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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 #include "dm.h"
 #include "persistent-data/dm-transaction-manager.h"
 #include "persistent-data/dm-bitset.h"
 #include "persistent-data/dm-space-map.h"
 
 #include <linux/dm-io.h>
 #include <linux/dm-kcopyd.h>
 #include <linux/init.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 
 #define DM_MSG_PREFIX "era"
 
 #define SUPERBLOCK_LOCATION 0
 #define SUPERBLOCK_MAGIC 2126579579
 #define SUPERBLOCK_CSUM_XOR 146538381
 #define MIN_ERA_VERSION 1
 #define MAX_ERA_VERSION 1
 #define INVALID_WRITESET_ROOT SUPERBLOCK_LOCATION
 #define MIN_BLOCK_SIZE 8
 
 /*----------------------------------------------------------------
  * Writeset
  *--------------------------------------------------------------*/
 struct writeset_metadata {
     uint32_t nr_bits;
     dm_block_t root;
 };
 
 struct writeset {
     struct writeset_metadata md;
 
     /*
      * An in core copy of the bits to save constantly doing look ups on
      * disk.
      */
     unsigned long *bits;
 };
 
 /*
  * This does not free off the on disk bitset as this will normally be done
  * after digesting into the era array.
  */
 static void writeset_free(struct writeset *ws)
 {
     vfree(ws->bits);
     ws->bits = NULL;
 }
 
 static int setup_on_disk_bitset(struct dm_disk_bitset *info,
                 unsigned nr_bits, dm_block_t *root)
 {
     int r;
 
     r = dm_bitset_empty(info, root);
     if (r)
         return r;
 
     return dm_bitset_resize(info, *root, 0, nr_bits, false, root);
 }
 
 static size_t bitset_size(unsigned nr_bits)
 {
     return sizeof(unsigned long) * dm_div_up(nr_bits, BITS_PER_LONG);
 }
 
 /*
  * Allocates memory for the in core bitset.
  */
 static int writeset_alloc(struct writeset *ws, dm_block_t nr_blocks)
 {
     ws->bits = vzalloc(bitset_size(nr_blocks));
     if (!ws->bits) {
         DMERR("%s: couldn't allocate in memory bitset", __func__);
         return -ENOMEM;
     }
 
     return 0;
 }
 
 /*
  * Wipes the in-core bitset, and creates a new on disk bitset.
  */
 static int writeset_init(struct dm_disk_bitset *info, struct writeset *ws,
              dm_block_t nr_blocks)
 {
     int r;
 
     memset(ws->bits, 0, bitset_size(nr_blocks));
 
     ws->md.nr_bits = nr_blocks;
     r = setup_on_disk_bitset(info, ws->md.nr_bits, &ws->md.root);
     if (r) {
         DMERR("%s: setup_on_disk_bitset failed", __func__);
         return r;
     }
 
     return 0;
 }
 
 static bool writeset_marked(struct writeset *ws, dm_block_t block)
 {
     return test_bit(block, ws->bits);
 }
 
 static int writeset_marked_on_disk(struct dm_disk_bitset *info,
                    struct writeset_metadata *m, dm_block_t block,
                    bool *result)
 {
     dm_block_t old = m->root;
 
     /*
      * The bitset was flushed when it was archived, so we know there'll
      * be no change to the root.
      */
     int r = dm_bitset_test_bit(info, m->root, block, &m->root, result);
     if (r) {
         DMERR("%s: dm_bitset_test_bit failed", __func__);
         return r;
     }
 
     BUG_ON(m->root != old);
 
     return r;
 }
 
 /*
  * Returns < 0 on error, 0 if the bit wasn't previously set, 1 if it was.
  */
 static int writeset_test_and_set(struct dm_disk_bitset *info,
                  struct writeset *ws, uint32_t block)
 {
     int r;
 
     if (!test_bit(block, ws->bits)) {
         r = dm_bitset_set_bit(info, ws->md.root, block, &ws->md.root);
         if (r) {
             /* FIXME: fail mode */
             return r;
         }
 
         return 0;
     }
 
     return 1;
 }
 
 /*----------------------------------------------------------------
  * On disk metadata layout
  *--------------------------------------------------------------*/
 #define SPACE_MAP_ROOT_SIZE 128
 #define UUID_LEN 16
 
 struct writeset_disk {
     __le32 nr_bits;
     __le64 root;
 } __packed;
 
 struct superblock_disk {
     __le32 csum;
     __le32 flags;
     __le64 blocknr;
 
     __u8 uuid[UUID_LEN];
     __le64 magic;
     __le32 version;
 
     __u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
 
     __le32 data_block_size;
     __le32 metadata_block_size;
     __le32 nr_blocks;
 
     __le32 current_era;
     struct writeset_disk current_writeset;
 
     /*
      * Only these two fields are valid within the metadata snapshot.
      */
     __le64 writeset_tree_root;
     __le64 era_array_root;
 
     __le64 metadata_snap;
 } __packed;
 
 /*----------------------------------------------------------------
  * Superblock validation
  *--------------------------------------------------------------*/
 static void sb_prepare_for_write(struct dm_block_validator *v,
                  struct dm_block *b,
                  size_t sb_block_size)
 {
     struct superblock_disk *disk = dm_block_data(b);
 
     disk->blocknr = cpu_to_le64(dm_block_location(b));
     disk->csum = cpu_to_le32(dm_bm_checksum(&disk->flags,
                         sb_block_size - sizeof(__le32),
                         SUPERBLOCK_CSUM_XOR));
 }
 
 static int check_metadata_version(struct superblock_disk *disk)
 {
     uint32_t metadata_version = le32_to_cpu(disk->version);
     if (metadata_version < MIN_ERA_VERSION || metadata_version > MAX_ERA_VERSION) {
         DMERR("Era metadata version %u found, but only versions between %u and %u supported.",
               metadata_version, MIN_ERA_VERSION, MAX_ERA_VERSION);
         return -EINVAL;
     }
 
     return 0;
 }
 
 static int sb_check(struct dm_block_validator *v,
             struct dm_block *b,
             size_t sb_block_size)
 {
     struct superblock_disk *disk = dm_block_data(b);
     __le32 csum_le;
 
     if (dm_block_location(b) != le64_to_cpu(disk->blocknr)) {
         DMERR("sb_check failed: blocknr %llu: wanted %llu",
               le64_to_cpu(disk->blocknr),
               (unsigned long long)dm_block_location(b));
         return -ENOTBLK;
     }
 
     if (le64_to_cpu(disk->magic) != SUPERBLOCK_MAGIC) {
         DMERR("sb_check failed: magic %llu: wanted %llu",
               le64_to_cpu(disk->magic),
               (unsigned long long) SUPERBLOCK_MAGIC);
         return -EILSEQ;
     }
 
     csum_le = cpu_to_le32(dm_bm_checksum(&disk->flags,
                          sb_block_size - sizeof(__le32),
                          SUPERBLOCK_CSUM_XOR));
     if (csum_le != disk->csum) {
         DMERR("sb_check failed: csum %u: wanted %u",
               le32_to_cpu(csum_le), le32_to_cpu(disk->csum));
         return -EILSEQ;
     }
 
     return check_metadata_version(disk);
 }
 
 static struct dm_block_validator sb_validator = {
     .name = "superblock",
     .prepare_for_write = sb_prepare_for_write,
     .check = sb_check
 };
 
 /*----------------------------------------------------------------
  * Low level metadata handling
  *--------------------------------------------------------------*/
 #define DM_ERA_METADATA_BLOCK_SIZE 4096
 #define ERA_MAX_CONCURRENT_LOCKS 5
 
 struct era_metadata {
     struct block_device *bdev;
     struct dm_block_manager *bm;
     struct dm_space_map *sm;
     struct dm_transaction_manager *tm;
 
     dm_block_t block_size;
     uint32_t nr_blocks;
 
     uint32_t current_era;
 
     /*
      * We preallocate 2 writesets.  When an era rolls over we
      * switch between them. This means the allocation is done at
      * preresume time, rather than on the io path.
      */
     struct writeset writesets[2];
     struct writeset *current_writeset;
 
     dm_block_t writeset_tree_root;
     dm_block_t era_array_root;
 
     struct dm_disk_bitset bitset_info;
     struct dm_btree_info writeset_tree_info;
     struct dm_array_info era_array_info;
 
     dm_block_t metadata_snap;
 
     /*
      * A flag that is set whenever a writeset has been archived.
      */
     bool archived_writesets;
 
     /*
      * 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];
 };
 
 static int superblock_read_lock(struct era_metadata *md,
                 struct dm_block **sblock)
 {
     return dm_bm_read_lock(md->bm, SUPERBLOCK_LOCATION,
                    &sb_validator, sblock);
 }
 
 static int superblock_lock_zero(struct era_metadata *md,
                 struct dm_block **sblock)
 {
     return dm_bm_write_lock_zero(md->bm, SUPERBLOCK_LOCATION,
                      &sb_validator, sblock);
 }
 
 static int superblock_lock(struct era_metadata *md,
                struct dm_block **sblock)
 {
     return dm_bm_write_lock(md->bm, SUPERBLOCK_LOCATION,
                 &sb_validator, sblock);
 }
 
 /* FIXME: duplication with cache and thin */
 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, 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;
         }
     }
 
     dm_bm_unlock(b);
 
     return 0;
 }
 
 /*----------------------------------------------------------------*/
 
 static void ws_pack(const struct writeset_metadata *core, struct writeset_disk *disk)
 {
     disk->nr_bits = cpu_to_le32(core->nr_bits);
     disk->root = cpu_to_le64(core->root);
 }
 
 static void ws_unpack(const struct writeset_disk *disk, struct writeset_metadata *core)
 {
     core->nr_bits = le32_to_cpu(disk->nr_bits);
     core->root = le64_to_cpu(disk->root);
 }
 
 static void ws_inc(void *context, const void *value, unsigned count)
 {
     struct era_metadata *md = context;
     struct writeset_disk ws_d;
     dm_block_t b;
     unsigned i;
 
     for (i = 0; i < count; i++) {
         memcpy(&ws_d, value + (i * sizeof(ws_d)), sizeof(ws_d));
         b = le64_to_cpu(ws_d.root);
         dm_tm_inc(md->tm, b);
     }
 }
 
 static void ws_dec(void *context, const void *value, unsigned count)
 {
     struct era_metadata *md = context;
     struct writeset_disk ws_d;
     dm_block_t b;
     unsigned i;
 
     for (i = 0; i < count; i++) {
         memcpy(&ws_d, value + (i * sizeof(ws_d)), sizeof(ws_d));
         b = le64_to_cpu(ws_d.root);
         dm_bitset_del(&md->bitset_info, b);
     }
 }
 
 static int ws_eq(void *context, const void *value1, const void *value2)
 {
     return !memcmp(value1, value2, sizeof(struct writeset_disk));
 }
 
 /*----------------------------------------------------------------*/
 
 static void setup_writeset_tree_info(struct era_metadata *md)
 {
     struct dm_btree_value_type *vt = &md->writeset_tree_info.value_type;
     md->writeset_tree_info.tm = md->tm;
     md->writeset_tree_info.levels = 1;
     vt->context = md;
     vt->size = sizeof(struct writeset_disk);
     vt->inc = ws_inc;
     vt->dec = ws_dec;
     vt->equal = ws_eq;
 }
 
 static void setup_era_array_info(struct era_metadata *md)
 
 {
     struct dm_btree_value_type vt;
     vt.context = NULL;
     vt.size = sizeof(__le32);
     vt.inc = NULL;
     vt.dec = NULL;
     vt.equal = NULL;
 
     dm_array_info_init(&md->era_array_info, md->tm, &vt);
 }
 
 static void setup_infos(struct era_metadata *md)
 {
     dm_disk_bitset_init(md->tm, &md->bitset_info);
     setup_writeset_tree_info(md);
     setup_era_array_info(md);
 }
 
 /*----------------------------------------------------------------*/
 
 static int create_fresh_metadata(struct era_metadata *md)
 {
     int r;
 
     r = dm_tm_create_with_sm(md->bm, SUPERBLOCK_LOCATION,
                  &md->tm, &md->sm);
     if (r < 0) {
         DMERR("dm_tm_create_with_sm failed");
         return r;
     }
 
     setup_infos(md);
 
     r = dm_btree_empty(&md->writeset_tree_info, &md->writeset_tree_root);
     if (r) {
         DMERR("couldn't create new writeset tree");
         goto bad;
     }
 
     r = dm_array_empty(&md->era_array_info, &md->era_array_root);
     if (r) {
         DMERR("couldn't create era array");
         goto bad;
     }
 
     return 0;
 
 bad:
     dm_sm_destroy(md->sm);
     dm_tm_destroy(md->tm);
 
     return r;
 }
 
 static int save_sm_root(struct era_metadata *md)
 {
     int r;
     size_t metadata_len;
 
     r = dm_sm_root_size(md->sm, &metadata_len);
     if (r < 0)
         return r;
 
     return dm_sm_copy_root(md->sm, &md->metadata_space_map_root,
                    metadata_len);
 }
 
 static void copy_sm_root(struct era_metadata *md, struct superblock_disk *disk)
 {
     memcpy(&disk->metadata_space_map_root,
            &md->metadata_space_map_root,
            sizeof(md->metadata_space_map_root));
 }
 
 /*
  * Writes a superblock, including the static fields that don't get updated
  * with every commit (possible optimisation here).  'md' should be fully
  * constructed when this is called.
  */
 static void prepare_superblock(struct era_metadata *md, struct superblock_disk *disk)
 {
     disk->magic = cpu_to_le64(SUPERBLOCK_MAGIC);
     disk->flags = cpu_to_le32(0ul);
 
     /* FIXME: can't keep blanking the uuid (uuid is currently unused though) */
     memset(disk->uuid, 0, sizeof(disk->uuid));
     disk->version = cpu_to_le32(MAX_ERA_VERSION);
 
     copy_sm_root(md, disk);
 
     disk->data_block_size = cpu_to_le32(md->block_size);
     disk->metadata_block_size = cpu_to_le32(DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);
     disk->nr_blocks = cpu_to_le32(md->nr_blocks);
     disk->current_era = cpu_to_le32(md->current_era);
 
     ws_pack(&md->current_writeset->md, &disk->current_writeset);
     disk->writeset_tree_root = cpu_to_le64(md->writeset_tree_root);
     disk->era_array_root = cpu_to_le64(md->era_array_root);
     disk->metadata_snap = cpu_to_le64(md->metadata_snap);
 }
 
 static int write_superblock(struct era_metadata *md)
 {
     int r;
     struct dm_block *sblock;
     struct superblock_disk *disk;
 
     r = save_sm_root(md);
     if (r) {
         DMERR("%s: save_sm_root failed", __func__);
         return r;
     }
 
     r = superblock_lock_zero(md, &sblock);
     if (r)
         return r;
 
     disk = dm_block_data(sblock);
     prepare_superblock(md, disk);
 
     return dm_tm_commit(md->tm, sblock);
 }
 
 /*
  * Assumes block_size and the infos are set.
  */
 static int format_metadata(struct era_metadata *md)
 {
     int r;
 
     r = create_fresh_metadata(md);
     if (r)
         return r;
 
     r = write_superblock(md);
     if (r) {
         dm_sm_destroy(md->sm);
         dm_tm_destroy(md->tm);
         return r;
     }
 
     return 0;
 }
 
 static int open_metadata(struct era_metadata *md)
 {
     int r;
     struct dm_block *sblock;
     struct superblock_disk *disk;
 
     r = superblock_read_lock(md, &sblock);
     if (r) {
         DMERR("couldn't read_lock superblock");
         return r;
     }
 
     disk = dm_block_data(sblock);
 
     /* Verify the data block size hasn't changed */
     if (le32_to_cpu(disk->data_block_size) != md->block_size) {
         DMERR("changing the data block size (from %u to %llu) is not supported",
               le32_to_cpu(disk->data_block_size), md->block_size);
         r = -EINVAL;
         goto bad;
     }
 
     r = dm_tm_open_with_sm(md->bm, SUPERBLOCK_LOCATION,
                    disk->metadata_space_map_root,
                    sizeof(disk->metadata_space_map_root),
                    &md->tm, &md->sm);
     if (r) {
         DMERR("dm_tm_open_with_sm failed");
         goto bad;
     }
 
     setup_infos(md);
 
     md->nr_blocks = le32_to_cpu(disk->nr_blocks);
     md->current_era = le32_to_cpu(disk->current_era);
 
     ws_unpack(&disk->current_writeset, &md->current_writeset->md);
     md->writeset_tree_root = le64_to_cpu(disk->writeset_tree_root);
     md->era_array_root = le64_to_cpu(disk->era_array_root);
     md->metadata_snap = le64_to_cpu(disk->metadata_snap);
     md->archived_writesets = true;
 
     dm_bm_unlock(sblock);
 
     return 0;
 
 bad:
     dm_bm_unlock(sblock);
     return r;
 }
 
 static int open_or_format_metadata(struct era_metadata *md,
                    bool may_format)
 {
     int r;
     bool unformatted = false;
 
     r = superblock_all_zeroes(md->bm, &unformatted);
     if (r)
         return r;
 
     if (unformatted)
         return may_format ? format_metadata(md) : -EPERM;
 
     return open_metadata(md);
 }
 
 static int create_persistent_data_objects(struct era_metadata *md,
                       bool may_format)
 {
     int r;
 
     md->bm = dm_block_manager_create(md->bdev, DM_ERA_METADATA_BLOCK_SIZE,
                      ERA_MAX_CONCURRENT_LOCKS);
     if (IS_ERR(md->bm)) {
         DMERR("could not create block manager");
         return PTR_ERR(md->bm);
     }
 
     r = open_or_format_metadata(md, may_format);
     if (r)
         dm_block_manager_destroy(md->bm);
 
     return r;
 }
 
 static void destroy_persistent_data_objects(struct era_metadata *md)
 {
     dm_sm_destroy(md->sm);
     dm_tm_destroy(md->tm);
     dm_block_manager_destroy(md->bm);
 }
 
 /*
  * This waits until all era_map threads have picked up the new filter.
  */
 static void swap_writeset(struct era_metadata *md, struct writeset *new_writeset)
 {
     rcu_assign_pointer(md->current_writeset, new_writeset);
     synchronize_rcu();
 }
 
 /*----------------------------------------------------------------
  * Writesets get 'digested' into the main era array.
  *
  * We're using a coroutine here so the worker thread can do the digestion,
  * thus avoiding synchronisation of the metadata.  Digesting a whole
  * writeset in one go would cause too much latency.
  *--------------------------------------------------------------*/
 struct digest {
     uint32_t era;
     unsigned nr_bits, current_bit;
     struct writeset_metadata writeset;
     __le32 value;
     struct dm_disk_bitset info;
 
     int (*step)(struct era_metadata *, struct digest *);
 };
 
 static int metadata_digest_lookup_writeset(struct era_metadata *md,
                        struct digest *d);
 
 static int metadata_digest_remove_writeset(struct era_metadata *md,
                        struct digest *d)
 {
     int r;
     uint64_t key = d->era;
 
     r = dm_btree_remove(&md->writeset_tree_info, md->writeset_tree_root,
                 &key, &md->writeset_tree_root);
     if (r) {
         DMERR("%s: dm_btree_remove failed", __func__);
         return r;
     }
 
     d->step = metadata_digest_lookup_writeset;
     return 0;
 }
 
 #define INSERTS_PER_STEP 100
 
 static int metadata_digest_transcribe_writeset(struct era_metadata *md,
                            struct digest *d)
 {
     int r;
     bool marked;
     unsigned b, e = min(d->current_bit + INSERTS_PER_STEP, d->nr_bits);
 
     for (b = d->current_bit; b < e; b++) {
         r = writeset_marked_on_disk(&d->info, &d->writeset, b, &marked);
         if (r) {
             DMERR("%s: writeset_marked_on_disk failed", __func__);
             return r;
         }
 
         if (!marked)
             continue;
 
         __dm_bless_for_disk(&d->value);
         r = dm_array_set_value(&md->era_array_info, md->era_array_root,
                        b, &d->value, &md->era_array_root);
         if (r) {
             DMERR("%s: dm_array_set_value failed", __func__);
             return r;
         }
     }
 
     if (b == d->nr_bits)
         d->step = metadata_digest_remove_writeset;
     else
         d->current_bit = b;
 
     return 0;
 }
 
 static int metadata_digest_lookup_writeset(struct era_metadata *md,
                        struct digest *d)
 {
     int r;
     uint64_t key;
     struct writeset_disk disk;
 
     r = dm_btree_find_lowest_key(&md->writeset_tree_info,
                      md->writeset_tree_root, &key);
     if (r < 0)
         return r;
 
     d->era = key;
 
     r = dm_btree_lookup(&md->writeset_tree_info,
                 md->writeset_tree_root, &key, &disk);
     if (r) {
         if (r == -ENODATA) {
             d->step = NULL;
             return 0;
         }
 
         DMERR("%s: dm_btree_lookup failed", __func__);
         return r;
     }
 
     ws_unpack(&disk, &d->writeset);
     d->value = cpu_to_le32(key);
 
     /*
      * We initialise another bitset info to avoid any caching side effects
      * with the previous one.
      */
     dm_disk_bitset_init(md->tm, &d->info);
 
     d->nr_bits = min(d->writeset.nr_bits, md->nr_blocks);
     d->current_bit = 0;
     d->step = metadata_digest_transcribe_writeset;
 
     return 0;
 }
 
 static int metadata_digest_start(struct era_metadata *md, struct digest *d)
 {
     if (d->step)
         return 0;
 
     memset(d, 0, sizeof(*d));
     d->step = metadata_digest_lookup_writeset;
 
     return 0;
 }
 
 /*----------------------------------------------------------------
  * High level metadata interface.  Target methods should use these, and not
  * the lower level ones.
  *--------------------------------------------------------------*/
 static struct era_metadata *metadata_open(struct block_device *bdev,
                       sector_t block_size,
                       bool may_format)
 {
     int r;
     struct era_metadata *md = kzalloc(sizeof(*md), GFP_KERNEL);
 
     if (!md)
         return NULL;
 
     md->bdev = bdev;
     md->block_size = block_size;
 
     md->writesets[0].md.root = INVALID_WRITESET_ROOT;
     md->writesets[1].md.root = INVALID_WRITESET_ROOT;
     md->current_writeset = &md->writesets[0];
 
     r = create_persistent_data_objects(md, may_format);
     if (r) {
         kfree(md);
         return ERR_PTR(r);
     }
 
     return md;
 }
 
 static void metadata_close(struct era_metadata *md)
 {
     writeset_free(&md->writesets[0]);
     writeset_free(&md->writesets[1]);
     destroy_persistent_data_objects(md);
     kfree(md);
 }
 
 static bool valid_nr_blocks(dm_block_t n)
 {
     /*
      * dm_bitset restricts us to 2^32.  test_bit & co. restrict us
      * further to 2^31 - 1
      */
     return n < (1ull << 31);
 }
 
 static int metadata_resize(struct era_metadata *md, void *arg)
 {
     int r;
     dm_block_t *new_size = arg;
     __le32 value;
 
     if (!valid_nr_blocks(*new_size)) {
         DMERR("Invalid number of origin blocks %llu",
               (unsigned long long) *new_size);
         return -EINVAL;
     }
 
     writeset_free(&md->writesets[0]);
     writeset_free(&md->writesets[1]);
 
     r = writeset_alloc(&md->writesets[0], *new_size);
     if (r) {
         DMERR("%s: writeset_alloc failed for writeset 0", __func__);
         return r;
     }
 
     r = writeset_alloc(&md->writesets[1], *new_size);
     if (r) {
         DMERR("%s: writeset_alloc failed for writeset 1", __func__);
         writeset_free(&md->writesets[0]);
         return r;
     }
 
     value = cpu_to_le32(0u);
     __dm_bless_for_disk(&value);
     r = dm_array_resize(&md->era_array_info, md->era_array_root,
                 md->nr_blocks, *new_size,
                 &value, &md->era_array_root);
     if (r) {
         DMERR("%s: dm_array_resize failed", __func__);
         writeset_free(&md->writesets[0]);
         writeset_free(&md->writesets[1]);
         return r;
     }
 
     md->nr_blocks = *new_size;
     return 0;
 }
 
 static int metadata_era_archive(struct era_metadata *md)
 {
     int r;
     uint64_t keys[1];
     struct writeset_disk value;
 
     r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,
                 &md->current_writeset->md.root);
     if (r) {
         DMERR("%s: dm_bitset_flush failed", __func__);
         return r;
     }
 
     ws_pack(&md->current_writeset->md, &value);
 
     keys[0] = md->current_era;
     __dm_bless_for_disk(&value);
     r = dm_btree_insert(&md->writeset_tree_info, md->writeset_tree_root,
                 keys, &value, &md->writeset_tree_root);
     if (r) {
         DMERR("%s: couldn't insert writeset into btree", __func__);
         /* FIXME: fail mode */
         return r;
     }
 
     md->current_writeset->md.root = INVALID_WRITESET_ROOT;
     md->archived_writesets = true;
 
     return 0;
 }
 
 static struct writeset *next_writeset(struct era_metadata *md)
 {
     return (md->current_writeset == &md->writesets[0]) ?
         &md->writesets[1] : &md->writesets[0];
 }
 
 static int metadata_new_era(struct era_metadata *md)
 {
     int r;
     struct writeset *new_writeset = next_writeset(md);
 
     r = writeset_init(&md->bitset_info, new_writeset, md->nr_blocks);
     if (r) {
         DMERR("%s: writeset_init failed", __func__);
         return r;
     }
 
     swap_writeset(md, new_writeset);
     md->current_era++;
 
     return 0;
 }
 
 static int metadata_era_rollover(struct era_metadata *md)
 {
     int r;
 
     if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) {
         r = metadata_era_archive(md);
         if (r) {
             DMERR("%s: metadata_archive_era failed", __func__);
             /* FIXME: fail mode? */
             return r;
         }
     }
 
     r = metadata_new_era(md);
     if (r) {
         DMERR("%s: new era failed", __func__);
         /* FIXME: fail mode */
         return r;
     }
 
     return 0;
 }
 
 static bool metadata_current_marked(struct era_metadata *md, dm_block_t block)
 {
     bool r;
     struct writeset *ws;
 
     rcu_read_lock();
     ws = rcu_dereference(md->current_writeset);
     r = writeset_marked(ws, block);
     rcu_read_unlock();
 
     return r;
 }
 
 static int metadata_commit(struct era_metadata *md)
 {
     int r;
     struct dm_block *sblock;
 
     if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) {
         r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,
                     &md->current_writeset->md.root);
         if (r) {
             DMERR("%s: bitset flush failed", __func__);
             return r;
         }
     }
 
     r = dm_tm_pre_commit(md->tm);
     if (r) {
         DMERR("%s: pre commit failed", __func__);
         return r;
     }
 
     r = save_sm_root(md);
     if (r) {
         DMERR("%s: save_sm_root failed", __func__);
         return r;
     }
 
     r = superblock_lock(md, &sblock);
     if (r) {
         DMERR("%s: superblock lock failed", __func__);
         return r;
     }
 
     prepare_superblock(md, dm_block_data(sblock));
 
     return dm_tm_commit(md->tm, sblock);
 }
 
 static int metadata_checkpoint(struct era_metadata *md)
 {
     /*
      * For now we just rollover, but later I want to put a check in to
      * avoid this if the filter is still pretty fresh.
      */
     return metadata_era_rollover(md);
 }
 
 /*
  * Metadata snapshots allow userland to access era data.
  */
 static int metadata_take_snap(struct era_metadata *md)
 {
     int r, inc;
     struct dm_block *clone;
 
     if (md->metadata_snap != SUPERBLOCK_LOCATION) {
         DMERR("%s: metadata snapshot already exists", __func__);
         return -EINVAL;
     }
 
     r = metadata_era_rollover(md);
     if (r) {
         DMERR("%s: era rollover failed", __func__);
         return r;
     }
 
     r = metadata_commit(md);
     if (r) {
         DMERR("%s: pre commit failed", __func__);
         return r;
     }
 
     r = dm_sm_inc_block(md->sm, SUPERBLOCK_LOCATION);
     if (r) {
         DMERR("%s: couldn't increment superblock", __func__);
         return r;
     }
 
     r = dm_tm_shadow_block(md->tm, SUPERBLOCK_LOCATION,
                    &sb_validator, &clone, &inc);
     if (r) {
         DMERR("%s: couldn't shadow superblock", __func__);
         dm_sm_dec_block(md->sm, SUPERBLOCK_LOCATION);
         return r;
     }
     BUG_ON(!inc);
 
     r = dm_sm_inc_block(md->sm, md->writeset_tree_root);
     if (r) {
         DMERR("%s: couldn't inc writeset tree root", __func__);
         dm_tm_unlock(md->tm, clone);
         return r;
     }
 
     r = dm_sm_inc_block(md->sm, md->era_array_root);
     if (r) {
         DMERR("%s: couldn't inc era tree root", __func__);
         dm_sm_dec_block(md->sm, md->writeset_tree_root);
         dm_tm_unlock(md->tm, clone);
         return r;
     }
 
     md->metadata_snap = dm_block_location(clone);
 
     dm_tm_unlock(md->tm, clone);
 
     return 0;
 }
 
 static int metadata_drop_snap(struct era_metadata *md)
 {
     int r;
     dm_block_t location;
     struct dm_block *clone;
     struct superblock_disk *disk;
 
     if (md->metadata_snap == SUPERBLOCK_LOCATION) {
         DMERR("%s: no snap to drop", __func__);
         return -EINVAL;
     }
 
     r = dm_tm_read_lock(md->tm, md->metadata_snap, &sb_validator, &clone);
     if (r) {
         DMERR("%s: couldn't read lock superblock clone", __func__);
         return r;
     }
 
     /*
      * Whatever happens now we'll commit with no record of the metadata
      * snap.
      */
     md->metadata_snap = SUPERBLOCK_LOCATION;
 
     disk = dm_block_data(clone);
     r = dm_btree_del(&md->writeset_tree_info,
              le64_to_cpu(disk->writeset_tree_root));
     if (r) {
         DMERR("%s: error deleting writeset tree clone", __func__);
         dm_tm_unlock(md->tm, clone);
         return r;
     }
 
     r = dm_array_del(&md->era_array_info, le64_to_cpu(disk->era_array_root));
     if (r) {
         DMERR("%s: error deleting era array clone", __func__);
         dm_tm_unlock(md->tm, clone);
         return r;
     }
 
     location = dm_block_location(clone);
     dm_tm_unlock(md->tm, clone);
 
     return dm_sm_dec_block(md->sm, location);
 }
 
 struct metadata_stats {
     dm_block_t used;
     dm_block_t total;
     dm_block_t snap;
     uint32_t era;
 };
 
 static int metadata_get_stats(struct era_metadata *md, void *ptr)
 {
     int r;
     struct metadata_stats *s = ptr;
     dm_block_t nr_free, nr_total;
 
     r = dm_sm_get_nr_free(md->sm, &nr_free);
     if (r) {
         DMERR("dm_sm_get_nr_free returned %d", r);
         return r;
     }
 
     r = dm_sm_get_nr_blocks(md->sm, &nr_total);
     if (r) {
         DMERR("dm_pool_get_metadata_dev_size returned %d", r);
         return r;
     }
 
     s->used = nr_total - nr_free;
     s->total = nr_total;
     s->snap = md->metadata_snap;
     s->era = md->current_era;
 
     return 0;
 }
 
 /*----------------------------------------------------------------*/
 
 struct era {
     struct dm_target *ti;
 
     struct dm_dev *metadata_dev;
     struct dm_dev *origin_dev;
 
     dm_block_t nr_blocks;
     uint32_t sectors_per_block;
     int sectors_per_block_shift;
     struct era_metadata *md;
 
     struct workqueue_struct *wq;
     struct work_struct worker;
 
     spinlock_t deferred_lock;
     struct bio_list deferred_bios;
 
     spinlock_t rpc_lock;
     struct list_head rpc_calls;
 
     struct digest digest;
     atomic_t suspended;
 };
 
 struct rpc {
     struct list_head list;
 
     int (*fn0)(struct era_metadata *);
     int (*fn1)(struct era_metadata *, void *);
     void *arg;
     int result;
 
     struct completion complete;
 };
 
 /*----------------------------------------------------------------
  * Remapping.
  *---------------------------------------------------------------*/
 static bool block_size_is_power_of_two(struct era *era)
 {
     return era->sectors_per_block_shift >= 0;
 }
 
 static dm_block_t get_block(struct era *era, struct bio *bio)
 {
     sector_t block_nr = bio->bi_iter.bi_sector;
 
     if (!block_size_is_power_of_two(era))
         (void) sector_div(block_nr, era->sectors_per_block);
     else
         block_nr >>= era->sectors_per_block_shift;
 
     return block_nr;
 }
 
 static void remap_to_origin(struct era *era, struct bio *bio)
 {
     bio_set_dev(bio, era->origin_dev->bdev);
 }
 
 /*----------------------------------------------------------------
  * Worker thread
  *--------------------------------------------------------------*/
 static void wake_worker(struct era *era)
 {
     if (!atomic_read(&era->suspended))
         queue_work(era->wq, &era->worker);
 }
 
 static void process_old_eras(struct era *era)
 {
     int r;
 
     if (!era->digest.step)
         return;
 
     r = era->digest.step(era->md, &era->digest);
     if (r < 0) {
         DMERR("%s: digest step failed, stopping digestion", __func__);
         era->digest.step = NULL;
 
     } else if (era->digest.step)
         wake_worker(era);
 }
 
 static void process_deferred_bios(struct era *era)
 {
     int r;
     struct bio_list deferred_bios, marked_bios;
     struct bio *bio;
     struct blk_plug plug;
     bool commit_needed = false;
     bool failed = false;
     struct writeset *ws = era->md->current_writeset;
 
     bio_list_init(&deferred_bios);
     bio_list_init(&marked_bios);
 
     spin_lock(&era->deferred_lock);
     bio_list_merge(&deferred_bios, &era->deferred_bios);
     bio_list_init(&era->deferred_bios);
     spin_unlock(&era->deferred_lock);
 
     if (bio_list_empty(&deferred_bios))
         return;
 
     while ((bio = bio_list_pop(&deferred_bios))) {
         r = writeset_test_and_set(&era->md->bitset_info, ws,
                       get_block(era, bio));
         if (r < 0) {
             /*
              * This is bad news, we need to rollback.
              * FIXME: finish.
              */
             failed = true;
         } else if (r == 0)
             commit_needed = true;
 
         bio_list_add(&marked_bios, bio);
     }
 
     if (commit_needed) {
         r = metadata_commit(era->md);
         if (r)
             failed = true;
     }
 
     if (failed)
         while ((bio = bio_list_pop(&marked_bios)))
             bio_io_error(bio);
     else {
         blk_start_plug(&plug);
         while ((bio = bio_list_pop(&marked_bios))) {
             /*
              * Only update the in-core writeset if the on-disk one
              * was updated too.
              */
             if (commit_needed)
                 set_bit(get_block(era, bio), ws->bits);
             submit_bio_noacct(bio);
         }
         blk_finish_plug(&plug);
     }
 }
 
 static void process_rpc_calls(struct era *era)
 {
     int r;
     bool need_commit = false;
     struct list_head calls;
     struct rpc *rpc, *tmp;
 
     INIT_LIST_HEAD(&calls);
     spin_lock(&era->rpc_lock);
     list_splice_init(&era->rpc_calls, &calls);
     spin_unlock(&era->rpc_lock);
 
     list_for_each_entry_safe(rpc, tmp, &calls, list) {
         rpc->result = rpc->fn0 ? rpc->fn0(era->md) : rpc->fn1(era->md, rpc->arg);
         need_commit = true;
     }
 
     if (need_commit) {
         r = metadata_commit(era->md);
         if (r)
             list_for_each_entry_safe(rpc, tmp, &calls, list)
                 rpc->result = r;
     }
 
     list_for_each_entry_safe(rpc, tmp, &calls, list)
         complete(&rpc->complete);
 }
 
 static void kick_off_digest(struct era *era)
 {
     if (era->md->archived_writesets) {
         era->md->archived_writesets = false;
         metadata_digest_start(era->md, &era->digest);
     }
 }
 
 static void do_work(struct work_struct *ws)
 {
     struct era *era = container_of(ws, struct era, worker);
 
     kick_off_digest(era);
     process_old_eras(era);
     process_deferred_bios(era);
     process_rpc_calls(era);
 }
 
 static void defer_bio(struct era *era, struct bio *bio)
 {
     spin_lock(&era->deferred_lock);
     bio_list_add(&era->deferred_bios, bio);
     spin_unlock(&era->deferred_lock);
 
     wake_worker(era);
 }
 
 /*
  * Make an rpc call to the worker to change the metadata.
  */
 static int perform_rpc(struct era *era, struct rpc *rpc)
 {
     rpc->result = 0;
     init_completion(&rpc->complete);
 
     spin_lock(&era->rpc_lock);
     list_add(&rpc->list, &era->rpc_calls);
     spin_unlock(&era->rpc_lock);
 
     wake_worker(era);
     wait_for_completion(&rpc->complete);
 
     return rpc->result;
 }
 
 static int in_worker0(struct era *era, int (*fn)(struct era_metadata *))
 {
     struct rpc rpc;
     rpc.fn0 = fn;
     rpc.fn1 = NULL;
 
     return perform_rpc(era, &rpc);
 }
 
 static int in_worker1(struct era *era,
               int (*fn)(struct era_metadata *, void *), void *arg)
 {
     struct rpc rpc;
     rpc.fn0 = NULL;
     rpc.fn1 = fn;
     rpc.arg = arg;
 
     return perform_rpc(era, &rpc);
 }
 
 static void start_worker(struct era *era)
 {
     atomic_set(&era->suspended, 0);
 }
 
 static void stop_worker(struct era *era)
 {
     atomic_set(&era->suspended, 1);
     drain_workqueue(era->wq);
 }
 
 /*----------------------------------------------------------------
  * Target methods
  *--------------------------------------------------------------*/
 static void era_destroy(struct era *era)
 {
     if (era->md)
         metadata_close(era->md);
 
     if (era->wq)
         destroy_workqueue(era->wq);
 
     if (era->origin_dev)
         dm_put_device(era->ti, era->origin_dev);
 
     if (era->metadata_dev)
         dm_put_device(era->ti, era->metadata_dev);
 
     kfree(era);
 }
 
 static dm_block_t calc_nr_blocks(struct era *era)
 {
     return dm_sector_div_up(era->ti->len, era->sectors_per_block);
 }
 
 static bool valid_block_size(dm_block_t block_size)
 {
     bool greater_than_zero = block_size > 0;
     bool multiple_of_min_block_size = (block_size & (MIN_BLOCK_SIZE - 1)) == 0;
 
     return greater_than_zero && multiple_of_min_block_size;
 }
 
 /*
  * <metadata dev> <data dev> <data block size (sectors)>
  */
 static int era_ctr(struct dm_target *ti, unsigned argc, char **argv)
 {
     int r;
     char dummy;
     struct era *era;
     struct era_metadata *md;
 
     if (argc != 3) {
         ti->error = "Invalid argument count";
         return -EINVAL;
     }
 
     era = kzalloc(sizeof(*era), GFP_KERNEL);
     if (!era) {
         ti->error = "Error allocating era structure";
         return -ENOMEM;
     }
 
     era->ti = ti;
 
     r = dm_get_device(ti, argv[0], FMODE_READ | FMODE_WRITE, &era->metadata_dev);
     if (r) {
         ti->error = "Error opening metadata device";
         era_destroy(era);
         return -EINVAL;
     }
 
     r = dm_get_device(ti, argv[1], FMODE_READ | FMODE_WRITE, &era->origin_dev);
     if (r) {
         ti->error = "Error opening data device";
         era_destroy(era);
         return -EINVAL;
     }
 
     r = sscanf(argv[2], "%u%c", &era->sectors_per_block, &dummy);
     if (r != 1) {
         ti->error = "Error parsing block size";
         era_destroy(era);
         return -EINVAL;
     }
 
     r = dm_set_target_max_io_len(ti, era->sectors_per_block);
     if (r) {
         ti->error = "could not set max io len";
         era_destroy(era);
         return -EINVAL;
     }
 
     if (!valid_block_size(era->sectors_per_block)) {
         ti->error = "Invalid block size";
         era_destroy(era);
         return -EINVAL;
     }
     if (era->sectors_per_block & (era->sectors_per_block - 1))
         era->sectors_per_block_shift = -1;
     else
         era->sectors_per_block_shift = __ffs(era->sectors_per_block);
 
     md = metadata_open(era->metadata_dev->bdev, era->sectors_per_block, true);
     if (IS_ERR(md)) {
         ti->error = "Error reading metadata";
         era_destroy(era);
         return PTR_ERR(md);
     }
     era->md = md;
 
     era->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
     if (!era->wq) {
         ti->error = "could not create workqueue for metadata object";
         era_destroy(era);
         return -ENOMEM;
     }
     INIT_WORK(&era->worker, do_work);
 
     spin_lock_init(&era->deferred_lock);
     bio_list_init(&era->deferred_bios);
 
     spin_lock_init(&era->rpc_lock);
     INIT_LIST_HEAD(&era->rpc_calls);
 
     ti->private = era;
     ti->num_flush_bios = 1;
     ti->flush_supported = true;
 
     ti->num_discard_bios = 1;
 
     return 0;
 }
 
 static void era_dtr(struct dm_target *ti)
 {
     era_destroy(ti->private);
 }
 
 static int era_map(struct dm_target *ti, struct bio *bio)
 {
     struct era *era = ti->private;
     dm_block_t block = get_block(era, bio);
 
     /*
      * All bios get remapped to the origin device.  We do this now, but
      * it may not get issued until later.  Depending on whether the
      * block is marked in this era.
      */
     remap_to_origin(era, bio);
 
     /*
      * REQ_PREFLUSH bios carry no data, so we're not interested in them.
      */
     if (!(bio->bi_opf & REQ_PREFLUSH) &&
         (bio_data_dir(bio) == WRITE) &&
         !metadata_current_marked(era->md, block)) {
         defer_bio(era, bio);
         return DM_MAPIO_SUBMITTED;
     }
 
     return DM_MAPIO_REMAPPED;
 }
 
 static void era_postsuspend(struct dm_target *ti)
 {
     int r;
     struct era *era = ti->private;
 
     r = in_worker0(era, metadata_era_archive);
     if (r) {
         DMERR("%s: couldn't archive current era", __func__);
         /* FIXME: fail mode */
     }
 
     stop_worker(era);
 
     r = metadata_commit(era->md);
     if (r) {
         DMERR("%s: metadata_commit failed", __func__);
         /* FIXME: fail mode */
     }
 }
 
 static int era_preresume(struct dm_target *ti)
 {
     int r;
     struct era *era = ti->private;
     dm_block_t new_size = calc_nr_blocks(era);
 
     if (era->nr_blocks != new_size) {
         r = metadata_resize(era->md, &new_size);
         if (r) {
             DMERR("%s: metadata_resize failed", __func__);
             return r;
         }
 
         r = metadata_commit(era->md);
         if (r) {
             DMERR("%s: metadata_commit failed", __func__);
             return r;
         }
 
         era->nr_blocks = new_size;
     }
 
     start_worker(era);
 
     r = in_worker0(era, metadata_era_rollover);
     if (r) {
         DMERR("%s: metadata_era_rollover failed", __func__);
         return r;
     }
 
     return 0;
 }
 
 /*
  * Status format:
  *
  * <metadata block size> <#used metadata blocks>/<#total metadata blocks>
  * <current era> <held metadata root | '-'>
  */
 static void era_status(struct dm_target *ti, status_type_t type,
                unsigned status_flags, char *result, unsigned maxlen)
 {
     int r;
     struct era *era = ti->private;
     ssize_t sz = 0;
     struct metadata_stats stats;
     char buf[BDEVNAME_SIZE];
 
     switch (type) {
     case STATUSTYPE_INFO:
         r = in_worker1(era, metadata_get_stats, &stats);
         if (r)
             goto err;
 
         DMEMIT("%u %llu/%llu %u",
                (unsigned) (DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),
                (unsigned long long) stats.used,
                (unsigned long long) stats.total,
                (unsigned) stats.era);
 
         if (stats.snap != SUPERBLOCK_LOCATION)
             DMEMIT(" %llu", stats.snap);
         else
             DMEMIT(" -");
         break;
 
     case STATUSTYPE_TABLE:
         format_dev_t(buf, era->metadata_dev->bdev->bd_dev);
         DMEMIT("%s ", buf);
         format_dev_t(buf, era->origin_dev->bdev->bd_dev);
         DMEMIT("%s %u", buf, era->sectors_per_block);
         break;
 
     case STATUSTYPE_IMA:
         *result = '\0';
         break;
     }
 
     return;
 
 err:
     DMEMIT("Error");
 }
 
 static int era_message(struct dm_target *ti, unsigned argc, char **argv,
                char *result, unsigned maxlen)
 {
     struct era *era = ti->private;
 
     if (argc != 1) {
         DMERR("incorrect number of message arguments");
         return -EINVAL;
     }
 
     if (!strcasecmp(argv[0], "checkpoint"))
         return in_worker0(era, metadata_checkpoint);
 
     if (!strcasecmp(argv[0], "take_metadata_snap"))
         return in_worker0(era, metadata_take_snap);
 
     if (!strcasecmp(argv[0], "drop_metadata_snap"))
         return in_worker0(era, metadata_drop_snap);
 
     DMERR("unsupported message '%s'", argv[0]);
     return -EINVAL;
 }
 
 static sector_t get_dev_size(struct dm_dev *dev)
 {
     return bdev_nr_sectors(dev->bdev);
 }
 
 static int era_iterate_devices(struct dm_target *ti,
                    iterate_devices_callout_fn fn, void *data)
 {
     struct era *era = ti->private;
     return fn(ti, era->origin_dev, 0, get_dev_size(era->origin_dev), data);
 }
 
 static void era_io_hints(struct dm_target *ti, struct queue_limits *limits)
 {
     struct era *era = ti->private;
     uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
 
     /*
      * If the system-determined stacked limits are compatible with the
      * era device's blocksize (io_opt is a factor) do not override them.
      */
     if (io_opt_sectors < era->sectors_per_block ||
         do_div(io_opt_sectors, era->sectors_per_block)) {
         blk_limits_io_min(limits, 0);
         blk_limits_io_opt(limits, era->sectors_per_block << SECTOR_SHIFT);
     }
 }
 
 /*----------------------------------------------------------------*/
 
 static struct target_type era_target = {
     .name = "era",
     .version = {1, 0, 0},
     .module = THIS_MODULE,
     .ctr = era_ctr,
     .dtr = era_dtr,
     .map = era_map,
     .postsuspend = era_postsuspend,
     .preresume = era_preresume,
     .status = era_status,
     .message = era_message,
     .iterate_devices = era_iterate_devices,
     .io_hints = era_io_hints
 };
 
 static int __init dm_era_init(void)
 {
     int r;
 
     r = dm_register_target(&era_target);
     if (r) {
         DMERR("era target registration failed: %d", r);
         return r;
     }
 
     return 0;
 }
 
 static void __exit dm_era_exit(void)
 {
     dm_unregister_target(&era_target);
 }
 
 module_init(dm_era_init);
 module_exit(dm_era_exit);
 
 MODULE_DESCRIPTION(DM_NAME " era target");
 MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
 MODULE_LICENSE("GPL");

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