Initial import

1 files changed, 1389 insertions, 0 deletions

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
new file mode 100644
index 000000000..c1c010498
--- /dev/null
+++ b/drivers/md/dm-cache-metadata.c
@@ -0,0 +1,1389 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-cache-metadata.h"
+
+#include "persistent-data/dm-array.h"
+#include "persistent-data/dm-bitset.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/device-mapper.h>
+
+/*----------------------------------------------------------------*/
+
+#define DM_MSG_PREFIX   "cache metadata"
+
+#define CACHE_SUPERBLOCK_MAGIC 06142003
+#define CACHE_SUPERBLOCK_LOCATION 0
+
+/*
+ * defines a range of metadata versions that this module can handle.
+ */
+#define MIN_CACHE_VERSION 1
+#define MAX_CACHE_VERSION 1
+
+#define CACHE_METADATA_CACHE_SIZE 64
+
+/*
+ *  3 for btree insert +
+ *  2 for btree lookup used within space map
+ */
+#define CACHE_MAX_CONCURRENT_LOCKS 5
+#define SPACE_MAP_ROOT_SIZE 128
+
+enum superblock_flag_bits {
+	/* for spotting crashes that would invalidate the dirty bitset */
+	CLEAN_SHUTDOWN,
+};
+
+/*
+ * Each mapping from cache block -> origin block carries a set of flags.
+ */
+enum mapping_bits {
+	/*
+	 * A valid mapping.  Because we're using an array we clear this
+	 * flag for an non existant mapping.
+	 */
+	M_VALID = 1,
+
+	/*
+	 * The data on the cache is different from that on the origin.
+	 */
+	M_DIRTY = 2
+};
+
+struct cache_disk_superblock {
+	__le32 csum;
+	__le32 flags;
+	__le64 blocknr;
+
+	__u8 uuid[16];
+	__le64 magic;
+	__le32 version;
+
+	__u8 policy_name[CACHE_POLICY_NAME_SIZE];
+	__le32 policy_hint_size;
+
+	__u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
+	__le64 mapping_root;
+	__le64 hint_root;
+
+	__le64 discard_root;
+	__le64 discard_block_size;
+	__le64 discard_nr_blocks;
+
+	__le32 data_block_size;
+	__le32 metadata_block_size;
+	__le32 cache_blocks;
+
+	__le32 compat_flags;
+	__le32 compat_ro_flags;
+	__le32 incompat_flags;
+
+	__le32 read_hits;
+	__le32 read_misses;
+	__le32 write_hits;
+	__le32 write_misses;
+
+	__le32 policy_version[CACHE_POLICY_VERSION_SIZE];
+} __packed;
+
+struct dm_cache_metadata {
+	atomic_t ref_count;
+	struct list_head list;
+
+	struct block_device *bdev;
+	struct dm_block_manager *bm;
+	struct dm_space_map *metadata_sm;
+	struct dm_transaction_manager *tm;
+
+	struct dm_array_info info;
+	struct dm_array_info hint_info;
+	struct dm_disk_bitset discard_info;
+
+	struct rw_semaphore root_lock;
+	dm_block_t root;
+	dm_block_t hint_root;
+	dm_block_t discard_root;
+
+	sector_t discard_block_size;
+	dm_dblock_t discard_nr_blocks;
+
+	sector_t data_block_size;
+	dm_cblock_t cache_blocks;
+	bool changed:1;
+	bool clean_when_opened:1;
+
+	char policy_name[CACHE_POLICY_NAME_SIZE];
+	unsigned policy_version[CACHE_POLICY_VERSION_SIZE];
+	size_t policy_hint_size;
+	struct dm_cache_statistics stats;
+
+	/*
+	 * Reading the space map root can fail, so we read it into this
+	 * buffer before the superblock is locked and updated.
+	 */
+	__u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
+};
+
+/*-------------------------------------------------------------------
+ * superblock validator
+ *-----------------------------------------------------------------*/
+
+#define SUPERBLOCK_CSUM_XOR 9031977
+
+static void sb_prepare_for_write(struct dm_block_validator *v,
+				 struct dm_block *b,
+				 size_t sb_block_size)
+{
+	struct cache_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,
+						      sb_block_size - sizeof(__le32),
+						      SUPERBLOCK_CSUM_XOR));
+}
+
+static int check_metadata_version(struct cache_disk_superblock *disk_super)
+{
+	uint32_t metadata_version = le32_to_cpu(disk_super->version);
+	if (metadata_version < MIN_CACHE_VERSION || metadata_version > MAX_CACHE_VERSION) {
+		DMERR("Cache metadata version %u found, but only versions between %u and %u supported.",
+		      metadata_version, MIN_CACHE_VERSION, MAX_CACHE_VERSION);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int sb_check(struct dm_block_validator *v,
+		    struct dm_block *b,
+		    size_t sb_block_size)
+{
+	struct cache_disk_superblock *disk_super = dm_block_data(b);
+	__le32 csum_le;
+
+	if (dm_block_location(b) != le64_to_cpu(disk_super->blocknr)) {
+		DMERR("sb_check failed: blocknr %llu: wanted %llu",
+		      le64_to_cpu(disk_super->blocknr),
+		      (unsigned long long)dm_block_location(b));
+		return -ENOTBLK;
+	}
+
+	if (le64_to_cpu(disk_super->magic) != CACHE_SUPERBLOCK_MAGIC) {
+		DMERR("sb_check failed: magic %llu: wanted %llu",
+		      le64_to_cpu(disk_super->magic),
+		      (unsigned long long)CACHE_SUPERBLOCK_MAGIC);
+		return -EILSEQ;
+	}
+
+	csum_le = cpu_to_le32(dm_bm_checksum(&disk_super->flags,
+					     sb_block_size - sizeof(__le32),
+					     SUPERBLOCK_CSUM_XOR));
+	if (csum_le != disk_super->csum) {
+		DMERR("sb_check failed: csum %u: wanted %u",
+		      le32_to_cpu(csum_le), le32_to_cpu(disk_super->csum));
+		return -EILSEQ;
+	}
+
+	return check_metadata_version(disk_super);
+}
+
+static struct dm_block_validator sb_validator = {
+	.name = "superblock",
+	.prepare_for_write = sb_prepare_for_write,
+	.check = sb_check
+};
+
+/*----------------------------------------------------------------*/
+
+static int superblock_read_lock(struct dm_cache_metadata *cmd,
+				struct dm_block **sblock)
+{
+	return dm_bm_read_lock(cmd->bm, CACHE_SUPERBLOCK_LOCATION,
+			       &sb_validator, sblock);
+}
+
+static int superblock_lock_zero(struct dm_cache_metadata *cmd,
+				struct dm_block **sblock)
+{
+	return dm_bm_write_lock_zero(cmd->bm, CACHE_SUPERBLOCK_LOCATION,
+				     &sb_validator, sblock);
+}
+
+static int superblock_lock(struct dm_cache_metadata *cmd,
+			   struct dm_block **sblock)
+{
+	return dm_bm_write_lock(cmd->bm, CACHE_SUPERBLOCK_LOCATION,
+				&sb_validator, sblock);
+}
+
+/*----------------------------------------------------------------*/
+
+static int __superblock_all_zeroes(struct dm_block_manager *bm, bool *result)
+{
+	int r;
+	unsigned i;
+	struct dm_block *b;
+	__le64 *data_le, zero = cpu_to_le64(0);
+	unsigned sb_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, CACHE_SUPERBLOCK_LOCATION, NULL, &b);
+	if (r)
+		return r;
+
+	data_le = dm_block_data(b);
+	*result = true;
+	for (i = 0; i < sb_block_size; i++) {
+		if (data_le[i] != zero) {
+			*result = false;
+			break;
+		}
+	}
+
+	return dm_bm_unlock(b);
+}
+
+static void __setup_mapping_info(struct dm_cache_metadata *cmd)
+{
+	struct dm_btree_value_type vt;
+
+	vt.context = NULL;
+	vt.size = sizeof(__le64);
+	vt.inc = NULL;
+	vt.dec = NULL;
+	vt.equal = NULL;
+	dm_array_info_init(&cmd->info, cmd->tm, &vt);
+
+	if (cmd->policy_hint_size) {
+		vt.size = sizeof(__le32);
+		dm_array_info_init(&cmd->hint_info, cmd->tm, &vt);
+	}
+}
+
+static int __save_sm_root(struct dm_cache_metadata *cmd)
+{
+	int r;
+	size_t metadata_len;
+
+	r = dm_sm_root_size(cmd->metadata_sm, &metadata_len);
+	if (r < 0)
+		return r;
+
+	return dm_sm_copy_root(cmd->metadata_sm, &cmd->metadata_space_map_root,
+			       metadata_len);
+}
+
+static void __copy_sm_root(struct dm_cache_metadata *cmd,
+			   struct cache_disk_superblock *disk_super)
+{
+	memcpy(&disk_super->metadata_space_map_root,
+	       &cmd->metadata_space_map_root,
+	       sizeof(cmd->metadata_space_map_root));
+}
+
+static int __write_initial_superblock(struct dm_cache_metadata *cmd)
+{
+	int r;
+	struct dm_block *sblock;
+	struct cache_disk_superblock *disk_super;
+	sector_t bdev_size = i_size_read(cmd->bdev->bd_inode) >> SECTOR_SHIFT;
+
+	/* FIXME: see if we can lose the max sectors limit */
+	if (bdev_size > DM_CACHE_METADATA_MAX_SECTORS)
+		bdev_size = DM_CACHE_METADATA_MAX_SECTORS;
+
+	r = dm_tm_pre_commit(cmd->tm);
+	if (r < 0)
+		return r;
+
+	/*
+	 * dm_sm_copy_root() can fail.  So we need to do it before we start
+	 * updating the superblock.
+	 */
+	r = __save_sm_root(cmd);
+	if (r)
+		return r;
+
+	r = superblock_lock_zero(cmd, &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(CACHE_SUPERBLOCK_MAGIC);
+	disk_super->version = cpu_to_le32(MAX_CACHE_VERSION);
+	memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name));
+	memset(disk_super->policy_version, 0, sizeof(disk_super->policy_version));
+	disk_super->policy_hint_size = 0;
+
+	__copy_sm_root(cmd, disk_super);
+
+	disk_super->mapping_root = cpu_to_le64(cmd->root);
+	disk_super->hint_root = cpu_to_le64(cmd->hint_root);
+	disk_super->discard_root = cpu_to_le64(cmd->discard_root);
+	disk_super->discard_block_size = cpu_to_le64(cmd->discard_block_size);
+	disk_super->discard_nr_blocks = cpu_to_le64(from_dblock(cmd->discard_nr_blocks));
+	disk_super->metadata_block_size = cpu_to_le32(DM_CACHE_METADATA_BLOCK_SIZE);
+	disk_super->data_block_size = cpu_to_le32(cmd->data_block_size);
+	disk_super->cache_blocks = cpu_to_le32(0);
+
+	disk_super->read_hits = cpu_to_le32(0);
+	disk_super->read_misses = cpu_to_le32(0);
+	disk_super->write_hits = cpu_to_le32(0);
+	disk_super->write_misses = cpu_to_le32(0);
+
+	return dm_tm_commit(cmd->tm, sblock);
+}
+
+static int __format_metadata(struct dm_cache_metadata *cmd)
+{
+	int r;
+
+	r = dm_tm_create_with_sm(cmd->bm, CACHE_SUPERBLOCK_LOCATION,
+				 &cmd->tm, &cmd->metadata_sm);
+	if (r < 0) {
+		DMERR("tm_create_with_sm failed");
+		return r;
+	}
+
+	__setup_mapping_info(cmd);
+
+	r = dm_array_empty(&cmd->info, &cmd->root);
+	if (r < 0)
+		goto bad;
+
+	dm_disk_bitset_init(cmd->tm, &cmd->discard_info);
+
+	r = dm_bitset_empty(&cmd->discard_info, &cmd->discard_root);
+	if (r < 0)
+		goto bad;
+
+	cmd->discard_block_size = 0;
+	cmd->discard_nr_blocks = 0;
+
+	r = __write_initial_superblock(cmd);
+	if (r)
+		goto bad;
+
+	cmd->clean_when_opened = true;
+	return 0;
+
+bad:
+	dm_tm_destroy(cmd->tm);
+	dm_sm_destroy(cmd->metadata_sm);
+
+	return r;
+}
+
+static int __check_incompat_features(struct cache_disk_superblock *disk_super,
+				     struct dm_cache_metadata *cmd)
+{
+	uint32_t features;
+
+	features = le32_to_cpu(disk_super->incompat_flags) & ~DM_CACHE_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(cmd->bdev->bd_disk))
+		return 0;
+
+	features = le32_to_cpu(disk_super->compat_ro_flags) & ~DM_CACHE_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_cache_metadata *cmd)
+{
+	int r;
+	struct dm_block *sblock;
+	struct cache_disk_superblock *disk_super;
+	unsigned long sb_flags;
+
+	r = superblock_read_lock(cmd, &sblock);
+	if (r < 0) {
+		DMERR("couldn't read lock 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) != cmd->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)cmd->data_block_size);
+		r = -EINVAL;
+		goto bad;
+	}
+
+	r = __check_incompat_features(disk_super, cmd);
+	if (r < 0)
+		goto bad;
+
+	r = dm_tm_open_with_sm(cmd->bm, CACHE_SUPERBLOCK_LOCATION,
+			       disk_super->metadata_space_map_root,
+			       sizeof(disk_super->metadata_space_map_root),
+			       &cmd->tm, &cmd->metadata_sm);
+	if (r < 0) {
+		DMERR("tm_open_with_sm failed");
+		goto bad;
+	}
+
+	__setup_mapping_info(cmd);
+	dm_disk_bitset_init(cmd->tm, &cmd->discard_info);
+	sb_flags = le32_to_cpu(disk_super->flags);
+	cmd->clean_when_opened = test_bit(CLEAN_SHUTDOWN, &sb_flags);
+	return dm_bm_unlock(sblock);
+
+bad:
+	dm_bm_unlock(sblock);
+	return r;
+}
+
+static int __open_or_format_metadata(struct dm_cache_metadata *cmd,
+				     bool format_device)
+{
+	int r;
+	bool unformatted = false;
+
+	r = __superblock_all_zeroes(cmd->bm, &unformatted);
+	if (r)
+		return r;
+
+	if (unformatted)
+		return format_device ? __format_metadata(cmd) : -EPERM;
+
+	return __open_metadata(cmd);
+}
+
+static int __create_persistent_data_objects(struct dm_cache_metadata *cmd,
+					    bool may_format_device)
+{
+	int r;
+	cmd->bm = dm_block_manager_create(cmd->bdev, DM_CACHE_METADATA_BLOCK_SIZE << SECTOR_SHIFT,
+					  CACHE_METADATA_CACHE_SIZE,
+					  CACHE_MAX_CONCURRENT_LOCKS);
+	if (IS_ERR(cmd->bm)) {
+		DMERR("could not create block manager");
+		return PTR_ERR(cmd->bm);
+	}
+
+	r = __open_or_format_metadata(cmd, may_format_device);
+	if (r)
+		dm_block_manager_destroy(cmd->bm);
+
+	return r;
+}
+
+static void __destroy_persistent_data_objects(struct dm_cache_metadata *cmd)
+{
+	dm_sm_destroy(cmd->metadata_sm);
+	dm_tm_destroy(cmd->tm);
+	dm_block_manager_destroy(cmd->bm);
+}
+
+typedef unsigned long (*flags_mutator)(unsigned long);
+
+static void update_flags(struct cache_disk_superblock *disk_super,
+			 flags_mutator mutator)
+{
+	uint32_t sb_flags = mutator(le32_to_cpu(disk_super->flags));
+	disk_super->flags = cpu_to_le32(sb_flags);
+}
+
+static unsigned long set_clean_shutdown(unsigned long flags)
+{
+	set_bit(CLEAN_SHUTDOWN, &flags);
+	return flags;
+}
+
+static unsigned long clear_clean_shutdown(unsigned long flags)
+{
+	clear_bit(CLEAN_SHUTDOWN, &flags);
+	return flags;
+}
+
+static void read_superblock_fields(struct dm_cache_metadata *cmd,
+				   struct cache_disk_superblock *disk_super)
+{
+	cmd->root = le64_to_cpu(disk_super->mapping_root);
+	cmd->hint_root = le64_to_cpu(disk_super->hint_root);
+	cmd->discard_root = le64_to_cpu(disk_super->discard_root);
+	cmd->discard_block_size = le64_to_cpu(disk_super->discard_block_size);
+	cmd->discard_nr_blocks = to_dblock(le64_to_cpu(disk_super->discard_nr_blocks));
+	cmd->data_block_size = le32_to_cpu(disk_super->data_block_size);
+	cmd->cache_blocks = to_cblock(le32_to_cpu(disk_super->cache_blocks));
+	strncpy(cmd->policy_name, disk_super->policy_name, sizeof(cmd->policy_name));
+	cmd->policy_version[0] = le32_to_cpu(disk_super->policy_version[0]);
+	cmd->policy_version[1] = le32_to_cpu(disk_super->policy_version[1]);
+	cmd->policy_version[2] = le32_to_cpu(disk_super->policy_version[2]);
+	cmd->policy_hint_size = le32_to_cpu(disk_super->policy_hint_size);
+
+	cmd->stats.read_hits = le32_to_cpu(disk_super->read_hits);
+	cmd->stats.read_misses = le32_to_cpu(disk_super->read_misses);
+	cmd->stats.write_hits = le32_to_cpu(disk_super->write_hits);
+	cmd->stats.write_misses = le32_to_cpu(disk_super->write_misses);
+
+	cmd->changed = false;
+}
+
+/*
+ * The mutator updates the superblock flags.
+ */
+static int __begin_transaction_flags(struct dm_cache_metadata *cmd,
+				     flags_mutator mutator)
+{
+	int r;
+	struct cache_disk_superblock *disk_super;
+	struct dm_block *sblock;
+
+	r = superblock_lock(cmd, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+	update_flags(disk_super, mutator);
+	read_superblock_fields(cmd, disk_super);
+	dm_bm_unlock(sblock);
+
+	return dm_bm_flush(cmd->bm);
+}
+
+static int __begin_transaction(struct dm_cache_metadata *cmd)
+{
+	int r;
+	struct cache_disk_superblock *disk_super;
+	struct dm_block *sblock;
+
+	/*
+	 * We re-read the superblock every time.  Shouldn't need to do this
+	 * really.
+	 */
+	r = superblock_read_lock(cmd, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+	read_superblock_fields(cmd, disk_super);
+	dm_bm_unlock(sblock);
+
+	return 0;
+}
+
+static int __commit_transaction(struct dm_cache_metadata *cmd,
+				flags_mutator mutator)
+{
+	int r;
+	struct cache_disk_superblock *disk_super;
+	struct dm_block *sblock;
+
+	/*
+	 * We need to know if the cache_disk_superblock exceeds a 512-byte sector.
+	 */
+	BUILD_BUG_ON(sizeof(struct cache_disk_superblock) > 512);
+
+	r = dm_bitset_flush(&cmd->discard_info, cmd->discard_root,
+			    &cmd->discard_root);
+	if (r)
+		return r;
+
+	r = dm_tm_pre_commit(cmd->tm);
+	if (r < 0)
+		return r;
+
+	r = __save_sm_root(cmd);
+	if (r)
+		return r;
+
+	r = superblock_lock(cmd, &sblock);
+	if (r)
+		return r;
+
+	disk_super = dm_block_data(sblock);
+
+	if (mutator)
+		update_flags(disk_super, mutator);
+
+	disk_super->mapping_root = cpu_to_le64(cmd->root);
+	disk_super->hint_root = cpu_to_le64(cmd->hint_root);
+	disk_super->discard_root = cpu_to_le64(cmd->discard_root);
+	disk_super->discard_block_size = cpu_to_le64(cmd->discard_block_size);
+	disk_super->discard_nr_blocks = cpu_to_le64(from_dblock(cmd->discard_nr_blocks));
+	disk_super->cache_blocks = cpu_to_le32(from_cblock(cmd->cache_blocks));
+	strncpy(disk_super->policy_name, cmd->policy_name, sizeof(disk_super->policy_name));
+	disk_super->policy_version[0] = cpu_to_le32(cmd->policy_version[0]);
+	disk_super->policy_version[1] = cpu_to_le32(cmd->policy_version[1]);
+	disk_super->policy_version[2] = cpu_to_le32(cmd->policy_version[2]);
+
+	disk_super->read_hits = cpu_to_le32(cmd->stats.read_hits);
+	disk_super->read_misses = cpu_to_le32(cmd->stats.read_misses);
+	disk_super->write_hits = cpu_to_le32(cmd->stats.write_hits);
+	disk_super->write_misses = cpu_to_le32(cmd->stats.write_misses);
+	__copy_sm_root(cmd, disk_super);
+
+	return dm_tm_commit(cmd->tm, sblock);
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The mappings are held in a dm-array that has 64-bit values stored in
+ * little-endian format.  The index is the cblock, the high 48bits of the
+ * value are the oblock and the low 16 bit the flags.
+ */
+#define FLAGS_MASK ((1 << 16) - 1)
+
+static __le64 pack_value(dm_oblock_t block, unsigned flags)
+{
+	uint64_t value = from_oblock(block);
+	value <<= 16;
+	value = value | (flags & FLAGS_MASK);
+	return cpu_to_le64(value);
+}
+
+static void unpack_value(__le64 value_le, dm_oblock_t *block, unsigned *flags)
+{
+	uint64_t value = le64_to_cpu(value_le);
+	uint64_t b = value >> 16;
+	*block = to_oblock(b);
+	*flags = value & FLAGS_MASK;
+}
+
+/*----------------------------------------------------------------*/
+
+static struct dm_cache_metadata *metadata_open(struct block_device *bdev,
+					       sector_t data_block_size,
+					       bool may_format_device,
+					       size_t policy_hint_size)
+{
+	int r;
+	struct dm_cache_metadata *cmd;
+
+	cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
+	if (!cmd) {
+		DMERR("could not allocate metadata struct");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	atomic_set(&cmd->ref_count, 1);
+	init_rwsem(&cmd->root_lock);
+	cmd->bdev = bdev;
+	cmd->data_block_size = data_block_size;
+	cmd->cache_blocks = 0;
+	cmd->policy_hint_size = policy_hint_size;
+	cmd->changed = true;
+
+	r = __create_persistent_data_objects(cmd, may_format_device);
+	if (r) {
+		kfree(cmd);
+		return ERR_PTR(r);
+	}
+
+	r = __begin_transaction_flags(cmd, clear_clean_shutdown);
+	if (r < 0) {
+		dm_cache_metadata_close(cmd);
+		return ERR_PTR(r);
+	}
+
+	return cmd;
+}
+
+/*
+ * We keep a little list of ref counted metadata objects to prevent two
+ * different target instances creating separate bufio instances.  This is
+ * an issue if a table is reloaded before the suspend.
+ */
+static DEFINE_MUTEX(table_lock);
+static LIST_HEAD(table);
+
+static struct dm_cache_metadata *lookup(struct block_device *bdev)
+{
+	struct dm_cache_metadata *cmd;
+
+	list_for_each_entry(cmd, &table, list)
+		if (cmd->bdev == bdev) {
+			atomic_inc(&cmd->ref_count);
+			return cmd;
+		}
+
+	return NULL;
+}
+
+static struct dm_cache_metadata *lookup_or_open(struct block_device *bdev,
+						sector_t data_block_size,
+						bool may_format_device,
+						size_t policy_hint_size)
+{
+	struct dm_cache_metadata *cmd, *cmd2;
+
+	mutex_lock(&table_lock);
+	cmd = lookup(bdev);
+	mutex_unlock(&table_lock);
+
+	if (cmd)
+		return cmd;
+
+	cmd = metadata_open(bdev, data_block_size, may_format_device, policy_hint_size);
+	if (!IS_ERR(cmd)) {
+		mutex_lock(&table_lock);
+		cmd2 = lookup(bdev);
+		if (cmd2) {
+			mutex_unlock(&table_lock);
+			__destroy_persistent_data_objects(cmd);
+			kfree(cmd);
+			return cmd2;
+		}
+		list_add(&cmd->list, &table);
+		mutex_unlock(&table_lock);
+	}
+
+	return cmd;
+}
+
+static bool same_params(struct dm_cache_metadata *cmd, sector_t data_block_size)
+{
+	if (cmd->data_block_size != data_block_size) {
+		DMERR("data_block_size (%llu) different from that in metadata (%llu)\n",
+		      (unsigned long long) data_block_size,
+		      (unsigned long long) cmd->data_block_size);
+		return false;
+	}
+
+	return true;
+}
+
+struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
+						 sector_t data_block_size,
+						 bool may_format_device,
+						 size_t policy_hint_size)
+{
+	struct dm_cache_metadata *cmd = lookup_or_open(bdev, data_block_size,
+						       may_format_device, policy_hint_size);
+
+	if (!IS_ERR(cmd) && !same_params(cmd, data_block_size)) {
+		dm_cache_metadata_close(cmd);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return cmd;
+}
+
+void dm_cache_metadata_close(struct dm_cache_metadata *cmd)
+{
+	if (atomic_dec_and_test(&cmd->ref_count)) {
+		mutex_lock(&table_lock);
+		list_del(&cmd->list);
+		mutex_unlock(&table_lock);
+
+		__destroy_persistent_data_objects(cmd);
+		kfree(cmd);
+	}
+}
+
+/*
+ * Checks that the given cache block is either unmapped or clean.
+ */
+static int block_unmapped_or_clean(struct dm_cache_metadata *cmd, dm_cblock_t b,
+				   bool *result)
+{
+	int r;
+	__le64 value;
+	dm_oblock_t ob;
+	unsigned flags;
+
+	r = dm_array_get_value(&cmd->info, cmd->root, from_cblock(b), &value);
+	if (r) {
+		DMERR("block_unmapped_or_clean failed");
+		return r;
+	}
+
+	unpack_value(value, &ob, &flags);
+	*result = !((flags & M_VALID) && (flags & M_DIRTY));
+
+	return 0;
+}
+
+static int blocks_are_unmapped_or_clean(struct dm_cache_metadata *cmd,
+					dm_cblock_t begin, dm_cblock_t end,
+					bool *result)
+{
+	int r;
+	*result = true;
+
+	while (begin != end) {
+		r = block_unmapped_or_clean(cmd, begin, result);
+		if (r)
+			return r;
+
+		if (!*result) {
+			DMERR("cache block %llu is dirty",
+			      (unsigned long long) from_cblock(begin));
+			return 0;
+		}
+
+		begin = to_cblock(from_cblock(begin) + 1);
+	}
+
+	return 0;
+}
+
+int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size)
+{
+	int r;
+	bool clean;
+	__le64 null_mapping = pack_value(0, 0);
+
+	down_write(&cmd->root_lock);
+	__dm_bless_for_disk(&null_mapping);
+
+	if (from_cblock(new_cache_size) < from_cblock(cmd->cache_blocks)) {
+		r = blocks_are_unmapped_or_clean(cmd, new_cache_size, cmd->cache_blocks, &clean);
+		if (r) {
+			__dm_unbless_for_disk(&null_mapping);
+			goto out;
+		}
+
+		if (!clean) {
+			DMERR("unable to shrink cache due to dirty blocks");
+			r = -EINVAL;
+			__dm_unbless_for_disk(&null_mapping);
+			goto out;
+		}
+	}
+
+	r = dm_array_resize(&cmd->info, cmd->root, from_cblock(cmd->cache_blocks),
+			    from_cblock(new_cache_size),
+			    &null_mapping, &cmd->root);
+	if (!r)
+		cmd->cache_blocks = new_cache_size;
+	cmd->changed = true;
+
+out:
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+int dm_cache_discard_bitset_resize(struct dm_cache_metadata *cmd,
+				   sector_t discard_block_size,
+				   dm_dblock_t new_nr_entries)
+{
+	int r;
+
+	down_write(&cmd->root_lock);
+	r = dm_bitset_resize(&cmd->discard_info,
+			     cmd->discard_root,
+			     from_dblock(cmd->discard_nr_blocks),
+			     from_dblock(new_nr_entries),
+			     false, &cmd->discard_root);
+	if (!r) {
+		cmd->discard_block_size = discard_block_size;
+		cmd->discard_nr_blocks = new_nr_entries;
+	}
+
+	cmd->changed = true;
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+static int __set_discard(struct dm_cache_metadata *cmd, dm_dblock_t b)
+{
+	return dm_bitset_set_bit(&cmd->discard_info, cmd->discard_root,
+				 from_dblock(b), &cmd->discard_root);
+}
+
+static int __clear_discard(struct dm_cache_metadata *cmd, dm_dblock_t b)
+{
+	return dm_bitset_clear_bit(&cmd->discard_info, cmd->discard_root,
+				   from_dblock(b), &cmd->discard_root);
+}
+
+static int __is_discarded(struct dm_cache_metadata *cmd, dm_dblock_t b,
+			  bool *is_discarded)
+{
+	return dm_bitset_test_bit(&cmd->discard_info, cmd->discard_root,
+				  from_dblock(b), &cmd->discard_root,
+				  is_discarded);
+}
+
+static int __discard(struct dm_cache_metadata *cmd,
+		     dm_dblock_t dblock, bool discard)
+{
+	int r;
+
+	r = (discard ? __set_discard : __clear_discard)(cmd, dblock);
+	if (r)
+		return r;
+
+	cmd->changed = true;
+	return 0;
+}
+
+int dm_cache_set_discard(struct dm_cache_metadata *cmd,
+			 dm_dblock_t dblock, bool discard)
+{
+	int r;
+
+	down_write(&cmd->root_lock);
+	r = __discard(cmd, dblock, discard);
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+static int __load_discards(struct dm_cache_metadata *cmd,
+			   load_discard_fn fn, void *context)
+{
+	int r = 0;
+	dm_block_t b;
+	bool discard;
+
+	for (b = 0; b < from_dblock(cmd->discard_nr_blocks); b++) {
+		dm_dblock_t dblock = to_dblock(b);
+
+		if (cmd->clean_when_opened) {
+			r = __is_discarded(cmd, dblock, &discard);
+			if (r)
+				return r;
+		} else
+			discard = false;
+
+		r = fn(context, cmd->discard_block_size, dblock, discard);
+		if (r)
+			break;
+	}
+
+	return r;
+}
+
+int dm_cache_load_discards(struct dm_cache_metadata *cmd,
+			   load_discard_fn fn, void *context)
+{
+	int r;
+
+	down_read(&cmd->root_lock);
+	r = __load_discards(cmd, fn, context);
+	up_read(&cmd->root_lock);
+
+	return r;
+}
+
+dm_cblock_t dm_cache_size(struct dm_cache_metadata *cmd)
+{
+	dm_cblock_t r;
+
+	down_read(&cmd->root_lock);
+	r = cmd->cache_blocks;
+	up_read(&cmd->root_lock);
+
+	return r;
+}
+
+static int __remove(struct dm_cache_metadata *cmd, dm_cblock_t cblock)
+{
+	int r;
+	__le64 value = pack_value(0, 0);
+
+	__dm_bless_for_disk(&value);
+	r = dm_array_set_value(&cmd->info, cmd->root, from_cblock(cblock),
+			       &value, &cmd->root);
+	if (r)
+		return r;
+
+	cmd->changed = true;
+	return 0;
+}
+
+int dm_cache_remove_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock)
+{
+	int r;
+
+	down_write(&cmd->root_lock);
+	r = __remove(cmd, cblock);
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+static int __insert(struct dm_cache_metadata *cmd,
+		    dm_cblock_t cblock, dm_oblock_t oblock)
+{
+	int r;
+	__le64 value = pack_value(oblock, M_VALID);
+	__dm_bless_for_disk(&value);
+
+	r = dm_array_set_value(&cmd->info, cmd->root, from_cblock(cblock),
+			       &value, &cmd->root);
+	if (r)
+		return r;
+
+	cmd->changed = true;
+	return 0;
+}
+
+int dm_cache_insert_mapping(struct dm_cache_metadata *cmd,
+			    dm_cblock_t cblock, dm_oblock_t oblock)
+{
+	int r;
+
+	down_write(&cmd->root_lock);
+	r = __insert(cmd, cblock, oblock);
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+struct thunk {
+	load_mapping_fn fn;
+	void *context;
+
+	struct dm_cache_metadata *cmd;
+	bool respect_dirty_flags;
+	bool hints_valid;
+};
+
+static bool policy_unchanged(struct dm_cache_metadata *cmd,
+			     struct dm_cache_policy *policy)
+{
+	const char *policy_name = dm_cache_policy_get_name(policy);
+	const unsigned *policy_version = dm_cache_policy_get_version(policy);
+	size_t policy_hint_size = dm_cache_policy_get_hint_size(policy);
+
+	/*
+	 * Ensure policy names match.
+	 */
+	if (strncmp(cmd->policy_name, policy_name, sizeof(cmd->policy_name)))
+		return false;
+
+	/*
+	 * Ensure policy major versions match.
+	 */
+	if (cmd->policy_version[0] != policy_version[0])
+		return false;
+
+	/*
+	 * Ensure policy hint sizes match.
+	 */
+	if (cmd->policy_hint_size != policy_hint_size)
+		return false;
+
+	return true;
+}
+
+static bool hints_array_initialized(struct dm_cache_metadata *cmd)
+{
+	return cmd->hint_root && cmd->policy_hint_size;
+}
+
+static bool hints_array_available(struct dm_cache_metadata *cmd,
+				  struct dm_cache_policy *policy)
+{
+	return cmd->clean_when_opened && policy_unchanged(cmd, policy) &&
+		hints_array_initialized(cmd);
+}
+
+static int __load_mapping(void *context, uint64_t cblock, void *leaf)
+{
+	int r = 0;
+	bool dirty;
+	__le64 value;
+	__le32 hint_value = 0;
+	dm_oblock_t oblock;
+	unsigned flags;
+	struct thunk *thunk = context;
+	struct dm_cache_metadata *cmd = thunk->cmd;
+
+	memcpy(&value, leaf, sizeof(value));
+	unpack_value(value, &oblock, &flags);
+
+	if (flags & M_VALID) {
+		if (thunk->hints_valid) {
+			r = dm_array_get_value(&cmd->hint_info, cmd->hint_root,
+					       cblock, &hint_value);
+			if (r && r != -ENODATA)
+				return r;
+		}
+
+		dirty = thunk->respect_dirty_flags ? (flags & M_DIRTY) : true;
+		r = thunk->fn(thunk->context, oblock, to_cblock(cblock),
+			      dirty, le32_to_cpu(hint_value), thunk->hints_valid);
+	}
+
+	return r;
+}
+
+static int __load_mappings(struct dm_cache_metadata *cmd,
+			   struct dm_cache_policy *policy,
+			   load_mapping_fn fn, void *context)
+{
+	struct thunk thunk;
+
+	thunk.fn = fn;
+	thunk.context = context;
+
+	thunk.cmd = cmd;
+	thunk.respect_dirty_flags = cmd->clean_when_opened;
+	thunk.hints_valid = hints_array_available(cmd, policy);
+
+	return dm_array_walk(&cmd->info, cmd->root, __load_mapping, &thunk);
+}
+
+int dm_cache_load_mappings(struct dm_cache_metadata *cmd,
+			   struct dm_cache_policy *policy,
+			   load_mapping_fn fn, void *context)
+{
+	int r;
+
+	down_read(&cmd->root_lock);
+	r = __load_mappings(cmd, policy, fn, context);
+	up_read(&cmd->root_lock);
+
+	return r;
+}
+
+static int __dump_mapping(void *context, uint64_t cblock, void *leaf)
+{
+	int r = 0;
+	__le64 value;
+	dm_oblock_t oblock;
+	unsigned flags;
+
+	memcpy(&value, leaf, sizeof(value));
+	unpack_value(value, &oblock, &flags);
+
+	return r;
+}
+
+static int __dump_mappings(struct dm_cache_metadata *cmd)
+{
+	return dm_array_walk(&cmd->info, cmd->root, __dump_mapping, NULL);
+}
+
+void dm_cache_dump(struct dm_cache_metadata *cmd)
+{
+	down_read(&cmd->root_lock);
+	__dump_mappings(cmd);
+	up_read(&cmd->root_lock);
+}
+
+int dm_cache_changed_this_transaction(struct dm_cache_metadata *cmd)
+{
+	int r;
+
+	down_read(&cmd->root_lock);
+	r = cmd->changed;
+	up_read(&cmd->root_lock);
+
+	return r;
+}
+
+static int __dirty(struct dm_cache_metadata *cmd, dm_cblock_t cblock, bool dirty)
+{
+	int r;
+	unsigned flags;
+	dm_oblock_t oblock;
+	__le64 value;
+
+	r = dm_array_get_value(&cmd->info, cmd->root, from_cblock(cblock), &value);
+	if (r)
+		return r;
+
+	unpack_value(value, &oblock, &flags);
+
+	if (((flags & M_DIRTY) && dirty) || (!(flags & M_DIRTY) && !dirty))
+		/* nothing to be done */
+		return 0;
+
+	value = pack_value(oblock, (flags & ~M_DIRTY) | (dirty ? M_DIRTY : 0));
+	__dm_bless_for_disk(&value);
+
+	r = dm_array_set_value(&cmd->info, cmd->root, from_cblock(cblock),
+			       &value, &cmd->root);
+	if (r)
+		return r;
+
+	cmd->changed = true;
+	return 0;
+
+}
+
+int dm_cache_set_dirty(struct dm_cache_metadata *cmd,
+		       dm_cblock_t cblock, bool dirty)
+{
+	int r;
+
+	down_write(&cmd->root_lock);
+	r = __dirty(cmd, cblock, dirty);
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+void dm_cache_metadata_get_stats(struct dm_cache_metadata *cmd,
+				 struct dm_cache_statistics *stats)
+{
+	down_read(&cmd->root_lock);
+	*stats = cmd->stats;
+	up_read(&cmd->root_lock);
+}
+
+void dm_cache_metadata_set_stats(struct dm_cache_metadata *cmd,
+				 struct dm_cache_statistics *stats)
+{
+	down_write(&cmd->root_lock);
+	cmd->stats = *stats;
+	up_write(&cmd->root_lock);
+}
+
+int dm_cache_commit(struct dm_cache_metadata *cmd, bool clean_shutdown)
+{
+	int r;
+	flags_mutator mutator = (clean_shutdown ? set_clean_shutdown :
+				 clear_clean_shutdown);
+
+	down_write(&cmd->root_lock);
+	r = __commit_transaction(cmd, mutator);
+	if (r)
+		goto out;
+
+	r = __begin_transaction(cmd);
+
+out:
+	up_write(&cmd->root_lock);
+	return r;
+}
+
+int dm_cache_get_free_metadata_block_count(struct dm_cache_metadata *cmd,
+					   dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&cmd->root_lock);
+	r = dm_sm_get_nr_free(cmd->metadata_sm, result);
+	up_read(&cmd->root_lock);
+
+	return r;
+}
+
+int dm_cache_get_metadata_dev_size(struct dm_cache_metadata *cmd,
+				   dm_block_t *result)
+{
+	int r = -EINVAL;
+
+	down_read(&cmd->root_lock);
+	r = dm_sm_get_nr_blocks(cmd->metadata_sm, result);
+	up_read(&cmd->root_lock);
+
+	return r;
+}
+
+/*----------------------------------------------------------------*/
+
+static int begin_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *policy)
+{
+	int r;
+	__le32 value;
+	size_t hint_size;
+	const char *policy_name = dm_cache_policy_get_name(policy);
+	const unsigned *policy_version = dm_cache_policy_get_version(policy);
+
+	if (!policy_name[0] ||
+	    (strlen(policy_name) > sizeof(cmd->policy_name) - 1))
+		return -EINVAL;
+
+	if (!policy_unchanged(cmd, policy)) {
+		strncpy(cmd->policy_name, policy_name, sizeof(cmd->policy_name));
+		memcpy(cmd->policy_version, policy_version, sizeof(cmd->policy_version));
+
+		hint_size = dm_cache_policy_get_hint_size(policy);
+		if (!hint_size)
+			return 0; /* short-circuit hints initialization */
+		cmd->policy_hint_size = hint_size;
+
+		if (cmd->hint_root) {
+			r = dm_array_del(&cmd->hint_info, cmd->hint_root);
+			if (r)
+				return r;
+		}
+
+		r = dm_array_empty(&cmd->hint_info, &cmd->hint_root);
+		if (r)
+			return r;
+
+		value = cpu_to_le32(0);
+		__dm_bless_for_disk(&value);
+		r = dm_array_resize(&cmd->hint_info, cmd->hint_root, 0,
+				    from_cblock(cmd->cache_blocks),
+				    &value, &cmd->hint_root);
+		if (r)
+			return r;
+	}
+
+	return 0;
+}
+
+static int save_hint(void *context, dm_cblock_t cblock, dm_oblock_t oblock, uint32_t hint)
+{
+	struct dm_cache_metadata *cmd = context;
+	__le32 value = cpu_to_le32(hint);
+	int r;
+
+	__dm_bless_for_disk(&value);
+
+	r = dm_array_set_value(&cmd->hint_info, cmd->hint_root,
+			       from_cblock(cblock), &value, &cmd->hint_root);
+	cmd->changed = true;
+
+	return r;
+}
+
+static int write_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *policy)
+{
+	int r;
+
+	r = begin_hints(cmd, policy);
+	if (r) {
+		DMERR("begin_hints failed");
+		return r;
+	}
+
+	return policy_walk_mappings(policy, save_hint, cmd);
+}
+
+int dm_cache_write_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *policy)
+{
+	int r;
+
+	down_write(&cmd->root_lock);
+	r = write_hints(cmd, policy);
+	up_write(&cmd->root_lock);
+
+	return r;
+}
+
+int dm_cache_metadata_all_clean(struct dm_cache_metadata *cmd, bool *result)
+{
+	return blocks_are_unmapped_or_clean(cmd, 0, cmd->cache_blocks, result);
+}