1 files changed, 179 insertions, 172 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 1d0fafda0f761..5281e0094072b 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -39,6 +39,9 @@
  */
 #define SNAPSHOT_PAGES 256
 
+struct workqueue_struct *ksnapd;
+static void flush_queued_bios(void *data);
+
 struct pending_exception {
 	struct exception e;
 
@@ -56,7 +59,7 @@ struct pending_exception {
 
 	/*
 	 * The primary pending_exception is the one that holds
-	 * the sibling_count and the list of origin_bios for a
+	 * the ref_count and the list of origin_bios for a
 	 * group of pending_exceptions.  It is always last to get freed.
 	 * These fields get set up when writing to the origin.
 	 */
@@ -69,7 +72,7 @@ struct pending_exception {
 	 * the sibling concerned and not pe->primary_pe->snap->lock unless
 	 * they are the same.
 	 */
-	atomic_t sibling_count;
+	atomic_t ref_count;
 
 	/* Pointer back to snapshot context */
 	struct dm_snapshot *snap;
@@ -387,15 +390,46 @@ static inline ulong round_up(ulong n, ulong size)
 	return (n + size) & ~size;
 }
 
-static void read_snapshot_metadata(struct dm_snapshot *s)
+static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg,
+			  char **error)
 {
-	if (s->store.read_metadata(&s->store)) {
-		down_write(&s->lock);
-		s->valid = 0;
-		up_write(&s->lock);
+	unsigned long chunk_size;
+	char *value;
+
+	chunk_size = simple_strtoul(chunk_size_arg, &value, 10);
+	if (*chunk_size_arg == '\0' || *value != '\0') {
+		*error = "Invalid chunk size";
+		return -EINVAL;
+	}
+
+	if (!chunk_size) {
+		s->chunk_size = s->chunk_mask = s->chunk_shift = 0;
+		return 0;
+	}
+
+	/*
+	 * Chunk size must be multiple of page size.  Silently
+	 * round up if it's not.
+	 */
+	chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
+
+	/* Check chunk_size is a power of 2 */
+	if (chunk_size & (chunk_size - 1)) {
+		*error = "Chunk size is not a power of 2";
+		return -EINVAL;
+	}
 
-		dm_table_event(s->table);
+	/* Validate the chunk size against the device block size */
+	if (chunk_size % (bdev_hardsect_size(s->cow->bdev) >> 9)) {
+		*error = "Chunk size is not a multiple of device blocksize";
+		return -EINVAL;
 	}
+
+	s->chunk_size = chunk_size;
+	s->chunk_mask = chunk_size - 1;
+	s->chunk_shift = ffs(chunk_size) - 1;
+
+	return 0;
 }
 
 /*
@@ -404,15 +438,12 @@ static void read_snapshot_metadata(struct dm_snapshot *s)
 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 {
 	struct dm_snapshot *s;
-	unsigned long chunk_size;
 	int r = -EINVAL;
 	char persistent;
 	char *origin_path;
 	char *cow_path;
-	char *value;
-	int blocksize;
 
-	if (argc < 4) {
+	if (argc != 4) {
 		ti->error = "requires exactly 4 arguments";
 		r = -EINVAL;
 		goto bad1;
@@ -428,13 +459,6 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad1;
 	}
 
-	chunk_size = simple_strtoul(argv[3], &value, 10);
-	if (chunk_size == 0 || value == NULL) {
-		ti->error = "Invalid chunk size";
-		r = -EINVAL;
-		goto bad1;
-	}
-
 	s = kmalloc(sizeof(*s), GFP_KERNEL);
 	if (s == NULL) {
 		ti->error = "Cannot allocate snapshot context private "
@@ -457,36 +481,17 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad2;
 	}
 
-	/*
-	 * Chunk size must be multiple of page size.  Silently
-	 * round up if it's not.
-	 */
-	chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
-
-	/* Validate the chunk size against the device block size */
-	blocksize = s->cow->bdev->bd_disk->queue->hardsect_size;
-	if (chunk_size % (blocksize >> 9)) {
-		ti->error = "Chunk size is not a multiple of device blocksize";
-		r = -EINVAL;
-		goto bad3;
-	}
-
-	/* Check chunk_size is a power of 2 */
-	if (chunk_size & (chunk_size - 1)) {
-		ti->error = "Chunk size is not a power of 2";
-		r = -EINVAL;
+	r = set_chunk_size(s, argv[3], &ti->error);
+	if (r)
 		goto bad3;
-	}
 
-	s->chunk_size = chunk_size;
-	s->chunk_mask = chunk_size - 1;
 	s->type = persistent;
-	s->chunk_shift = ffs(chunk_size) - 1;
 
 	s->valid = 1;
 	s->active = 0;
 	s->last_percent = 0;
 	init_rwsem(&s->lock);
+	spin_lock_init(&s->pe_lock);
 	s->table = ti->table;
 
 	/* Allocate hash table for COW data */
@@ -496,16 +501,12 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad3;
 	}
 
-	/*
-	 * Check the persistent flag - done here because we need the iobuf
-	 * to check the LV header
-	 */
 	s->store.snap = s;
 
 	if (persistent == 'P')
-		r = dm_create_persistent(&s->store, chunk_size);
+		r = dm_create_persistent(&s->store);
 	else
-		r = dm_create_transient(&s->store, s, blocksize);
+		r = dm_create_transient(&s->store);
 
 	if (r) {
 		ti->error = "Couldn't create exception store";
@@ -520,7 +521,14 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	}
 
 	/* Metadata must only be loaded into one table at once */
-	read_snapshot_metadata(s);
+	r = s->store.read_metadata(&s->store);
+	if (r) {
+		ti->error = "Failed to read snapshot metadata";
+		goto bad6;
+	}
+
+	bio_list_init(&s->queued_bios);
+	INIT_WORK(&s->queued_bios_work, flush_queued_bios, s);
 
 	/* Add snapshot to the list of snapshots for this origin */
 	/* Exceptions aren't triggered till snapshot_resume() is called */
@@ -560,6 +568,8 @@ static void snapshot_dtr(struct dm_target *ti)
 {
 	struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
 
+	flush_workqueue(ksnapd);
+
 	/* Prevent further origin writes from using this snapshot. */
 	/* After this returns there can be no new kcopyd jobs. */
 	unregister_snapshot(s);
@@ -593,6 +603,19 @@ static void flush_bios(struct bio *bio)
 	}
 }
 
+static void flush_queued_bios(void *data)
+{
+	struct dm_snapshot *s = (struct dm_snapshot *) data;
+	struct bio *queued_bios;
+	unsigned long flags;
+
+	spin_lock_irqsave(&s->pe_lock, flags);
+	queued_bios = bio_list_get(&s->queued_bios);
+	spin_unlock_irqrestore(&s->pe_lock, flags);
+
+	flush_bios(queued_bios);
+}
+
 /*
  * Error a list of buffers.
  */
@@ -608,28 +631,7 @@ static void error_bios(struct bio *bio)
 	}
 }
 
-static inline void error_snapshot_bios(struct pending_exception *pe)
-{
-	error_bios(bio_list_get(&pe->snapshot_bios));
-}
-
-static struct bio *__flush_bios(struct pending_exception *pe)
-{
-	/*
-	 * If this pe is involved in a write to the origin and
-	 * it is the last sibling to complete then release
-	 * the bios for the original write to the origin.
-	 */
-
-	if (pe->primary_pe &&
-	    atomic_dec_and_test(&pe->primary_pe->sibling_count))
-		return bio_list_get(&pe->primary_pe->origin_bios);
-
-	return NULL;
-}
-
-static void __invalidate_snapshot(struct dm_snapshot *s,
-				struct pending_exception *pe, int err)
+static void __invalidate_snapshot(struct dm_snapshot *s, int err)
 {
 	if (!s->valid)
 		return;
@@ -639,9 +641,6 @@ static void __invalidate_snapshot(struct dm_snapshot *s,
 	else if (err == -ENOMEM)
 		DMERR("Invalidating snapshot: Unable to allocate exception.");
 
-	if (pe)
-		remove_exception(&pe->e);
-
 	if (s->store.drop_snapshot)
 		s->store.drop_snapshot(&s->store);
 
@@ -650,78 +649,95 @@ static void __invalidate_snapshot(struct dm_snapshot *s,
 	dm_table_event(s->table);
 }
 
+static void get_pending_exception(struct pending_exception *pe)
+{
+	atomic_inc(&pe->ref_count);
+}
+
+static struct bio *put_pending_exception(struct pending_exception *pe)
+{
+	struct pending_exception *primary_pe;
+	struct bio *origin_bios = NULL;
+
+	primary_pe = pe->primary_pe;
+
+	/*
+	 * If this pe is involved in a write to the origin and
+	 * it is the last sibling to complete then release
+	 * the bios for the original write to the origin.
+	 */
+	if (primary_pe &&
+	    atomic_dec_and_test(&primary_pe->ref_count))
+		origin_bios = bio_list_get(&primary_pe->origin_bios);
+
+	/*
+	 * Free the pe if it's not linked to an origin write or if
+	 * it's not itself a primary pe.
+	 */
+	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;
+}
+
 static void pending_complete(struct pending_exception *pe, int success)
 {
 	struct exception *e;
-	struct pending_exception *primary_pe;
 	struct dm_snapshot *s = pe->snap;
-	struct bio *flush = NULL;
+	struct bio *origin_bios = NULL;
+	struct bio *snapshot_bios = NULL;
+	int error = 0;
 
 	if (!success) {
 		/* Read/write error - snapshot is unusable */
 		down_write(&s->lock);
-		__invalidate_snapshot(s, pe, -EIO);
-		flush = __flush_bios(pe);
-		up_write(&s->lock);
-
-		error_snapshot_bios(pe);
+		__invalidate_snapshot(s, -EIO);
+		error = 1;
 		goto out;
 	}
 
 	e = alloc_exception();
 	if (!e) {
 		down_write(&s->lock);
-		__invalidate_snapshot(s, pe, -ENOMEM);
-		flush = __flush_bios(pe);
-		up_write(&s->lock);
-
-		error_snapshot_bios(pe);
+		__invalidate_snapshot(s, -ENOMEM);
+		error = 1;
 		goto out;
 	}
 	*e = pe->e;
 
-	/*
-	 * Add a proper exception, and remove the
-	 * in-flight exception from the list.
-	 */
 	down_write(&s->lock);
 	if (!s->valid) {
-		flush = __flush_bios(pe);
-		up_write(&s->lock);
-
 		free_exception(e);
-
-		error_snapshot_bios(pe);
+		error = 1;
 		goto out;
 	}
 
+	/*
+	 * Add a proper exception, and remove the
+	 * in-flight exception from the list.
+	 */
 	insert_exception(&s->complete, e);
+
+ out:
 	remove_exception(&pe->e);
-	flush = __flush_bios(pe);
+	snapshot_bios = bio_list_get(&pe->snapshot_bios);
+	origin_bios = put_pending_exception(pe);
 
 	up_write(&s->lock);
 
 	/* Submit any pending write bios */
-	flush_bios(bio_list_get(&pe->snapshot_bios));
-
- out:
-	primary_pe = pe->primary_pe;
-
-	/*
-	 * Free the pe if it's not linked to an origin write or if
-	 * it's not itself a primary pe.
-	 */
-	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->sibling_count))
-		free_pending_exception(primary_pe);
+	if (error)
+		error_bios(snapshot_bios);
+	else
+		flush_bios(snapshot_bios);
 
-	if (flush)
-		flush_bios(flush);
+	flush_bios(origin_bios);
 }
 
 static void commit_callback(void *context, int success)
@@ -822,7 +838,7 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
 	bio_list_init(&pe->origin_bios);
 	bio_list_init(&pe->snapshot_bios);
 	pe->primary_pe = NULL;
-	atomic_set(&pe->sibling_count, 1);
+	atomic_set(&pe->ref_count, 0);
 	pe->snap = s;
 	pe->started = 0;
 
@@ -831,6 +847,7 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
 		return NULL;
 	}
 
+	get_pending_exception(pe);
 	insert_exception(&s->pending, &pe->e);
 
  out:
@@ -850,7 +867,6 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
 {
 	struct exception *e;
 	struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
-	int copy_needed = 0;
 	int r = 1;
 	chunk_t chunk;
 	struct pending_exception *pe = NULL;
@@ -865,32 +881,31 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
 	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 (!s->valid) {
+		r = -EIO;
+		goto out_unlock;
+	}
+
+	/* If the block is already remapped - use that, else remap it */
+	e = lookup_exception(&s->complete, chunk);
+	if (e) {
+		remap_exception(s, e, bio);
+		goto out_unlock;
+	}
+
 	/*
 	 * Write to snapshot - higher level takes care of RW/RO
 	 * flags so we should only get this if we are
 	 * writeable.
 	 */
 	if (bio_rw(bio) == WRITE) {
-
-		/* FIXME: should only take write lock if we need
-		 * to copy an exception */
-		down_write(&s->lock);
-
-		if (!s->valid) {
-			r = -EIO;
-			goto out_unlock;
-		}
-
-		/* If the block is already remapped - use that, else remap it */
-		e = lookup_exception(&s->complete, chunk);
-		if (e) {
-			remap_exception(s, e, bio);
-			goto out_unlock;
-		}
-
 		pe = __find_pending_exception(s, bio);
 		if (!pe) {
-			__invalidate_snapshot(s, pe, -ENOMEM);
+			__invalidate_snapshot(s, -ENOMEM);
 			r = -EIO;
 			goto out_unlock;
 		}
@@ -898,45 +913,27 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
 		remap_exception(s, &pe->e, bio);
 		bio_list_add(&pe->snapshot_bios, bio);
 
+		r = 0;
+
 		if (!pe->started) {
 			/* this is protected by snap->lock */
 			pe->started = 1;
-			copy_needed = 1;
-		}
-
-		r = 0;
-
- out_unlock:
-		up_write(&s->lock);
-
-		if (copy_needed)
+			up_write(&s->lock);
 			start_copy(pe);
-	} else {
+			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.
 		 */
+		bio->bi_bdev = s->origin->bdev;
 
-		/* Do reads */
-		down_read(&s->lock);
-
-		if (!s->valid) {
-			up_read(&s->lock);
-			return -EIO;
-		}
-
-		/* See if it it has been remapped */
-		e = lookup_exception(&s->complete, chunk);
-		if (e)
-			remap_exception(s, e, bio);
-		else
-			bio->bi_bdev = s->origin->bdev;
-
-		up_read(&s->lock);
-	}
-
+ out_unlock:
+	up_write(&s->lock);
+ out:
 	return r;
 }
 
@@ -1025,7 +1022,7 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
 		 * is already remapped in this snapshot
 		 * and trigger an exception if not.
 		 *
-		 * sibling_count is initialised to 1 so pending_complete()
+		 * ref_count is initialised to 1 so pending_complete()
 		 * won't destroy the primary_pe while we're inside this loop.
 		 */
 		e = lookup_exception(&snap->complete, chunk);
@@ -1034,7 +1031,7 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
 
 		pe = __find_pending_exception(snap, bio);
 		if (!pe) {
-			__invalidate_snapshot(snap, pe, ENOMEM);
+			__invalidate_snapshot(snap, -ENOMEM);
 			goto next_snapshot;
 		}
 
@@ -1056,8 +1053,8 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
 		}
 
 		if (!pe->primary_pe) {
-			atomic_inc(&primary_pe->sibling_count);
 			pe->primary_pe = primary_pe;
+			get_pending_exception(primary_pe);
 		}
 
 		if (!pe->started) {
@@ -1070,20 +1067,20 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
 	}
 
 	if (!primary_pe)
-		goto out;
+		return r;
 
 	/*
 	 * If this is the first time we're processing this chunk and
-	 * sibling_count is now 1 it means all the pending exceptions
+	 * ref_count is now 1 it means all the pending exceptions
 	 * got completed while we were in the loop above, so it falls to
 	 * us here to remove the primary_pe and submit any origin_bios.
 	 */
 
-	if (first && atomic_dec_and_test(&primary_pe->sibling_count)) {
+	if (first && atomic_dec_and_test(&primary_pe->ref_count)) {
 		flush_bios(bio_list_get(&primary_pe->origin_bios));
 		free_pending_exception(primary_pe);
 		/* If we got here, pe_queue is necessarily empty. */
-		goto out;
+		return r;
 	}
 
 	/*
@@ -1092,7 +1089,6 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
 	list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
 		start_copy(pe);
 
- out:
 	return r;
 }
 
@@ -1205,7 +1201,7 @@ static int origin_status(struct dm_target *ti, status_type_t type, char *result,
 
 static struct target_type origin_target = {
 	.name    = "snapshot-origin",
-	.version = {1, 4, 0},
+	.version = {1, 5, 0},
 	.module  = THIS_MODULE,
 	.ctr     = origin_ctr,
 	.dtr     = origin_dtr,
@@ -1216,7 +1212,7 @@ static struct target_type origin_target = {
 
 static struct target_type snapshot_target = {
 	.name    = "snapshot",
-	.version = {1, 4, 0},
+	.version = {1, 5, 0},
 	.module  = THIS_MODULE,
 	.ctr     = snapshot_ctr,
 	.dtr     = snapshot_dtr,
@@ -1275,8 +1271,17 @@ static int __init dm_snapshot_init(void)
 		goto bad5;
 	}
 
+	ksnapd = create_singlethread_workqueue("ksnapd");
+	if (!ksnapd) {
+		DMERR("Failed to create ksnapd workqueue.");
+		r = -ENOMEM;
+		goto bad6;
+	}
+
 	return 0;
 
+      bad6:
+	mempool_destroy(pending_pool);
       bad5:
 	kmem_cache_destroy(pending_cache);
       bad4:
@@ -1294,6 +1299,8 @@ 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);