1 files changed, 461 insertions, 308 deletions

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 3e2907f0bc46..693e149e9727 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011 Red Hat, Inc.
+ * Copyright (C) 2011-2012 Red Hat, Inc.
  *
  * This file is released under the GPL.
  */
@@ -80,6 +80,12 @@
 #define THIN_METADATA_CACHE_SIZE 64
 #define SECTOR_TO_BLOCK_SHIFT 3
 
+/*
+ *  3 for btree insert +
+ *  2 for btree lookup used within space map
+ */
+#define THIN_MAX_CONCURRENT_LOCKS 5
+
 /* This should be plenty */
 #define SPACE_MAP_ROOT_SIZE 128
 
@@ -172,13 +178,20 @@ struct dm_pool_metadata {
 
 	struct rw_semaphore root_lock;
 	uint32_t time;
-	int need_commit;
 	dm_block_t root;
 	dm_block_t details_root;
 	struct list_head thin_devices;
 	uint64_t trans_id;
 	unsigned long flags;
 	sector_t data_block_size;
+	bool read_only:1;
+
+	/*
+	 * Set if a transaction has to be aborted but the attempt to roll back
+	 * to the previous (good) transaction failed.  The only pool metadata
+	 * operation possible in this state is the closing of the device.
+	 */
+	bool fail_io:1;
 };
 
 struct dm_thin_device {
@@ -187,7 +200,8 @@ struct dm_thin_device {
 	dm_thin_id id;
 
 	int open_count;
-	int changed;
+	bool changed:1;
+	bool aborted_with_changes:1;
 	uint64_t mapped_blocks;
 	uint64_t transaction_id;
 	uint32_t creation_time;
@@ -338,7 +352,21 @@ static int subtree_equal(void *context, void *value1_le, void *value2_le)
 
 /*----------------------------------------------------------------*/
 
-static int superblock_all_zeroes(struct dm_block_manager *bm, int *result)
+static int superblock_lock_zero(struct dm_pool_metadata *pmd,
+				struct dm_block **sblock)
+{
+	return dm_bm_write_lock_zero(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+				     &sb_validator, sblock);
+}
+
+static int superblock_lock(struct dm_pool_metadata *pmd,
+			   struct dm_block **sblock)
+{
+	return dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+				&sb_validator, sblock);
+}
+
+static int __superblock_all_zeroes(struct dm_block_manager *bm, int *result)
 {
 	int r;
 	unsigned i;
@@ -365,72 +393,9 @@ static int superblock_all_zeroes(struct dm_block_manager *bm, int *result)
 	return dm_bm_unlock(b);
 }
 
-static int init_pmd(struct dm_pool_metadata *pmd,
-		    struct dm_block_manager *bm,
-		    dm_block_t nr_blocks, int create)
+static void __setup_btree_details(struct dm_pool_metadata *pmd)
 {
-	int r;
-	struct dm_space_map *sm, *data_sm;
-	struct dm_transaction_manager *tm;
-	struct dm_block *sblock;
-
-	if (create) {
-		r = dm_tm_create_with_sm(bm, THIN_SUPERBLOCK_LOCATION,
-					 &sb_validator, &tm, &sm, &sblock);
-		if (r < 0) {
-			DMERR("tm_create_with_sm failed");
-			return r;
-		}
-
-		data_sm = dm_sm_disk_create(tm, nr_blocks);
-		if (IS_ERR(data_sm)) {
-			DMERR("sm_disk_create failed");
-			dm_tm_unlock(tm, sblock);
-			r = PTR_ERR(data_sm);
-			goto bad;
-		}
-	} else {
-		struct thin_disk_superblock *disk_super = NULL;
-		size_t space_map_root_offset =
-			offsetof(struct thin_disk_superblock, metadata_space_map_root);
-
-		r = dm_tm_open_with_sm(bm, THIN_SUPERBLOCK_LOCATION,
-				       &sb_validator, space_map_root_offset,
-				       SPACE_MAP_ROOT_SIZE, &tm, &sm, &sblock);
-		if (r < 0) {
-			DMERR("tm_open_with_sm failed");
-			return r;
-		}
-
-		disk_super = dm_block_data(sblock);
-		data_sm = dm_sm_disk_open(tm, disk_super->data_space_map_root,
-					  sizeof(disk_super->data_space_map_root));
-		if (IS_ERR(data_sm)) {
-			DMERR("sm_disk_open failed");
-			r = PTR_ERR(data_sm);
-			goto bad;
-		}
-	}
-
-
-	r = dm_tm_unlock(tm, sblock);
-	if (r < 0) {
-		DMERR("couldn't unlock superblock");
-		goto bad_data_sm;
-	}
-
-	pmd->bm = bm;
-	pmd->metadata_sm = sm;
-	pmd->data_sm = data_sm;
-	pmd->tm = tm;
-	pmd->nb_tm = dm_tm_create_non_blocking_clone(tm);
-	if (!pmd->nb_tm) {
-		DMERR("could not create clone tm");
-		r = -ENOMEM;
-		goto bad_data_sm;
-	}
-
-	pmd->info.tm = tm;
+	pmd->info.tm = pmd->tm;
 	pmd->info.levels = 2;
 	pmd->info.value_type.context = pmd->data_sm;
 	pmd->info.value_type.size = sizeof(__le64);
@@ -441,7 +406,7 @@ static int init_pmd(struct dm_pool_metadata *pmd,
 	memcpy(&pmd->nb_info, &pmd->info, sizeof(pmd->nb_info));
 	pmd->nb_info.tm = pmd->nb_tm;
 
-	pmd->tl_info.tm = tm;
+	pmd->tl_info.tm = pmd->tm;
 	pmd->tl_info.levels = 1;
 	pmd->tl_info.value_type.context = &pmd->info;
 	pmd->tl_info.value_type.size = sizeof(__le64);
@@ -449,7 +414,7 @@ static int init_pmd(struct dm_pool_metadata *pmd,
 	pmd->tl_info.value_type.dec = subtree_dec;
 	pmd->tl_info.value_type.equal = subtree_equal;
 
-	pmd->bl_info.tm = tm;
+	pmd->bl_info.tm = pmd->tm;
 	pmd->bl_info.levels = 1;
 	pmd->bl_info.value_type.context = pmd->data_sm;
 	pmd->bl_info.value_type.size = sizeof(__le64);
@@ -457,48 +422,266 @@ static int init_pmd(struct dm_pool_metadata *pmd,
 	pmd->bl_info.value_type.dec = data_block_dec;
 	pmd->bl_info.value_type.equal = data_block_equal;
 
-	pmd->details_info.tm = tm;
+	pmd->details_info.tm = pmd->tm;
 	pmd->details_info.levels = 1;
 	pmd->details_info.value_type.context = NULL;
 	pmd->details_info.value_type.size = sizeof(struct disk_device_details);
 	pmd->details_info.value_type.inc = NULL;
 	pmd->details_info.value_type.dec = NULL;
 	pmd->details_info.value_type.equal = NULL;
+}
 
-	pmd->root = 0;
+static int __write_initial_superblock(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct dm_block *sblock;
+	size_t metadata_len, data_len;
+	struct thin_disk_superblock *disk_super;
+	sector_t bdev_size = i_size_read(pmd->bdev->bd_inode) >> SECTOR_SHIFT;
 
-	init_rwsem(&pmd->root_lock);
-	pmd->time = 0;
-	pmd->need_commit = 0;
-	pmd->details_root = 0;
-	pmd->trans_id = 0;
-	pmd->flags = 0;
-	INIT_LIST_HEAD(&pmd->thin_devices);
+	if (bdev_size > THIN_METADATA_MAX_SECTORS)
+		bdev_size = THIN_METADATA_MAX_SECTORS;
+
+	r = dm_sm_root_size(pmd->metadata_sm, &metadata_len);
+	if (r < 0)
+		return r;
+
+	r = dm_sm_root_size(pmd->data_sm, &data_len);
+	if (r < 0)
+		return r;
+
+	r = dm_sm_commit(pmd->data_sm);
+	if (r < 0)
+		return r;
+
+	r = dm_tm_pre_commit(pmd->tm);
+	if (r < 0)
+		return r;
+
+	r = superblock_lock_zero(pmd, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+	disk_super->flags = 0;
+	memset(disk_super->uuid, 0, sizeof(disk_super->uuid));
+	disk_super->magic = cpu_to_le64(THIN_SUPERBLOCK_MAGIC);
+	disk_super->version = cpu_to_le32(THIN_VERSION);
+	disk_super->time = 0;
+	disk_super->trans_id = 0;
+	disk_super->held_root = 0;
+
+	r = dm_sm_copy_root(pmd->metadata_sm, &disk_super->metadata_space_map_root,
+			    metadata_len);
+	if (r < 0)
+		goto bad_locked;
+
+	r = dm_sm_copy_root(pmd->data_sm, &disk_super->data_space_map_root,
+			    data_len);
+	if (r < 0)
+		goto bad_locked;
+
+	disk_super->data_mapping_root = cpu_to_le64(pmd->root);
+	disk_super->device_details_root = cpu_to_le64(pmd->details_root);
+	disk_super->metadata_block_size = cpu_to_le32(THIN_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);
+	disk_super->metadata_nr_blocks = cpu_to_le64(bdev_size >> SECTOR_TO_BLOCK_SHIFT);
+	disk_super->data_block_size = cpu_to_le32(pmd->data_block_size);
+
+	return dm_tm_commit(pmd->tm, sblock);
+
+bad_locked:
+	dm_bm_unlock(sblock);
+	return r;
+}
+
+static int __format_metadata(struct dm_pool_metadata *pmd)
+{
+	int r;
+
+	r = dm_tm_create_with_sm(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+				 &pmd->tm, &pmd->metadata_sm);
+	if (r < 0) {
+		DMERR("tm_create_with_sm failed");
+		return r;
+	}
+
+	pmd->data_sm = dm_sm_disk_create(pmd->tm, 0);
+	if (IS_ERR(pmd->data_sm)) {
+		DMERR("sm_disk_create failed");
+		r = PTR_ERR(pmd->data_sm);
+		goto bad_cleanup_tm;
+	}
+
+	pmd->nb_tm = dm_tm_create_non_blocking_clone(pmd->tm);
+	if (!pmd->nb_tm) {
+		DMERR("could not create non-blocking clone tm");
+		r = -ENOMEM;
+		goto bad_cleanup_data_sm;
+	}
+
+	__setup_btree_details(pmd);
+
+	r = dm_btree_empty(&pmd->info, &pmd->root);
+	if (r < 0)
+		goto bad_cleanup_nb_tm;
+
+	r = dm_btree_empty(&pmd->details_info, &pmd->details_root);
+	if (r < 0) {
+		DMERR("couldn't create devices root");
+		goto bad_cleanup_nb_tm;
+	}
+
+	r = __write_initial_superblock(pmd);
+	if (r)
+		goto bad_cleanup_nb_tm;
 
 	return 0;
 
-bad_data_sm:
-	dm_sm_destroy(data_sm);
-bad:
-	dm_tm_destroy(tm);
-	dm_sm_destroy(sm);
+bad_cleanup_nb_tm:
+	dm_tm_destroy(pmd->nb_tm);
+bad_cleanup_data_sm:
+	dm_sm_destroy(pmd->data_sm);
+bad_cleanup_tm:
+	dm_tm_destroy(pmd->tm);
+	dm_sm_destroy(pmd->metadata_sm);
+
+	return r;
+}
+
+static int __check_incompat_features(struct thin_disk_superblock *disk_super,
+				     struct dm_pool_metadata *pmd)
+{
+	uint32_t features;
+
+	features = le32_to_cpu(disk_super->incompat_flags) & ~THIN_FEATURE_INCOMPAT_SUPP;
+	if (features) {
+		DMERR("could not access metadata due to unsupported optional features (%lx).",
+		      (unsigned long)features);
+		return -EINVAL;
+	}
+
+	/*
+	 * Check for read-only metadata to skip the following RDWR checks.
+	 */
+	if (get_disk_ro(pmd->bdev->bd_disk))
+		return 0;
+
+	features = le32_to_cpu(disk_super->compat_ro_flags) & ~THIN_FEATURE_COMPAT_RO_SUPP;
+	if (features) {
+		DMERR("could not access metadata RDWR due to unsupported optional features (%lx).",
+		      (unsigned long)features);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int __open_metadata(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct dm_block *sblock;
+	struct thin_disk_superblock *disk_super;
+
+	r = dm_bm_read_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+			    &sb_validator, &sblock);
+	if (r < 0) {
+		DMERR("couldn't read superblock");
+		return r;
+	}
+
+	disk_super = dm_block_data(sblock);
+
+	r = __check_incompat_features(disk_super, pmd);
+	if (r < 0)
+		goto bad_unlock_sblock;
+
+	r = dm_tm_open_with_sm(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+			       disk_super->metadata_space_map_root,
+			       sizeof(disk_super->metadata_space_map_root),
+			       &pmd->tm, &pmd->metadata_sm);
+	if (r < 0) {
+		DMERR("tm_open_with_sm failed");
+		goto bad_unlock_sblock;
+	}
+
+	pmd->data_sm = dm_sm_disk_open(pmd->tm, disk_super->data_space_map_root,
+				       sizeof(disk_super->data_space_map_root));
+	if (IS_ERR(pmd->data_sm)) {
+		DMERR("sm_disk_open failed");
+		r = PTR_ERR(pmd->data_sm);
+		goto bad_cleanup_tm;
+	}
+
+	pmd->nb_tm = dm_tm_create_non_blocking_clone(pmd->tm);
+	if (!pmd->nb_tm) {
+		DMERR("could not create non-blocking clone tm");
+		r = -ENOMEM;
+		goto bad_cleanup_data_sm;
+	}
+
+	__setup_btree_details(pmd);
+	return dm_bm_unlock(sblock);
+
+bad_cleanup_data_sm:
+	dm_sm_destroy(pmd->data_sm);
+bad_cleanup_tm:
+	dm_tm_destroy(pmd->tm);
+	dm_sm_destroy(pmd->metadata_sm);
+bad_unlock_sblock:
+	dm_bm_unlock(sblock);
+
+	return r;
+}
+
+static int __open_or_format_metadata(struct dm_pool_metadata *pmd, bool format_device)
+{
+	int r, unformatted;
+
+	r = __superblock_all_zeroes(pmd->bm, &unformatted);
+	if (r)
+		return r;
+
+	if (unformatted)
+		return format_device ? __format_metadata(pmd) : -EPERM;
+
+	return __open_metadata(pmd);
+}
+
+static int __create_persistent_data_objects(struct dm_pool_metadata *pmd, bool format_device)
+{
+	int r;
+
+	pmd->bm = dm_block_manager_create(pmd->bdev, THIN_METADATA_BLOCK_SIZE,
+					  THIN_METADATA_CACHE_SIZE,
+					  THIN_MAX_CONCURRENT_LOCKS);
+	if (IS_ERR(pmd->bm)) {
+		DMERR("could not create block manager");
+		return PTR_ERR(pmd->bm);
+	}
+
+	r = __open_or_format_metadata(pmd, format_device);
+	if (r)
+		dm_block_manager_destroy(pmd->bm);
 
 	return r;
 }
 
+static void __destroy_persistent_data_objects(struct dm_pool_metadata *pmd)
+{
+	dm_sm_destroy(pmd->data_sm);
+	dm_sm_destroy(pmd->metadata_sm);
+	dm_tm_destroy(pmd->nb_tm);
+	dm_tm_destroy(pmd->tm);
+	dm_block_manager_destroy(pmd->bm);
+}
+
 static int __begin_transaction(struct dm_pool_metadata *pmd)
 {
 	int r;
-	u32 features;
 	struct thin_disk_superblock *disk_super;
 	struct dm_block *sblock;
 
 	/*
-	 * __maybe_commit_transaction() resets these
-	 */
-	WARN_ON(pmd->need_commit);
-
-	/*
 	 * We re-read the superblock every time.  Shouldn't need to do this
 	 * really.
 	 */
@@ -515,32 +698,8 @@ static int __begin_transaction(struct dm_pool_metadata *pmd)
 	pmd->flags = le32_to_cpu(disk_super->flags);
 	pmd->data_block_size = le32_to_cpu(disk_super->data_block_size);
 
-	features = le32_to_cpu(disk_super->incompat_flags) & ~THIN_FEATURE_INCOMPAT_SUPP;
-	if (features) {
-		DMERR("could not access metadata due to "
-		      "unsupported optional features (%lx).",
-		      (unsigned long)features);
-		r = -EINVAL;
-		goto out;
-	}
-
-	/*
-	 * Check for read-only metadata to skip the following RDWR checks.
-	 */
-	if (get_disk_ro(pmd->bdev->bd_disk))
-		goto out;
-
-	features = le32_to_cpu(disk_super->compat_ro_flags) & ~THIN_FEATURE_COMPAT_RO_SUPP;
-	if (features) {
-		DMERR("could not access metadata RDWR due to "
-		      "unsupported optional features (%lx).",
-		      (unsigned long)features);
-		r = -EINVAL;
-	}
-
-out:
 	dm_bm_unlock(sblock);
-	return r;
+	return 0;
 }
 
 static int __write_changed_details(struct dm_pool_metadata *pmd)
@@ -573,8 +732,6 @@ static int __write_changed_details(struct dm_pool_metadata *pmd)
 			list_del(&td->list);
 			kfree(td);
 		}
-
-		pmd->need_commit = 1;
 	}
 
 	return 0;
@@ -582,9 +739,6 @@ static int __write_changed_details(struct dm_pool_metadata *pmd)
 
 static int __commit_transaction(struct dm_pool_metadata *pmd)
 {
-	/*
-	 * FIXME: Associated pool should be made read-only on failure.
-	 */
 	int r;
 	size_t metadata_len, data_len;
 	struct thin_disk_superblock *disk_super;
@@ -597,31 +751,27 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
 
 	r = __write_changed_details(pmd);
 	if (r < 0)
-		goto out;
-
-	if (!pmd->need_commit)
-		goto out;
+		return r;
 
 	r = dm_sm_commit(pmd->data_sm);
 	if (r < 0)
-		goto out;
+		return r;
 
 	r = dm_tm_pre_commit(pmd->tm);
 	if (r < 0)
-		goto out;
+		return r;
 
 	r = dm_sm_root_size(pmd->metadata_sm, &metadata_len);
 	if (r < 0)
-		goto out;
+		return r;
 
 	r = dm_sm_root_size(pmd->data_sm, &data_len);
 	if (r < 0)
-		goto out;
+		return r;
 
-	r = dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
-			     &sb_validator, &sblock);
+	r = superblock_lock(pmd, &sblock);
 	if (r)
-		goto out;
+		return r;
 
 	disk_super = dm_block_data(sblock);
 	disk_super->time = cpu_to_le32(pmd->time);
@@ -640,12 +790,7 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
 	if (r < 0)
 		goto out_locked;
 
-	r = dm_tm_commit(pmd->tm, sblock);
-	if (!r)
-		pmd->need_commit = 0;
-
-out:
-	return r;
+	return dm_tm_commit(pmd->tm, sblock);
 
 out_locked:
 	dm_bm_unlock(sblock);
@@ -653,15 +798,11 @@ out_locked:
 }
 
 struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
-					       sector_t data_block_size)
+					       sector_t data_block_size,
+					       bool format_device)
 {
 	int r;
-	struct thin_disk_superblock *disk_super;
 	struct dm_pool_metadata *pmd;
-	sector_t bdev_size = i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
-	struct dm_block_manager *bm;
-	int create;
-	struct dm_block *sblock;
 
 	pmd = kmalloc(sizeof(*pmd), GFP_KERNEL);
 	if (!pmd) {
@@ -669,90 +810,28 @@ struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
 		return ERR_PTR(-ENOMEM);
 	}
 
-	/*
-	 * Max hex locks:
-	 *  3 for btree insert +
-	 *  2 for btree lookup used within space map
-	 */
-	bm = dm_block_manager_create(bdev, THIN_METADATA_BLOCK_SIZE,
-				     THIN_METADATA_CACHE_SIZE, 5);
-	if (!bm) {
-		DMERR("could not create block manager");
-		kfree(pmd);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	r = superblock_all_zeroes(bm, &create);
-	if (r) {
-		dm_block_manager_destroy(bm);
-		kfree(pmd);
-		return ERR_PTR(r);
-	}
-
+	init_rwsem(&pmd->root_lock);
+	pmd->time = 0;
+	INIT_LIST_HEAD(&pmd->thin_devices);
+	pmd->read_only = false;
+	pmd->fail_io = false;
+	pmd->bdev = bdev;
+	pmd->data_block_size = data_block_size;
 
-	r = init_pmd(pmd, bm, 0, create);
+	r = __create_persistent_data_objects(pmd, format_device);
 	if (r) {
-		dm_block_manager_destroy(bm);
 		kfree(pmd);
 		return ERR_PTR(r);
 	}
-	pmd->bdev = bdev;
-
-	if (!create) {
-		r = __begin_transaction(pmd);
-		if (r < 0)
-			goto bad;
-		return pmd;
-	}
-
-	/*
-	 * Create.
-	 */
-	r = dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
-			     &sb_validator, &sblock);
-	if (r)
-		goto bad;
-
-	if (bdev_size > THIN_METADATA_MAX_SECTORS)
-		bdev_size = THIN_METADATA_MAX_SECTORS;
-
-	disk_super = dm_block_data(sblock);
-	disk_super->magic = cpu_to_le64(THIN_SUPERBLOCK_MAGIC);
-	disk_super->version = cpu_to_le32(THIN_VERSION);
-	disk_super->time = 0;
-	disk_super->metadata_block_size = cpu_to_le32(THIN_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);
-	disk_super->metadata_nr_blocks = cpu_to_le64(bdev_size >> SECTOR_TO_BLOCK_SHIFT);
-	disk_super->data_block_size = cpu_to_le32(data_block_size);
-
-	r = dm_bm_unlock(sblock);
-	if (r < 0)
-		goto bad;
-
-	r = dm_btree_empty(&pmd->info, &pmd->root);
-	if (r < 0)
-		goto bad;
-
-	r = dm_btree_empty(&pmd->details_info, &pmd->details_root);
-	if (r < 0) {
-		DMERR("couldn't create devices root");
-		goto bad;
-	}
 
-	pmd->flags = 0;
-	pmd->need_commit = 1;
-	r = dm_pool_commit_metadata(pmd);
+	r = __begin_transaction(pmd);
 	if (r < 0) {
-		DMERR("%s: dm_pool_commit_metadata() failed, error = %d",
-		      __func__, r);
-		goto bad;
+		if (dm_pool_metadata_close(pmd) < 0)
+			DMWARN("%s: dm_pool_metadata_close() failed.", __func__);
+		return ERR_PTR(r);
 	}
 
 	return pmd;
-
-bad:
-	if (dm_pool_metadata_close(pmd) < 0)
-		DMWARN("%s: dm_pool_metadata_close() failed.", __func__);
-	return ERR_PTR(r);
 }
 
 int dm_pool_metadata_close(struct dm_pool_metadata *pmd)
@@ -778,18 +857,17 @@ int dm_pool_metadata_close(struct dm_pool_metadata *pmd)
 		return -EBUSY;
 	}
 
-	r = __commit_transaction(pmd);
-	if (r < 0)
-		DMWARN("%s: __commit_transaction() failed, error = %d",
-		       __func__, r);
+	if (!pmd->read_only && !pmd->fail_io) {
+		r = __commit_transaction(pmd);
+		if (r < 0)
+			DMWARN("%s: __commit_transaction() failed, error = %d",
+			       __func__, r);
+	}
 
-	dm_tm_destroy(pmd->tm);
-	dm_tm_destroy(pmd->nb_tm);
-	dm_block_manager_destroy(pmd->bm);
-	dm_sm_destroy(pmd->metadata_sm);
-	dm_sm_destroy(pmd->data_sm);
-	kfree(pmd);
+	if (!pmd->fail_io)
+		__destroy_persistent_data_objects(pmd);
 
+	kfree(pmd);
 	return 0;
 }
 
@@ -850,6 +928,7 @@ static int __open_device(struct dm_pool_metadata *pmd,
 	(*td)->id = dev;
 	(*td)->open_count = 1;
 	(*td)->changed = changed;
+	(*td)->aborted_with_changes = false;
 	(*td)->mapped_blocks = le64_to_cpu(details_le.mapped_blocks);
 	(*td)->transaction_id = le64_to_cpu(details_le.transaction_id);
 	(*td)->creation_time = le32_to_cpu(details_le.creation_time);
@@ -911,10 +990,11 @@ static int __create_thin(struct dm_pool_metadata *pmd,
 
 int dm_pool_create_thin(struct dm_pool_metadata *pmd, dm_thin_id dev)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __create_thin(pmd, dev);
+	if (!pmd->fail_io)
+		r = __create_thin(pmd, dev);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1001,10 +1081,11 @@ int dm_pool_create_snap(struct dm_pool_metadata *pmd,
 				 dm_thin_id dev,
 				 dm_thin_id origin)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __create_snap(pmd, dev, origin);
+	if (!pmd->fail_io)
+		r = __create_snap(pmd, dev, origin);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1037,18 +1118,17 @@ static int __delete_device(struct dm_pool_metadata *pmd, dm_thin_id dev)
 	if (r)
 		return r;
 
-	pmd->need_commit = 1;
-
 	return 0;
 }
 
 int dm_pool_delete_thin_device(struct dm_pool_metadata *pmd,
 			       dm_thin_id dev)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __delete_device(pmd, dev);
+	if (!pmd->fail_io)
+		r = __delete_device(pmd, dev);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1058,28 +1138,40 @@ int dm_pool_set_metadata_transaction_id(struct dm_pool_metadata *pmd,
 					uint64_t current_id,
 					uint64_t new_id)
 {
+	int r = -EINVAL;
+
 	down_write(&pmd->root_lock);
+
+	if (pmd->fail_io)
+		goto out;
+
 	if (pmd->trans_id != current_id) {
-		up_write(&pmd->root_lock);
 		DMERR("mismatched transaction id");
-		return -EINVAL;
+		goto out;
 	}
 
 	pmd->trans_id = new_id;
-	pmd->need_commit = 1;
+	r = 0;
+
+out:
 	up_write(&pmd->root_lock);
 
-	return 0;
+	return r;
 }
 
 int dm_pool_get_metadata_transaction_id(struct dm_pool_metadata *pmd,
 					uint64_t *result)
 {
+	int r = -EINVAL;
+
 	down_read(&pmd->root_lock);
-	*result = pmd->trans_id;
+	if (!pmd->fail_io) {
+		*result = pmd->trans_id;
+		r = 0;
+	}
 	up_read(&pmd->root_lock);
 
-	return 0;
+	return r;
 }
 
 static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
@@ -1108,8 +1200,6 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 
 		dm_tm_dec(pmd->tm, held_root);
 		dm_tm_unlock(pmd->tm, copy);
-		pmd->need_commit = 1;
-
 		return -EBUSY;
 	}
 
@@ -1131,29 +1221,25 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
 	/*
 	 * Write the held root into the superblock.
 	 */
-	r = dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
-			     &sb_validator, &sblock);
+	r = superblock_lock(pmd, &sblock);
 	if (r) {
 		dm_tm_dec(pmd->tm, held_root);
-		pmd->need_commit = 1;
 		return r;
 	}
 
 	disk_super = dm_block_data(sblock);
 	disk_super->held_root = cpu_to_le64(held_root);
 	dm_bm_unlock(sblock);
-
-	pmd->need_commit = 1;
-
 	return 0;
 }
 
 int dm_pool_reserve_metadata_snap(struct dm_pool_metadata *pmd)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __reserve_metadata_snap(pmd);
+	if (!pmd->fail_io)
+		r = __reserve_metadata_snap(pmd);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1166,15 +1252,13 @@ static int __release_metadata_snap(struct dm_pool_metadata *pmd)
 	struct dm_block *sblock, *copy;
 	dm_block_t held_root;
 
-	r = dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
-			     &sb_validator, &sblock);
+	r = superblock_lock(pmd, &sblock);
 	if (r)
 		return r;
 
 	disk_super = dm_block_data(sblock);
 	held_root = le64_to_cpu(disk_super->held_root);
 	disk_super->held_root = cpu_to_le64(0);
-	pmd->need_commit = 1;
 
 	dm_bm_unlock(sblock);
 
@@ -1197,10 +1281,11 @@ static int __release_metadata_snap(struct dm_pool_metadata *pmd)
 
 int dm_pool_release_metadata_snap(struct dm_pool_metadata *pmd)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __release_metadata_snap(pmd);
+	if (!pmd->fail_io)
+		r = __release_metadata_snap(pmd);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1227,10 +1312,11 @@ static int __get_metadata_snap(struct dm_pool_metadata *pmd,
 int dm_pool_get_metadata_snap(struct dm_pool_metadata *pmd,
 			      dm_block_t *result)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_read(&pmd->root_lock);
-	r = __get_metadata_snap(pmd, result);
+	if (!pmd->fail_io)
+		r = __get_metadata_snap(pmd, result);
 	up_read(&pmd->root_lock);
 
 	return r;
@@ -1239,10 +1325,11 @@ int dm_pool_get_metadata_snap(struct dm_pool_metadata *pmd,
 int dm_pool_open_thin_device(struct dm_pool_metadata *pmd, dm_thin_id dev,
 			     struct dm_thin_device **td)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __open_device(pmd, dev, 0, td);
+	if (!pmd->fail_io)
+		r = __open_device(pmd, dev, 0, td);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1262,7 +1349,7 @@ dm_thin_id dm_thin_dev_id(struct dm_thin_device *td)
 	return td->id;
 }
 
-static int __snapshotted_since(struct dm_thin_device *td, uint32_t time)
+static bool __snapshotted_since(struct dm_thin_device *td, uint32_t time)
 {
 	return td->snapshotted_time > time;
 }
@@ -1270,28 +1357,31 @@ static int __snapshotted_since(struct dm_thin_device *td, uint32_t time)
 int dm_thin_find_block(struct dm_thin_device *td, dm_block_t block,
 		       int can_block, struct dm_thin_lookup_result *result)
 {
-	int r;
+	int r = -EINVAL;
 	uint64_t block_time = 0;
 	__le64 value;
 	struct dm_pool_metadata *pmd = td->pmd;
 	dm_block_t keys[2] = { td->id, block };
+	struct dm_btree_info *info;
 
 	if (can_block) {
 		down_read(&pmd->root_lock);
-		r = dm_btree_lookup(&pmd->info, pmd->root, keys, &value);
-		if (!r)
-			block_time = le64_to_cpu(value);
-		up_read(&pmd->root_lock);
-
-	} else if (down_read_trylock(&pmd->root_lock)) {
-		r = dm_btree_lookup(&pmd->nb_info, pmd->root, keys, &value);
-		if (!r)
-			block_time = le64_to_cpu(value);
-		up_read(&pmd->root_lock);
-
-	} else
+		info = &pmd->info;
+	} else if (down_read_trylock(&pmd->root_lock))
+		info = &pmd->nb_info;
+	else
 		return -EWOULDBLOCK;
 
+	if (pmd->fail_io)
+		goto out;
+
+	r = dm_btree_lookup(info, pmd->root, keys, &value);
+	if (!r)
+		block_time = le64_to_cpu(value);
+
+out:
+	up_read(&pmd->root_lock);
+
 	if (!r) {
 		dm_block_t exception_block;
 		uint32_t exception_time;
@@ -1312,7 +1402,6 @@ static int __insert(struct dm_thin_device *td, dm_block_t block,
 	struct dm_pool_metadata *pmd = td->pmd;
 	dm_block_t keys[2] = { td->id, block };
 
-	pmd->need_commit = 1;
 	value = cpu_to_le64(pack_block_time(data_block, pmd->time));
 	__dm_bless_for_disk(&value);
 
@@ -1321,10 +1410,9 @@ static int __insert(struct dm_thin_device *td, dm_block_t block,
 	if (r)
 		return r;
 
-	if (inserted) {
+	td->changed = 1;
+	if (inserted)
 		td->mapped_blocks++;
-		td->changed = 1;
-	}
 
 	return 0;
 }
@@ -1332,10 +1420,11 @@ static int __insert(struct dm_thin_device *td, dm_block_t block,
 int dm_thin_insert_block(struct dm_thin_device *td, dm_block_t block,
 			 dm_block_t data_block)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&td->pmd->root_lock);
-	r = __insert(td, block, data_block);
+	if (!td->pmd->fail_io)
+		r = __insert(td, block, data_block);
 	up_write(&td->pmd->root_lock);
 
 	return r;
@@ -1353,31 +1442,51 @@ static int __remove(struct dm_thin_device *td, dm_block_t block)
 
 	td->mapped_blocks--;
 	td->changed = 1;
-	pmd->need_commit = 1;
 
 	return 0;
 }
 
 int dm_thin_remove_block(struct dm_thin_device *td, dm_block_t block)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&td->pmd->root_lock);
-	r = __remove(td, block);
+	if (!td->pmd->fail_io)
+		r = __remove(td, block);
 	up_write(&td->pmd->root_lock);
 
 	return r;
 }
 
-int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result)
+bool dm_thin_changed_this_transaction(struct dm_thin_device *td)
 {
 	int r;
 
-	down_write(&pmd->root_lock);
+	down_read(&td->pmd->root_lock);
+	r = td->changed;
+	up_read(&td->pmd->root_lock);
 
-	r = dm_sm_new_block(pmd->data_sm, result);
-	pmd->need_commit = 1;
+	return r;
+}
+
+bool dm_thin_aborted_changes(struct dm_thin_device *td)
+{
+	bool r;
 
+	down_read(&td->pmd->root_lock);
+	r = td->aborted_with_changes;
+	up_read(&td->pmd->root_lock);
+
+	return r;
+}
+
+int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_write(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = dm_sm_new_block(pmd->data_sm, result);
 	up_write(&pmd->root_lock);
 
 	return r;
@@ -1385,9 +1494,11 @@ int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result)
 
 int dm_pool_commit_metadata(struct dm_pool_metadata *pmd)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
+	if (pmd->fail_io)
+		goto out;
 
 	r = __commit_transaction(pmd);
 	if (r <= 0)
@@ -1402,12 +1513,41 @@ out:
 	return r;
 }
 
+static void __set_abort_with_changes_flags(struct dm_pool_metadata *pmd)
+{
+	struct dm_thin_device *td;
+
+	list_for_each_entry(td, &pmd->thin_devices, list)
+		td->aborted_with_changes = td->changed;
+}
+
+int dm_pool_abort_metadata(struct dm_pool_metadata *pmd)
+{
+	int r = -EINVAL;
+
+	down_write(&pmd->root_lock);
+	if (pmd->fail_io)
+		goto out;
+
+	__set_abort_with_changes_flags(pmd);
+	__destroy_persistent_data_objects(pmd);
+	r = __create_persistent_data_objects(pmd, false);
+	if (r)
+		pmd->fail_io = true;
+
+out:
+	up_write(&pmd->root_lock);
+
+	return r;
+}
+
 int dm_pool_get_free_block_count(struct dm_pool_metadata *pmd, dm_block_t *result)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_read(&pmd->root_lock);
-	r = dm_sm_get_nr_free(pmd->data_sm, result);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_free(pmd->data_sm, result);
 	up_read(&pmd->root_lock);
 
 	return r;
@@ -1416,10 +1556,11 @@ int dm_pool_get_free_block_count(struct dm_pool_metadata *pmd, dm_block_t *resul
 int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
 					  dm_block_t *result)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_read(&pmd->root_lock);
-	r = dm_sm_get_nr_free(pmd->metadata_sm, result);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_free(pmd->metadata_sm, result);
 	up_read(&pmd->root_lock);
 
 	return r;
@@ -1428,10 +1569,11 @@ int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
 int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd,
 				  dm_block_t *result)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_read(&pmd->root_lock);
-	r = dm_sm_get_nr_blocks(pmd->metadata_sm, result);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_blocks(pmd->metadata_sm, result);
 	up_read(&pmd->root_lock);
 
 	return r;
@@ -1448,10 +1590,11 @@ int dm_pool_get_data_block_size(struct dm_pool_metadata *pmd, sector_t *result)
 
 int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_read(&pmd->root_lock);
-	r = dm_sm_get_nr_blocks(pmd->data_sm, result);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_blocks(pmd->data_sm, result);
 	up_read(&pmd->root_lock);
 
 	return r;
@@ -1459,13 +1602,17 @@ int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result)
 
 int dm_thin_get_mapped_count(struct dm_thin_device *td, dm_block_t *result)
 {
+	int r = -EINVAL;
 	struct dm_pool_metadata *pmd = td->pmd;
 
 	down_read(&pmd->root_lock);
-	*result = td->mapped_blocks;
+	if (!pmd->fail_io) {
+		*result = td->mapped_blocks;
+		r = 0;
+	}
 	up_read(&pmd->root_lock);
 
-	return 0;
+	return r;
 }
 
 static int __highest_block(struct dm_thin_device *td, dm_block_t *result)
@@ -1487,11 +1634,12 @@ static int __highest_block(struct dm_thin_device *td, dm_block_t *result)
 int dm_thin_get_highest_mapped_block(struct dm_thin_device *td,
 				     dm_block_t *result)
 {
-	int r;
+	int r = -EINVAL;
 	struct dm_pool_metadata *pmd = td->pmd;
 
 	down_read(&pmd->root_lock);
-	r = __highest_block(td, result);
+	if (!pmd->fail_io)
+		r = __highest_block(td, result);
 	up_read(&pmd->root_lock);
 
 	return r;
@@ -1514,20 +1662,25 @@ static int __resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
 		return -EINVAL;
 	}
 
-	r = dm_sm_extend(pmd->data_sm, new_count - old_count);
-	if (!r)
-		pmd->need_commit = 1;
-
-	return r;
+	return dm_sm_extend(pmd->data_sm, new_count - old_count);
 }
 
 int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
 {
-	int r;
+	int r = -EINVAL;
 
 	down_write(&pmd->root_lock);
-	r = __resize_data_dev(pmd, new_count);
+	if (!pmd->fail_io)
+		r = __resize_data_dev(pmd, new_count);
 	up_write(&pmd->root_lock);
 
 	return r;
 }
+
+void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd)
+{
+	down_write(&pmd->root_lock);
+	pmd->read_only = true;
+	dm_bm_set_read_only(pmd->bm);
+	up_write(&pmd->root_lock);
+}