md: replace R5_WantPrexor with R5_WantDrain, add 'prexor' reconstruct_states

From: Dan Williams <dan.j.williams@intel.com>

Currently ops_run_biodrain and other locations have extra logic to determine
which blocks are processed in the prexor and non-prexor cases.  This can be
eliminated if handle_write_operations5 flags the blocks to be processed in all
cases via R5_Wantdrain.  The presence of the prexor operation is tracked in
sh->reconstruct_state.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b915936..c712460 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -637,7 +637,7 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
        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;
        }
 
@@ -649,16 +649,10 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 }
 
 static struct dma_async_tx_descriptor *
-ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
-                unsigned long ops_request)
+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, &ops_request);
+       int i;
 
        pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
@@ -666,20 +660,8 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
        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);
@@ -704,18 +686,6 @@ 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", __func__,
-               (unsigned long long)sh->sector);
-
-       sh->reconstruct_state = reconstruct_state_result;
-       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", __func__,
@@ -727,14 +697,21 @@ static void ops_complete_write(void *stripe_head_ref)
                        set_bit(R5_UPTODATE, &dev->flags);
        }
 
-       sh->reconstruct_state = reconstruct_state_drain_result;
+       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);
 }
 
 static void
-ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
-               unsigned long ops_request)
+ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 {
        /* kernel stack size limits the total number of disks */
        int disks = sh->disks;
@@ -742,9 +719,8 @@ 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, &ops_request);
+       int prexor = 0;
        unsigned long flags;
-       dma_async_tx_callback callback;
 
        pr_debug("%s: stripe %llu\n", __func__,
                (unsigned long long)sh->sector);
@@ -752,7 +728,8 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
        /* 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];
@@ -768,10 +745,6 @@ 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, &ops_request) ?
-               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
@@ -785,10 +758,10 @@ 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)
@@ -847,12 +820,12 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
                tx = ops_run_prexor(sh, tx);
 
        if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
-               tx = ops_run_biodrain(sh, tx, ops_request);
+               tx = ops_run_biodrain(sh, tx);
                overlap_clear++;
        }
 
        if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
-               ops_run_postxor(sh, tx, ops_request);
+               ops_run_postxor(sh, tx);
 
        if (test_bit(STRIPE_OP_CHECK, &ops_request))
                ops_run_check(sh);
@@ -1669,6 +1642,7 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
 
                        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++;
@@ -1681,7 +1655,7 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
                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_drain_run;
+               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);
@@ -1691,15 +1665,10 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
                        if (i == pd_idx)
                                continue;
 
-                       /* For a read-modify write there may be blocks that are
-                        * locked for reading while others are ready to be
-                        * written so we distinguish these blocks by the
-                        * R5_Wantprexor bit
-                        */
                        if (dev->towrite &&
                            (test_bit(R5_UPTODATE, &dev->flags) ||
-                           test_bit(R5_Wantcompute, &dev->flags))) {
-                               set_bit(R5_Wantprexor, &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++;
@@ -2660,11 +2629,11 @@ static void handle_stripe5(struct stripe_head *sh)
         * completed
         */
        prexor = 0;
-       if (sh->reconstruct_state == reconstruct_state_drain_result) {
+       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;
-               for (i = disks; i--; )
-                       prexor += test_and_clear_bit(R5_Wantprexor,
-                                                    &sh->dev[i].flags);
 
                /* All the 'written' buffers and the parity block are ready to
                 * be written back to disk

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 5f3e674..3b26727 100644 (file)
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -187,8 +187,10 @@ enum check_states {
  */
 enum reconstruct_states {
        reconstruct_state_idle = 0,
+       reconstruct_state_prexor_drain_run,     /* prexor-write */
        reconstruct_state_drain_run,            /* write */
        reconstruct_state_run,                  /* expand */
+       reconstruct_state_prexor_drain_result,
        reconstruct_state_drain_result,
        reconstruct_state_result,
 };
@@ -258,9 +260,7 @@ struct r6_state {
 #define        R5_Wantfill     12 /* dev->toread contains a bio that needs
                                    * filling
                                    */
-#define        R5_Wantprexor   13 /* distinguish blocks ready for rmw from
-                                   * other "towrites"
-                                   */
+#define R5_Wantdrain   13 /* dev->towrite needs to be drained */
 /*
  * Write method
  */