -2833,7 +3033,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                                copy_data(0, rbi, dev->page, dev->sector);
                                rbi2 = r5_next_bio(rbi, dev->sector);
                                spin_lock_irq(&conf->device_lock);
-                               if (--rbi->bi_phys_segments == 0) {
+                               if (!raid5_dec_bi_phys_segments(rbi)) {
                                        rbi->bi_next = return_bi;
                                        return_bi = rbi;
                                }
@@ -2857,6 +3057,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                if (dev->written)
                        s.written++;
                rdev = rcu_dereference(conf->disks[i].rdev);
+               if (blocked_rdev == NULL &&
+                   rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+                       blocked_rdev = rdev;
+                       atomic_inc(&rdev->nr_pending);
+               }
                if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                        /* The ReadError flag will just be confusing now */
                        clear_bit(R5_ReadError, &dev->flags);
@@ -2871,6 +3076,18 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                        set_bit(R5_Insync, &dev->flags);
        }
        rcu_read_unlock();
+
+       if (unlikely(blocked_rdev)) {
+               if (s.syncing || s.expanding || s.expanded ||
+                   s.to_write || s.written) {
+                       set_bit(STRIPE_HANDLE, &sh->state);
+                       goto unlock;
+               }
+               /* There is nothing for the blocked_rdev to block */
+               rdev_dec_pending(blocked_rdev, conf->mddev);
+               blocked_rdev = NULL;
+       }
+
        pr_debug("locked=%d uptodate=%d to_read=%d"
               " to_write=%d failed=%d failed_num=%d,%d\n",
               s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
@@ -2879,8 +3096,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
         * might need to be failed
         */
        if (s.failed > 2 && s.to_read+s.to_write+s.written)
-               handle_requests_to_failed_array(conf, sh, &s, disks,
-                                               &return_bi);
+               handle_failed_stripe(conf, sh, &s, disks, &return_bi);
        if (s.failed > 2 && s.syncing) {
                md_done_sync(conf->mddev, STRIPE_SECTORS,0);
                clear_bit(STRIPE_SYNCING, &sh->state);
@@ -2905,7 +3121,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
             ( r6s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
                             && !test_bit(R5_LOCKED, &qdev->flags)
                             && test_bit(R5_UPTODATE, &qdev->flags)))))
-               handle_completed_write_requests(conf, sh, disks, &return_bi);
+               handle_stripe_clean_event(conf, sh, disks, &return_bi);
 
        /* Now we might consider reading some blocks, either to check/generate
         * parity, or to satisfy requests
@@ -2913,11 +3129,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
         */
        if (s.to_read || s.non_overwrite || (s.to_write && s.failed) ||
            (s.syncing && (s.uptodate < disks)) || s.expanding)
-               handle_issuing_new_read_requests6(sh, &s, &r6s, disks);
+               handle_stripe_fill6(sh, &s, &r6s, disks);
 
        /* now to consider writing and what else, if anything should be read */
        if (s.to_write)
-               handle_issuing_new_write_requests6(conf, sh, &s, &r6s, disks);
+               handle_stripe_dirtying6(conf, sh, &s, &r6s, disks);
 
        /* maybe we need to check and possibly fix the parity for this stripe
         * Any reads will already have been scheduled, so we just see if enough
@@ -2956,8 +3172,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
        if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
                /* Need to write out all blocks after computing P&Q */
                sh->disks = conf->raid_disks;
-               sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
-                                            conf->raid_disks);
+               stripe_set_idx(sh->sector, conf, 0, sh);
                compute_parity6(sh, RECONSTRUCT_WRITE);
                for (i = conf->raid_disks ; i-- ;  ) {
                        set_bit(R5_LOCKED, &sh->dev[i].flags);
@@ -2972,79 +3187,31 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
        }
 
-       if (s.expanding && s.locked == 0)
+       if (s.expanding && s.locked == 0 &&
+           !test_bit(STRIPE_COMPUTE_RUN, &sh->state))
                handle_stripe_expansion(conf, sh, &r6s);
 
+ unlock:
        spin_unlock(&sh->lock);
 
-       return_io(return_bi);
+       /* wait for this device to become unblocked */
+       if (unlikely(blocked_rdev))
+               md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
 
-       for (i=disks; i-- ;) {
-               int rw;
-               struct bio *bi;
-               mdk_rdev_t *rdev;
-               if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
-                       rw = WRITE;
-               else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
-                       rw = READ;
-               else
-                       continue;
+       ops_run_io(sh, &s);
 
-               bi = &sh->dev[i].req;
-
-               bi->bi_rw = rw;
-               if (rw == WRITE)
-                       bi->bi_end_io = raid5_end_write_request;
-               else
-                       bi->bi_end_io = raid5_end_read_request;
-
-               rcu_read_lock();
-               rdev = rcu_dereference(conf->disks[i].rdev);
-               if (rdev && test_bit(Faulty, &rdev->flags))
-                       rdev = NULL;
-               if (rdev)
-                       atomic_inc(&rdev->nr_pending);
-               rcu_read_unlock();
-
-               if (rdev) {
-                       if (s.syncing || s.expanding || s.expanded)
-                               md_sync_acct(rdev->bdev, STRIPE_SECTORS);
+       return_io(return_bi);
 
-                       bi->bi_bdev = rdev->bdev;
-                       pr_debug("for %llu schedule op %ld on disc %d\n",
-                               (unsigned long long)sh->sector, bi->bi_rw, i);
-                       atomic_inc(&sh->count);
-                       bi->bi_sector = sh->sector + rdev->data_offset;
-                       bi->bi_flags = 1 << BIO_UPTODATE;
-                       bi->bi_vcnt = 1;
-                       bi->bi_max_vecs = 1;
-                       bi->bi_idx = 0;
-                       bi->bi_io_vec = &sh->dev[i].vec;
-                       bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
-                       bi->bi_io_vec[0].bv_offset = 0;
-                       bi->bi_size = STRIPE_SIZE;
-                       bi->bi_next = NULL;
-                       if (rw == WRITE &&
-                           test_bit(R5_ReWrite, &sh->dev[i].flags))
-                               atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
-                       generic_make_request(bi);
-               } else {
-                       if (rw == WRITE)
-                               set_bit(STRIPE_DEGRADED, &sh->state);
-                       pr_debug("skip op %ld on disc %d for sector %llu\n",
-                               bi->bi_rw, i, (unsigned long long)sh->sector);
-                       clear_bit(R5_LOCKED, &sh->dev[i].flags);
-                       set_bit(STRIPE_HANDLE, &sh->state);
-               }
-       }
+       return blocked_rdev == NULL;
 }
 
-static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
+/* returns true if the stripe was handled */
+static bool handle_stripe(struct stripe_head *sh, struct page *tmp_page)
 {
        if (sh->raid_conf->level == 6)
-               handle_stripe6(sh, tmp_page);
+               return handle_stripe6(sh, tmp_page);
        else
-               handle_stripe5(sh);
+               return handle_stripe5(sh);
 }
 
 
@@ -3060,9 +3227,10 @@ static void raid5_activate_delayed(raid5_conf_t *conf)
                        clear_bit(STRIPE_DELAYED, &sh->state);
                        if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
                                atomic_inc(&conf->preread_active_stripes);
-                       list_add_tail(&sh->lru, &conf->handle_list);
+                       list_add_tail(&sh->lru, &conf->hold_list);
                }
-       }
+       } else
+               blk_plug_device(conf->mddev->queue);
 }
 
 static void activate_bit_delay(raid5_conf_t *conf)
@@ -3088,13 +3256,12 @@ static void unplug_slaves(mddev_t *mddev)
        for (i=0; i<mddev->raid_disks; i++) {
                mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
                if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
-                       request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
+                       struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
 
                        atomic_inc(&rdev->nr_pending);
                        rcu_read_unlock();
 
-                       if (r_queue->unplug_fn)
-                               r_queue->unplug_fn(r_queue);
+                       blk_unplug(r_queue);
 
                        rdev_dec_pending(rdev, mddev);
                        rcu_read_lock();
@@ -3103,7 +3270,7 @@ static void unplug_slaves(mddev_t *mddev)
        rcu_read_unlock();
 }
 
-static void raid5_unplug_device(request_queue_t *q)
+static void raid5_unplug_device(struct request_queue *q)
 {
        mddev_t *mddev = q->queuedata;
        raid5_conf_t *conf = mddev_to_conf(mddev);
@@ -3122,36 +3289,6 @@ static void raid5_unplug_device(request_queue_t *q)
        unplug_slaves(mddev);
 }
 
-static int raid5_issue_flush(request_queue_t *q, struct gendisk *disk,
-                            sector_t *error_sector)
-{
-       mddev_t *mddev = q->queuedata;
-       raid5_conf_t *conf = mddev_to_conf(mddev);
-       int i, ret = 0;
-
-       rcu_read_lock();
-       for (i=0; i<mddev->raid_disks && ret == 0; i++) {
-               mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
-               if (rdev && !test_bit(Faulty, &rdev->flags)) {
-                       struct block_device *bdev = rdev->bdev;
-                       request_queue_t *r_queue = bdev_get_queue(bdev);
-
-                       if (!r_queue->issue_flush_fn)
-                               ret = -EOPNOTSUPP;
-                       else {
-                               atomic_inc(&rdev->nr_pending);
-                               rcu_read_unlock();
-                               ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
-                                                             error_sector);
-                               rdev_dec_pending(rdev, mddev);
-                               rcu_read_lock();
-                       }
-               }
-       }
-       rcu_read_unlock();
-       return ret;
-}
-
 static int raid5_congested(void *data, int bits)
 {
        mddev_t *mddev = data;
@@ -3173,15 +3310,17 @@ static int raid5_congested(void *data, int bits)
 /* We want read requests to align with chunks where possible,
  * but write requests don't need to.
  */
-static int raid5_mergeable_bvec(request_queue_t *q, struct bio *bio, struct bio_vec *biovec)
+static int raid5_mergeable_bvec(struct request_queue *q,
+                               struct bvec_merge_data *bvm,
+                               struct bio_vec *biovec)
 {
        mddev_t *mddev = q->queuedata;
-       sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
+       sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
        int max;
        unsigned int chunk_sectors = mddev->chunk_size >> 9;
-       unsigned int bio_sectors = bio->bi_size >> 9;
+       unsigned int bio_sectors = bvm->bi_size >> 9;
 
-       if (bio_data_dir(bio) == WRITE)
+       if ((bvm->bi_rw & 1) == WRITE)
                return biovec->bv_len; /* always allow writes to be mergeable */
 
        max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
@@ -3234,8 +3373,11 @@ static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
        if(bi) {
                conf->retry_read_aligned_list = bi->bi_next;
                bi->bi_next = NULL;
+               /*
+                * this sets the active strip count to 1 and the processed
+                * strip count to zero (upper 8 bits)
+                */
                bi->bi_phys_segments = 1; /* biased count of active stripes */
-               bi->bi_hw_segments = 0; /* count of processed stripes */
        }
 
        return bi;
@@ -3248,7 +3390,7 @@ static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
  *  first).
  *  If the read failed..
  */
-static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error)
+static void raid5_align_endio(struct bio *bi, int error)
 {
        struct bio* raid_bi  = bi->bi_private;
        mddev_t *mddev;
@@ -3256,8 +3398,6 @@ static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error)
        int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
        mdk_rdev_t *rdev;
 
-       if (bi->bi_size)
-               return 1;
        bio_put(bi);
 
        mddev = raid_bi->bi_bdev->bd_disk->queue->queuedata;
@@ -3268,28 +3408,26 @@ static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error)
        rdev_dec_pending(rdev, conf->mddev);
 
        if (!error && uptodate) {
-               bio_endio(raid_bi, bytes, 0);
+               bio_endio(raid_bi, 0);
                if (atomic_dec_and_test(&conf->active_aligned_reads))
                        wake_up(&conf->wait_for_stripe);
-               return 0;
+               return;
        }
 
 
        pr_debug("raid5_align_endio : io error...handing IO for a retry\n");
 
        add_bio_to_retry(raid_bi, conf);
-       return 0;
 }
 
 static int bio_fits_rdev(struct bio *bi)
 {
-       request_queue_t *q = bdev_get_queue(bi->bi_bdev);
+       struct request_queue *q = bdev_get_queue(bi->bi_bdev);
 
        if ((bi->bi_size>>9) > q->max_sectors)
                return 0;
        blk_recount_segments(q, bi);
-       if (bi->bi_phys_segments > q->max_phys_segments ||
-           bi->bi_hw_segments > q->max_hw_segments)
+       if (bi->bi_phys_segments > q->max_phys_segments)
                return 0;
 
        if (q->merge_bvec_fn)
@@ -3302,13 +3440,11 @@ static int bio_fits_rdev(struct bio *bi)
 }
 
 
-static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
+static int chunk_aligned_read(struct request_queue *q, struct bio * raid_bio)
 {
        mddev_t *mddev = q->queuedata;
        raid5_conf_t *conf = mddev_to_conf(mddev);
-       const unsigned int raid_disks = conf->raid_disks;
-       const unsigned int data_disks = raid_disks - conf->max_degraded;
-       unsigned int dd_idx, pd_idx;
+       unsigned int dd_idx;
        struct bio* align_bi;
        mdk_rdev_t *rdev;
 
@@ -3317,7 +3453,7 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
                return 0;
        }
        /*
-        * use bio_clone to make a copy of the bio
+        * use bio_clone to make a copy of the bio
         */
        align_bi = bio_clone(raid_bio, GFP_NOIO);
        if (!align_bi)
@@ -3331,12 +3467,9 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
        /*
         *      compute position
         */
-       align_bi->bi_sector =  raid5_compute_sector(raid_bio->bi_sector,
-                                       raid_disks,
-                                       data_disks,
-                                       &dd_idx,
-                                       &pd_idx,
-                                       conf);
+       align_bi->bi_sector =  raid5_compute_sector(conf, raid_bio->bi_sector,
+                                                   0,
+                                                   &dd_idx, NULL);
 
        rcu_read_lock();
        rdev = rcu_dereference(conf->disks[dd_idx].rdev);
@@ -3371,32 +3504,87 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
        }
 }
 
+/* __get_priority_stripe - get the next stripe to process
+ *
+ * Full stripe writes are allowed to pass preread active stripes up until
+ * the bypass_threshold is exceeded.  In general the bypass_count
+ * increments when the handle_list is handled before the hold_list; however, it
+ * will not be incremented when STRIPE_IO_STARTED is sampled set signifying a
+ * stripe with in flight i/o.  The bypass_count will be reset when the
+ * head of the hold_list has changed, i.e. the head was promoted to the
+ * handle_list.
+ */
+static struct stripe_head *__get_priority_stripe(raid5_conf_t *conf)
+{
+       struct stripe_head *sh;
+
+       pr_debug("%s: handle: %s hold: %s full_writes: %d bypass_count: %d\n",
+                 __func__,
+                 list_empty(&conf->handle_list) ? "empty" : "busy",
+                 list_empty(&conf->hold_list) ? "empty" : "busy",
+                 atomic_read(&conf->pending_full_writes), conf->bypass_count);
+
+       if (!list_empty(&conf->handle_list)) {
+               sh = list_entry(conf->handle_list.next, typeof(*sh), lru);
 
-static int make_request(request_queue_t *q, struct bio * bi)
+               if (list_empty(&conf->hold_list))
+                       conf->bypass_count = 0;
+               else if (!test_bit(STRIPE_IO_STARTED, &sh->state)) {
+                       if (conf->hold_list.next == conf->last_hold)
+                               conf->bypass_count++;
+                       else {
+                               conf->last_hold = conf->hold_list.next;
+                               conf->bypass_count -= conf->bypass_threshold;
+                               if (conf->bypass_count < 0)
+                                       conf->bypass_count = 0;
+                       }
+               }
+       } else if (!list_empty(&conf->hold_list) &&
+                  ((conf->bypass_threshold &&
+                    conf->bypass_count > conf->bypass_threshold) ||
+                   atomic_read(&conf->pending_full_writes) == 0)) {
+               sh = list_entry(conf->hold_list.next,
+                               typeof(*sh), lru);
+               conf->bypass_count -= conf->bypass_threshold;
+               if (conf->bypass_count < 0)
+                       conf->bypass_count = 0;
+       } else
+               return NULL;
+
+       list_del_init(&sh->lru);
+       atomic_inc(&sh->count);
+       BUG_ON(atomic_read(&sh->count) != 1);
+       return sh;
+}
+
+static int make_request(struct request_queue *q, struct bio * bi)
 {
        mddev_t *mddev = q->queuedata;
        raid5_conf_t *conf = mddev_to_conf(mddev);
-       unsigned int dd_idx, pd_idx;
+       int dd_idx;
        sector_t new_sector;
        sector_t logical_sector, last_sector;
        struct stripe_head *sh;
        const int rw = bio_data_dir(bi);
-       int remaining;
+       int cpu, remaining;
 
        if (unlikely(bio_barrier(bi))) {
-               bio_endio(bi, bi->bi_size, -EOPNOTSUPP);
+               bio_endio(bi, -EOPNOTSUPP);
                return 0;
        }
 
        md_write_start(mddev, bi);
 
-       disk_stat_inc(mddev->gendisk, ios[rw]);
-       disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bi));
+       cpu = part_stat_lock();
+       part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
+       part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
+                     bio_sectors(bi));
+       part_stat_unlock();
 
        if (rw == READ &&
             mddev->reshape_position == MaxSector &&
             chunk_aligned_read(q,bi))
-               return 0;
+               return 0;
 
        logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
        last_sector = bi->bi_sector + (bi->bi_size>>9);
@@ -3406,8 +3594,10 @@ static int make_request(request_queue_t *q, struct bio * bi)
        for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
                DEFINE_WAIT(w);
                int disks, data_disks;
+               int previous;
 
        retry:
+               previous = 0;
                prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
                if (likely(conf->expand_progress == MaxSector))
                        disks = conf->raid_disks;
@@ -3422,9 +3612,10 @@ static int make_request(request_queue_t *q, struct bio * bi)
                         */
                        spin_lock_irq(&conf->device_lock);
                        disks = conf->raid_disks;
-                       if (logical_sector >= conf->expand_progress)
+                       if (logical_sector >= conf->expand_progress) {
                                disks = conf->previous_raid_disks;
-                       else {
+                               previous = 1;
+                       } else {
                                if (logical_sector >= conf->expand_lo) {
                                        spin_unlock_irq(&conf->device_lock);
                                        schedule();
@@ -3435,13 +3626,15 @@ static int make_request(request_queue_t *q, struct bio * bi)
                }
                data_disks = disks - conf->max_degraded;
 
-               new_sector = raid5_compute_sector(logical_sector, disks, data_disks,
-                                                 &dd_idx, &pd_idx, conf);
+               new_sector = raid5_compute_sector(conf, logical_sector,
+                                                 previous,
+                                                 &dd_idx, NULL);
                pr_debug("raid5: make_request, sector %llu logical %llu\n",
                        (unsigned long long)new_sector, 
                        (unsigned long long)logical_sector);
 
-               sh = get_active_stripe(conf, new_sector, disks, pd_idx, (bi->bi_rw&RWA_MASK));
+               sh = get_active_stripe(conf, new_sector, previous,
+                                      (bi->bi_rw&RWA_MASK));
                if (sh) {
                        if (unlikely(conf->expand_progress != MaxSector)) {
                                /* expansion might have moved on while waiting for a
@@ -3486,7 +3679,8 @@ static int make_request(request_queue_t *q, struct bio * bi)
                                goto retry;
                        }
                        finish_wait(&conf->wait_for_overlap, &w);
-                       handle_stripe(sh, NULL);
+                       set_bit(STRIPE_HANDLE, &sh->state);
+                       clear_bit(STRIPE_DELAYED, &sh->state);
                        release_stripe(sh);
                } else {
                        /* cannot get stripe for read-ahead, just give-up */
@@ -3497,17 +3691,14 @@ static int make_request(request_queue_t *q, struct bio * bi)
                        
        }
        spin_lock_irq(&conf->device_lock);
-       remaining = --bi->bi_phys_segments;
+       remaining = raid5_dec_bi_phys_segments(bi);
        spin_unlock_irq(&conf->device_lock);
        if (remaining == 0) {
-               int bytes = bi->bi_size;
 
                if ( rw == WRITE )
                        md_write_end(mddev);
-               bi->bi_size = 0;
-               bi->bi_end_io(bi, bytes,
-                             test_bit(BIO_UPTODATE, &bi->bi_flags)
-                               ? 0 : -EIO);
+
+               bio_endio(bi, 0);
        }
        return 0;
 }
@@ -3525,7 +3716,6 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
         */
        raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
        struct stripe_head *sh;
-       int pd_idx;
        sector_t first_sector, last_sector;
        int raid_disks = conf->previous_raid_disks;
        int data_disks = raid_disks - conf->max_degraded;
@@ -3577,9 +3767,7 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
        for (i=0; i < conf->chunk_size/512; i+= STRIPE_SECTORS) {
                int j;
                int skipped = 0;
-               pd_idx = stripe_to_pdidx(sector_nr+i, conf, conf->raid_disks);
-               sh = get_active_stripe(conf, sector_nr+i,
-                                      conf->raid_disks, pd_idx, 0);
+               sh = get_active_stripe(conf, sector_nr+i, 0, 0);
                set_bit(STRIPE_EXPANDING, &sh->state);
                atomic_inc(&conf->reshape_stripes);
                /* If any of this stripe is beyond the end of the old
@@ -3590,10 +3778,10 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
                        if (j == sh->pd_idx)
                                continue;
                        if (conf->level == 6 &&
-                           j == raid6_next_disk(sh->pd_idx, sh->disks))
+                           j == sh->qd_idx)
                                continue;
                        s = compute_blocknr(sh, j);
-                       if (s < (mddev->array_size<<1)) {
+                       if (s < mddev->array_sectors) {
                                skipped = 1;
                                continue;
                        }
@@ -3616,26 +3804,40 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
         * block on the destination stripes.
         */
        first_sector =
-               raid5_compute_sector(sector_nr*(new_data_disks),
-                                    raid_disks, data_disks,
-                                    &dd_idx, &pd_idx, conf);
+               raid5_compute_sector(conf, sector_nr*(new_data_disks),
+                                    1, &dd_idx, NULL);
        last_sector =
-               raid5_compute_sector((sector_nr+conf->chunk_size/512)
-                                    *(new_data_disks) -1,
-                                    raid_disks, data_disks,
-                                    &dd_idx, &pd_idx, conf);
-       if (last_sector >= (mddev->size<<1))
-               last_sector = (mddev->size<<1)-1;
+               raid5_compute_sector(conf, ((sector_nr+conf->chunk_size/512)
+                                           *(new_data_disks) - 1),
+                                    1, &dd_idx, NULL);
+       if (last_sector >= mddev->dev_sectors)
+               last_sector = mddev->dev_sectors - 1;
        while (first_sector <= last_sector) {
-               pd_idx = stripe_to_pdidx(first_sector, conf,
-                                        conf->previous_raid_disks);
-               sh = get_active_stripe(conf, first_sector,
-                                      conf->previous_raid_disks, pd_idx, 0);
+               sh = get_active_stripe(conf, first_sector, 1, 0);
                set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
                set_bit(STRIPE_HANDLE, &sh->state);
                release_stripe(sh);
                first_sector += STRIPE_SECTORS;
        }
+       /* If this takes us to the resync_max point where we have to pause,
+        * then we need to write out the superblock.
+        */
+       sector_nr += conf->chunk_size>>9;
+       if (sector_nr >= mddev->resync_max) {
+               /* Cannot proceed until we've updated the superblock... */
+               wait_event(conf->wait_for_overlap,
+                          atomic_read(&conf->reshape_stripes) == 0);
+               mddev->reshape_position = conf->expand_progress;
+               set_bit(MD_CHANGE_DEVS, &mddev->flags);
+               md_wakeup_thread(mddev->thread);
+               wait_event(mddev->sb_wait,
+                          !test_bit(MD_CHANGE_DEVS, &mddev->flags)
+                          || kthread_should_stop());
+               spin_lock_irq(&conf->device_lock);
+               conf->expand_lo = mddev->reshape_position;
+               spin_unlock_irq(&conf->device_lock);
+               wake_up(&conf->wait_for_overlap);
+       }
        return conf->chunk_size>>9;
 }
 
@@ -3644,9 +3846,7 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
 {
        raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
        struct stripe_head *sh;
-       int pd_idx;
-       int raid_disks = conf->raid_disks;
-       sector_t max_sector = mddev->size << 1;
+       sector_t max_sector = mddev->dev_sectors;
        int sync_blocks;
        int still_degraded = 0;
        int i;
@@ -3672,13 +3872,19 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
        if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
                return reshape_request(mddev, sector_nr, skipped);
 
+       /* No need to check resync_max as we never do more than one
+        * stripe, and as resync_max will always be on a chunk boundary,
+        * if the check in md_do_sync didn't fire, there is no chance
+        * of overstepping resync_max here
+        */
+
        /* if there is too many failed drives and we are trying
         * to resync, then assert that we are finished, because there is
         * nothing we can do.
         */
        if (mddev->degraded >= conf->max_degraded &&
            test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
-               sector_t rv = (mddev->size << 1) - sector_nr;
+               sector_t rv = mddev->dev_sectors - sector_nr;
                *skipped = 1;
                return rv;
        }
@@ -3691,10 +3897,12 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
                return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
        }
 
-       pd_idx = stripe_to_pdidx(sector_nr, conf, raid_disks);
-       sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 1);
+
+       bitmap_cond_end_sync(mddev->bitmap, sector_nr);
+
+       sh = get_active_stripe(conf, sector_nr, 0, 1);
        if (sh == NULL) {
-               sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 0);
+               sh = get_active_stripe(conf, sector_nr, 0, 0);
                /* make sure we don't swamp the stripe cache if someone else
                 * is trying to get access
                 */
@@ -3715,7 +3923,9 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
        clear_bit(STRIPE_INSYNC, &sh->state);
        spin_unlock(&sh->lock);
 
-       handle_stripe(sh, NULL);
+       /* wait for any blocked device to be handled */
+       while(unlikely(!handle_stripe(sh, NULL)))
+               ;
        release_stripe(sh);
 
        return STRIPE_SECTORS;
@@ -3734,19 +3944,15 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
         * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
         */
        struct stripe_head *sh;
-       int dd_idx, pd_idx;
+       int dd_idx;
        sector_t sector, logical_sector, last_sector;
        int scnt = 0;
        int remaining;
        int handled = 0;
 
        logical_sector = raid_bio->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
-       sector = raid5_compute_sector(  logical_sector,
-                                       conf->raid_disks,
-                                       conf->raid_disks - conf->max_degraded,
-                                       &dd_idx,
-                                       &pd_idx,
-                                       conf);
+       sector = raid5_compute_sector(conf, logical_sector,
+                                     0, &dd_idx, NULL);
        last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);
 
        for (; logical_sector < last_sector;
@@ -3754,15 +3960,15 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                     sector += STRIPE_SECTORS,
                     scnt++) {
 
-               if (scnt < raid_bio->bi_hw_segments)
+               if (scnt < raid5_bi_hw_segments(raid_bio))
                        /* already done this stripe */
                        continue;
 
-               sh = get_active_stripe(conf, sector, conf->raid_disks, pd_idx, 1);
+               sh = get_active_stripe(conf, sector, 0, 1);
 
                if (!sh) {
                        /* failed to get a stripe - must wait */
-                       raid_bio->bi_hw_segments = scnt;
+                       raid5_set_bi_hw_segments(raid_bio, scnt);
                        conf->retry_read_aligned = raid_bio;
                        return handled;
                }
@@ -3770,7 +3976,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
                if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
                        release_stripe(sh);
-                       raid_bio->bi_hw_segments = scnt;
+                       raid5_set_bi_hw_segments(raid_bio, scnt);
                        conf->retry_read_aligned = raid_bio;
                        return handled;
                }
@@ -3780,16 +3986,10 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                handled++;
        }
        spin_lock_irq(&conf->device_lock);
-       remaining = --raid_bio->bi_phys_segments;
+       remaining = raid5_dec_bi_phys_segments(raid_bio);
        spin_unlock_irq(&conf->device_lock);
-       if (remaining == 0) {
-               int bytes = raid_bio->bi_size;
-
-               raid_bio->bi_size = 0;
-               raid_bio->bi_end_io(raid_bio, bytes,
-                             test_bit(BIO_UPTODATE, &raid_bio->bi_flags)
-                               ? 0 : -EIO);
-       }
+       if (remaining == 0)
+               bio_endio(raid_bio, 0);
        if (atomic_dec_and_test(&conf->active_aligned_reads))
                wake_up(&conf->wait_for_stripe);
        return handled;
@@ -3804,7 +4004,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
  * During the scan, completed stripes are saved for us by the interrupt
  * handler, so that they will not have to wait for our next wakeup.
  */
-static void raid5d (mddev_t *mddev)
+static void raid5d(mddev_t *mddev)
 {
        struct stripe_head *sh;
        raid5_conf_t *conf = mddev_to_conf(mddev);
@@ -3817,7 +4017,6 @@ static void raid5d (mddev_t *mddev)
        handled = 0;
        spin_lock_irq(&conf->device_lock);
        while (1) {
-               struct list_head *first;
                struct bio *bio;
 
                if (conf->seq_flush != conf->seq_write) {
@@ -3829,12 +4028,6 @@ static void raid5d (mddev_t *mddev)
                        activate_bit_delay(conf);
                }
 
-               if (list_empty(&conf->handle_list) &&
-                   atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD &&
-                   !blk_queue_plugged(mddev->queue) &&
-                   !list_empty(&conf->delayed_list))
-                       raid5_activate_delayed(conf);
-
                while ((bio = remove_bio_from_retry(conf))) {
                        int ok;
                        spin_unlock_irq(&conf->device_lock);
@@ -3845,17 +4038,10 @@ static void raid5d (mddev_t *mddev)
                        handled++;
                }
 
-               if (list_empty(&conf->handle_list)) {
-                       async_tx_issue_pending_all();
-                       break;
-               }
-
-               first = conf->handle_list.next;
-               sh = list_entry(first, struct stripe_head, lru);
+               sh = __get_priority_stripe(conf);
 
-               list_del_init(first);
-               atomic_inc(&sh->count);
-               BUG_ON(atomic_read(&sh->count)!= 1);
+               if (!sh)
+                       break;
                spin_unlock_irq(&conf->device_lock);
                
                handled++;
@@ -3868,6 +4054,7 @@ static void raid5d (mddev_t *mddev)
 
        spin_unlock_irq(&conf->device_lock);
 
+       async_tx_issue_pending_all();
        unplug_slaves(mddev);
 
        pr_debug("--- raid5d inactive\n");
@@ -3887,15 +4074,15 @@ static ssize_t
 raid5_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
 {
        raid5_conf_t *conf = mddev_to_conf(mddev);
-       char *end;
-       int new;
+       unsigned long new;
+       int err;
+
        if (len >= PAGE_SIZE)
                return -EINVAL;
        if (!conf)
                return -ENODEV;
 
-       new = simple_strtoul(page, &end, 10);
-       if (!*page || (*end && *end != '\n') )
+       if (strict_strtoul(page, 10, &new))
                return -EINVAL;
        if (new <= 16 || new > 32768)
                return -EINVAL;
@@ -3905,7 +4092,9 @@ raid5_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
                else
                        break;
        }
-       md_allow_write(mddev);
+       err = md_allow_write(mddev);
+       if (err)
+               return err;
        while (new > conf->max_nr_stripes) {
                if (grow_one_stripe(conf))
                        conf->max_nr_stripes++;
@@ -3920,6 +4109,40 @@ raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
                                raid5_store_stripe_cache_size);
 
 static ssize_t
+raid5_show_preread_threshold(mddev_t *mddev, char *page)
+{
+       raid5_conf_t *conf = mddev_to_conf(mddev);
+       if (conf)
+               return sprintf(page, "%d\n", conf->bypass_threshold);
+       else
+               return 0;
+}
+
+static ssize_t
+raid5_store_preread_threshold(mddev_t *mddev, const char *page, size_t len)
+{
+       raid5_conf_t *conf = mddev_to_conf(mddev);
+       unsigned long new;
+       if (len >= PAGE_SIZE)
+               return -EINVAL;
+       if (!conf)
+               return -ENODEV;
+
+       if (strict_strtoul(page, 10, &new))
+               return -EINVAL;
+       if (new > conf->max_nr_stripes)
+               return -EINVAL;
+       conf->bypass_threshold = new;
+       return len;
+}
+
+static struct md_sysfs_entry
+raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold,
+                                       S_IRUGO | S_IWUSR,
+                                       raid5_show_preread_threshold,
+                                       raid5_store_preread_threshold);
+
+static ssize_t
 stripe_cache_active_show(mddev_t *mddev, char *page)
 {
        raid5_conf_t *conf = mddev_to_conf(mddev);
@@ -3935,6 +4158,7 @@ raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
 static struct attribute *raid5_attrs[] =  {
        &raid5_stripecache_size.attr,
        &raid5_stripecache_active.attr,
+       &raid5_preread_bypass_threshold.attr,
        NULL,
 };
 static struct attribute_group raid5_attrs_group = {
@@ -3942,21 +4166,147 @@ static struct attribute_group raid5_attrs_group = {
        .attrs = raid5_attrs,
 };
 
-static int run(mddev_t *mddev)
+static raid5_conf_t *setup_conf(mddev_t *mddev)
 {
        raid5_conf_t *conf;
        int raid_disk, memory;
        mdk_rdev_t *rdev;
        struct disk_info *disk;
-       struct list_head *tmp;
-       int working_disks = 0;
 
-       if (mddev->level != 5 && mddev->level != 4 && mddev->level != 6) {
+       if (mddev->new_level != 5
+           && mddev->new_level != 4
+           && mddev->new_level != 6) {
                printk(KERN_ERR "raid5: %s: raid level not set to 4/5/6 (%d)\n",
-                      mdname(mddev), mddev->level);
-               return -EIO;
+                      mdname(mddev), mddev->new_level);
+               return ERR_PTR(-EIO);
+       }
+       if ((mddev->new_level == 5
+            && !algorithm_valid_raid5(mddev->new_layout)) ||
+           (mddev->new_level == 6
+            && !algorithm_valid_raid6(mddev->new_layout))) {
+               printk(KERN_ERR "raid5: %s: layout %d not supported\n",
+                      mdname(mddev), mddev->new_layout);
+               return ERR_PTR(-EIO);
+       }
+       if (mddev->new_level == 6 && mddev->raid_disks < 4) {
+               printk(KERN_ERR "raid6: not enough configured devices for %s (%d, minimum 4)\n",
+                      mdname(mddev), mddev->raid_disks);
+               return ERR_PTR(-EINVAL);
+       }
+
+       if (!mddev->new_chunk || mddev->new_chunk % PAGE_SIZE) {
+               printk(KERN_ERR "raid5: invalid chunk size %d for %s\n",
+                       mddev->new_chunk, mdname(mddev));
+               return ERR_PTR(-EINVAL);
        }
 
+       conf = kzalloc(sizeof(raid5_conf_t), GFP_KERNEL);
+       if (conf == NULL)
+               goto abort;
+
+       conf->raid_disks = mddev->raid_disks;
+       if (mddev->reshape_position == MaxSector)
+               conf->previous_raid_disks = mddev->raid_disks;
+       else
+               conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
+
+       conf->disks = kzalloc(conf->raid_disks * sizeof(struct disk_info),
+                             GFP_KERNEL);
+       if (!conf->disks)
+               goto abort;
+
+       conf->mddev = mddev;
+
+       if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
+               goto abort;
+
+       if (mddev->new_level == 6) {
+               conf->spare_page = alloc_page(GFP_KERNEL);
+               if (!conf->spare_page)
+                       goto abort;
+       }
+       spin_lock_init(&conf->device_lock);
+       init_waitqueue_head(&conf->wait_for_stripe);
+       init_waitqueue_head(&conf->wait_for_overlap);
+       INIT_LIST_HEAD(&conf->handle_list);
+       INIT_LIST_HEAD(&conf->hold_list);
+       INIT_LIST_HEAD(&conf->delayed_list);
+       INIT_LIST_HEAD(&conf->bitmap_list);
+       INIT_LIST_HEAD(&conf->inactive_list);
+       atomic_set(&conf->active_stripes, 0);
+       atomic_set(&conf->preread_active_stripes, 0);
+       atomic_set(&conf->active_aligned_reads, 0);
+       conf->bypass_threshold = BYPASS_THRESHOLD;
+
+       pr_debug("raid5: run(%s) called.\n", mdname(mddev));
+
+       list_for_each_entry(rdev, &mddev->disks, same_set) {
+               raid_disk = rdev->raid_disk;
+               if (raid_disk >= conf->raid_disks
+                   || raid_disk < 0)
+                       continue;
+               disk = conf->disks + raid_disk;
+
+               disk->rdev = rdev;
+
+               if (test_bit(In_sync, &rdev->flags)) {
+                       char b[BDEVNAME_SIZE];
+                       printk(KERN_INFO "raid5: device %s operational as raid"
+                               " disk %d\n", bdevname(rdev->bdev,b),
+                               raid_disk);
+               } else
+                       /* Cannot rely on bitmap to complete recovery */
+                       conf->fullsync = 1;
+       }
+
+       conf->chunk_size = mddev->new_chunk;
+       conf->level = mddev->new_level;
+       if (conf->level == 6)
+               conf->max_degraded = 2;
+       else
+               conf->max_degraded = 1;
+       conf->algorithm = mddev->new_layout;
+       conf->max_nr_stripes = NR_STRIPES;
+       conf->expand_progress = mddev->reshape_position;
+
+       memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
+                conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
+       if (grow_stripes(conf, conf->max_nr_stripes)) {
+               printk(KERN_ERR
+                       "raid5: couldn't allocate %dkB for buffers\n", memory);
+               goto abort;
+       } else
+               printk(KERN_INFO "raid5: allocated %dkB for %s\n",
+                       memory, mdname(mddev));
+
+       conf->thread = md_register_thread(raid5d, mddev, "%s_raid5");
+       if (!conf->thread) {
+               printk(KERN_ERR
+                      "raid5: couldn't allocate thread for %s\n",
+                      mdname(mddev));
+               goto abort;
+       }
+
+       return conf;
+
+ abort:
+       if (conf) {
+               shrink_stripes(conf);
+               safe_put_page(conf->spare_page);
+               kfree(conf->disks);
+               kfree(conf->stripe_hashtbl);
+               kfree(conf);
+               return ERR_PTR(-EIO);
+       } else
+               return ERR_PTR(-ENOMEM);
+}
+
+static int run(mddev_t *mddev)
+{
+       raid5_conf_t *conf;
+       int working_disks = 0;
+       mdk_rdev_t *rdev;
+
        if (mddev->reshape_position != MaxSector) {
                /* Check that we can continue the reshape.
                 * Currently only disks can change, it must
@@ -4007,100 +4357,35 @@ static int run(mddev_t *mddev)
                }
                printk(KERN_INFO "raid5: reshape will continue\n");
                /* OK, we should be able to continue; */
-       }
-
-
-       mddev->private = kzalloc(sizeof (raid5_conf_t), GFP_KERNEL);
-       if ((conf = mddev->private) == NULL)
-               goto abort;
-       if (mddev->reshape_position == MaxSector) {
-               conf->previous_raid_disks = conf->raid_disks = mddev->raid_disks;
        } else {
-               conf->raid_disks = mddev->raid_disks;
-               conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
-       }
-
-       conf->disks = kzalloc(conf->raid_disks * sizeof(struct disk_info),
-                             GFP_KERNEL);
-       if (!conf->disks)
-               goto abort;
-
-       conf->mddev = mddev;
-
-       if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
-               goto abort;
-
-       if (mddev->level == 6) {
-               conf->spare_page = alloc_page(GFP_KERNEL);
-               if (!conf->spare_page)
-                       goto abort;
+               BUG_ON(mddev->level != mddev->new_level);
+               BUG_ON(mddev->layout != mddev->new_layout);
+               BUG_ON(mddev->chunk_size != mddev->new_chunk);
+               BUG_ON(mddev->delta_disks != 0);
        }
-       spin_lock_init(&conf->device_lock);
-       init_waitqueue_head(&conf->wait_for_stripe);
-       init_waitqueue_head(&conf->wait_for_overlap);
-       INIT_LIST_HEAD(&conf->handle_list);
-       INIT_LIST_HEAD(&conf->delayed_list);
-       INIT_LIST_HEAD(&conf->bitmap_list);
-       INIT_LIST_HEAD(&conf->inactive_list);
-       atomic_set(&conf->active_stripes, 0);
-       atomic_set(&conf->preread_active_stripes, 0);
-       atomic_set(&conf->active_aligned_reads, 0);
-
-       pr_debug("raid5: run(%s) called.\n", mdname(mddev));
 
-       ITERATE_RDEV(mddev,rdev,tmp) {
-               raid_disk = rdev->raid_disk;
-               if (raid_disk >= conf->raid_disks
-                   || raid_disk < 0)
-                       continue;
-               disk = conf->disks + raid_disk;
+       if (mddev->private == NULL)
+               conf = setup_conf(mddev);
+       else
+               conf = mddev->private;
 
-               disk->rdev = rdev;
+       if (IS_ERR(conf))
+               return PTR_ERR(conf);
 
-               if (test_bit(In_sync, &rdev->flags)) {
-                       char b[BDEVNAME_SIZE];
-                       printk(KERN_INFO "raid5: device %s operational as raid"
-                               " disk %d\n", bdevname(rdev->bdev,b),
-                               raid_disk);
-                       working_disks++;
-               }
-       }
+       mddev->thread = conf->thread;
+       conf->thread = NULL;
+       mddev->private = conf;
 
        /*
         * 0 for a fully functional array, 1 or 2 for a degraded array.
         */
-       mddev->degraded = conf->raid_disks - working_disks;
-       conf->mddev = mddev;
-       conf->chunk_size = mddev->chunk_size;
-       conf->level = mddev->level;
-       if (conf->level == 6)
-               conf->max_degraded = 2;
-       else
-               conf->max_degraded = 1;
-       conf->algorithm = mddev->layout;
-       conf->max_nr_stripes = NR_STRIPES;
-       conf->expand_progress = mddev->reshape_position;
+       list_for_each_entry(rdev, &mddev->disks, same_set)
+               if (rdev->raid_disk >= 0 &&
+                   test_bit(In_sync, &rdev->flags))
+                       working_disks++;
 
-       /* device size must be a multiple of chunk size */
-       mddev->size &= ~(mddev->chunk_size/1024 -1);
-       mddev->resync_max_sectors = mddev->size << 1;
+       mddev->degraded = conf->raid_disks - working_disks;
 
-       if (conf->level == 6 && conf->raid_disks < 4) {
-               printk(KERN_ERR "raid6: not enough configured devices for %s (%d, minimum 4)\n",
-                      mdname(mddev), conf->raid_disks);
-               goto abort;
-       }
-       if (!conf->chunk_size || conf->chunk_size % 4) {
-               printk(KERN_ERR "raid5: invalid chunk size %d for %s\n",
-                       conf->chunk_size, mdname(mddev));
-               goto abort;
-       }
-       if (conf->algorithm > ALGORITHM_RIGHT_SYMMETRIC) {
-               printk(KERN_ERR 
-                       "raid5: unsupported parity algorithm %d for %s\n",
-                       conf->algorithm, mdname(mddev));
-               goto abort;
-       }
        if (mddev->degraded > conf->max_degraded) {
                printk(KERN_ERR "raid5: not enough operational devices for %s"
                        " (%d/%d failed)\n",
@@ -4108,6 +4393,10 @@ static int run(mddev_t *mddev)
                goto abort;
        }
 
+       /* device size must be a multiple of chunk size */
+       mddev->dev_sectors &= ~(mddev->chunk_size / 512 - 1);
+       mddev->resync_max_sectors = mddev->dev_sectors;
+
        if (mddev->degraded > 0 &&
            mddev->recovery_cp != MaxSector) {
                if (mddev->ok_start_degraded)
@@ -4123,27 +4412,6 @@ static int run(mddev_t *mddev)
                }
        }
 
-       {
-               mddev->thread = md_register_thread(raid5d, mddev, "%s_raid5");
-               if (!mddev->thread) {
-                       printk(KERN_ERR 
-                               "raid5: couldn't allocate thread for %s\n",
-                               mdname(mddev));
-                       goto abort;
-               }
-       }
-       memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
-                conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
-       if (grow_stripes(conf, conf->max_nr_stripes)) {
-               printk(KERN_ERR 
-                       "raid5: couldn't allocate %dkB for buffers\n", memory);
-               shrink_stripes(conf);
-               md_unregister_thread(mddev->thread);
-               goto abort;
-       } else
-               printk(KERN_INFO "raid5: allocated %dkB for %s\n",
-                       memory, mdname(mddev));
-
        if (mddev->degraded == 0)
                printk("raid5: raid level %d set %s active with %d out of %d"
                        " devices, algorithm %d\n", conf->level, mdname(mddev), 
@@ -4186,19 +4454,23 @@ static int run(mddev_t *mddev)
                       "raid5: failed to create sysfs attributes for %s\n",
                       mdname(mddev));
 
+       mddev->queue->queue_lock = &conf->device_lock;
+
        mddev->queue->unplug_fn = raid5_unplug_device;
-       mddev->queue->issue_flush_fn = raid5_issue_flush;
        mddev->queue->backing_dev_info.congested_data = mddev;
        mddev->queue->backing_dev_info.congested_fn = raid5_congested;
 
-       mddev->array_size =  mddev->size * (conf->previous_raid_disks -
-                                           conf->max_degraded);
+       mddev->array_sectors = mddev->dev_sectors *
+               (conf->previous_raid_disks - conf->max_degraded);
 
        blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
 
        return 0;
 abort:
+       md_unregister_thread(mddev->thread);
+       mddev->thread = NULL;
        if (conf) {
+               shrink_stripes(conf);
                print_raid5_conf(conf);
                safe_put_page(conf->spare_page);
                kfree(conf->disks);
@@ -4230,7 +4502,7 @@ static int stop(mddev_t *mddev)
 }
 
 #ifdef DEBUG
-static void print_sh (struct seq_file *seq, struct stripe_head *sh)
+static void print_sh(struct seq_file *seq, struct stripe_head *sh)
 {
        int i;
 
@@ -4246,7 +4518,7 @@ static void print_sh (struct seq_file *seq, struct stripe_head *sh)
        seq_printf(seq, "\n");
 }
 
-static void printall (struct seq_file *seq, raid5_conf_t *conf)
+static void printall(struct seq_file *seq, raid5_conf_t *conf)
 {
        struct stripe_head *sh;
        struct hlist_node *hn;
@@ -4264,7 +4536,7 @@ static void printall (struct seq_file *seq, raid5_conf_t *conf)
 }
 #endif
 
-static void status (struct seq_file *seq, mddev_t *mddev)
+static void status(struct seq_file *seq, mddev_t *mddev)
 {
        raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
        int i;
@@ -4341,6 +4613,14 @@ static int raid5_remove_disk(mddev_t *mddev, int number)
                        err = -EBUSY;
                        goto abort;
                }
+               /* Only remove non-faulty devices if recovery
+                * isn't possible.
+                */
+               if (!test_bit(Faulty, &rdev->flags) &&
+                   mddev->degraded <= conf->max_degraded) {
+                       err = -EBUSY;
+                       goto abort;
+               }
                p->rdev = NULL;
                synchronize_rcu();
                if (atomic_read(&rdev->nr_pending)) {
@@ -4358,35 +4638,41 @@ abort:
 static int raid5_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 {
        raid5_conf_t *conf = mddev->private;
-       int found = 0;
+       int err = -EEXIST;
        int disk;
        struct disk_info *p;
+       int first = 0;
+       int last = conf->raid_disks - 1;
 
        if (mddev->degraded > conf->max_degraded)
                /* no point adding a device */
-               return 0;
+               return -EINVAL;
+
+       if (rdev->raid_disk >= 0)
+               first = last = rdev->raid_disk;
 
        /*
         * find the disk ... but prefer rdev->saved_raid_disk
         * if possible.
         */
        if (rdev->saved_raid_disk >= 0 &&
+           rdev->saved_raid_disk >= first &&
            conf->disks[rdev->saved_raid_disk].rdev == NULL)
                disk = rdev->saved_raid_disk;
        else
-               disk = 0;
-       for ( ; disk < conf->raid_disks; disk++)
+               disk = first;
+       for ( ; disk <= last ; disk++)
                if ((p=conf->disks + disk)->rdev == NULL) {
                        clear_bit(In_sync, &rdev->flags);
                        rdev->raid_disk = disk;
-                       found = 1;
+                       err = 0;
                        if (rdev->saved_raid_disk != disk)
                                conf->fullsync = 1;
                        rcu_assign_pointer(p->rdev, rdev);
                        break;
                }
        print_raid5_conf(conf);
-       return found;
+       return err;
 }
 
 static int raid5_resize(mddev_t *mddev, sector_t sectors)
@@ -4401,14 +4687,15 @@ static int raid5_resize(mddev_t *mddev, sector_t sectors)
        raid5_conf_t *conf = mddev_to_conf(mddev);
 
        sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
-       mddev->array_size = (sectors * (mddev->raid_disks-conf->max_degraded))>>1;
-       set_capacity(mddev->gendisk, mddev->array_size << 1);
+       mddev->array_sectors = sectors * (mddev->raid_disks
+                                         - conf->max_degraded);
+       set_capacity(mddev->gendisk, mddev->array_sectors);
        mddev->changed = 1;
-       if (sectors/2  > mddev->size && mddev->recovery_cp == MaxSector) {
-               mddev->recovery_cp = mddev->size << 1;
+       if (sectors > mddev->dev_sectors && mddev->recovery_cp == MaxSector) {
+               mddev->recovery_cp = mddev->dev_sectors;
                set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
        }
-       mddev->size = sectors /2;
+       mddev->dev_sectors = sectors;
        mddev->resync_max_sectors = sectors;
        return 0;
 }
@@ -4424,6 +4711,9 @@ static int raid5_check_reshape(mddev_t *mddev)
                return -EINVAL; /* Cannot shrink array or change level yet */
        if (mddev->delta_disks == 0)
                return 0; /* nothing to do */
+       if (mddev->bitmap)
+               /* Cannot grow a bitmap yet */
+               return -EBUSY;
 
        /* Can only proceed if there are plenty of stripe_heads.
         * We need a minimum of one full stripe,, and for sensible progress
@@ -4454,7 +4744,6 @@ static int raid5_start_reshape(mddev_t *mddev)
 {
        raid5_conf_t *conf = mddev_to_conf(mddev);
        mdk_rdev_t *rdev;
-       struct list_head *rtmp;
        int spares = 0;
        int added_devices = 0;
        unsigned long flags;
@@ -4462,7 +4751,7 @@ static int raid5_start_reshape(mddev_t *mddev)
        if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
                return -EBUSY;
 
-       ITERATE_RDEV(mddev, rdev, rtmp)
+       list_for_each_entry(rdev, &mddev->disks, same_set)
                if (rdev->raid_disk < 0 &&
                    !test_bit(Faulty, &rdev->flags))
                        spares++;
@@ -4484,10 +4773,10 @@ static int raid5_start_reshape(mddev_t *mddev)
        /* Add some new drives, as many as will fit.
         * We know there are enough to make the newly sized array work.
         */
-       ITERATE_RDEV(mddev, rdev, rtmp)
+       list_for_each_entry(rdev, &mddev->disks, same_set)
                if (rdev->raid_disk < 0 &&
                    !test_bit(Faulty, &rdev->flags)) {
-                       if (raid5_add_disk(mddev, rdev)) {
+                       if (raid5_add_disk(mddev, rdev) == 0) {
                                char nm[20];
                                set_bit(In_sync, &rdev->flags);
                                added_devices++;
@@ -4535,15 +4824,16 @@ static void end_reshape(raid5_conf_t *conf)
        struct block_device *bdev;
 
        if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
-               conf->mddev->array_size = conf->mddev->size *
+               conf->mddev->array_sectors = conf->mddev->dev_sectors *
                        (conf->raid_disks - conf->max_degraded);
-               set_capacity(conf->mddev->gendisk, conf->mddev->array_size << 1);
+               set_capacity(conf->mddev->gendisk, conf->mddev->array_sectors);
                conf->mddev->changed = 1;
 
                bdev = bdget_disk(conf->mddev->gendisk, 0);
                if (bdev) {
                        mutex_lock(&bdev->bd_inode->i_mutex);
-                       i_size_write(bdev->bd_inode, (loff_t)conf->mddev->array_size << 10);
+                       i_size_write(bdev->bd_inode,
+                                    (loff_t)conf->mddev->array_sectors << 9);
                        mutex_unlock(&bdev->bd_inode->i_mutex);
                        bdput(bdev);
                }
@@ -4594,6 +4884,102 @@ static void raid5_quiesce(mddev_t *mddev, int state)
        }
 }
 
+
+static void *raid5_takeover_raid1(mddev_t *mddev)
+{
+       int chunksect;
+
+       if (mddev->raid_disks != 2 ||
+           mddev->degraded > 1)
+               return ERR_PTR(-EINVAL);
+
+       /* Should check if there are write-behind devices? */
+
+       chunksect = 64*2; /* 64K by default */
+
+       /* The array must be an exact multiple of chunksize */
+       while (chunksect && (mddev->array_sectors & (chunksect-1)))
+               chunksect >>= 1;
+
+       if ((chunksect<<9) < STRIPE_SIZE)
+               /* array size does not allow a suitable chunk size */
+               return ERR_PTR(-EINVAL);
+
+       mddev->new_level = 5;
+       mddev->new_layout = ALGORITHM_LEFT_SYMMETRIC;
+       mddev->new_chunk = chunksect << 9;
+
+       return setup_conf(mddev);
+}
+
+
+static void *raid5_takeover(mddev_t *mddev)
+{
+       /* raid5 can take over:
+        *  raid0 - if all devices are the same - make it a raid4 layout
+        *  raid1 - if there are two drives.  We need to know the chunk size
+        *  raid4 - trivial - just use a raid4 layout.
+        *  raid6 - Providing it is a *_6 layout
+        *
+        * For now, just do raid1
+        */
+
+       if (mddev->level == 1)
+               return raid5_takeover_raid1(mddev);
+
+       return ERR_PTR(-EINVAL);
+}
+
+
+static struct mdk_personality raid5_personality;
+
+static void *raid6_takeover(mddev_t *mddev)
+{
+       /* Currently can only take over a raid5.  We map the
+        * personality to an equivalent raid6 personality
+        * with the Q block at the end.
+        */
+       int new_layout;
+
+       if (mddev->pers != &raid5_personality)
+               return ERR_PTR(-EINVAL);
+       if (mddev->degraded > 1)
+               return ERR_PTR(-EINVAL);
+       if (mddev->raid_disks > 253)
+               return ERR_PTR(-EINVAL);
+       if (mddev->raid_disks < 3)
+               return ERR_PTR(-EINVAL);
+
+       switch (mddev->layout) {
+       case ALGORITHM_LEFT_ASYMMETRIC:
+               new_layout = ALGORITHM_LEFT_ASYMMETRIC_6;
+               break;
+       case ALGORITHM_RIGHT_ASYMMETRIC:
+               new_layout = ALGORITHM_RIGHT_ASYMMETRIC_6;
+               break;
+       case ALGORITHM_LEFT_SYMMETRIC:
+               new_layout = ALGORITHM_LEFT_SYMMETRIC_6;
+               break;
+       case ALGORITHM_RIGHT_SYMMETRIC:
+               new_layout = ALGORITHM_RIGHT_SYMMETRIC_6;
+               break;
+       case ALGORITHM_PARITY_0:
+               new_layout = ALGORITHM_PARITY_0_6;
+               break;
+       case ALGORITHM_PARITY_N:
+               new_layout = ALGORITHM_PARITY_N;
+               break;
+       default:
+               return ERR_PTR(-EINVAL);
+       }
+       mddev->new_level = 6;
+       mddev->new_layout = new_layout;
+       mddev->delta_disks = 1;
+       mddev->raid_disks += 1;
+       return setup_conf(mddev);
+}
+
+
 static struct mdk_personality raid6_personality =
 {
        .name           = "raid6",
@@ -4614,6 +5000,7 @@ static struct mdk_personality raid6_personality =
        .start_reshape  = raid5_start_reshape,
 #endif
        .quiesce        = raid5_quiesce,
+       .takeover       = raid6_takeover,
 };
 static struct mdk_personality raid5_personality =
 {
@@ -4635,6 +5022,7 @@ static struct mdk_personality raid5_personality =
        .start_reshape  = raid5_start_reshape,
 #endif
        .quiesce        = raid5_quiesce,
+       .takeover       = raid5_takeover,
 };
 
 static struct mdk_personality raid4_personality =