Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2160 insertions, 0 deletions

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
new file mode 100644
index 0000000000..6022189c13
--- /dev/null
+++ b/drivers/md/dm-thin-metadata.c
@@ -0,0 +1,2160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2011-2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-thin-metadata.h"
+#include "persistent-data/dm-btree.h"
+#include "persistent-data/dm-space-map.h"
+#include "persistent-data/dm-space-map-disk.h"
+#include "persistent-data/dm-transaction-manager.h"
+
+#include <linux/list.h>
+#include <linux/device-mapper.h>
+#include <linux/workqueue.h>
+
+/*
+ *--------------------------------------------------------------------------
+ * As far as the metadata goes, there is:
+ *
+ * - A superblock in block zero, taking up fewer than 512 bytes for
+ *   atomic writes.
+ *
+ * - A space map managing the metadata blocks.
+ *
+ * - A space map managing the data blocks.
+ *
+ * - A btree mapping our internal thin dev ids onto struct disk_device_details.
+ *
+ * - A hierarchical btree, with 2 levels which effectively maps (thin
+ *   dev id, virtual block) -> block_time.  Block time is a 64-bit
+ *   field holding the time in the low 24 bits, and block in the top 40
+ *   bits.
+ *
+ * BTrees consist solely of btree_nodes, that fill a block.  Some are
+ * internal nodes, as such their values are a __le64 pointing to other
+ * nodes.  Leaf nodes can store data of any reasonable size (ie. much
+ * smaller than the block size).  The nodes consist of the header,
+ * followed by an array of keys, followed by an array of values.  We have
+ * to binary search on the keys so they're all held together to help the
+ * cpu cache.
+ *
+ * Space maps have 2 btrees:
+ *
+ * - One maps a uint64_t onto a struct index_entry.  Which points to a
+ *   bitmap block, and has some details about how many free entries there
+ *   are etc.
+ *
+ * - The bitmap blocks have a header (for the checksum).  Then the rest
+ *   of the block is pairs of bits.  With the meaning being:
+ *
+ *   0 - ref count is 0
+ *   1 - ref count is 1
+ *   2 - ref count is 2
+ *   3 - ref count is higher than 2
+ *
+ * - If the count is higher than 2 then the ref count is entered in a
+ *   second btree that directly maps the block_address to a uint32_t ref
+ *   count.
+ *
+ * The space map metadata variant doesn't have a bitmaps btree.  Instead
+ * it has one single blocks worth of index_entries.  This avoids
+ * recursive issues with the bitmap btree needing to allocate space in
+ * order to insert.  With a small data block size such as 64k the
+ * metadata support data devices that are hundreds of terrabytes.
+ *
+ * The space maps allocate space linearly from front to back.  Space that
+ * is freed in a transaction is never recycled within that transaction.
+ * To try and avoid fragmenting _free_ space the allocator always goes
+ * back and fills in gaps.
+ *
+ * All metadata io is in THIN_METADATA_BLOCK_SIZE sized/aligned chunks
+ * from the block manager.
+ *--------------------------------------------------------------------------
+ */
+
+#define DM_MSG_PREFIX   "thin metadata"
+
+#define THIN_SUPERBLOCK_MAGIC 27022010
+#define THIN_SUPERBLOCK_LOCATION 0
+#define THIN_VERSION 2
+#define SECTOR_TO_BLOCK_SHIFT 3
+
+/*
+ * For btree insert:
+ *  3 for btree insert +
+ *  2 for btree lookup used within space map
+ * For btree remove:
+ *  2 for shadow spine +
+ *  4 for rebalance 3 child node
+ */
+#define THIN_MAX_CONCURRENT_LOCKS 6
+
+/* This should be plenty */
+#define SPACE_MAP_ROOT_SIZE 128
+
+/*
+ * Little endian on-disk superblock and device details.
+ */
+struct thin_disk_superblock {
+	__le32 csum;	/* Checksum of superblock except for this field. */
+	__le32 flags;
+	__le64 blocknr;	/* This block number, dm_block_t. */
+
+	__u8 uuid[16];
+	__le64 magic;
+	__le32 version;
+	__le32 time;
+
+	__le64 trans_id;
+
+	/*
+	 * Root held by userspace transactions.
+	 */
+	__le64 held_root;
+
+	__u8 data_space_map_root[SPACE_MAP_ROOT_SIZE];
+	__u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
+
+	/*
+	 * 2-level btree mapping (dev_id, (dev block, time)) -> data block
+	 */
+	__le64 data_mapping_root;
+
+	/*
+	 * Device detail root mapping dev_id -> device_details
+	 */
+	__le64 device_details_root;
+
+	__le32 data_block_size;		/* In 512-byte sectors. */
+
+	__le32 metadata_block_size;	/* In 512-byte sectors. */
+	__le64 metadata_nr_blocks;
+
+	__le32 compat_flags;
+	__le32 compat_ro_flags;
+	__le32 incompat_flags;
+} __packed;
+
+struct disk_device_details {
+	__le64 mapped_blocks;
+	__le64 transaction_id;		/* When created. */
+	__le32 creation_time;
+	__le32 snapshotted_time;
+} __packed;
+
+struct dm_pool_metadata {
+	struct hlist_node hash;
+
+	struct block_device *bdev;
+	struct dm_block_manager *bm;
+	struct dm_space_map *metadata_sm;
+	struct dm_space_map *data_sm;
+	struct dm_transaction_manager *tm;
+	struct dm_transaction_manager *nb_tm;
+
+	/*
+	 * Two-level btree.
+	 * First level holds thin_dev_t.
+	 * Second level holds mappings.
+	 */
+	struct dm_btree_info info;
+
+	/*
+	 * Non-blocking version of the above.
+	 */
+	struct dm_btree_info nb_info;
+
+	/*
+	 * Just the top level for deleting whole devices.
+	 */
+	struct dm_btree_info tl_info;
+
+	/*
+	 * Just the bottom level for creating new devices.
+	 */
+	struct dm_btree_info bl_info;
+
+	/*
+	 * Describes the device details btree.
+	 */
+	struct dm_btree_info details_info;
+
+	struct rw_semaphore root_lock;
+	uint32_t time;
+	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;
+
+	/*
+	 * Pre-commit callback.
+	 *
+	 * This allows the thin provisioning target to run a callback before
+	 * the metadata are committed.
+	 */
+	dm_pool_pre_commit_fn pre_commit_fn;
+	void *pre_commit_context;
+
+	/*
+	 * We reserve a section of the metadata for commit overhead.
+	 * All reported space does *not* include this.
+	 */
+	dm_block_t metadata_reserve;
+
+	/*
+	 * 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;
+
+	/*
+	 * Set once a thin-pool has been accessed through one of the interfaces
+	 * that imply the pool is in-service (e.g. thin devices created/deleted,
+	 * thin-pool message, metadata snapshots, etc).
+	 */
+	bool in_service:1;
+
+	/*
+	 * Reading the space map roots can fail, so we read it into these
+	 * buffers before the superblock is locked and updated.
+	 */
+	__u8 data_space_map_root[SPACE_MAP_ROOT_SIZE];
+	__u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
+};
+
+struct dm_thin_device {
+	struct list_head list;
+	struct dm_pool_metadata *pmd;
+	dm_thin_id id;
+
+	int open_count;
+	bool changed:1;
+	bool aborted_with_changes:1;
+	uint64_t mapped_blocks;
+	uint64_t transaction_id;
+	uint32_t creation_time;
+	uint32_t snapshotted_time;
+};
+
+/*
+ *--------------------------------------------------------------
+ * superblock validator
+ *--------------------------------------------------------------
+ */
+#define SUPERBLOCK_CSUM_XOR 160774
+
+static void sb_prepare_for_write(struct dm_block_validator *v,
+				 struct dm_block *b,
+				 size_t block_size)
+{
+	struct thin_disk_superblock *disk_super = dm_block_data(b);
+
+	disk_super->blocknr = cpu_to_le64(dm_block_location(b));
+	disk_super->csum = cpu_to_le32(dm_bm_checksum(&disk_super->flags,
+						      block_size - sizeof(__le32),
+						      SUPERBLOCK_CSUM_XOR));
+}
+
+static int sb_check(struct dm_block_validator *v,
+		    struct dm_block *b,
+		    size_t block_size)
+{
+	struct thin_disk_superblock *disk_super = dm_block_data(b);
+	__le32 csum_le;
+
+	if (dm_block_location(b) != le64_to_cpu(disk_super->blocknr)) {
+		DMERR("%s failed: blocknr %llu: wanted %llu",
+		      __func__, le64_to_cpu(disk_super->blocknr),
+		      (unsigned long long)dm_block_location(b));
+		return -ENOTBLK;
+	}
+
+	if (le64_to_cpu(disk_super->magic) != THIN_SUPERBLOCK_MAGIC) {
+		DMERR("%s failed: magic %llu: wanted %llu",
+		      __func__, le64_to_cpu(disk_super->magic),
+		      (unsigned long long)THIN_SUPERBLOCK_MAGIC);
+		return -EILSEQ;
+	}
+
+	csum_le = cpu_to_le32(dm_bm_checksum(&disk_super->flags,
+					     block_size - sizeof(__le32),
+					     SUPERBLOCK_CSUM_XOR));
+	if (csum_le != disk_super->csum) {
+		DMERR("%s failed: csum %u: wanted %u",
+		      __func__, le32_to_cpu(csum_le), le32_to_cpu(disk_super->csum));
+		return -EILSEQ;
+	}
+
+	return 0;
+}
+
+static struct dm_block_validator sb_validator = {
+	.name = "superblock",
+	.prepare_for_write = sb_prepare_for_write,
+	.check = sb_check
+};
+
+/*
+ *--------------------------------------------------------------
+ * Methods for the btree value types
+ *--------------------------------------------------------------
+ */
+static uint64_t pack_block_time(dm_block_t b, uint32_t t)
+{
+	return (b << 24) | t;
+}
+
+static void unpack_block_time(uint64_t v, dm_block_t *b, uint32_t *t)
+{
+	*b = v >> 24;
+	*t = v & ((1 << 24) - 1);
+}
+
+/*
+ * It's more efficient to call dm_sm_{inc,dec}_blocks as few times as
+ * possible.  'with_runs' reads contiguous runs of blocks, and calls the
+ * given sm function.
+ */
+typedef int (*run_fn)(struct dm_space_map *, dm_block_t, dm_block_t);
+
+static void with_runs(struct dm_space_map *sm, const __le64 *value_le, unsigned int count, run_fn fn)
+{
+	uint64_t b, begin, end;
+	uint32_t t;
+	bool in_run = false;
+	unsigned int i;
+
+	for (i = 0; i < count; i++, value_le++) {
+		/* We know value_le is 8 byte aligned */
+		unpack_block_time(le64_to_cpu(*value_le), &b, &t);
+
+		if (in_run) {
+			if (b == end) {
+				end++;
+			} else {
+				fn(sm, begin, end);
+				begin = b;
+				end = b + 1;
+			}
+		} else {
+			in_run = true;
+			begin = b;
+			end = b + 1;
+		}
+	}
+
+	if (in_run)
+		fn(sm, begin, end);
+}
+
+static void data_block_inc(void *context, const void *value_le, unsigned int count)
+{
+	with_runs((struct dm_space_map *) context,
+		  (const __le64 *) value_le, count, dm_sm_inc_blocks);
+}
+
+static void data_block_dec(void *context, const void *value_le, unsigned int count)
+{
+	with_runs((struct dm_space_map *) context,
+		  (const __le64 *) value_le, count, dm_sm_dec_blocks);
+}
+
+static int data_block_equal(void *context, const void *value1_le, const void *value2_le)
+{
+	__le64 v1_le, v2_le;
+	uint64_t b1, b2;
+	uint32_t t;
+
+	memcpy(&v1_le, value1_le, sizeof(v1_le));
+	memcpy(&v2_le, value2_le, sizeof(v2_le));
+	unpack_block_time(le64_to_cpu(v1_le), &b1, &t);
+	unpack_block_time(le64_to_cpu(v2_le), &b2, &t);
+
+	return b1 == b2;
+}
+
+static void subtree_inc(void *context, const void *value, unsigned int count)
+{
+	struct dm_btree_info *info = context;
+	const __le64 *root_le = value;
+	unsigned int i;
+
+	for (i = 0; i < count; i++, root_le++)
+		dm_tm_inc(info->tm, le64_to_cpu(*root_le));
+}
+
+static void subtree_dec(void *context, const void *value, unsigned int count)
+{
+	struct dm_btree_info *info = context;
+	const __le64 *root_le = value;
+	unsigned int i;
+
+	for (i = 0; i < count; i++, root_le++)
+		if (dm_btree_del(info, le64_to_cpu(*root_le)))
+			DMERR("btree delete failed");
+}
+
+static int subtree_equal(void *context, const void *value1_le, const void *value2_le)
+{
+	__le64 v1_le, v2_le;
+
+	memcpy(&v1_le, value1_le, sizeof(v1_le));
+	memcpy(&v2_le, value2_le, sizeof(v2_le));
+
+	return v1_le == v2_le;
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Variant that is used for in-core only changes or code that
+ * shouldn't put the pool in service on its own (e.g. commit).
+ */
+static inline void pmd_write_lock_in_core(struct dm_pool_metadata *pmd)
+	__acquires(pmd->root_lock)
+{
+	down_write(&pmd->root_lock);
+}
+
+static inline void pmd_write_lock(struct dm_pool_metadata *pmd)
+{
+	pmd_write_lock_in_core(pmd);
+	if (unlikely(!pmd->in_service))
+		pmd->in_service = true;
+}
+
+static inline void pmd_write_unlock(struct dm_pool_metadata *pmd)
+	__releases(pmd->root_lock)
+{
+	up_write(&pmd->root_lock);
+}
+
+/*----------------------------------------------------------------*/
+
+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 int i;
+	struct dm_block *b;
+	__le64 *data_le, zero = cpu_to_le64(0);
+	unsigned int block_size = dm_bm_block_size(bm) / sizeof(__le64);
+
+	/*
+	 * We can't use a validator here - it may be all zeroes.
+	 */
+	r = dm_bm_read_lock(bm, THIN_SUPERBLOCK_LOCATION, NULL, &b);
+	if (r)
+		return r;
+
+	data_le = dm_block_data(b);
+	*result = 1;
+	for (i = 0; i < block_size; i++) {
+		if (data_le[i] != zero) {
+			*result = 0;
+			break;
+		}
+	}
+
+	dm_bm_unlock(b);
+
+	return 0;
+}
+
+static void __setup_btree_details(struct dm_pool_metadata *pmd)
+{
+	pmd->info.tm = pmd->tm;
+	pmd->info.levels = 2;
+	pmd->info.value_type.context = pmd->data_sm;
+	pmd->info.value_type.size = sizeof(__le64);
+	pmd->info.value_type.inc = data_block_inc;
+	pmd->info.value_type.dec = data_block_dec;
+	pmd->info.value_type.equal = data_block_equal;
+
+	memcpy(&pmd->nb_info, &pmd->info, sizeof(pmd->nb_info));
+	pmd->nb_info.tm = pmd->nb_tm;
+
+	pmd->tl_info.tm = pmd->tm;
+	pmd->tl_info.levels = 1;
+	pmd->tl_info.value_type.context = &pmd->bl_info;
+	pmd->tl_info.value_type.size = sizeof(__le64);
+	pmd->tl_info.value_type.inc = subtree_inc;
+	pmd->tl_info.value_type.dec = subtree_dec;
+	pmd->tl_info.value_type.equal = subtree_equal;
+
+	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);
+	pmd->bl_info.value_type.inc = data_block_inc;
+	pmd->bl_info.value_type.dec = data_block_dec;
+	pmd->bl_info.value_type.equal = data_block_equal;
+
+	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;
+}
+
+static int save_sm_roots(struct dm_pool_metadata *pmd)
+{
+	int r;
+	size_t len;
+
+	r = dm_sm_root_size(pmd->metadata_sm, &len);
+	if (r < 0)
+		return r;
+
+	r = dm_sm_copy_root(pmd->metadata_sm, &pmd->metadata_space_map_root, len);
+	if (r < 0)
+		return r;
+
+	r = dm_sm_root_size(pmd->data_sm, &len);
+	if (r < 0)
+		return r;
+
+	return dm_sm_copy_root(pmd->data_sm, &pmd->data_space_map_root, len);
+}
+
+static void copy_sm_roots(struct dm_pool_metadata *pmd,
+			  struct thin_disk_superblock *disk)
+{
+	memcpy(&disk->metadata_space_map_root,
+	       &pmd->metadata_space_map_root,
+	       sizeof(pmd->metadata_space_map_root));
+
+	memcpy(&disk->data_space_map_root,
+	       &pmd->data_space_map_root,
+	       sizeof(pmd->data_space_map_root));
+}
+
+static int __write_initial_superblock(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct dm_block *sblock;
+	struct thin_disk_superblock *disk_super;
+	sector_t bdev_size = bdev_nr_sectors(pmd->bdev);
+
+	if (bdev_size > THIN_METADATA_MAX_SECTORS)
+		bdev_size = THIN_METADATA_MAX_SECTORS;
+
+	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 = save_sm_roots(pmd);
+	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;
+
+	copy_sm_roots(pmd, disk_super);
+
+	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);
+	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);
+}
+
+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) {
+		pmd->tm = NULL;
+		pmd->metadata_sm = NULL;
+		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);
+		pmd->data_sm = NULL;
+		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_cleanup_nb_tm:
+	dm_tm_destroy(pmd->nb_tm);
+	pmd->nb_tm = NULL;
+bad_cleanup_data_sm:
+	dm_sm_destroy(pmd->data_sm);
+	pmd->data_sm = NULL;
+bad_cleanup_tm:
+	dm_tm_destroy(pmd->tm);
+	pmd->tm = NULL;
+	dm_sm_destroy(pmd->metadata_sm);
+	pmd->metadata_sm = NULL;
+
+	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 (bdev_read_only(pmd->bdev))
+		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);
+
+	/* Verify the data block size hasn't changed */
+	if (le32_to_cpu(disk_super->data_block_size) != pmd->data_block_size) {
+		DMERR("changing the data block size (from %u to %llu) is not supported",
+		      le32_to_cpu(disk_super->data_block_size),
+		      (unsigned long long)pmd->data_block_size);
+		r = -EINVAL;
+		goto bad_unlock_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) {
+		pmd->tm = NULL;
+		pmd->metadata_sm = NULL;
+		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);
+		pmd->data_sm = NULL;
+		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;
+	}
+
+	/*
+	 * For pool metadata opening process, root setting is redundant
+	 * because it will be set again in __begin_transaction(). But dm
+	 * pool aborting process really needs to get last transaction's
+	 * root to avoid accessing broken btree.
+	 */
+	pmd->root = le64_to_cpu(disk_super->data_mapping_root);
+	pmd->details_root = le64_to_cpu(disk_super->device_details_root);
+
+	__setup_btree_details(pmd);
+	dm_bm_unlock(sblock);
+
+	return 0;
+
+bad_cleanup_data_sm:
+	dm_sm_destroy(pmd->data_sm);
+	pmd->data_sm = NULL;
+bad_cleanup_tm:
+	dm_tm_destroy(pmd->tm);
+	pmd->tm = NULL;
+	dm_sm_destroy(pmd->metadata_sm);
+	pmd->metadata_sm = NULL;
+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 << SECTOR_SHIFT,
+					  THIN_MAX_CONCURRENT_LOCKS);
+	if (IS_ERR(pmd->bm)) {
+		DMERR("could not create block manager");
+		r = PTR_ERR(pmd->bm);
+		pmd->bm = NULL;
+		return r;
+	}
+
+	r = __open_or_format_metadata(pmd, format_device);
+	if (r) {
+		dm_block_manager_destroy(pmd->bm);
+		pmd->bm = NULL;
+	}
+
+	return r;
+}
+
+static void __destroy_persistent_data_objects(struct dm_pool_metadata *pmd,
+					      bool destroy_bm)
+{
+	dm_sm_destroy(pmd->data_sm);
+	pmd->data_sm = NULL;
+	dm_sm_destroy(pmd->metadata_sm);
+	pmd->metadata_sm = NULL;
+	dm_tm_destroy(pmd->nb_tm);
+	pmd->nb_tm = NULL;
+	dm_tm_destroy(pmd->tm);
+	pmd->tm = NULL;
+	if (destroy_bm)
+		dm_block_manager_destroy(pmd->bm);
+}
+
+static int __begin_transaction(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct thin_disk_superblock *disk_super;
+	struct dm_block *sblock;
+
+	/*
+	 * We re-read the superblock every time.  Shouldn't need to do this
+	 * really.
+	 */
+	r = dm_bm_read_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+			    &sb_validator, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+	pmd->time = le32_to_cpu(disk_super->time);
+	pmd->root = le64_to_cpu(disk_super->data_mapping_root);
+	pmd->details_root = le64_to_cpu(disk_super->device_details_root);
+	pmd->trans_id = le64_to_cpu(disk_super->trans_id);
+	pmd->flags = le32_to_cpu(disk_super->flags);
+	pmd->data_block_size = le32_to_cpu(disk_super->data_block_size);
+
+	dm_bm_unlock(sblock);
+	return 0;
+}
+
+static int __write_changed_details(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct dm_thin_device *td, *tmp;
+	struct disk_device_details details;
+	uint64_t key;
+
+	list_for_each_entry_safe(td, tmp, &pmd->thin_devices, list) {
+		if (!td->changed)
+			continue;
+
+		key = td->id;
+
+		details.mapped_blocks = cpu_to_le64(td->mapped_blocks);
+		details.transaction_id = cpu_to_le64(td->transaction_id);
+		details.creation_time = cpu_to_le32(td->creation_time);
+		details.snapshotted_time = cpu_to_le32(td->snapshotted_time);
+		__dm_bless_for_disk(&details);
+
+		r = dm_btree_insert(&pmd->details_info, pmd->details_root,
+				    &key, &details, &pmd->details_root);
+		if (r)
+			return r;
+
+		if (td->open_count)
+			td->changed = false;
+		else {
+			list_del(&td->list);
+			kfree(td);
+		}
+	}
+
+	return 0;
+}
+
+static int __commit_transaction(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct thin_disk_superblock *disk_super;
+	struct dm_block *sblock;
+
+	/*
+	 * We need to know if the thin_disk_superblock exceeds a 512-byte sector.
+	 */
+	BUILD_BUG_ON(sizeof(struct thin_disk_superblock) > 512);
+	BUG_ON(!rwsem_is_locked(&pmd->root_lock));
+
+	if (unlikely(!pmd->in_service))
+		return 0;
+
+	if (pmd->pre_commit_fn) {
+		r = pmd->pre_commit_fn(pmd->pre_commit_context);
+		if (r < 0) {
+			DMERR("pre-commit callback failed");
+			return r;
+		}
+	}
+
+	r = __write_changed_details(pmd);
+	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 = save_sm_roots(pmd);
+	if (r < 0)
+		return r;
+
+	r = superblock_lock(pmd, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+	disk_super->time = cpu_to_le32(pmd->time);
+	disk_super->data_mapping_root = cpu_to_le64(pmd->root);
+	disk_super->device_details_root = cpu_to_le64(pmd->details_root);
+	disk_super->trans_id = cpu_to_le64(pmd->trans_id);
+	disk_super->flags = cpu_to_le32(pmd->flags);
+
+	copy_sm_roots(pmd, disk_super);
+
+	return dm_tm_commit(pmd->tm, sblock);
+}
+
+static void __set_metadata_reserve(struct dm_pool_metadata *pmd)
+{
+	int r;
+	dm_block_t total;
+	dm_block_t max_blocks = 4096; /* 16M */
+
+	r = dm_sm_get_nr_blocks(pmd->metadata_sm, &total);
+	if (r) {
+		DMERR("could not get size of metadata device");
+		pmd->metadata_reserve = max_blocks;
+	} else
+		pmd->metadata_reserve = min(max_blocks, div_u64(total, 10));
+}
+
+struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
+					       sector_t data_block_size,
+					       bool format_device)
+{
+	int r;
+	struct dm_pool_metadata *pmd;
+
+	pmd = kmalloc(sizeof(*pmd), GFP_KERNEL);
+	if (!pmd) {
+		DMERR("could not allocate metadata struct");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	init_rwsem(&pmd->root_lock);
+	pmd->time = 0;
+	INIT_LIST_HEAD(&pmd->thin_devices);
+	pmd->fail_io = false;
+	pmd->in_service = false;
+	pmd->bdev = bdev;
+	pmd->data_block_size = data_block_size;
+	pmd->pre_commit_fn = NULL;
+	pmd->pre_commit_context = NULL;
+
+	r = __create_persistent_data_objects(pmd, format_device);
+	if (r) {
+		kfree(pmd);
+		return ERR_PTR(r);
+	}
+
+	r = __begin_transaction(pmd);
+	if (r < 0) {
+		if (dm_pool_metadata_close(pmd) < 0)
+			DMWARN("%s: dm_pool_metadata_close() failed.", __func__);
+		return ERR_PTR(r);
+	}
+
+	__set_metadata_reserve(pmd);
+
+	return pmd;
+}
+
+int dm_pool_metadata_close(struct dm_pool_metadata *pmd)
+{
+	int r;
+	unsigned int open_devices = 0;
+	struct dm_thin_device *td, *tmp;
+
+	down_read(&pmd->root_lock);
+	list_for_each_entry_safe(td, tmp, &pmd->thin_devices, list) {
+		if (td->open_count)
+			open_devices++;
+		else {
+			list_del(&td->list);
+			kfree(td);
+		}
+	}
+	up_read(&pmd->root_lock);
+
+	if (open_devices) {
+		DMERR("attempt to close pmd when %u device(s) are still open",
+		       open_devices);
+		return -EBUSY;
+	}
+
+	pmd_write_lock_in_core(pmd);
+	if (!pmd->fail_io && !dm_bm_is_read_only(pmd->bm)) {
+		r = __commit_transaction(pmd);
+		if (r < 0)
+			DMWARN("%s: __commit_transaction() failed, error = %d",
+			       __func__, r);
+	}
+	pmd_write_unlock(pmd);
+	__destroy_persistent_data_objects(pmd, true);
+
+	kfree(pmd);
+	return 0;
+}
+
+/*
+ * __open_device: Returns @td corresponding to device with id @dev,
+ * creating it if @create is set and incrementing @td->open_count.
+ * On failure, @td is undefined.
+ */
+static int __open_device(struct dm_pool_metadata *pmd,
+			 dm_thin_id dev, int create,
+			 struct dm_thin_device **td)
+{
+	int r, changed = 0;
+	struct dm_thin_device *td2;
+	uint64_t key = dev;
+	struct disk_device_details details_le;
+
+	/*
+	 * If the device is already open, return it.
+	 */
+	list_for_each_entry(td2, &pmd->thin_devices, list)
+		if (td2->id == dev) {
+			/*
+			 * May not create an already-open device.
+			 */
+			if (create)
+				return -EEXIST;
+
+			td2->open_count++;
+			*td = td2;
+			return 0;
+		}
+
+	/*
+	 * Check the device exists.
+	 */
+	r = dm_btree_lookup(&pmd->details_info, pmd->details_root,
+			    &key, &details_le);
+	if (r) {
+		if (r != -ENODATA || !create)
+			return r;
+
+		/*
+		 * Create new device.
+		 */
+		changed = 1;
+		details_le.mapped_blocks = 0;
+		details_le.transaction_id = cpu_to_le64(pmd->trans_id);
+		details_le.creation_time = cpu_to_le32(pmd->time);
+		details_le.snapshotted_time = cpu_to_le32(pmd->time);
+	}
+
+	*td = kmalloc(sizeof(**td), GFP_NOIO);
+	if (!*td)
+		return -ENOMEM;
+
+	(*td)->pmd = 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);
+	(*td)->snapshotted_time = le32_to_cpu(details_le.snapshotted_time);
+
+	list_add(&(*td)->list, &pmd->thin_devices);
+
+	return 0;
+}
+
+static void __close_device(struct dm_thin_device *td)
+{
+	--td->open_count;
+}
+
+static int __create_thin(struct dm_pool_metadata *pmd,
+			 dm_thin_id dev)
+{
+	int r;
+	dm_block_t dev_root;
+	uint64_t key = dev;
+	struct dm_thin_device *td;
+	__le64 value;
+
+	r = dm_btree_lookup(&pmd->details_info, pmd->details_root,
+			    &key, NULL);
+	if (!r)
+		return -EEXIST;
+
+	/*
+	 * Create an empty btree for the mappings.
+	 */
+	r = dm_btree_empty(&pmd->bl_info, &dev_root);
+	if (r)
+		return r;
+
+	/*
+	 * Insert it into the main mapping tree.
+	 */
+	value = cpu_to_le64(dev_root);
+	__dm_bless_for_disk(&value);
+	r = dm_btree_insert(&pmd->tl_info, pmd->root, &key, &value, &pmd->root);
+	if (r) {
+		dm_btree_del(&pmd->bl_info, dev_root);
+		return r;
+	}
+
+	r = __open_device(pmd, dev, 1, &td);
+	if (r) {
+		dm_btree_remove(&pmd->tl_info, pmd->root, &key, &pmd->root);
+		dm_btree_del(&pmd->bl_info, dev_root);
+		return r;
+	}
+	__close_device(td);
+
+	return r;
+}
+
+int dm_pool_create_thin(struct dm_pool_metadata *pmd, dm_thin_id dev)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = __create_thin(pmd, dev);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+static int __set_snapshot_details(struct dm_pool_metadata *pmd,
+				  struct dm_thin_device *snap,
+				  dm_thin_id origin, uint32_t time)
+{
+	int r;
+	struct dm_thin_device *td;
+
+	r = __open_device(pmd, origin, 0, &td);
+	if (r)
+		return r;
+
+	td->changed = true;
+	td->snapshotted_time = time;
+
+	snap->mapped_blocks = td->mapped_blocks;
+	snap->snapshotted_time = time;
+	__close_device(td);
+
+	return 0;
+}
+
+static int __create_snap(struct dm_pool_metadata *pmd,
+			 dm_thin_id dev, dm_thin_id origin)
+{
+	int r;
+	dm_block_t origin_root;
+	uint64_t key = origin, dev_key = dev;
+	struct dm_thin_device *td;
+	__le64 value;
+
+	/* check this device is unused */
+	r = dm_btree_lookup(&pmd->details_info, pmd->details_root,
+			    &dev_key, NULL);
+	if (!r)
+		return -EEXIST;
+
+	/* find the mapping tree for the origin */
+	r = dm_btree_lookup(&pmd->tl_info, pmd->root, &key, &value);
+	if (r)
+		return r;
+	origin_root = le64_to_cpu(value);
+
+	/* clone the origin, an inc will do */
+	dm_tm_inc(pmd->tm, origin_root);
+
+	/* insert into the main mapping tree */
+	value = cpu_to_le64(origin_root);
+	__dm_bless_for_disk(&value);
+	key = dev;
+	r = dm_btree_insert(&pmd->tl_info, pmd->root, &key, &value, &pmd->root);
+	if (r) {
+		dm_tm_dec(pmd->tm, origin_root);
+		return r;
+	}
+
+	pmd->time++;
+
+	r = __open_device(pmd, dev, 1, &td);
+	if (r)
+		goto bad;
+
+	r = __set_snapshot_details(pmd, td, origin, pmd->time);
+	__close_device(td);
+
+	if (r)
+		goto bad;
+
+	return 0;
+
+bad:
+	dm_btree_remove(&pmd->tl_info, pmd->root, &key, &pmd->root);
+	dm_btree_remove(&pmd->details_info, pmd->details_root,
+			&key, &pmd->details_root);
+	return r;
+}
+
+int dm_pool_create_snap(struct dm_pool_metadata *pmd,
+				 dm_thin_id dev,
+				 dm_thin_id origin)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = __create_snap(pmd, dev, origin);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+static int __delete_device(struct dm_pool_metadata *pmd, dm_thin_id dev)
+{
+	int r;
+	uint64_t key = dev;
+	struct dm_thin_device *td;
+
+	/* TODO: failure should mark the transaction invalid */
+	r = __open_device(pmd, dev, 0, &td);
+	if (r)
+		return r;
+
+	if (td->open_count > 1) {
+		__close_device(td);
+		return -EBUSY;
+	}
+
+	list_del(&td->list);
+	kfree(td);
+	r = dm_btree_remove(&pmd->details_info, pmd->details_root,
+			    &key, &pmd->details_root);
+	if (r)
+		return r;
+
+	r = dm_btree_remove(&pmd->tl_info, pmd->root, &key, &pmd->root);
+	if (r)
+		return r;
+
+	return 0;
+}
+
+int dm_pool_delete_thin_device(struct dm_pool_metadata *pmd,
+			       dm_thin_id dev)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = __delete_device(pmd, dev);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+int dm_pool_set_metadata_transaction_id(struct dm_pool_metadata *pmd,
+					uint64_t current_id,
+					uint64_t new_id)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+
+	if (pmd->fail_io)
+		goto out;
+
+	if (pmd->trans_id != current_id) {
+		DMERR("mismatched transaction id");
+		goto out;
+	}
+
+	pmd->trans_id = new_id;
+	r = 0;
+
+out:
+	pmd_write_unlock(pmd);
+
+	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);
+	if (!pmd->fail_io) {
+		*result = pmd->trans_id;
+		r = 0;
+	}
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
+{
+	int r, inc;
+	struct thin_disk_superblock *disk_super;
+	struct dm_block *copy, *sblock;
+	dm_block_t held_root;
+
+	/*
+	 * We commit to ensure the btree roots which we increment in a
+	 * moment are up to date.
+	 */
+	r = __commit_transaction(pmd);
+	if (r < 0) {
+		DMWARN("%s: __commit_transaction() failed, error = %d",
+		       __func__, r);
+		return r;
+	}
+
+	/*
+	 * Copy the superblock.
+	 */
+	dm_sm_inc_block(pmd->metadata_sm, THIN_SUPERBLOCK_LOCATION);
+	r = dm_tm_shadow_block(pmd->tm, THIN_SUPERBLOCK_LOCATION,
+			       &sb_validator, &copy, &inc);
+	if (r)
+		return r;
+
+	BUG_ON(!inc);
+
+	held_root = dm_block_location(copy);
+	disk_super = dm_block_data(copy);
+
+	if (le64_to_cpu(disk_super->held_root)) {
+		DMWARN("Pool metadata snapshot already exists: release this before taking another.");
+
+		dm_tm_dec(pmd->tm, held_root);
+		dm_tm_unlock(pmd->tm, copy);
+		return -EBUSY;
+	}
+
+	/*
+	 * Wipe the spacemap since we're not publishing this.
+	 */
+	memset(&disk_super->data_space_map_root, 0,
+	       sizeof(disk_super->data_space_map_root));
+	memset(&disk_super->metadata_space_map_root, 0,
+	       sizeof(disk_super->metadata_space_map_root));
+
+	/*
+	 * Increment the data structures that need to be preserved.
+	 */
+	dm_tm_inc(pmd->tm, le64_to_cpu(disk_super->data_mapping_root));
+	dm_tm_inc(pmd->tm, le64_to_cpu(disk_super->device_details_root));
+	dm_tm_unlock(pmd->tm, copy);
+
+	/*
+	 * Write the held root into the superblock.
+	 */
+	r = superblock_lock(pmd, &sblock);
+	if (r) {
+		dm_tm_dec(pmd->tm, held_root);
+		return r;
+	}
+
+	disk_super = dm_block_data(sblock);
+	disk_super->held_root = cpu_to_le64(held_root);
+	dm_bm_unlock(sblock);
+	return 0;
+}
+
+int dm_pool_reserve_metadata_snap(struct dm_pool_metadata *pmd)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = __reserve_metadata_snap(pmd);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+static int __release_metadata_snap(struct dm_pool_metadata *pmd)
+{
+	int r;
+	struct thin_disk_superblock *disk_super;
+	struct dm_block *sblock, *copy;
+	dm_block_t held_root;
+
+	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);
+
+	dm_bm_unlock(sblock);
+
+	if (!held_root) {
+		DMWARN("No pool metadata snapshot found: nothing to release.");
+		return -EINVAL;
+	}
+
+	r = dm_tm_read_lock(pmd->tm, held_root, &sb_validator, &copy);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(copy);
+	dm_btree_del(&pmd->info, le64_to_cpu(disk_super->data_mapping_root));
+	dm_btree_del(&pmd->details_info, le64_to_cpu(disk_super->device_details_root));
+	dm_sm_dec_block(pmd->metadata_sm, held_root);
+
+	dm_tm_unlock(pmd->tm, copy);
+
+	return 0;
+}
+
+int dm_pool_release_metadata_snap(struct dm_pool_metadata *pmd)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = __release_metadata_snap(pmd);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+static int __get_metadata_snap(struct dm_pool_metadata *pmd,
+			       dm_block_t *result)
+{
+	int r;
+	struct thin_disk_superblock *disk_super;
+	struct dm_block *sblock;
+
+	r = dm_bm_read_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+			    &sb_validator, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+	*result = le64_to_cpu(disk_super->held_root);
+
+	dm_bm_unlock(sblock);
+
+	return 0;
+}
+
+int dm_pool_get_metadata_snap(struct dm_pool_metadata *pmd,
+			      dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = __get_metadata_snap(pmd, result);
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+int dm_pool_open_thin_device(struct dm_pool_metadata *pmd, dm_thin_id dev,
+			     struct dm_thin_device **td)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock_in_core(pmd);
+	if (!pmd->fail_io)
+		r = __open_device(pmd, dev, 0, td);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+int dm_pool_close_thin_device(struct dm_thin_device *td)
+{
+	pmd_write_lock_in_core(td->pmd);
+	__close_device(td);
+	pmd_write_unlock(td->pmd);
+
+	return 0;
+}
+
+dm_thin_id dm_thin_dev_id(struct dm_thin_device *td)
+{
+	return td->id;
+}
+
+/*
+ * Check whether @time (of block creation) is older than @td's last snapshot.
+ * If so then the associated block is shared with the last snapshot device.
+ * Any block on a device created *after* the device last got snapshotted is
+ * necessarily not shared.
+ */
+static bool __snapshotted_since(struct dm_thin_device *td, uint32_t time)
+{
+	return td->snapshotted_time > time;
+}
+
+static void unpack_lookup_result(struct dm_thin_device *td, __le64 value,
+				 struct dm_thin_lookup_result *result)
+{
+	uint64_t block_time = 0;
+	dm_block_t exception_block;
+	uint32_t exception_time;
+
+	block_time = le64_to_cpu(value);
+	unpack_block_time(block_time, &exception_block, &exception_time);
+	result->block = exception_block;
+	result->shared = __snapshotted_since(td, exception_time);
+}
+
+static int __find_block(struct dm_thin_device *td, dm_block_t block,
+			int can_issue_io, struct dm_thin_lookup_result *result)
+{
+	int r;
+	__le64 value;
+	struct dm_pool_metadata *pmd = td->pmd;
+	dm_block_t keys[2] = { td->id, block };
+	struct dm_btree_info *info;
+
+	if (can_issue_io)
+		info = &pmd->info;
+	else
+		info = &pmd->nb_info;
+
+	r = dm_btree_lookup(info, pmd->root, keys, &value);
+	if (!r)
+		unpack_lookup_result(td, value, result);
+
+	return r;
+}
+
+int dm_thin_find_block(struct dm_thin_device *td, dm_block_t block,
+		       int can_issue_io, struct dm_thin_lookup_result *result)
+{
+	int r;
+	struct dm_pool_metadata *pmd = td->pmd;
+
+	down_read(&pmd->root_lock);
+	if (pmd->fail_io) {
+		up_read(&pmd->root_lock);
+		return -EINVAL;
+	}
+
+	r = __find_block(td, block, can_issue_io, result);
+
+	up_read(&pmd->root_lock);
+	return r;
+}
+
+static int __find_next_mapped_block(struct dm_thin_device *td, dm_block_t block,
+					  dm_block_t *vblock,
+					  struct dm_thin_lookup_result *result)
+{
+	int r;
+	__le64 value;
+	struct dm_pool_metadata *pmd = td->pmd;
+	dm_block_t keys[2] = { td->id, block };
+
+	r = dm_btree_lookup_next(&pmd->info, pmd->root, keys, vblock, &value);
+	if (!r)
+		unpack_lookup_result(td, value, result);
+
+	return r;
+}
+
+static int __find_mapped_range(struct dm_thin_device *td,
+			       dm_block_t begin, dm_block_t end,
+			       dm_block_t *thin_begin, dm_block_t *thin_end,
+			       dm_block_t *pool_begin, bool *maybe_shared)
+{
+	int r;
+	dm_block_t pool_end;
+	struct dm_thin_lookup_result lookup;
+
+	if (end < begin)
+		return -ENODATA;
+
+	r = __find_next_mapped_block(td, begin, &begin, &lookup);
+	if (r)
+		return r;
+
+	if (begin >= end)
+		return -ENODATA;
+
+	*thin_begin = begin;
+	*pool_begin = lookup.block;
+	*maybe_shared = lookup.shared;
+
+	begin++;
+	pool_end = *pool_begin + 1;
+	while (begin != end) {
+		r = __find_block(td, begin, true, &lookup);
+		if (r) {
+			if (r == -ENODATA)
+				break;
+
+			return r;
+		}
+
+		if ((lookup.block != pool_end) ||
+		    (lookup.shared != *maybe_shared))
+			break;
+
+		pool_end++;
+		begin++;
+	}
+
+	*thin_end = begin;
+	return 0;
+}
+
+int dm_thin_find_mapped_range(struct dm_thin_device *td,
+			      dm_block_t begin, dm_block_t end,
+			      dm_block_t *thin_begin, dm_block_t *thin_end,
+			      dm_block_t *pool_begin, bool *maybe_shared)
+{
+	int r = -EINVAL;
+	struct dm_pool_metadata *pmd = td->pmd;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io) {
+		r = __find_mapped_range(td, begin, end, thin_begin, thin_end,
+					pool_begin, maybe_shared);
+	}
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+static int __insert(struct dm_thin_device *td, dm_block_t block,
+		    dm_block_t data_block)
+{
+	int r, inserted;
+	__le64 value;
+	struct dm_pool_metadata *pmd = td->pmd;
+	dm_block_t keys[2] = { td->id, block };
+
+	value = cpu_to_le64(pack_block_time(data_block, pmd->time));
+	__dm_bless_for_disk(&value);
+
+	r = dm_btree_insert_notify(&pmd->info, pmd->root, keys, &value,
+				   &pmd->root, &inserted);
+	if (r)
+		return r;
+
+	td->changed = true;
+	if (inserted)
+		td->mapped_blocks++;
+
+	return 0;
+}
+
+int dm_thin_insert_block(struct dm_thin_device *td, dm_block_t block,
+			 dm_block_t data_block)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(td->pmd);
+	if (!td->pmd->fail_io)
+		r = __insert(td, block, data_block);
+	pmd_write_unlock(td->pmd);
+
+	return r;
+}
+
+static int __remove_range(struct dm_thin_device *td, dm_block_t begin, dm_block_t end)
+{
+	int r;
+	unsigned int count, total_count = 0;
+	struct dm_pool_metadata *pmd = td->pmd;
+	dm_block_t keys[1] = { td->id };
+	__le64 value;
+	dm_block_t mapping_root;
+
+	/*
+	 * Find the mapping tree
+	 */
+	r = dm_btree_lookup(&pmd->tl_info, pmd->root, keys, &value);
+	if (r)
+		return r;
+
+	/*
+	 * Remove from the mapping tree, taking care to inc the
+	 * ref count so it doesn't get deleted.
+	 */
+	mapping_root = le64_to_cpu(value);
+	dm_tm_inc(pmd->tm, mapping_root);
+	r = dm_btree_remove(&pmd->tl_info, pmd->root, keys, &pmd->root);
+	if (r)
+		return r;
+
+	/*
+	 * Remove leaves stops at the first unmapped entry, so we have to
+	 * loop round finding mapped ranges.
+	 */
+	while (begin < end) {
+		r = dm_btree_lookup_next(&pmd->bl_info, mapping_root, &begin, &begin, &value);
+		if (r == -ENODATA)
+			break;
+
+		if (r)
+			return r;
+
+		if (begin >= end)
+			break;
+
+		r = dm_btree_remove_leaves(&pmd->bl_info, mapping_root, &begin, end, &mapping_root, &count);
+		if (r)
+			return r;
+
+		total_count += count;
+	}
+
+	td->mapped_blocks -= total_count;
+	td->changed = true;
+
+	/*
+	 * Reinsert the mapping tree.
+	 */
+	value = cpu_to_le64(mapping_root);
+	__dm_bless_for_disk(&value);
+	return dm_btree_insert(&pmd->tl_info, pmd->root, keys, &value, &pmd->root);
+}
+
+int dm_thin_remove_range(struct dm_thin_device *td,
+			 dm_block_t begin, dm_block_t end)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(td->pmd);
+	if (!td->pmd->fail_io)
+		r = __remove_range(td, begin, end);
+	pmd_write_unlock(td->pmd);
+
+	return r;
+}
+
+int dm_pool_block_is_shared(struct dm_pool_metadata *pmd, dm_block_t b, bool *result)
+{
+	int r = -EINVAL;
+	uint32_t ref_count;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io) {
+		r = dm_sm_get_count(pmd->data_sm, b, &ref_count);
+		if (!r)
+			*result = (ref_count > 1);
+	}
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+int dm_pool_inc_data_range(struct dm_pool_metadata *pmd, dm_block_t b, dm_block_t e)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = dm_sm_inc_blocks(pmd->data_sm, b, e);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+int dm_pool_dec_data_range(struct dm_pool_metadata *pmd, dm_block_t b, dm_block_t e)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = dm_sm_dec_blocks(pmd->data_sm, b, e);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+bool dm_thin_changed_this_transaction(struct dm_thin_device *td)
+{
+	int r;
+
+	down_read(&td->pmd->root_lock);
+	r = td->changed;
+	up_read(&td->pmd->root_lock);
+
+	return r;
+}
+
+bool dm_pool_changed_this_transaction(struct dm_pool_metadata *pmd)
+{
+	bool r = false;
+	struct dm_thin_device *td, *tmp;
+
+	down_read(&pmd->root_lock);
+	list_for_each_entry_safe(td, tmp, &pmd->thin_devices, list) {
+		if (td->changed) {
+			r = td->changed;
+			break;
+		}
+	}
+	up_read(&pmd->root_lock);
+
+	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;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = dm_sm_new_block(pmd->data_sm, result);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+int dm_pool_commit_metadata(struct dm_pool_metadata *pmd)
+{
+	int r = -EINVAL;
+
+	/*
+	 * Care is taken to not have commit be what
+	 * triggers putting the thin-pool in-service.
+	 */
+	pmd_write_lock_in_core(pmd);
+	if (pmd->fail_io)
+		goto out;
+
+	r = __commit_transaction(pmd);
+	if (r < 0)
+		goto out;
+
+	/*
+	 * Open the next transaction.
+	 */
+	r = __begin_transaction(pmd);
+out:
+	pmd_write_unlock(pmd);
+	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;
+
+	/* fail_io is double-checked with pmd->root_lock held below */
+	if (unlikely(pmd->fail_io))
+		return r;
+
+	pmd_write_lock(pmd);
+	if (pmd->fail_io) {
+		pmd_write_unlock(pmd);
+		return r;
+	}
+	__set_abort_with_changes_flags(pmd);
+
+	/* destroy data_sm/metadata_sm/nb_tm/tm */
+	__destroy_persistent_data_objects(pmd, false);
+
+	/* reset bm */
+	dm_block_manager_reset(pmd->bm);
+
+	/* rebuild data_sm/metadata_sm/nb_tm/tm */
+	r = __open_or_format_metadata(pmd, false);
+	if (r)
+		pmd->fail_io = true;
+	pmd_write_unlock(pmd);
+	return r;
+}
+
+int dm_pool_get_free_block_count(struct dm_pool_metadata *pmd, dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_free(pmd->data_sm, result);
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
+					  dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_free(pmd->metadata_sm, result);
+
+	if (!r) {
+		if (*result < pmd->metadata_reserve)
+			*result = 0;
+		else
+			*result -= pmd->metadata_reserve;
+	}
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd,
+				  dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_blocks(pmd->metadata_sm, result);
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = dm_sm_get_nr_blocks(pmd->data_sm, result);
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+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);
+	if (!pmd->fail_io) {
+		*result = td->mapped_blocks;
+		r = 0;
+	}
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+static int __highest_block(struct dm_thin_device *td, dm_block_t *result)
+{
+	int r;
+	__le64 value_le;
+	dm_block_t thin_root;
+	struct dm_pool_metadata *pmd = td->pmd;
+
+	r = dm_btree_lookup(&pmd->tl_info, pmd->root, &td->id, &value_le);
+	if (r)
+		return r;
+
+	thin_root = le64_to_cpu(value_le);
+
+	return dm_btree_find_highest_key(&pmd->bl_info, thin_root, result);
+}
+
+int dm_thin_get_highest_mapped_block(struct dm_thin_device *td,
+				     dm_block_t *result)
+{
+	int r = -EINVAL;
+	struct dm_pool_metadata *pmd = td->pmd;
+
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		r = __highest_block(td, result);
+	up_read(&pmd->root_lock);
+
+	return r;
+}
+
+static int __resize_space_map(struct dm_space_map *sm, dm_block_t new_count)
+{
+	int r;
+	dm_block_t old_count;
+
+	r = dm_sm_get_nr_blocks(sm, &old_count);
+	if (r)
+		return r;
+
+	if (new_count == old_count)
+		return 0;
+
+	if (new_count < old_count) {
+		DMERR("cannot reduce size of space map");
+		return -EINVAL;
+	}
+
+	return dm_sm_extend(sm, new_count - old_count);
+}
+
+int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io)
+		r = __resize_space_map(pmd->data_sm, new_count);
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+int dm_pool_resize_metadata_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock(pmd);
+	if (!pmd->fail_io) {
+		r = __resize_space_map(pmd->metadata_sm, new_count);
+		if (!r)
+			__set_metadata_reserve(pmd);
+	}
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd)
+{
+	pmd_write_lock_in_core(pmd);
+	dm_bm_set_read_only(pmd->bm);
+	pmd_write_unlock(pmd);
+}
+
+void dm_pool_metadata_read_write(struct dm_pool_metadata *pmd)
+{
+	pmd_write_lock_in_core(pmd);
+	dm_bm_set_read_write(pmd->bm);
+	pmd_write_unlock(pmd);
+}
+
+int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
+					dm_block_t threshold,
+					dm_sm_threshold_fn fn,
+					void *context)
+{
+	int r = -EINVAL;
+
+	pmd_write_lock_in_core(pmd);
+	if (!pmd->fail_io) {
+		r = dm_sm_register_threshold_callback(pmd->metadata_sm,
+						      threshold, fn, context);
+	}
+	pmd_write_unlock(pmd);
+
+	return r;
+}
+
+void dm_pool_register_pre_commit_callback(struct dm_pool_metadata *pmd,
+					  dm_pool_pre_commit_fn fn,
+					  void *context)
+{
+	pmd_write_lock_in_core(pmd);
+	pmd->pre_commit_fn = fn;
+	pmd->pre_commit_context = context;
+	pmd_write_unlock(pmd);
+}
+
+int dm_pool_metadata_set_needs_check(struct dm_pool_metadata *pmd)
+{
+	int r = -EINVAL;
+	struct dm_block *sblock;
+	struct thin_disk_superblock *disk_super;
+
+	pmd_write_lock(pmd);
+	if (pmd->fail_io)
+		goto out;
+
+	pmd->flags |= THIN_METADATA_NEEDS_CHECK_FLAG;
+
+	r = superblock_lock(pmd, &sblock);
+	if (r) {
+		DMERR("couldn't lock superblock");
+		goto out;
+	}
+
+	disk_super = dm_block_data(sblock);
+	disk_super->flags = cpu_to_le32(pmd->flags);
+
+	dm_bm_unlock(sblock);
+out:
+	pmd_write_unlock(pmd);
+	return r;
+}
+
+bool dm_pool_metadata_needs_check(struct dm_pool_metadata *pmd)
+{
+	bool needs_check;
+
+	down_read(&pmd->root_lock);
+	needs_check = pmd->flags & THIN_METADATA_NEEDS_CHECK_FLAG;
+	up_read(&pmd->root_lock);
+
+	return needs_check;
+}
+
+void dm_pool_issue_prefetches(struct dm_pool_metadata *pmd)
+{
+	down_read(&pmd->root_lock);
+	if (!pmd->fail_io)
+		dm_tm_issue_prefetches(pmd->tm);
+	up_read(&pmd->root_lock);
+}