123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750751752753754755756757758759760761762763764765766767768769770771772773774775776777778779780781782783784785786787788789790791792793794795796797798799800801802803804805806807808809810811812813814815816817818819820821822823824825826827828829830831832833834835836837838839840841842843844845846847848849850851852853854855856857858859860861862863864865866867868869870871872873874875876877878879880881882883884885886887888889890891892893894895896897898899900901902903904905906907908909910911912913914915916917918919920921922923924925926927928929930931932933934935936937938939940941942943944945946947948949950951952953954955956957958959960961962963964965966967968969970971972973974975976977978979980981982983984985986987988989990991992993994995996997998999100010011002100310041005100610071008100910101011101210131014101510161017101810191020102110221023102410251026102710281029103010311032103310341035103610371038103910401041104210431044104510461047104810491050105110521053105410551056105710581059106010611062106310641065106610671068106910701071107210731074107510761077107810791080108110821083108410851086108710881089109010911092109310941095109610971098109911001101110211031104110511061107110811091110111111121113111411151116111711181119112011211122112311241125112611271128112911301131113211331134113511361137113811391140114111421143114411451146114711481149115011511152115311541155115611571158115911601161116211631164116511661167116811691170117111721173117411751176117711781179118011811182118311841185118611871188118911901191119211931194119511961197119811991200120112021203120412051206120712081209121012111212121312141215121612171218121912201221122212231224122512261227122812291230123112321233123412351236123712381239124012411242124312441245124612471248124912501251125212531254125512561257125812591260126112621263126412651266126712681269127012711272127312741275127612771278127912801281128212831284128512861287128812891290129112921293129412951296129712981299130013011302130313041305130613071308130913101311131213131314131513161317131813191320132113221323132413251326132713281329133013311332133313341335133613371338133913401341134213431344134513461347134813491350135113521353135413551356135713581359136013611362136313641365136613671368136913701371137213731374137513761377137813791380138113821383138413851386138713881389139013911392139313941395139613971398139914001401140214031404140514061407140814091410141114121413141414151416141714181419142014211422142314241425142614271428142914301431143214331434143514361437143814391440144114421443144414451446144714481449145014511452145314541455145614571458145914601461146214631464146514661467146814691470147114721473147414751476147714781479148014811482148314841485148614871488148914901491149214931494149514961497149814991500150115021503150415051506150715081509151015111512151315141515151615171518151915201521152215231524152515261527152815291530153115321533153415351536153715381539154015411542154315441545154615471548154915501551155215531554155515561557155815591560156115621563156415651566156715681569157015711572157315741575157615771578157915801581158215831584158515861587158815891590159115921593159415951596159715981599160016011602160316041605160616071608160916101611161216131614161516161617161816191620162116221623162416251626162716281629163016311632163316341635163616371638163916401641164216431644164516461647164816491650165116521653165416551656165716581659166016611662166316641665166616671668166916701671167216731674167516761677167816791680168116821683168416851686168716881689169016911692169316941695169616971698169917001701170217031704170517061707170817091710171117121713171417151716171717181719172017211722172317241725172617271728172917301731173217331734173517361737173817391740174117421743174417451746174717481749175017511752175317541755175617571758175917601761176217631764176517661767176817691770177117721773177417751776177717781779178017811782178317841785178617871788178917901791179217931794179517961797179817991800180118021803180418051806180718081809181018111812181318141815181618171818181918201821182218231824182518261827182818291830183118321833183418351836183718381839184018411842184318441845184618471848184918501851185218531854185518561857185818591860186118621863186418651866186718681869187018711872187318741875187618771878187918801881188218831884188518861887188818891890189118921893189418951896189718981899190019011902190319041905190619071908190919101911191219131914191519161917191819191920192119221923192419251926192719281929193019311932193319341935193619371938193919401941194219431944194519461947194819491950195119521953195419551956195719581959196019611962196319641965196619671968196919701971197219731974197519761977197819791980198119821983198419851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201120122013201420152016201720182019202020212022202320242025202620272028202920302031203220332034203520362037203820392040204120422043/*
 * 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 48
 *   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;

	/*
	 * 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;

	/*
	 * 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("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) != THIN_SUPERBLOCK_MAGIC) {
		DMERR("sb_check failed: magic %llu: "
		      "wanted %llu", 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("sb_check failed: csum %u: wanted %u",
		      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);
}

static void data_block_inc(void *context, const void *value_le)
{
	struct dm_space_map *sm = context;
	__le64 v_le;
	uint64_t b;
	uint32_t t;

	memcpy(&v_le, value_le, sizeof(v_le));
	unpack_block_time(le64_to_cpu(v_le), &b, &t);
	dm_sm_inc_block(sm, b);
}

static void data_block_dec(void *context, const void *value_le)
{
	struct dm_space_map *sm = context;
	__le64 v_le;
	uint64_t b;
	uint32_t t;

	memcpy(&v_le, value_le, sizeof(v_le));
	unpack_block_time(le64_to_cpu(v_le), &b, &t);
	dm_sm_dec_block(sm, b);
}

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)
{
	struct dm_btree_info *info = context;
	__le64 root_le;
	uint64_t root;

	memcpy(&root_le, value, sizeof(root_le));
	root = le64_to_cpu(root_le);
	dm_tm_inc(info->tm, root);
}

static void subtree_dec(void *context, const void *value)
{
	struct dm_btree_info *info = context;
	__le64 root_le;
	uint64_t root;

	memcpy(&root_le, value, sizeof(root_le));
	root = le64_to_cpu(root_le);
	if (dm_btree_del(info, root))
		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;
}

/*----------------------------------------------------------------*/

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;
	struct dm_block *b;
	__le64 *data_le, zero = cpu_to_le64(0);
	unsigned 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 = i_size_read(pmd->bdev->bd_inode) >> SECTOR_SHIFT;

	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) {
		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_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);

	/* 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) {
		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);
	dm_bm_unlock(sblock);

	return 0;

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 << SECTOR_SHIFT,
					  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;
	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 = 0;
		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);

	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->bdev = bdev;
	pmd->data_block_size = data_block_size;

	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 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;
	}

	if (!dm_bm_is_read_only(pmd->bm) && !pmd->fail_io) {
		r = __commit_transaction(pmd);
		if (r < 0)
			DMWARN("%s: __commit_transaction() failed, error = %d",
			       __func__, r);
	}

	if (!pmd->fail_io)
		__destroy_persistent_data_objects(pmd);

	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 disk_device_details details_le;
	struct dm_thin_device *td;
	__le64 value;

	r = dm_btree_lookup(&pmd->details_info, pmd->details_root,
			    &key, &details_le);
	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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __create_thin(pmd, dev);
	up_write(&pmd->root_lock);

	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 = 1;
	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;
	struct disk_device_details details_le;
	__le64 value;

	/* check this device is unused */
	r = dm_btree_lookup(&pmd->details_info, pmd->details_root,
			    &dev_key, &details_le);
	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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __create_snap(pmd, dev, origin);
	up_write(&pmd->root_lock);

	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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __delete_device(pmd, dev);
	up_write(&pmd->root_lock);

	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;

	down_write(&pmd->root_lock);

	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:
	up_write(&pmd->root_lock);

	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.
	 */
	__commit_transaction(pmd);

	/*
	 * 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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __reserve_metadata_snap(pmd);
	up_write(&pmd->root_lock);

	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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __release_metadata_snap(pmd);
	up_write(&pmd->root_lock);

	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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __open_device(pmd, dev, 0, td);
	up_write(&pmd->root_lock);

	return r;
}

int dm_pool_close_thin_device(struct dm_thin_device *td)
{
	down_write(&td->pmd->root_lock);
	__close_device(td);
	up_write(&td->pmd->root_lock);

	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;
			else
				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 = 1;
	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;

	down_write(&td->pmd->root_lock);
	if (!td->pmd->fail_io)
		r = __insert(td, block, data_block);
	up_write(&td->pmd->root_lock);

	return r;
}

static int __remove(struct dm_thin_device *td, dm_block_t block)
{
	int r;
	struct dm_pool_metadata *pmd = td->pmd;
	dm_block_t keys[2] = { td->id, block };

	r = dm_btree_remove(&pmd->info, pmd->root, keys, &pmd->root);
	if (r)
		return r;

	td->mapped_blocks--;
	td->changed = 1;

	return 0;
}

static int __remove_range(struct dm_thin_device *td, dm_block_t begin, dm_block_t end)
{
	int r;
	unsigned 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 = 1;

	/*
	 * 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_block(struct dm_thin_device *td, dm_block_t block)
{
	int r = -EINVAL;

	down_write(&td->pmd->root_lock);
	if (!td->pmd->fail_io)
		r = __remove(td, block);
	up_write(&td->pmd->root_lock);

	return r;
}

int dm_thin_remove_range(struct dm_thin_device *td,
			 dm_block_t begin, dm_block_t end)
{
	int r = -EINVAL;

	down_write(&td->pmd->root_lock);
	if (!td->pmd->fail_io)
		r = __remove_range(td, begin, end);
	up_write(&td->pmd->root_lock);

	return r;
}

int dm_pool_block_is_used(struct dm_pool_metadata *pmd, dm_block_t b, bool *result)
{
	int r;
	uint32_t ref_count;

	down_read(&pmd->root_lock);
	r = dm_sm_get_count(pmd->data_sm, b, &ref_count);
	if (!r)
		*result = (ref_count != 0);
	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 = 0;

	down_write(&pmd->root_lock);
	for (; b != e; b++) {
		r = dm_sm_inc_block(pmd->data_sm, b);
		if (r)
			break;
	}
	up_write(&pmd->root_lock);

	return r;
}

int dm_pool_dec_data_range(struct dm_pool_metadata *pmd, dm_block_t b, dm_block_t e)
{
	int r = 0;

	down_write(&pmd->root_lock);
	for (; b != e; b++) {
		r = dm_sm_dec_block(pmd->data_sm, b);
		if (r)
			break;
	}
	up_write(&pmd->root_lock);

	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;

	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;
}

int dm_pool_commit_metadata(struct dm_pool_metadata *pmd)
{
	int r = -EINVAL;

	down_write(&pmd->root_lock);
	if (pmd->fail_io)
		goto out;

	r = __commit_transaction(pmd);
	if (r <= 0)
		goto out;

	/*
	 * Open the next transaction.
	 */
	r = __begin_transaction(pmd);
out:
	up_write(&pmd->root_lock);
	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 = -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;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io)
		r = __resize_space_map(pmd->data_sm, new_count);
	up_write(&pmd->root_lock);

	return r;
}

int dm_pool_resize_metadata_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
{
	int r = -EINVAL;

	down_write(&pmd->root_lock);
	if (!pmd->fail_io) {
		r = __resize_space_map(pmd->metadata_sm, new_count);
		if (!r)
			__set_metadata_reserve(pmd);
	}
	up_write(&pmd->root_lock);

	return r;
}

void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd)
{
	down_write(&pmd->root_lock);
	dm_bm_set_read_only(pmd->bm);
	up_write(&pmd->root_lock);
}

void dm_pool_metadata_read_write(struct dm_pool_metadata *pmd)
{
	down_write(&pmd->root_lock);
	dm_bm_set_read_write(pmd->bm);
	up_write(&pmd->root_lock);
}

int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
					dm_block_t threshold,
					dm_sm_threshold_fn fn,
					void *context)
{
	int r;

	down_write(&pmd->root_lock);
	r = dm_sm_register_threshold_callback(pmd->metadata_sm, threshold, fn, context);
	up_write(&pmd->root_lock);

	return r;
}

int dm_pool_metadata_set_needs_check(struct dm_pool_metadata *pmd)
{
	int r;
	struct dm_block *sblock;
	struct thin_disk_superblock *disk_super;

	down_write(&pmd->root_lock);
	pmd->flags |= THIN_METADATA_NEEDS_CHECK_FLAG;

	r = superblock_lock(pmd, &sblock);
	if (r) {
		DMERR("couldn't read superblock");
		goto out;
	}

	disk_super = dm_block_data(sblock);
	disk_super->flags = cpu_to_le32(pmd->flags);

	dm_bm_unlock(sblock);
out:
	up_write(&pmd->root_lock);
	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);
}