diff options
author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2008-08-08 16:21:02 -0400 |
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committer | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2008-08-08 16:21:02 -0400 |
commit | e4ddcb0a6bf04d53ce77b4eb87bbbb32c4261d11 (patch) | |
tree | d27d2fea50a384d97aa2d0cf5c8657c916f761d4 /drivers/md/dm-snap.c | |
parent | f2afa7711f8585ffc088ba538b9a510e0d5dca12 (diff) | |
parent | 6e86841d05f371b5b9b86ce76c02aaee83352298 (diff) |
Merge commit 'v2.6.27-rc1' into for-linus
Diffstat (limited to 'drivers/md/dm-snap.c')
-rw-r--r-- | drivers/md/dm-snap.c | 163 |
1 files changed, 141 insertions, 22 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 1ba8a47d61b..6e5528aecc9 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -40,6 +40,11 @@ */ #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); @@ -91,7 +96,63 @@ struct dm_snap_pending_exception { */ 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 @@ -302,14 +363,19 @@ static void free_exception(struct dm_snap_exception *e) 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); + + pe->snap = s; + + return pe; } static void free_pending_exception(struct dm_snap_pending_exception *pe) { - mempool_free(pe, pending_pool); + mempool_free(pe, pe->snap->pending_pool); } static void insert_completed_exception(struct dm_snapshot *s, @@ -482,6 +548,7 @@ static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg, 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; @@ -564,11 +631,30 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) 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); 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."); @@ -582,7 +668,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) if (register_snapshot(s)) { r = -EINVAL; ti->error = "Cannot register snapshot origin"; - goto bad6; + goto bad_load_and_register; } ti->private = s; @@ -590,6 +676,12 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) return 0; + bad_load_and_register: + mempool_destroy(s->tracked_chunk_pool); + + bad_tracked_chunk_pool: + mempool_destroy(s->pending_pool); + bad6: dm_kcopyd_client_destroy(s->kcopyd_client); @@ -624,6 +716,9 @@ static void __free_exceptions(struct dm_snapshot *s) static void snapshot_dtr(struct dm_target *ti) { +#ifdef CONFIG_DM_DEBUG + int i; +#endif struct dm_snapshot *s = ti->private; flush_workqueue(ksnapd); @@ -632,8 +727,17 @@ static void snapshot_dtr(struct dm_target *ti) /* After this returns there can be no new kcopyd jobs. */ unregister_snapshot(s); +#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); @@ -772,6 +876,13 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) } /* + * Check for conflicting reads. This is extremely improbable, + * so yield() is sufficient and there is no need for a wait queue. + */ + while (__chunk_is_tracked(s, pe->e.old_chunk)) + yield(); + + /* * Add a proper exception, and remove the * in-flight exception from the list. */ @@ -873,7 +984,7 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio) * 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) { @@ -893,7 +1004,6 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio) 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)) { @@ -974,14 +1084,10 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, 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); @@ -989,6 +1095,18 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, 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; @@ -1266,6 +1384,7 @@ static struct target_type snapshot_target = { .ctr = snapshot_ctr, .dtr = snapshot_dtr, .map = snapshot_map, + .end_io = snapshot_end_io, .resume = snapshot_resume, .status = snapshot_status, }; @@ -1306,9 +1425,9 @@ static int __init dm_snapshot_init(void) 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; } @@ -1317,13 +1436,13 @@ static int __init dm_snapshot_init(void) if (!ksnapd) { DMERR("Failed to create ksnapd workqueue."); r = -ENOMEM; - goto bad6; + goto bad_pending_pool; } return 0; - bad6: - mempool_destroy(pending_pool); + bad_pending_pool: + kmem_cache_destroy(tracked_chunk_cache); bad5: kmem_cache_destroy(pending_cache); bad4: @@ -1352,9 +1471,9 @@ static void __exit dm_snapshot_exit(void) DMERR("origin unregister failed %d", r); exit_origin_hash(); - mempool_destroy(pending_pool); kmem_cache_destroy(pending_cache); kmem_cache_destroy(exception_cache); + kmem_cache_destroy(tracked_chunk_cache); } /* Module hooks */ |