#include <linux/blkdev.h>
#include <linux/ctype.h>
#include <linux/device-mapper.h>
+#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kdev_t.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
+#include <linux/log2.h>
+#include <linux/dm-kcopyd.h>
+#include "dm-exception-store.h"
#include "dm-snap.h"
#include "dm-bio-list.h"
-#include "kcopyd.h"
#define DM_MSG_PREFIX "snapshots"
#define SNAPSHOT_COPY_PRIORITY 2
/*
- * Each snapshot reserves this many pages for io
+ * Reserve 1MB for each snapshot initially (with minimum of 1 page).
*/
-#define SNAPSHOT_PAGES 256
+#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
+
+/*
+ * The size of the mempool used to track chunks in use.
+ */
+#define MIN_IOS 256
static struct workqueue_struct *ksnapd;
static void flush_queued_bios(struct work_struct *work);
*/
static struct kmem_cache *exception_cache;
static struct kmem_cache *pending_cache;
-static mempool_t *pending_pool;
+
+struct dm_snap_tracked_chunk {
+ struct hlist_node node;
+ chunk_t chunk;
+};
+
+static struct kmem_cache *tracked_chunk_cache;
+
+static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
+ chunk_t chunk)
+{
+ struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
+ GFP_NOIO);
+ unsigned long flags;
+
+ c->chunk = chunk;
+
+ spin_lock_irqsave(&s->tracked_chunk_lock, flags);
+ hlist_add_head(&c->node,
+ &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
+ spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
+
+ return c;
+}
+
+static void stop_tracking_chunk(struct dm_snapshot *s,
+ struct dm_snap_tracked_chunk *c)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&s->tracked_chunk_lock, flags);
+ hlist_del(&c->node);
+ spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
+
+ mempool_free(c, s->tracked_chunk_pool);
+}
+
+static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
+{
+ struct dm_snap_tracked_chunk *c;
+ struct hlist_node *hn;
+ int found = 0;
+
+ spin_lock_irq(&s->tracked_chunk_lock);
+
+ hlist_for_each_entry(c, hn,
+ &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
+ if (c->chunk == chunk) {
+ found = 1;
+ break;
+ }
+ }
+
+ spin_unlock_irq(&s->tracked_chunk_lock);
+
+ return found;
+}
/*
* One of these per registered origin, held in the snapshot_origins hash
*/
static int register_snapshot(struct dm_snapshot *snap)
{
- struct origin *o;
+ struct origin *o, *new_o;
struct block_device *bdev = snap->origin->bdev;
+ new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
+ if (!new_o)
+ return -ENOMEM;
+
down_write(&_origins_lock);
o = __lookup_origin(bdev);
- if (!o) {
+ if (o)
+ kfree(new_o);
+ else {
/* New origin */
- o = kmalloc(sizeof(*o), GFP_KERNEL);
- if (!o) {
- up_write(&_origins_lock);
- return -ENOMEM;
- }
+ o = new_o;
/* Initialise the struct */
INIT_LIST_HEAD(&o->snapshots);
/*
* Implementation of the exception hash tables.
+ * The lowest hash_shift bits of the chunk number are ignored, allowing
+ * some consecutive chunks to be grouped together.
*/
-static int init_exception_table(struct exception_table *et, uint32_t size)
+static int init_exception_table(struct exception_table *et, uint32_t size,
+ unsigned hash_shift)
{
unsigned int i;
+ et->hash_shift = hash_shift;
et->hash_mask = size - 1;
et->table = dm_vcalloc(size, sizeof(struct list_head));
if (!et->table)
static uint32_t exception_hash(struct exception_table *et, chunk_t chunk)
{
- return chunk & et->hash_mask;
+ return (chunk >> et->hash_shift) & et->hash_mask;
}
static void insert_exception(struct exception_table *eh,
slot = &et->table[exception_hash(et, chunk)];
list_for_each_entry (e, slot, hash_list)
- if (e->old_chunk == chunk)
+ if (chunk >= e->old_chunk &&
+ chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
return e;
return NULL;
kmem_cache_free(exception_cache, e);
}
-static struct dm_snap_pending_exception *alloc_pending_exception(void)
+static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
{
- return mempool_alloc(pending_pool, GFP_NOIO);
+ struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
+ GFP_NOIO);
+
+ atomic_inc(&s->pending_exceptions_count);
+ pe->snap = s;
+
+ return pe;
}
static void free_pending_exception(struct dm_snap_pending_exception *pe)
{
- mempool_free(pe, pending_pool);
+ struct dm_snapshot *s = pe->snap;
+
+ mempool_free(pe, s->pending_pool);
+ smp_mb__before_atomic_dec();
+ atomic_dec(&s->pending_exceptions_count);
}
-int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
+static void insert_completed_exception(struct dm_snapshot *s,
+ struct dm_snap_exception *new_e)
{
+ struct exception_table *eh = &s->complete;
+ struct list_head *l;
+ struct dm_snap_exception *e = NULL;
+
+ l = &eh->table[exception_hash(eh, new_e->old_chunk)];
+
+ /* Add immediately if this table doesn't support consecutive chunks */
+ if (!eh->hash_shift)
+ goto out;
+
+ /* List is ordered by old_chunk */
+ list_for_each_entry_reverse(e, l, hash_list) {
+ /* Insert after an existing chunk? */
+ if (new_e->old_chunk == (e->old_chunk +
+ dm_consecutive_chunk_count(e) + 1) &&
+ new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
+ dm_consecutive_chunk_count(e) + 1)) {
+ dm_consecutive_chunk_count_inc(e);
+ free_exception(new_e);
+ return;
+ }
+
+ /* Insert before an existing chunk? */
+ if (new_e->old_chunk == (e->old_chunk - 1) &&
+ new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
+ dm_consecutive_chunk_count_inc(e);
+ e->old_chunk--;
+ e->new_chunk--;
+ free_exception(new_e);
+ return;
+ }
+
+ if (new_e->old_chunk > e->old_chunk)
+ break;
+ }
+
+out:
+ list_add(&new_e->hash_list, e ? &e->hash_list : l);
+}
+
+/*
+ * Callback used by the exception stores to load exceptions when
+ * initialising.
+ */
+static int dm_add_exception(void *context, chunk_t old, chunk_t new)
+{
+ struct dm_snapshot *s = context;
struct dm_snap_exception *e;
e = alloc_exception();
return -ENOMEM;
e->old_chunk = old;
+
+ /* Consecutive_count is implicitly initialised to zero */
e->new_chunk = new;
- insert_exception(&s->complete, e);
+
+ insert_completed_exception(s, e);
+
return 0;
}
}
/*
- * Rounds a number down to a power of 2.
- */
-static uint32_t round_down(uint32_t n)
-{
- while (n & (n - 1))
- n &= (n - 1);
- return n;
-}
-
-/*
* Allocate room for a suitable hash table.
*/
static int init_hash_tables(struct dm_snapshot *s)
hash_size = min(origin_dev_size, cow_dev_size) >> s->chunk_shift;
hash_size = min(hash_size, max_buckets);
- /* Round it down to a power of 2 */
- hash_size = round_down(hash_size);
- if (init_exception_table(&s->complete, hash_size))
+ hash_size = rounddown_pow_of_two(hash_size);
+ if (init_exception_table(&s->complete, hash_size,
+ DM_CHUNK_CONSECUTIVE_BITS))
return -ENOMEM;
/*
if (hash_size < 64)
hash_size = 64;
- if (init_exception_table(&s->pending, hash_size)) {
+ if (init_exception_table(&s->pending, hash_size, 0)) {
exit_exception_table(&s->complete, exception_cache);
return -ENOMEM;
}
chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
/* Check chunk_size is a power of 2 */
- if (chunk_size & (chunk_size - 1)) {
+ if (!is_power_of_2(chunk_size)) {
*error = "Chunk size is not a power of 2";
return -EINVAL;
}
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct dm_snapshot *s;
+ int i;
int r = -EINVAL;
char persistent;
char *origin_path;
s->valid = 1;
s->active = 0;
- s->last_percent = 0;
+ atomic_set(&s->pending_exceptions_count, 0);
init_rwsem(&s->lock);
spin_lock_init(&s->pe_lock);
- s->table = ti->table;
+ s->ti = ti;
/* Allocate hash table for COW data */
if (init_hash_tables(s)) {
goto bad4;
}
- r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
+ r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
if (r) {
ti->error = "Could not create kcopyd client";
goto bad5;
}
+ s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
+ if (!s->pending_pool) {
+ ti->error = "Could not allocate mempool for pending exceptions";
+ goto bad6;
+ }
+
+ s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
+ tracked_chunk_cache);
+ if (!s->tracked_chunk_pool) {
+ ti->error = "Could not allocate tracked_chunk mempool for "
+ "tracking reads";
+ goto bad_tracked_chunk_pool;
+ }
+
+ for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
+
+ spin_lock_init(&s->tracked_chunk_lock);
+
/* Metadata must only be loaded into one table at once */
- r = s->store.read_metadata(&s->store);
+ r = s->store.read_metadata(&s->store, dm_add_exception, (void *)s);
if (r < 0) {
ti->error = "Failed to read snapshot metadata";
- goto bad6;
+ goto bad_load_and_register;
} else if (r > 0) {
s->valid = 0;
DMWARN("Snapshot is marked invalid.");
if (register_snapshot(s)) {
r = -EINVAL;
ti->error = "Cannot register snapshot origin";
- goto bad6;
+ goto bad_load_and_register;
}
ti->private = s;
return 0;
+ bad_load_and_register:
+ mempool_destroy(s->tracked_chunk_pool);
+
+ bad_tracked_chunk_pool:
+ mempool_destroy(s->pending_pool);
+
bad6:
- kcopyd_client_destroy(s->kcopyd_client);
+ dm_kcopyd_client_destroy(s->kcopyd_client);
bad5:
s->store.destroy(&s->store);
static void __free_exceptions(struct dm_snapshot *s)
{
- kcopyd_client_destroy(s->kcopyd_client);
+ dm_kcopyd_client_destroy(s->kcopyd_client);
s->kcopyd_client = NULL;
exit_exception_table(&s->pending, pending_cache);
static void snapshot_dtr(struct dm_target *ti)
{
+#ifdef CONFIG_DM_DEBUG
+ int i;
+#endif
struct dm_snapshot *s = ti->private;
flush_workqueue(ksnapd);
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
+ while (atomic_read(&s->pending_exceptions_count))
+ msleep(1);
+ /*
+ * Ensure instructions in mempool_destroy aren't reordered
+ * before atomic_read.
+ */
+ smp_mb();
+
+#ifdef CONFIG_DM_DEBUG
+ for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
+ BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
+#endif
+
+ mempool_destroy(s->tracked_chunk_pool);
+
__free_exceptions(s);
+ mempool_destroy(s->pending_pool);
+
dm_put_device(ti, s->origin);
dm_put_device(ti, s->cow);
while (bio) {
n = bio->bi_next;
bio->bi_next = NULL;
- bio_io_error(bio, bio->bi_size);
+ bio_io_error(bio);
bio = n;
}
}
s->valid = 0;
- dm_table_event(s->table);
+ dm_table_event(s->ti->table);
}
static void get_pending_exception(struct dm_snap_pending_exception *pe)
* the bios for the original write to the origin.
*/
if (primary_pe &&
- atomic_dec_and_test(&primary_pe->ref_count))
+ atomic_dec_and_test(&primary_pe->ref_count)) {
origin_bios = bio_list_get(&primary_pe->origin_bios);
+ free_pending_exception(primary_pe);
+ }
/*
* Free the pe if it's not linked to an origin write or if
if (!primary_pe || primary_pe != pe)
free_pending_exception(pe);
- /*
- * Free the primary pe if nothing references it.
- */
- if (primary_pe && !atomic_read(&primary_pe->ref_count))
- free_pending_exception(primary_pe);
-
return origin_bios;
}
}
/*
+ * Check for conflicting reads. This is extremely improbable,
+ * so msleep(1) is sufficient and there is no need for a wait queue.
+ */
+ while (__chunk_is_tracked(s, pe->e.old_chunk))
+ msleep(1);
+
+ /*
* Add a proper exception, and remove the
* in-flight exception from the list.
*/
- insert_exception(&s->complete, e);
+ insert_completed_exception(s, e);
out:
remove_exception(&pe->e);
* Called when the copy I/O has finished. kcopyd actually runs
* this code so don't block.
*/
-static void copy_callback(int read_err, unsigned int write_err, void *context)
+static void copy_callback(int read_err, unsigned long write_err, void *context)
{
struct dm_snap_pending_exception *pe = context;
struct dm_snapshot *s = pe->snap;
static void start_copy(struct dm_snap_pending_exception *pe)
{
struct dm_snapshot *s = pe->snap;
- struct io_region src, dest;
+ struct dm_io_region src, dest;
struct block_device *bdev = s->origin->bdev;
sector_t dev_size;
dest.count = src.count;
/* Hand over to kcopyd */
- kcopyd_copy(s->kcopyd_client,
+ dm_kcopyd_copy(s->kcopyd_client,
&src, 1, &dest, 0, copy_callback, pe);
}
* to hold the lock while we do this.
*/
up_write(&s->lock);
- pe = alloc_pending_exception();
+ pe = alloc_pending_exception(s);
down_write(&s->lock);
if (!s->valid) {
bio_list_init(&pe->snapshot_bios);
pe->primary_pe = NULL;
atomic_set(&pe->ref_count, 0);
- pe->snap = s;
pe->started = 0;
if (s->store.prepare_exception(&s->store, &pe->e)) {
}
static void remap_exception(struct dm_snapshot *s, struct dm_snap_exception *e,
- struct bio *bio)
+ struct bio *bio, chunk_t chunk)
{
bio->bi_bdev = s->cow->bdev;
- bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
- (bio->bi_sector & s->chunk_mask);
+ bio->bi_sector = chunk_to_sector(s, dm_chunk_number(e->new_chunk) +
+ (chunk - e->old_chunk)) +
+ (bio->bi_sector & s->chunk_mask);
}
static int snapshot_map(struct dm_target *ti, struct bio *bio,
if (!s->valid)
return -EIO;
- if (unlikely(bio_barrier(bio)))
- return -EOPNOTSUPP;
-
/* FIXME: should only take write lock if we need
* to copy an exception */
down_write(&s->lock);
/* If the block is already remapped - use that, else remap it */
e = lookup_exception(&s->complete, chunk);
if (e) {
- remap_exception(s, e, bio);
+ remap_exception(s, e, bio, chunk);
goto out_unlock;
}
goto out_unlock;
}
- remap_exception(s, &pe->e, bio);
+ remap_exception(s, &pe->e, bio, chunk);
bio_list_add(&pe->snapshot_bios, bio);
r = DM_MAPIO_SUBMITTED;
start_copy(pe);
goto out;
}
- } else
- /*
- * FIXME: this read path scares me because we
- * always use the origin when we have a pending
- * exception. However I can't think of a
- * situation where this is wrong - ejt.
- */
+ } else {
bio->bi_bdev = s->origin->bdev;
+ map_context->ptr = track_chunk(s, chunk);
+ }
out_unlock:
up_write(&s->lock);
return r;
}
+static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
+ int error, union map_info *map_context)
+{
+ struct dm_snapshot *s = ti->private;
+ struct dm_snap_tracked_chunk *c = map_context->ptr;
+
+ if (c)
+ stop_tracking_chunk(s, c);
+
+ return 0;
+}
+
static void snapshot_resume(struct dm_target *ti)
{
struct dm_snapshot *s = ti->private;
goto next_snapshot;
/* Nothing to do if writing beyond end of snapshot */
- if (bio->bi_sector >= dm_table_get_size(snap->table))
+ if (bio->bi_sector >= dm_table_get_size(snap->ti->table))
goto next_snapshot;
/*
struct dm_dev *dev = ti->private;
bio->bi_bdev = dev->bdev;
- if (unlikely(bio_barrier(bio)))
- return -EOPNOTSUPP;
-
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
}
static struct target_type origin_target = {
.name = "snapshot-origin",
- .version = {1, 5, 0},
+ .version = {1, 6, 0},
.module = THIS_MODULE,
.ctr = origin_ctr,
.dtr = origin_dtr,
static struct target_type snapshot_target = {
.name = "snapshot",
- .version = {1, 5, 0},
+ .version = {1, 6, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
+ .end_io = snapshot_end_io,
.resume = snapshot_resume,
.status = snapshot_status,
};
{
int r;
+ r = dm_exception_store_init();
+ if (r) {
+ DMERR("Failed to initialize exception stores");
+ return r;
+ }
+
r = dm_register_target(&snapshot_target);
if (r) {
DMERR("snapshot target register failed %d", r);
goto bad4;
}
- pending_pool = mempool_create_slab_pool(128, pending_cache);
- if (!pending_pool) {
- DMERR("Couldn't create pending pool.");
+ tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
+ if (!tracked_chunk_cache) {
+ DMERR("Couldn't create cache to track chunks in use.");
r = -ENOMEM;
goto bad5;
}
if (!ksnapd) {
DMERR("Failed to create ksnapd workqueue.");
r = -ENOMEM;
- goto bad6;
+ goto bad_pending_pool;
}
return 0;
- bad6:
- mempool_destroy(pending_pool);
- bad5:
+bad_pending_pool:
+ kmem_cache_destroy(tracked_chunk_cache);
+bad5:
kmem_cache_destroy(pending_cache);
- bad4:
+bad4:
kmem_cache_destroy(exception_cache);
- bad3:
+bad3:
exit_origin_hash();
- bad2:
+bad2:
dm_unregister_target(&origin_target);
- bad1:
+bad1:
dm_unregister_target(&snapshot_target);
return r;
}
static void __exit dm_snapshot_exit(void)
{
- int r;
-
destroy_workqueue(ksnapd);
- r = dm_unregister_target(&snapshot_target);
- if (r)
- DMERR("snapshot unregister failed %d", r);
-
- r = dm_unregister_target(&origin_target);
- if (r)
- DMERR("origin unregister failed %d", r);
+ dm_unregister_target(&snapshot_target);
+ dm_unregister_target(&origin_target);
exit_origin_hash();
- mempool_destroy(pending_pool);
kmem_cache_destroy(pending_cache);
kmem_cache_destroy(exception_cache);
+ kmem_cache_destroy(tracked_chunk_cache);
+
+ dm_exception_store_exit();
}
/* Module hooks */
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff