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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
 /*
  * bcache setup/teardown code, and some metadata io - read a superblock and
  * figure out what to do with it.
  *
  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
  * Copyright 2012 Google, Inc.
  */
 
 #include "bcache.h"
 #include "btree.h"
 #include "debug.h"
 #include "extents.h"
 #include "request.h"
 #include "writeback.h"
 #include "features.h"
 
 #include <linux/blkdev.h>
 #include <linux/pagemap.h>
 #include <linux/debugfs.h>
 #include <linux/idr.h>
 #include <linux/kthread.h>
 #include <linux/workqueue.h>
 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/reboot.h>
 #include <linux/sysfs.h>
 
 unsigned int bch_cutoff_writeback;
 unsigned int bch_cutoff_writeback_sync;
 
 static const char bcache_magic[] = {
     0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
     0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81
 };
 
 static const char invalid_uuid[] = {
     0xa0, 0x3e, 0xf8, 0xed, 0x3e, 0xe1, 0xb8, 0x78,
     0xc8, 0x50, 0xfc, 0x5e, 0xcb, 0x16, 0xcd, 0x99
 };
 
 static struct kobject *bcache_kobj;
 struct mutex bch_register_lock;
 bool bcache_is_reboot;
 LIST_HEAD(bch_cache_sets);
 static LIST_HEAD(uncached_devices);
 
 static int bcache_major;
 static DEFINE_IDA(bcache_device_idx);
 static wait_queue_head_t unregister_wait;
 struct workqueue_struct *bcache_wq;
 struct workqueue_struct *bch_flush_wq;
 struct workqueue_struct *bch_journal_wq;
 
 
 #define BTREE_MAX_PAGES     (256 * 1024 / PAGE_SIZE)
 /* limitation of partitions number on single bcache device */
 #define BCACHE_MINORS       128
 /* limitation of bcache devices number on single system */
 #define BCACHE_DEVICE_IDX_MAX   ((1U << MINORBITS)/BCACHE_MINORS)
 
 /* Superblock */
 
 static unsigned int get_bucket_size(struct cache_sb *sb, struct cache_sb_disk *s)
 {
     unsigned int bucket_size = le16_to_cpu(s->bucket_size);
 
     if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
         if (bch_has_feature_large_bucket(sb)) {
             unsigned int max, order;
 
             max = sizeof(unsigned int) * BITS_PER_BYTE - 1;
             order = le16_to_cpu(s->bucket_size);
             /*
              * bcache tool will make sure the overflow won't
              * happen, an error message here is enough.
              */
             if (order > max)
                 pr_err("Bucket size (1 << %u) overflows\n",
                     order);
             bucket_size = 1 << order;
         } else if (bch_has_feature_obso_large_bucket(sb)) {
             bucket_size +=
                 le16_to_cpu(s->obso_bucket_size_hi) << 16;
         }
     }
 
     return bucket_size;
 }
 
 static const char *read_super_common(struct cache_sb *sb,  struct block_device *bdev,
                      struct cache_sb_disk *s)
 {
     const char *err;
     unsigned int i;
 
     sb->first_bucket= le16_to_cpu(s->first_bucket);
     sb->nbuckets    = le64_to_cpu(s->nbuckets);
     sb->bucket_size = get_bucket_size(sb, s);
 
     sb->nr_in_set   = le16_to_cpu(s->nr_in_set);
     sb->nr_this_dev = le16_to_cpu(s->nr_this_dev);
 
     err = "Too many journal buckets";
     if (sb->keys > SB_JOURNAL_BUCKETS)
         goto err;
 
     err = "Too many buckets";
     if (sb->nbuckets > LONG_MAX)
         goto err;
 
     err = "Not enough buckets";
     if (sb->nbuckets < 1 << 7)
         goto err;
 
     err = "Bad block size (not power of 2)";
     if (!is_power_of_2(sb->block_size))
         goto err;
 
     err = "Bad block size (larger than page size)";
     if (sb->block_size > PAGE_SECTORS)
         goto err;
 
     err = "Bad bucket size (not power of 2)";
     if (!is_power_of_2(sb->bucket_size))
         goto err;
 
     err = "Bad bucket size (smaller than page size)";
     if (sb->bucket_size < PAGE_SECTORS)
         goto err;
 
     err = "Invalid superblock: device too small";
     if (get_capacity(bdev->bd_disk) <
         sb->bucket_size * sb->nbuckets)
         goto err;
 
     err = "Bad UUID";
     if (bch_is_zero(sb->set_uuid, 16))
         goto err;
 
     err = "Bad cache device number in set";
     if (!sb->nr_in_set ||
         sb->nr_in_set <= sb->nr_this_dev ||
         sb->nr_in_set > MAX_CACHES_PER_SET)
         goto err;
 
     err = "Journal buckets not sequential";
     for (i = 0; i < sb->keys; i++)
         if (sb->d[i] != sb->first_bucket + i)
             goto err;
 
     err = "Too many journal buckets";
     if (sb->first_bucket + sb->keys > sb->nbuckets)
         goto err;
 
     err = "Invalid superblock: first bucket comes before end of super";
     if (sb->first_bucket * sb->bucket_size < 16)
         goto err;
 
     err = NULL;
 err:
     return err;
 }
 
 
 static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
                   struct cache_sb_disk **res)
 {
     const char *err;
     struct cache_sb_disk *s;
     struct page *page;
     unsigned int i;
 
     page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
                    SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
     if (IS_ERR(page))
         return "IO error";
     s = page_address(page) + offset_in_page(SB_OFFSET);
 
     sb->offset      = le64_to_cpu(s->offset);
     sb->version     = le64_to_cpu(s->version);
 
     memcpy(sb->magic,   s->magic, 16);
     memcpy(sb->uuid,    s->uuid, 16);
     memcpy(sb->set_uuid,    s->set_uuid, 16);
     memcpy(sb->label,   s->label, SB_LABEL_SIZE);
 
     sb->flags       = le64_to_cpu(s->flags);
     sb->seq         = le64_to_cpu(s->seq);
     sb->last_mount      = le32_to_cpu(s->last_mount);
     sb->keys        = le16_to_cpu(s->keys);
 
     for (i = 0; i < SB_JOURNAL_BUCKETS; i++)
         sb->d[i] = le64_to_cpu(s->d[i]);
 
     pr_debug("read sb version %llu, flags %llu, seq %llu, journal size %u\n",
          sb->version, sb->flags, sb->seq, sb->keys);
 
     err = "Not a bcache superblock (bad offset)";
     if (sb->offset != SB_SECTOR)
         goto err;
 
     err = "Not a bcache superblock (bad magic)";
     if (memcmp(sb->magic, bcache_magic, 16))
         goto err;
 
     err = "Bad checksum";
     if (s->csum != csum_set(s))
         goto err;
 
     err = "Bad UUID";
     if (bch_is_zero(sb->uuid, 16))
         goto err;
 
     sb->block_size  = le16_to_cpu(s->block_size);
 
     err = "Superblock block size smaller than device block size";
     if (sb->block_size << 9 < bdev_logical_block_size(bdev))
         goto err;
 
     switch (sb->version) {
     case BCACHE_SB_VERSION_BDEV:
         sb->data_offset = BDEV_DATA_START_DEFAULT;
         break;
     case BCACHE_SB_VERSION_BDEV_WITH_OFFSET:
     case BCACHE_SB_VERSION_BDEV_WITH_FEATURES:
         sb->data_offset = le64_to_cpu(s->data_offset);
 
         err = "Bad data offset";
         if (sb->data_offset < BDEV_DATA_START_DEFAULT)
             goto err;
 
         break;
     case BCACHE_SB_VERSION_CDEV:
     case BCACHE_SB_VERSION_CDEV_WITH_UUID:
         err = read_super_common(sb, bdev, s);
         if (err)
             goto err;
         break;
     case BCACHE_SB_VERSION_CDEV_WITH_FEATURES:
         /*
          * Feature bits are needed in read_super_common(),
          * convert them firstly.
          */
         sb->feature_compat = le64_to_cpu(s->feature_compat);
         sb->feature_incompat = le64_to_cpu(s->feature_incompat);
         sb->feature_ro_compat = le64_to_cpu(s->feature_ro_compat);
 
         /* Check incompatible features */
         err = "Unsupported compatible feature found";
         if (bch_has_unknown_compat_features(sb))
             goto err;
 
         err = "Unsupported read-only compatible feature found";
         if (bch_has_unknown_ro_compat_features(sb))
             goto err;
 
         err = "Unsupported incompatible feature found";
         if (bch_has_unknown_incompat_features(sb))
             goto err;
 
         err = read_super_common(sb, bdev, s);
         if (err)
             goto err;
         break;
     default:
         err = "Unsupported superblock version";
         goto err;
     }
 
     sb->last_mount = (u32)ktime_get_real_seconds();
     *res = s;
     return NULL;
 err:
     put_page(page);
     return err;
 }
 
 static void write_bdev_super_endio(struct bio *bio)
 {
     struct cached_dev *dc = bio->bi_private;
 
     if (bio->bi_status)
         bch_count_backing_io_errors(dc, bio);
 
     closure_put(&dc->sb_write);
 }
 
 static void __write_super(struct cache_sb *sb, struct cache_sb_disk *out,
         struct bio *bio)
 {
     unsigned int i;
 
     bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_META;
     bio->bi_iter.bi_sector  = SB_SECTOR;
     __bio_add_page(bio, virt_to_page(out), SB_SIZE,
             offset_in_page(out));
 
     out->offset     = cpu_to_le64(sb->offset);
 
     memcpy(out->uuid,   sb->uuid, 16);
     memcpy(out->set_uuid,   sb->set_uuid, 16);
     memcpy(out->label,  sb->label, SB_LABEL_SIZE);
 
     out->flags      = cpu_to_le64(sb->flags);
     out->seq        = cpu_to_le64(sb->seq);
 
     out->last_mount     = cpu_to_le32(sb->last_mount);
     out->first_bucket   = cpu_to_le16(sb->first_bucket);
     out->keys       = cpu_to_le16(sb->keys);
 
     for (i = 0; i < sb->keys; i++)
         out->d[i] = cpu_to_le64(sb->d[i]);
 
     if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
         out->feature_compat    = cpu_to_le64(sb->feature_compat);
         out->feature_incompat  = cpu_to_le64(sb->feature_incompat);
         out->feature_ro_compat = cpu_to_le64(sb->feature_ro_compat);
     }
 
     out->version        = cpu_to_le64(sb->version);
     out->csum = csum_set(out);
 
     pr_debug("ver %llu, flags %llu, seq %llu\n",
          sb->version, sb->flags, sb->seq);
 
     submit_bio(bio);
 }
 
 static void bch_write_bdev_super_unlock(struct closure *cl)
 {
     struct cached_dev *dc = container_of(cl, struct cached_dev, sb_write);
 
     up(&dc->sb_write_mutex);
 }
 
 void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent)
 {
     struct closure *cl = &dc->sb_write;
     struct bio *bio = &dc->sb_bio;
 
     down(&dc->sb_write_mutex);
     closure_init(cl, parent);
 
     bio_init(bio, dc->bdev, dc->sb_bv, 1, 0);
     bio->bi_end_io  = write_bdev_super_endio;
     bio->bi_private = dc;
 
     closure_get(cl);
     /* I/O request sent to backing device */
     __write_super(&dc->sb, dc->sb_disk, bio);
 
     closure_return_with_destructor(cl, bch_write_bdev_super_unlock);
 }
 
 static void write_super_endio(struct bio *bio)
 {
     struct cache *ca = bio->bi_private;
 
     /* is_read = 0 */
     bch_count_io_errors(ca, bio->bi_status, 0,
                 "writing superblock");
     closure_put(&ca->set->sb_write);
 }
 
 static void bcache_write_super_unlock(struct closure *cl)
 {
     struct cache_set *c = container_of(cl, struct cache_set, sb_write);
 
     up(&c->sb_write_mutex);
 }
 
 void bcache_write_super(struct cache_set *c)
 {
     struct closure *cl = &c->sb_write;
     struct cache *ca = c->cache;
     struct bio *bio = &ca->sb_bio;
     unsigned int version = BCACHE_SB_VERSION_CDEV_WITH_UUID;
 
     down(&c->sb_write_mutex);
     closure_init(cl, &c->cl);
 
     ca->sb.seq++;
 
     if (ca->sb.version < version)
         ca->sb.version = version;
 
     bio_init(bio, ca->bdev, ca->sb_bv, 1, 0);
     bio->bi_end_io  = write_super_endio;
     bio->bi_private = ca;
 
     closure_get(cl);
     __write_super(&ca->sb, ca->sb_disk, bio);
 
     closure_return_with_destructor(cl, bcache_write_super_unlock);
 }
 
 /* UUID io */
 
 static void uuid_endio(struct bio *bio)
 {
     struct closure *cl = bio->bi_private;
     struct cache_set *c = container_of(cl, struct cache_set, uuid_write);
 
     cache_set_err_on(bio->bi_status, c, "accessing uuids");
     bch_bbio_free(bio, c);
     closure_put(cl);
 }
 
 static void uuid_io_unlock(struct closure *cl)
 {
     struct cache_set *c = container_of(cl, struct cache_set, uuid_write);
 
     up(&c->uuid_write_mutex);
 }
 
 static void uuid_io(struct cache_set *c, blk_opf_t opf, struct bkey *k,
             struct closure *parent)
 {
     struct closure *cl = &c->uuid_write;
     struct uuid_entry *u;
     unsigned int i;
     char buf[80];
 
     BUG_ON(!parent);
     down(&c->uuid_write_mutex);
     closure_init(cl, parent);
 
     for (i = 0; i < KEY_PTRS(k); i++) {
         struct bio *bio = bch_bbio_alloc(c);
 
         bio->bi_opf = opf | REQ_SYNC | REQ_META;
         bio->bi_iter.bi_size = KEY_SIZE(k) << 9;
 
         bio->bi_end_io  = uuid_endio;
         bio->bi_private = cl;
         bch_bio_map(bio, c->uuids);
 
         bch_submit_bbio(bio, c, k, i);
 
         if ((opf & REQ_OP_MASK) != REQ_OP_WRITE)
             break;
     }
 
     bch_extent_to_text(buf, sizeof(buf), k);
     pr_debug("%s UUIDs at %s\n", (opf & REQ_OP_MASK) == REQ_OP_WRITE ?
          "wrote" : "read", buf);
 
     for (u = c->uuids; u < c->uuids + c->nr_uuids; u++)
         if (!bch_is_zero(u->uuid, 16))
             pr_debug("Slot %zi: %pU: %s: 1st: %u last: %u inv: %u\n",
                  u - c->uuids, u->uuid, u->label,
                  u->first_reg, u->last_reg, u->invalidated);
 
     closure_return_with_destructor(cl, uuid_io_unlock);
 }
 
 static char *uuid_read(struct cache_set *c, struct jset *j, struct closure *cl)
 {
     struct bkey *k = &j->uuid_bucket;
 
     if (__bch_btree_ptr_invalid(c, k))
         return "bad uuid pointer";
 
     bkey_copy(&c->uuid_bucket, k);
     uuid_io(c, REQ_OP_READ, k, cl);
 
     if (j->version < BCACHE_JSET_VERSION_UUIDv1) {
         struct uuid_entry_v0    *u0 = (void *) c->uuids;
         struct uuid_entry   *u1 = (void *) c->uuids;
         int i;
 
         closure_sync(cl);
 
         /*
          * Since the new uuid entry is bigger than the old, we have to
          * convert starting at the highest memory address and work down
          * in order to do it in place
          */
 
         for (i = c->nr_uuids - 1;
              i >= 0;
              --i) {
             memcpy(u1[i].uuid,  u0[i].uuid, 16);
             memcpy(u1[i].label, u0[i].label, 32);
 
             u1[i].first_reg     = u0[i].first_reg;
             u1[i].last_reg      = u0[i].last_reg;
             u1[i].invalidated   = u0[i].invalidated;
 
             u1[i].flags = 0;
             u1[i].sectors   = 0;
         }
     }
 
     return NULL;
 }
 
 static int __uuid_write(struct cache_set *c)
 {
     BKEY_PADDED(key) k;
     struct closure cl;
     struct cache *ca = c->cache;
     unsigned int size;
 
     closure_init_stack(&cl);
     lockdep_assert_held(&bch_register_lock);
 
     if (bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, true))
         return 1;
 
     size =  meta_bucket_pages(&ca->sb) * PAGE_SECTORS;
     SET_KEY_SIZE(&k.key, size);
     uuid_io(c, REQ_OP_WRITE, &k.key, &cl);
     closure_sync(&cl);
 
     /* Only one bucket used for uuid write */
     atomic_long_add(ca->sb.bucket_size, &ca->meta_sectors_written);
 
     bkey_copy(&c->uuid_bucket, &k.key);
     bkey_put(c, &k.key);
     return 0;
 }
 
 int bch_uuid_write(struct cache_set *c)
 {
     int ret = __uuid_write(c);
 
     if (!ret)
         bch_journal_meta(c, NULL);
 
     return ret;
 }
 
 static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
 {
     struct uuid_entry *u;
 
     for (u = c->uuids;
          u < c->uuids + c->nr_uuids; u++)
         if (!memcmp(u->uuid, uuid, 16))
             return u;
 
     return NULL;
 }
 
 static struct uuid_entry *uuid_find_empty(struct cache_set *c)
 {
     static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
 
     return uuid_find(c, zero_uuid);
 }
 
 /*
  * Bucket priorities/gens:
  *
  * For each bucket, we store on disk its
  *   8 bit gen
  *  16 bit priority
  *
  * See alloc.c for an explanation of the gen. The priority is used to implement
  * lru (and in the future other) cache replacement policies; for most purposes
  * it's just an opaque integer.
  *
  * The gens and the priorities don't have a whole lot to do with each other, and
  * it's actually the gens that must be written out at specific times - it's no
  * big deal if the priorities don't get written, if we lose them we just reuse
  * buckets in suboptimal order.
  *
  * On disk they're stored in a packed array, and in as many buckets are required
  * to fit them all. The buckets we use to store them form a list; the journal
  * header points to the first bucket, the first bucket points to the second
  * bucket, et cetera.
  *
  * This code is used by the allocation code; periodically (whenever it runs out
  * of buckets to allocate from) the allocation code will invalidate some
  * buckets, but it can't use those buckets until their new gens are safely on
  * disk.
  */
 
 static void prio_endio(struct bio *bio)
 {
     struct cache *ca = bio->bi_private;
 
     cache_set_err_on(bio->bi_status, ca->set, "accessing priorities");
     bch_bbio_free(bio, ca->set);
     closure_put(&ca->prio);
 }
 
 static void prio_io(struct cache *ca, uint64_t bucket, blk_opf_t opf)
 {
     struct closure *cl = &ca->prio;
     struct bio *bio = bch_bbio_alloc(ca->set);
 
     closure_init_stack(cl);
 
     bio->bi_iter.bi_sector  = bucket * ca->sb.bucket_size;
     bio_set_dev(bio, ca->bdev);
     bio->bi_iter.bi_size    = meta_bucket_bytes(&ca->sb);
 
     bio->bi_end_io  = prio_endio;
     bio->bi_private = ca;
     bio->bi_opf = opf | REQ_SYNC | REQ_META;
     bch_bio_map(bio, ca->disk_buckets);
 
     closure_bio_submit(ca->set, bio, &ca->prio);
     closure_sync(cl);
 }
 
 int bch_prio_write(struct cache *ca, bool wait)
 {
     int i;
     struct bucket *b;
     struct closure cl;
 
     pr_debug("free_prio=%zu, free_none=%zu, free_inc=%zu\n",
          fifo_used(&ca->free[RESERVE_PRIO]),
          fifo_used(&ca->free[RESERVE_NONE]),
          fifo_used(&ca->free_inc));
 
     /*
      * Pre-check if there are enough free buckets. In the non-blocking
      * scenario it's better to fail early rather than starting to allocate
      * buckets and do a cleanup later in case of failure.
      */
     if (!wait) {
         size_t avail = fifo_used(&ca->free[RESERVE_PRIO]) +
                    fifo_used(&ca->free[RESERVE_NONE]);
         if (prio_buckets(ca) > avail)
             return -ENOMEM;
     }
 
     closure_init_stack(&cl);
 
     lockdep_assert_held(&ca->set->bucket_lock);
 
     ca->disk_buckets->seq++;
 
     atomic_long_add(ca->sb.bucket_size * prio_buckets(ca),
             &ca->meta_sectors_written);
 
     for (i = prio_buckets(ca) - 1; i >= 0; --i) {
         long bucket;
         struct prio_set *p = ca->disk_buckets;
         struct bucket_disk *d = p->data;
         struct bucket_disk *end = d + prios_per_bucket(ca);
 
         for (b = ca->buckets + i * prios_per_bucket(ca);
              b < ca->buckets + ca->sb.nbuckets && d < end;
              b++, d++) {
             d->prio = cpu_to_le16(b->prio);
             d->gen = b->gen;
         }
 
         p->next_bucket  = ca->prio_buckets[i + 1];
         p->magic    = pset_magic(&ca->sb);
         p->csum     = bch_crc64(&p->magic, meta_bucket_bytes(&ca->sb) - 8);
 
         bucket = bch_bucket_alloc(ca, RESERVE_PRIO, wait);
         BUG_ON(bucket == -1);
 
         mutex_unlock(&ca->set->bucket_lock);
         prio_io(ca, bucket, REQ_OP_WRITE);
         mutex_lock(&ca->set->bucket_lock);
 
         ca->prio_buckets[i] = bucket;
         atomic_dec_bug(&ca->buckets[bucket].pin);
     }
 
     mutex_unlock(&ca->set->bucket_lock);
 
     bch_journal_meta(ca->set, &cl);
     closure_sync(&cl);
 
     mutex_lock(&ca->set->bucket_lock);
 
     /*
      * Don't want the old priorities to get garbage collected until after we
      * finish writing the new ones, and they're journalled
      */
     for (i = 0; i < prio_buckets(ca); i++) {
         if (ca->prio_last_buckets[i])
             __bch_bucket_free(ca,
                 &ca->buckets[ca->prio_last_buckets[i]]);
 
         ca->prio_last_buckets[i] = ca->prio_buckets[i];
     }
     return 0;
 }
 
 static int prio_read(struct cache *ca, uint64_t bucket)
 {
     struct prio_set *p = ca->disk_buckets;
     struct bucket_disk *d = p->data + prios_per_bucket(ca), *end = d;
     struct bucket *b;
     unsigned int bucket_nr = 0;
     int ret = -EIO;
 
     for (b = ca->buckets;
          b < ca->buckets + ca->sb.nbuckets;
          b++, d++) {
         if (d == end) {
             ca->prio_buckets[bucket_nr] = bucket;
             ca->prio_last_buckets[bucket_nr] = bucket;
             bucket_nr++;
 
             prio_io(ca, bucket, REQ_OP_READ);
 
             if (p->csum !=
                 bch_crc64(&p->magic, meta_bucket_bytes(&ca->sb) - 8)) {
                 pr_warn("bad csum reading priorities\n");
                 goto out;
             }
 
             if (p->magic != pset_magic(&ca->sb)) {
                 pr_warn("bad magic reading priorities\n");
                 goto out;
             }
 
             bucket = p->next_bucket;
             d = p->data;
         }
 
         b->prio = le16_to_cpu(d->prio);
         b->gen = b->last_gc = d->gen;
     }
 
     ret = 0;
 out:
     return ret;
 }
 
 /* Bcache device */
 
 static int open_dev(struct block_device *b, fmode_t mode)
 {
     struct bcache_device *d = b->bd_disk->private_data;
 
     if (test_bit(BCACHE_DEV_CLOSING, &d->flags))
         return -ENXIO;
 
     closure_get(&d->cl);
     return 0;
 }
 
 static void release_dev(struct gendisk *b, fmode_t mode)
 {
     struct bcache_device *d = b->private_data;
 
     closure_put(&d->cl);
 }
 
 static int ioctl_dev(struct block_device *b, fmode_t mode,
              unsigned int cmd, unsigned long arg)
 {
     struct bcache_device *d = b->bd_disk->private_data;
 
     return d->ioctl(d, mode, cmd, arg);
 }
 
 static const struct block_device_operations bcache_cached_ops = {
     .submit_bio = cached_dev_submit_bio,
     .open       = open_dev,
     .release    = release_dev,
     .ioctl      = ioctl_dev,
     .owner      = THIS_MODULE,
 };
 
 static const struct block_device_operations bcache_flash_ops = {
     .submit_bio = flash_dev_submit_bio,
     .open       = open_dev,
     .release    = release_dev,
     .ioctl      = ioctl_dev,
     .owner      = THIS_MODULE,
 };
 
 void bcache_device_stop(struct bcache_device *d)
 {
     if (!test_and_set_bit(BCACHE_DEV_CLOSING, &d->flags))
         /*
          * closure_fn set to
          * - cached device: cached_dev_flush()
          * - flash dev: flash_dev_flush()
          */
         closure_queue(&d->cl);
 }
 
 static void bcache_device_unlink(struct bcache_device *d)
 {
     lockdep_assert_held(&bch_register_lock);
 
     if (d->c && !test_and_set_bit(BCACHE_DEV_UNLINK_DONE, &d->flags)) {
         struct cache *ca = d->c->cache;
 
         sysfs_remove_link(&d->c->kobj, d->name);
         sysfs_remove_link(&d->kobj, "cache");
 
         bd_unlink_disk_holder(ca->bdev, d->disk);
     }
 }
 
 static void bcache_device_link(struct bcache_device *d, struct cache_set *c,
                    const char *name)
 {
     struct cache *ca = c->cache;
     int ret;
 
     bd_link_disk_holder(ca->bdev, d->disk);
 
     snprintf(d->name, BCACHEDEVNAME_SIZE,
          "%s%u", name, d->id);
 
     ret = sysfs_create_link(&d->kobj, &c->kobj, "cache");
     if (ret < 0)
         pr_err("Couldn't create device -> cache set symlink\n");
 
     ret = sysfs_create_link(&c->kobj, &d->kobj, d->name);
     if (ret < 0)
         pr_err("Couldn't create cache set -> device symlink\n");
 
     clear_bit(BCACHE_DEV_UNLINK_DONE, &d->flags);
 }
 
 static void bcache_device_detach(struct bcache_device *d)
 {
     lockdep_assert_held(&bch_register_lock);
 
     atomic_dec(&d->c->attached_dev_nr);
 
     if (test_bit(BCACHE_DEV_DETACHING, &d->flags)) {
         struct uuid_entry *u = d->c->uuids + d->id;
 
         SET_UUID_FLASH_ONLY(u, 0);
         memcpy(u->uuid, invalid_uuid, 16);
         u->invalidated = cpu_to_le32((u32)ktime_get_real_seconds());
         bch_uuid_write(d->c);
     }
 
     bcache_device_unlink(d);
 
     d->c->devices[d->id] = NULL;
     closure_put(&d->c->caching);
     d->c = NULL;
 }
 
 static void bcache_device_attach(struct bcache_device *d, struct cache_set *c,
                  unsigned int id)
 {
     d->id = id;
     d->c = c;
     c->devices[id] = d;
 
     if (id >= c->devices_max_used)
         c->devices_max_used = id + 1;
 
     closure_get(&c->caching);
 }
 
 static inline int first_minor_to_idx(int first_minor)
 {
     return (first_minor/BCACHE_MINORS);
 }
 
 static inline int idx_to_first_minor(int idx)
 {
     return (idx * BCACHE_MINORS);
 }
 
 static void bcache_device_free(struct bcache_device *d)
 {
     struct gendisk *disk = d->disk;
 
     lockdep_assert_held(&bch_register_lock);
 
     if (disk)
         pr_info("%s stopped\n", disk->disk_name);
     else
         pr_err("bcache device (NULL gendisk) stopped\n");
 
     if (d->c)
         bcache_device_detach(d);
 
     if (disk) {
         ida_simple_remove(&bcache_device_idx,
                   first_minor_to_idx(disk->first_minor));
         put_disk(disk);
     }
 
     bioset_exit(&d->bio_split);
     kvfree(d->full_dirty_stripes);
     kvfree(d->stripe_sectors_dirty);
 
     closure_debug_destroy(&d->cl);
 }
 
 static int bcache_device_init(struct bcache_device *d, unsigned int block_size,
         sector_t sectors, struct block_device *cached_bdev,
         const struct block_device_operations *ops)
 {
     struct request_queue *q;
     const size_t max_stripes = min_t(size_t, INT_MAX,
                      SIZE_MAX / sizeof(atomic_t));
     uint64_t n;
     int idx;
 
     if (!d->stripe_size)
         d->stripe_size = 1 << 31;
 
     n = DIV_ROUND_UP_ULL(sectors, d->stripe_size);
     if (!n || n > max_stripes) {
         pr_err("nr_stripes too large or invalid: %llu (start sector beyond end of disk?)\n",
             n);
         return -ENOMEM;
     }
     d->nr_stripes = n;
 
     n = d->nr_stripes * sizeof(atomic_t);
     d->stripe_sectors_dirty = kvzalloc(n, GFP_KERNEL);
     if (!d->stripe_sectors_dirty)
         return -ENOMEM;
 
     n = BITS_TO_LONGS(d->nr_stripes) * sizeof(unsigned long);
     d->full_dirty_stripes = kvzalloc(n, GFP_KERNEL);
     if (!d->full_dirty_stripes)
         goto out_free_stripe_sectors_dirty;
 
     idx = ida_simple_get(&bcache_device_idx, 0,
                 BCACHE_DEVICE_IDX_MAX, GFP_KERNEL);
     if (idx < 0)
         goto out_free_full_dirty_stripes;
 
     if (bioset_init(&d->bio_split, 4, offsetof(struct bbio, bio),
             BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER))
         goto out_ida_remove;
 
     d->disk = blk_alloc_disk(NUMA_NO_NODE);
     if (!d->disk)
         goto out_bioset_exit;
 
     set_capacity(d->disk, sectors);
     snprintf(d->disk->disk_name, DISK_NAME_LEN, "bcache%i", idx);
 
     d->disk->major      = bcache_major;
     d->disk->first_minor    = idx_to_first_minor(idx);
     d->disk->minors     = BCACHE_MINORS;
     d->disk->fops       = ops;
     d->disk->private_data   = d;
 
     q = d->disk->queue;
     q->limits.max_hw_sectors    = UINT_MAX;
     q->limits.max_sectors       = UINT_MAX;
     q->limits.max_segment_size  = UINT_MAX;
     q->limits.max_segments      = BIO_MAX_VECS;
     blk_queue_max_discard_sectors(q, UINT_MAX);
     q->limits.discard_granularity   = 512;
     q->limits.io_min        = block_size;
     q->limits.logical_block_size    = block_size;
     q->limits.physical_block_size   = block_size;
 
     if (q->limits.logical_block_size > PAGE_SIZE && cached_bdev) {
         /*
          * This should only happen with BCACHE_SB_VERSION_BDEV.
          * Block/page size is checked for BCACHE_SB_VERSION_CDEV.
          */
         pr_info("%s: sb/logical block size (%u) greater than page size (%lu) falling back to device logical block size (%u)\n",
             d->disk->disk_name, q->limits.logical_block_size,
             PAGE_SIZE, bdev_logical_block_size(cached_bdev));
 
         /* This also adjusts physical block size/min io size if needed */
         blk_queue_logical_block_size(q, bdev_logical_block_size(cached_bdev));
     }
 
     blk_queue_flag_set(QUEUE_FLAG_NONROT, d->disk->queue);
     blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, d->disk->queue);
 
     blk_queue_write_cache(q, true, true);
 
     return 0;
 
 out_bioset_exit:
     bioset_exit(&d->bio_split);
 out_ida_remove:
     ida_simple_remove(&bcache_device_idx, idx);
 out_free_full_dirty_stripes:
     kvfree(d->full_dirty_stripes);
 out_free_stripe_sectors_dirty:
     kvfree(d->stripe_sectors_dirty);
     return -ENOMEM;
 
 }
 
 /* Cached device */
 
 static void calc_cached_dev_sectors(struct cache_set *c)
 {
     uint64_t sectors = 0;
     struct cached_dev *dc;
 
     list_for_each_entry(dc, &c->cached_devs, list)
         sectors += bdev_nr_sectors(dc->bdev);
 
     c->cached_dev_sectors = sectors;
 }
 
 #define BACKING_DEV_OFFLINE_TIMEOUT 5
 static int cached_dev_status_update(void *arg)
 {
     struct cached_dev *dc = arg;
     struct request_queue *q;
 
     /*
      * If this delayed worker is stopping outside, directly quit here.
      * dc->io_disable might be set via sysfs interface, so check it
      * here too.
      */
     while (!kthread_should_stop() && !dc->io_disable) {
         q = bdev_get_queue(dc->bdev);
         if (blk_queue_dying(q))
             dc->offline_seconds++;
         else
             dc->offline_seconds = 0;
 
         if (dc->offline_seconds >= BACKING_DEV_OFFLINE_TIMEOUT) {
             pr_err("%pg: device offline for %d seconds\n",
                    dc->bdev,
                    BACKING_DEV_OFFLINE_TIMEOUT);
             pr_err("%s: disable I/O request due to backing device offline\n",
                    dc->disk.name);
             dc->io_disable = true;
             /* let others know earlier that io_disable is true */
             smp_mb();
             bcache_device_stop(&dc->disk);
             break;
         }
         schedule_timeout_interruptible(HZ);
     }
 
     wait_for_kthread_stop();
     return 0;
 }
 
 
 int bch_cached_dev_run(struct cached_dev *dc)
 {
     int ret = 0;
     struct bcache_device *d = &dc->disk;
     char *buf = kmemdup_nul(dc->sb.label, SB_LABEL_SIZE, GFP_KERNEL);
     char *env[] = {
         "DRIVER=bcache",
         kasprintf(GFP_KERNEL, "CACHED_UUID=%pU", dc->sb.uuid),
         kasprintf(GFP_KERNEL, "CACHED_LABEL=%s", buf ? : ""),
         NULL,
     };
 
     if (dc->io_disable) {
         pr_err("I/O disabled on cached dev %pg\n", dc->bdev);
         ret = -EIO;
         goto out;
     }
 
     if (atomic_xchg(&dc->running, 1)) {
         pr_info("cached dev %pg is running already\n", dc->bdev);
         ret = -EBUSY;
         goto out;
     }
 
     if (!d->c &&
         BDEV_STATE(&dc->sb) != BDEV_STATE_NONE) {
         struct closure cl;
 
         closure_init_stack(&cl);
 
         SET_BDEV_STATE(&dc->sb, BDEV_STATE_STALE);
         bch_write_bdev_super(dc, &cl);
         closure_sync(&cl);
     }
 
     ret = add_disk(d->disk);
     if (ret)
         goto out;
     bd_link_disk_holder(dc->bdev, dc->disk.disk);
     /*
      * won't show up in the uevent file, use udevadm monitor -e instead
      * only class / kset properties are persistent
      */
     kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env);
 
     if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") ||
         sysfs_create_link(&disk_to_dev(d->disk)->kobj,
                   &d->kobj, "bcache")) {
         pr_err("Couldn't create bcache dev <-> disk sysfs symlinks\n");
         ret = -ENOMEM;
         goto out;
     }
 
     dc->status_update_thread = kthread_run(cached_dev_status_update,
                            dc, "bcache_status_update");
     if (IS_ERR(dc->status_update_thread)) {
         pr_warn("failed to create bcache_status_update kthread, continue to run without monitoring backing device status\n");
     }
 
 out:
     kfree(env[1]);
     kfree(env[2]);
     kfree(buf);
     return ret;
 }
 
 /*
  * If BCACHE_DEV_RATE_DW_RUNNING is set, it means routine of the delayed
  * work dc->writeback_rate_update is running. Wait until the routine
  * quits (BCACHE_DEV_RATE_DW_RUNNING is clear), then continue to
  * cancel it. If BCACHE_DEV_RATE_DW_RUNNING is not clear after time_out
  * seconds, give up waiting here and continue to cancel it too.
  */
 static void cancel_writeback_rate_update_dwork(struct cached_dev *dc)
 {
     int time_out = WRITEBACK_RATE_UPDATE_SECS_MAX * HZ;
 
     do {
         if (!test_bit(BCACHE_DEV_RATE_DW_RUNNING,
                   &dc->disk.flags))
             break;
         time_out--;
         schedule_timeout_interruptible(1);
     } while (time_out > 0);
 
     if (time_out == 0)
         pr_warn("give up waiting for dc->writeback_write_update to quit\n");
 
     cancel_delayed_work_sync(&dc->writeback_rate_update);
 }
 
 static void cached_dev_detach_finish(struct work_struct *w)
 {
     struct cached_dev *dc = container_of(w, struct cached_dev, detach);
     struct cache_set *c = dc->disk.c;
 
     BUG_ON(!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags));
     BUG_ON(refcount_read(&dc->count));
 
 
     if (test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
         cancel_writeback_rate_update_dwork(dc);
 
     if (!IS_ERR_OR_NULL(dc->writeback_thread)) {
         kthread_stop(dc->writeback_thread);
         dc->writeback_thread = NULL;
     }
 
     mutex_lock(&bch_register_lock);
 
     bcache_device_detach(&dc->disk);
     list_move(&dc->list, &uncached_devices);
     calc_cached_dev_sectors(c);
 
     clear_bit(BCACHE_DEV_DETACHING, &dc->disk.flags);
     clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags);
 
     mutex_unlock(&bch_register_lock);
 
     pr_info("Caching disabled for %pg\n", dc->bdev);
 
     /* Drop ref we took in cached_dev_detach() */
     closure_put(&dc->disk.cl);
 }
 
 void bch_cached_dev_detach(struct cached_dev *dc)
 {
     lockdep_assert_held(&bch_register_lock);
 
     if (test_bit(BCACHE_DEV_CLOSING, &dc->disk.flags))
         return;
 
     if (test_and_set_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
         return;
 
     /*
      * Block the device from being closed and freed until we're finished
      * detaching
      */
     closure_get(&dc->disk.cl);
 
     bch_writeback_queue(dc);
 
     cached_dev_put(dc);
 }
 
 int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
               uint8_t *set_uuid)
 {
     uint32_t rtime = cpu_to_le32((u32)ktime_get_real_seconds());
     struct uuid_entry *u;
     struct cached_dev *exist_dc, *t;
     int ret = 0;
 
     if ((set_uuid && memcmp(set_uuid, c->set_uuid, 16)) ||
         (!set_uuid && memcmp(dc->sb.set_uuid, c->set_uuid, 16)))
         return -ENOENT;
 
     if (dc->disk.c) {
         pr_err("Can't attach %pg: already attached\n", dc->bdev);
         return -EINVAL;
     }
 
     if (test_bit(CACHE_SET_STOPPING, &c->flags)) {
         pr_err("Can't attach %pg: shutting down\n", dc->bdev);
         return -EINVAL;
     }
 
     if (dc->sb.block_size < c->cache->sb.block_size) {
         /* Will die */
         pr_err("Couldn't attach %pg: block size less than set's block size\n",
                dc->bdev);
         return -EINVAL;
     }
 
     /* Check whether already attached */
     list_for_each_entry_safe(exist_dc, t, &c->cached_devs, list) {
         if (!memcmp(dc->sb.uuid, exist_dc->sb.uuid, 16)) {
             pr_err("Tried to attach %pg but duplicate UUID already attached\n",
                 dc->bdev);
 
             return -EINVAL;
         }
     }
 
     u = uuid_find(c, dc->sb.uuid);
 
     if (u &&
         (BDEV_STATE(&dc->sb) == BDEV_STATE_STALE ||
          BDEV_STATE(&dc->sb) == BDEV_STATE_NONE)) {
         memcpy(u->uuid, invalid_uuid, 16);
         u->invalidated = cpu_to_le32((u32)ktime_get_real_seconds());
         u = NULL;
     }
 
     if (!u) {
         if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
             pr_err("Couldn't find uuid for %pg in set\n", dc->bdev);
             return -ENOENT;
         }
 
         u = uuid_find_empty(c);
         if (!u) {
             pr_err("Not caching %pg, no room for UUID\n", dc->bdev);
             return -EINVAL;
         }
     }
 
     /*
      * Deadlocks since we're called via sysfs...
      * sysfs_remove_file(&dc->kobj, &sysfs_attach);
      */
 
     if (bch_is_zero(u->uuid, 16)) {
         struct closure cl;
 
         closure_init_stack(&cl);
 
         memcpy(u->uuid, dc->sb.uuid, 16);
         memcpy(u->label, dc->sb.label, SB_LABEL_SIZE);
         u->first_reg = u->last_reg = rtime;
         bch_uuid_write(c);
 
         memcpy(dc->sb.set_uuid, c->set_uuid, 16);
         SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
 
         bch_write_bdev_super(dc, &cl);
         closure_sync(&cl);
     } else {
         u->last_reg = rtime;
         bch_uuid_write(c);
     }
 
     bcache_device_attach(&dc->disk, c, u - c->uuids);
     list_move(&dc->list, &c->cached_devs);
     calc_cached_dev_sectors(c);
 
     /*
      * dc->c must be set before dc->count != 0 - paired with the mb in
      * cached_dev_get()
      */
     smp_wmb();
     refcount_set(&dc->count, 1);
 
     /* Block writeback thread, but spawn it */
     down_write(&dc->writeback_lock);
     if (bch_cached_dev_writeback_start(dc)) {
         up_write(&dc->writeback_lock);
         pr_err("Couldn't start writeback facilities for %s\n",
                dc->disk.disk->disk_name);
         return -ENOMEM;
     }
 
     if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
         atomic_set(&dc->has_dirty, 1);
         bch_writeback_queue(dc);
     }
 
     bch_sectors_dirty_init(&dc->disk);
 
     ret = bch_cached_dev_run(dc);
     if (ret && (ret != -EBUSY)) {
         up_write(&dc->writeback_lock);
         /*
          * bch_register_lock is held, bcache_device_stop() is not
          * able to be directly called. The kthread and kworker
          * created previously in bch_cached_dev_writeback_start()
          * have to be stopped manually here.
          */
         kthread_stop(dc->writeback_thread);
         cancel_writeback_rate_update_dwork(dc);
         pr_err("Couldn't run cached device %pg\n", dc->bdev);
         return ret;
     }
 
     bcache_device_link(&dc->disk, c, "bdev");
     atomic_inc(&c->attached_dev_nr);
 
     if (bch_has_feature_obso_large_bucket(&(c->cache->sb))) {
         pr_err("The obsoleted large bucket layout is unsupported, set the bcache device into read-only\n");
         pr_err("Please update to the latest bcache-tools to create the cache device\n");
         set_disk_ro(dc->disk.disk, 1);
     }
 
     /* Allow the writeback thread to proceed */
     up_write(&dc->writeback_lock);
 
     pr_info("Caching %pg as %s on set %pU\n",
         dc->bdev,
         dc->disk.disk->disk_name,
         dc->disk.c->set_uuid);
     return 0;
 }
 
 /* when dc->disk.kobj released */
 void bch_cached_dev_release(struct kobject *kobj)
 {
     struct cached_dev *dc = container_of(kobj, struct cached_dev,
                          disk.kobj);
     kfree(dc);
     module_put(THIS_MODULE);
 }
 
 static void cached_dev_free(struct closure *cl)
 {
     struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
 
     if (test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
         cancel_writeback_rate_update_dwork(dc);
 
     if (!IS_ERR_OR_NULL(dc->writeback_thread))
         kthread_stop(dc->writeback_thread);
     if (!IS_ERR_OR_NULL(dc->status_update_thread))
         kthread_stop(dc->status_update_thread);
 
     mutex_lock(&bch_register_lock);
 
     if (atomic_read(&dc->running)) {
         bd_unlink_disk_holder(dc->bdev, dc->disk.disk);
         del_gendisk(dc->disk.disk);
     }
     bcache_device_free(&dc->disk);
     list_del(&dc->list);
 
     mutex_unlock(&bch_register_lock);
 
     if (dc->sb_disk)
         put_page(virt_to_page(dc->sb_disk));
 
     if (!IS_ERR_OR_NULL(dc->bdev))
         blkdev_put(dc->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 
     wake_up(&unregister_wait);
 
     kobject_put(&dc->disk.kobj);
 }
 
 static void cached_dev_flush(struct closure *cl)
 {
     struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
     struct bcache_device *d = &dc->disk;
 
     mutex_lock(&bch_register_lock);
     bcache_device_unlink(d);
     mutex_unlock(&bch_register_lock);
 
     bch_cache_accounting_destroy(&dc->accounting);
     kobject_del(&d->kobj);
 
     continue_at(cl, cached_dev_free, system_wq);
 }
 
 static int cached_dev_init(struct cached_dev *dc, unsigned int block_size)
 {
     int ret;
     struct io *io;
     struct request_queue *q = bdev_get_queue(dc->bdev);
 
     __module_get(THIS_MODULE);
     INIT_LIST_HEAD(&dc->list);
     closure_init(&dc->disk.cl, NULL);
     set_closure_fn(&dc->disk.cl, cached_dev_flush, system_wq);
     kobject_init(&dc->disk.kobj, &bch_cached_dev_ktype);
     INIT_WORK(&dc->detach, cached_dev_detach_finish);
     sema_init(&dc->sb_write_mutex, 1);
     INIT_LIST_HEAD(&dc->io_lru);
     spin_lock_init(&dc->io_lock);
     bch_cache_accounting_init(&dc->accounting, &dc->disk.cl);
 
     dc->sequential_cutoff       = 4 << 20;
 
     for (io = dc->io; io < dc->io + RECENT_IO; io++) {
         list_add(&io->lru, &dc->io_lru);
         hlist_add_head(&io->hash, dc->io_hash + RECENT_IO);
     }
 
     dc->disk.stripe_size = q->limits.io_opt >> 9;
 
     if (dc->disk.stripe_size)
         dc->partial_stripes_expensive =
             q->limits.raid_partial_stripes_expensive;
 
     ret = bcache_device_init(&dc->disk, block_size,
              bdev_nr_sectors(dc->bdev) - dc->sb.data_offset,
              dc->bdev, &bcache_cached_ops);
     if (ret)
         return ret;
 
     blk_queue_io_opt(dc->disk.disk->queue,
         max(queue_io_opt(dc->disk.disk->queue), queue_io_opt(q)));
 
     atomic_set(&dc->io_errors, 0);
     dc->io_disable = false;
     dc->error_limit = DEFAULT_CACHED_DEV_ERROR_LIMIT;
     /* default to auto */
     dc->stop_when_cache_set_failed = BCH_CACHED_DEV_STOP_AUTO;
 
     bch_cached_dev_request_init(dc);
     bch_cached_dev_writeback_init(dc);
     return 0;
 }
 
 /* Cached device - bcache superblock */
 
 static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
                  struct block_device *bdev,
                  struct cached_dev *dc)
 {
     const char *err = "cannot allocate memory";
     struct cache_set *c;
     int ret = -ENOMEM;
 
     memcpy(&dc->sb, sb, sizeof(struct cache_sb));
     dc->bdev = bdev;
     dc->bdev->bd_holder = dc;
     dc->sb_disk = sb_disk;
 
     if (cached_dev_init(dc, sb->block_size << 9))
         goto err;
 
     err = "error creating kobject";
     if (kobject_add(&dc->disk.kobj, bdev_kobj(bdev), "bcache"))
         goto err;
     if (bch_cache_accounting_add_kobjs(&dc->accounting, &dc->disk.kobj))
         goto err;
 
     pr_info("registered backing device %pg\n", dc->bdev);
 
     list_add(&dc->list, &uncached_devices);
     /* attach to a matched cache set if it exists */
     list_for_each_entry(c, &bch_cache_sets, list)
         bch_cached_dev_attach(dc, c, NULL);
 
     if (BDEV_STATE(&dc->sb) == BDEV_STATE_NONE ||
         BDEV_STATE(&dc->sb) == BDEV_STATE_STALE) {
         err = "failed to run cached device";
         ret = bch_cached_dev_run(dc);
         if (ret)
             goto err;
     }
 
     return 0;
 err:
     pr_notice("error %pg: %s\n", dc->bdev, err);
     bcache_device_stop(&dc->disk);
     return ret;
 }
 
 /* Flash only volumes */
 
 /* When d->kobj released */
 void bch_flash_dev_release(struct kobject *kobj)
 {
     struct bcache_device *d = container_of(kobj, struct bcache_device,
                            kobj);
     kfree(d);
 }
 
 static void flash_dev_free(struct closure *cl)
 {
     struct bcache_device *d = container_of(cl, struct bcache_device, cl);
 
     mutex_lock(&bch_register_lock);
     atomic_long_sub(bcache_dev_sectors_dirty(d),
             &d->c->flash_dev_dirty_sectors);
     del_gendisk(d->disk);
     bcache_device_free(d);
     mutex_unlock(&bch_register_lock);
     kobject_put(&d->kobj);
 }
 
 static void flash_dev_flush(struct closure *cl)
 {
     struct bcache_device *d = container_of(cl, struct bcache_device, cl);
 
     mutex_lock(&bch_register_lock);
     bcache_device_unlink(d);
     mutex_unlock(&bch_register_lock);
     kobject_del(&d->kobj);
     continue_at(cl, flash_dev_free, system_wq);
 }
 
 static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
 {
     int err = -ENOMEM;
     struct bcache_device *d = kzalloc(sizeof(struct bcache_device),
                       GFP_KERNEL);
     if (!d)
         goto err_ret;
 
     closure_init(&d->cl, NULL);
     set_closure_fn(&d->cl, flash_dev_flush, system_wq);
 
     kobject_init(&d->kobj, &bch_flash_dev_ktype);
 
     if (bcache_device_init(d, block_bytes(c->cache), u->sectors,
             NULL, &bcache_flash_ops))
         goto err;
 
     bcache_device_attach(d, c, u - c->uuids);
     bch_sectors_dirty_init(d);
     bch_flash_dev_request_init(d);
     err = add_disk(d->disk);
     if (err)
         goto err;
 
     err = kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache");
     if (err)
         goto err;
 
     bcache_device_link(d, c, "volume");
 
     if (bch_has_feature_obso_large_bucket(&c->cache->sb)) {
         pr_err("The obsoleted large bucket layout is unsupported, set the bcache device into read-only\n");
         pr_err("Please update to the latest bcache-tools to create the cache device\n");
         set_disk_ro(d->disk, 1);
     }
 
     return 0;
 err:
     kobject_put(&d->kobj);
 err_ret:
     return err;
 }
 
 static int flash_devs_run(struct cache_set *c)
 {
     int ret = 0;
     struct uuid_entry *u;
 
     for (u = c->uuids;
          u < c->uuids + c->nr_uuids && !ret;
          u++)
         if (UUID_FLASH_ONLY(u))
             ret = flash_dev_run(c, u);
 
     return ret;
 }
 
 int bch_flash_dev_create(struct cache_set *c, uint64_t size)
 {
     struct uuid_entry *u;
 
     if (test_bit(CACHE_SET_STOPPING, &c->flags))
         return -EINTR;
 
     if (!test_bit(CACHE_SET_RUNNING, &c->flags))
         return -EPERM;
 
     u = uuid_find_empty(c);
     if (!u) {
         pr_err("Can't create volume, no room for UUID\n");
         return -EINVAL;
     }
 
     get_random_bytes(u->uuid, 16);
     memset(u->label, 0, 32);
     u->first_reg = u->last_reg = cpu_to_le32((u32)ktime_get_real_seconds());
 
     SET_UUID_FLASH_ONLY(u, 1);
     u->sectors = size >> 9;
 
     bch_uuid_write(c);
 
     return flash_dev_run(c, u);
 }
 
 bool bch_cached_dev_error(struct cached_dev *dc)
 {
     if (!dc || test_bit(BCACHE_DEV_CLOSING, &dc->disk.flags))
         return false;
 
     dc->io_disable = true;
     /* make others know io_disable is true earlier */
     smp_mb();
 
     pr_err("stop %s: too many IO errors on backing device %pg\n",
            dc->disk.disk->disk_name, dc->bdev);
 
     bcache_device_stop(&dc->disk);
     return true;
 }
 
 /* Cache set */
 
 __printf(2, 3)
 bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...)
 {
     struct va_format vaf;
     va_list args;
 
     if (c->on_error != ON_ERROR_PANIC &&
         test_bit(CACHE_SET_STOPPING, &c->flags))
         return false;
 
     if (test_and_set_bit(CACHE_SET_IO_DISABLE, &c->flags))
         pr_info("CACHE_SET_IO_DISABLE already set\n");
 
     /*
      * XXX: we can be called from atomic context
      * acquire_console_sem();
      */
 
     va_start(args, fmt);
 
     vaf.fmt = fmt;
     vaf.va = &args;
 
     pr_err("error on %pU: %pV, disabling caching\n",
            c->set_uuid, &vaf);
 
     va_end(args);
 
     if (c->on_error == ON_ERROR_PANIC)
         panic("panic forced after error\n");
 
     bch_cache_set_unregister(c);
     return true;
 }
 
 /* When c->kobj released */
 void bch_cache_set_release(struct kobject *kobj)
 {
     struct cache_set *c = container_of(kobj, struct cache_set, kobj);
 
     kfree(c);
     module_put(THIS_MODULE);
 }
 
 static void cache_set_free(struct closure *cl)
 {
     struct cache_set *c = container_of(cl, struct cache_set, cl);
     struct cache *ca;
 
     debugfs_remove(c->debug);
 
     bch_open_buckets_free(c);
     bch_btree_cache_free(c);
     bch_journal_free(c);
 
     mutex_lock(&bch_register_lock);
     bch_bset_sort_state_free(&c->sort);
     free_pages((unsigned long) c->uuids, ilog2(meta_bucket_pages(&c->cache->sb)));
 
     ca = c->cache;
     if (ca) {
         ca->set = NULL;
         c->cache = NULL;
         kobject_put(&ca->kobj);
     }
 
 
     if (c->moving_gc_wq)
         destroy_workqueue(c->moving_gc_wq);
     bioset_exit(&c->bio_split);
     mempool_exit(&c->fill_iter);
     mempool_exit(&c->bio_meta);
     mempool_exit(&c->search);
     kfree(c->devices);
 
     list_del(&c->list);
     mutex_unlock(&bch_register_lock);
 
     pr_info("Cache set %pU unregistered\n", c->set_uuid);
     wake_up(&unregister_wait);
 
     closure_debug_destroy(&c->cl);
     kobject_put(&c->kobj);
 }
 
 static void cache_set_flush(struct closure *cl)
 {
     struct cache_set *c = container_of(cl, struct cache_set, caching);
     struct cache *ca = c->cache;
     struct btree *b;
 
     bch_cache_accounting_destroy(&c->accounting);
 
     kobject_put(&c->internal);
     kobject_del(&c->kobj);
 
     if (!IS_ERR_OR_NULL(c->gc_thread))
         kthread_stop(c->gc_thread);
 
     if (!IS_ERR_OR_NULL(c->root))
         list_add(&c->root->list, &c->btree_cache);
 
     /*
      * Avoid flushing cached nodes if cache set is retiring
      * due to too many I/O errors detected.
      */
     if (!test_bit(CACHE_SET_IO_DISABLE, &c->flags))
         list_for_each_entry(b, &c->btree_cache, list) {
             mutex_lock(&b->write_lock);
             if (btree_node_dirty(b))
                 __bch_btree_node_write(b, NULL);
             mutex_unlock(&b->write_lock);
         }
 
     if (ca->alloc_thread)
         kthread_stop(ca->alloc_thread);
 
     if (c->journal.cur) {
         cancel_delayed_work_sync(&c->journal.work);
         /* flush last journal entry if needed */
         c->journal.work.work.func(&c->journal.work.work);
     }
 
     closure_return(cl);
 }
 
 /*
  * This function is only called when CACHE_SET_IO_DISABLE is set, which means
  * cache set is unregistering due to too many I/O errors. In this condition,
  * the bcache device might be stopped, it depends on stop_when_cache_set_failed
  * value and whether the broken cache has dirty data:
  *
  * dc->stop_when_cache_set_failed    dc->has_dirty   stop bcache device
  *  BCH_CACHED_STOP_AUTO               0               NO
  *  BCH_CACHED_STOP_AUTO               1               YES
  *  BCH_CACHED_DEV_STOP_ALWAYS         0               YES
  *  BCH_CACHED_DEV_STOP_ALWAYS         1               YES
  *
  * The expected behavior is, if stop_when_cache_set_failed is configured to
  * "auto" via sysfs interface, the bcache device will not be stopped if the
  * backing device is clean on the broken cache device.
  */
 static void conditional_stop_bcache_device(struct cache_set *c,
                        struct bcache_device *d,
                        struct cached_dev *dc)
 {
     if (dc->stop_when_cache_set_failed == BCH_CACHED_DEV_STOP_ALWAYS) {
         pr_warn("stop_when_cache_set_failed of %s is \"always\", stop it for failed cache set %pU.\n",
             d->disk->disk_name, c->set_uuid);
         bcache_device_stop(d);
     } else if (atomic_read(&dc->has_dirty)) {
         /*
          * dc->stop_when_cache_set_failed == BCH_CACHED_STOP_AUTO
          * and dc->has_dirty == 1
          */
         pr_warn("stop_when_cache_set_failed of %s is \"auto\" and cache is dirty, stop it to avoid potential data corruption.\n",
             d->disk->disk_name);
         /*
          * There might be a small time gap that cache set is
          * released but bcache device is not. Inside this time
          * gap, regular I/O requests will directly go into
          * backing device as no cache set attached to. This
          * behavior may also introduce potential inconsistence
          * data in writeback mode while cache is dirty.
          * Therefore before calling bcache_device_stop() due
          * to a broken cache device, dc->io_disable should be
          * explicitly set to true.
          */
         dc->io_disable = true;
         /* make others know io_disable is true earlier */
         smp_mb();
         bcache_device_stop(d);
     } else {
         /*
          * dc->stop_when_cache_set_failed == BCH_CACHED_STOP_AUTO
          * and dc->has_dirty == 0
          */
         pr_warn("stop_when_cache_set_failed of %s is \"auto\" and cache is clean, keep it alive.\n",
             d->disk->disk_name);
     }
 }
 
 static void __cache_set_unregister(struct closure *cl)
 {
     struct cache_set *c = container_of(cl, struct cache_set, caching);
     struct cached_dev *dc;
     struct bcache_device *d;
     size_t i;
 
     mutex_lock(&bch_register_lock);
 
     for (i = 0; i < c->devices_max_used; i++) {
         d = c->devices[i];
         if (!d)
             continue;
 
         if (!UUID_FLASH_ONLY(&c->uuids[i]) &&
             test_bit(CACHE_SET_UNREGISTERING, &c->flags)) {
             dc = container_of(d, struct cached_dev, disk);
             bch_cached_dev_detach(dc);
             if (test_bit(CACHE_SET_IO_DISABLE, &c->flags))
                 conditional_stop_bcache_device(c, d, dc);
         } else {
             bcache_device_stop(d);
         }
     }
 
     mutex_unlock(&bch_register_lock);
 
     continue_at(cl, cache_set_flush, system_wq);
 }
 
 void bch_cache_set_stop(struct cache_set *c)
 {
     if (!test_and_set_bit(CACHE_SET_STOPPING, &c->flags))
         /* closure_fn set to __cache_set_unregister() */
         closure_queue(&c->caching);
 }
 
 void bch_cache_set_unregister(struct cache_set *c)
 {
     set_bit(CACHE_SET_UNREGISTERING, &c->flags);
     bch_cache_set_stop(c);
 }
 
 #define alloc_meta_bucket_pages(gfp, sb)        \
     ((void *) __get_free_pages(__GFP_ZERO|__GFP_COMP|gfp, ilog2(meta_bucket_pages(sb))))
 
 struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
 {
     int iter_size;
     struct cache *ca = container_of(sb, struct cache, sb);
     struct cache_set *c = kzalloc(sizeof(struct cache_set), GFP_KERNEL);
 
     if (!c)
         return NULL;
 
     __module_get(THIS_MODULE);
     closure_init(&c->cl, NULL);
     set_closure_fn(&c->cl, cache_set_free, system_wq);
 
     closure_init(&c->caching, &c->cl);
     set_closure_fn(&c->caching, __cache_set_unregister, system_wq);
 
     /* Maybe create continue_at_noreturn() and use it here? */
     closure_set_stopped(&c->cl);
     closure_put(&c->cl);
 
     kobject_init(&c->kobj, &bch_cache_set_ktype);
     kobject_init(&c->internal, &bch_cache_set_internal_ktype);
 
     bch_cache_accounting_init(&c->accounting, &c->cl);
 
     memcpy(c->set_uuid, sb->set_uuid, 16);
 
     c->cache        = ca;
     c->cache->set       = c;
     c->bucket_bits      = ilog2(sb->bucket_size);
     c->block_bits       = ilog2(sb->block_size);
     c->nr_uuids     = meta_bucket_bytes(sb) / sizeof(struct uuid_entry);
     c->devices_max_used = 0;
     atomic_set(&c->attached_dev_nr, 0);
     c->btree_pages      = meta_bucket_pages(sb);
     if (c->btree_pages > BTREE_MAX_PAGES)
         c->btree_pages = max_t(int, c->btree_pages / 4,
                        BTREE_MAX_PAGES);
 
     sema_init(&c->sb_write_mutex, 1);
     mutex_init(&c->bucket_lock);
     init_waitqueue_head(&c->btree_cache_wait);
     spin_lock_init(&c->btree_cannibalize_lock);
     init_waitqueue_head(&c->bucket_wait);
     init_waitqueue_head(&c->gc_wait);
     sema_init(&c->uuid_write_mutex, 1);
 
     spin_lock_init(&c->btree_gc_time.lock);
     spin_lock_init(&c->btree_split_time.lock);
     spin_lock_init(&c->btree_read_time.lock);
 
     bch_moving_init_cache_set(c);
 
     INIT_LIST_HEAD(&c->list);
     INIT_LIST_HEAD(&c->cached_devs);
     INIT_LIST_HEAD(&c->btree_cache);
     INIT_LIST_HEAD(&c->btree_cache_freeable);
     INIT_LIST_HEAD(&c->btree_cache_freed);
     INIT_LIST_HEAD(&c->data_buckets);
 
     iter_size = ((meta_bucket_pages(sb) * PAGE_SECTORS) / sb->block_size + 1) *
         sizeof(struct btree_iter_set);
 
     c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL);
     if (!c->devices)
         goto err;
 
     if (mempool_init_slab_pool(&c->search, 32, bch_search_cache))
         goto err;
 
     if (mempool_init_kmalloc_pool(&c->bio_meta, 2,
             sizeof(struct bbio) +
             sizeof(struct bio_vec) * meta_bucket_pages(sb)))
         goto err;
 
     if (mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size))
         goto err;
 
     if (bioset_init(&c->bio_split, 4, offsetof(struct bbio, bio),
             BIOSET_NEED_RESCUER))
         goto err;
 
     c->uuids = alloc_meta_bucket_pages(GFP_KERNEL, sb);
     if (!c->uuids)
         goto err;
 
     c->moving_gc_wq = alloc_workqueue("bcache_gc", WQ_MEM_RECLAIM, 0);
     if (!c->moving_gc_wq)
         goto err;
 
     if (bch_journal_alloc(c))
         goto err;
 
     if (bch_btree_cache_alloc(c))
         goto err;
 
     if (bch_open_buckets_alloc(c))
         goto err;
 
     if (bch_bset_sort_state_init(&c->sort, ilog2(c->btree_pages)))
         goto err;
 
     c->congested_read_threshold_us  = 2000;
     c->congested_write_threshold_us = 20000;
     c->error_limit  = DEFAULT_IO_ERROR_LIMIT;
     c->idle_max_writeback_rate_enabled = 1;
     WARN_ON(test_and_clear_bit(CACHE_SET_IO_DISABLE, &c->flags));
 
     return c;
 err:
     bch_cache_set_unregister(c);
     return NULL;
 }
 
 static int run_cache_set(struct cache_set *c)
 {
     const char *err = "cannot allocate memory";
     struct cached_dev *dc, *t;
     struct cache *ca = c->cache;
     struct closure cl;
     LIST_HEAD(journal);
     struct journal_replay *l;
 
     closure_init_stack(&cl);
 
     c->nbuckets = ca->sb.nbuckets;
     set_gc_sectors(c);
 
     if (CACHE_SYNC(&c->cache->sb)) {
         struct bkey *k;
         struct jset *j;
 
         err = "cannot allocate memory for journal";
         if (bch_journal_read(c, &journal))
             goto err;
 
         pr_debug("btree_journal_read() done\n");
 
         err = "no journal entries found";
         if (list_empty(&journal))
             goto err;
 
         j = &list_entry(journal.prev, struct journal_replay, list)->j;
 
         err = "IO error reading priorities";
         if (prio_read(ca, j->prio_bucket[ca->sb.nr_this_dev]))
             goto err;
 
         /*
          * If prio_read() fails it'll call cache_set_error and we'll
          * tear everything down right away, but if we perhaps checked
          * sooner we could avoid journal replay.
          */
 
         k = &j->btree_root;
 
         err = "bad btree root";
         if (__bch_btree_ptr_invalid(c, k))
             goto err;
 
         err = "error reading btree root";
         c->root = bch_btree_node_get(c, NULL, k,
                          j->btree_level,
                          true, NULL);
         if (IS_ERR_OR_NULL(c->root))
             goto err;
 
         list_del_init(&c->root->list);
         rw_unlock(true, c->root);
 
         err = uuid_read(c, j, &cl);
         if (err)
             goto err;
 
         err = "error in recovery";
         if (bch_btree_check(c))
             goto err;
 
         bch_journal_mark(c, &journal);
         bch_initial_gc_finish(c);
         pr_debug("btree_check() done\n");
 
         /*
          * bcache_journal_next() can't happen sooner, or
          * btree_gc_finish() will give spurious errors about last_gc >
          * gc_gen - this is a hack but oh well.
          */
         bch_journal_next(&c->journal);
 
         err = "error starting allocator thread";
         if (bch_cache_allocator_start(ca))
             goto err;
 
         /*
          * First place it's safe to allocate: btree_check() and
          * btree_gc_finish() have to run before we have buckets to
          * allocate, and bch_bucket_alloc_set() might cause a journal
          * entry to be written so bcache_journal_next() has to be called
          * first.
          *
          * If the uuids were in the old format we have to rewrite them
          * before the next journal entry is written:
          */
         if (j->version < BCACHE_JSET_VERSION_UUID)
             __uuid_write(c);
 
         err = "bcache: replay journal failed";
         if (bch_journal_replay(c, &journal))
             goto err;
     } else {
         unsigned int j;
 
         pr_notice("invalidating existing data\n");
         ca->sb.keys = clamp_t(int, ca->sb.nbuckets >> 7,
                     2, SB_JOURNAL_BUCKETS);
 
         for (j = 0; j < ca->sb.keys; j++)
             ca->sb.d[j] = ca->sb.first_bucket + j;
 
         bch_initial_gc_finish(c);
 
         err = "error starting allocator thread";
         if (bch_cache_allocator_start(ca))
             goto err;
 
         mutex_lock(&c->bucket_lock);
         bch_prio_write(ca, true);
         mutex_unlock(&c->bucket_lock);
 
         err = "cannot allocate new UUID bucket";
         if (__uuid_write(c))
             goto err;
 
         err = "cannot allocate new btree root";
         c->root = __bch_btree_node_alloc(c, NULL, 0, true, NULL);
         if (IS_ERR_OR_NULL(c->root))
             goto err;
 
         mutex_lock(&c->root->write_lock);
         bkey_copy_key(&c->root->key, &MAX_KEY);
         bch_btree_node_write(c->root, &cl);
         mutex_unlock(&c->root->write_lock);
 
         bch_btree_set_root(c->root);
         rw_unlock(true, c->root);
 
         /*
          * We don't want to write the first journal entry until
          * everything is set up - fortunately journal entries won't be
          * written until the SET_CACHE_SYNC() here:
          */
         SET_CACHE_SYNC(&c->cache->sb, true);
 
         bch_journal_next(&c->journal);
         bch_journal_meta(c, &cl);
     }
 
     err = "error starting gc thread";
     if (bch_gc_thread_start(c))
         goto err;
 
     closure_sync(&cl);
     c->cache->sb.last_mount = (u32)ktime_get_real_seconds();
     bcache_write_super(c);
 
     if (bch_has_feature_obso_large_bucket(&c->cache->sb))
         pr_err("Detect obsoleted large bucket layout, all attached bcache device will be read-only\n");
 
     list_for_each_entry_safe(dc, t, &uncached_devices, list)
         bch_cached_dev_attach(dc, c, NULL);
 
     flash_devs_run(c);
 
     bch_journal_space_reserve(&c->journal);
     set_bit(CACHE_SET_RUNNING, &c->flags);
     return 0;
 err:
     while (!list_empty(&journal)) {
         l = list_first_entry(&journal, struct journal_replay, list);
         list_del(&l->list);
         kfree(l);
     }
 
     closure_sync(&cl);
 
     bch_cache_set_error(c, "%s", err);
 
     return -EIO;
 }
 
 static const char *register_cache_set(struct cache *ca)
 {
     char buf[12];
     const char *err = "cannot allocate memory";
     struct cache_set *c;
 
     list_for_each_entry(c, &bch_cache_sets, list)
         if (!memcmp(c->set_uuid, ca->sb.set_uuid, 16)) {
             if (c->cache)
                 return "duplicate cache set member";
 
             goto found;
         }
 
     c = bch_cache_set_alloc(&ca->sb);
     if (!c)
         return err;
 
     err = "error creating kobject";
     if (kobject_add(&c->kobj, bcache_kobj, "%pU", c->set_uuid) ||
         kobject_add(&c->internal, &c->kobj, "internal"))
         goto err;
 
     if (bch_cache_accounting_add_kobjs(&c->accounting, &c->kobj))
         goto err;
 
     bch_debug_init_cache_set(c);
 
     list_add(&c->list, &bch_cache_sets);
 found:
     sprintf(buf, "cache%i", ca->sb.nr_this_dev);
     if (sysfs_create_link(&ca->kobj, &c->kobj, "set") ||
         sysfs_create_link(&c->kobj, &ca->kobj, buf))
         goto err;
 
     kobject_get(&ca->kobj);
     ca->set = c;
     ca->set->cache = ca;
 
     err = "failed to run cache set";
     if (run_cache_set(c) < 0)
         goto err;
 
     return NULL;
 err:
     bch_cache_set_unregister(c);
     return err;
 }
 
 /* Cache device */
 
 /* When ca->kobj released */
 void bch_cache_release(struct kobject *kobj)
 {
     struct cache *ca = container_of(kobj, struct cache, kobj);
     unsigned int i;
 
     if (ca->set) {
         BUG_ON(ca->set->cache != ca);
         ca->set->cache = NULL;
     }
 
     free_pages((unsigned long) ca->disk_buckets, ilog2(meta_bucket_pages(&ca->sb)));
     kfree(ca->prio_buckets);
     vfree(ca->buckets);
 
     free_heap(&ca->heap);
     free_fifo(&ca->free_inc);
 
     for (i = 0; i < RESERVE_NR; i++)
         free_fifo(&ca->free[i]);
 
     if (ca->sb_disk)
         put_page(virt_to_page(ca->sb_disk));
 
     if (!IS_ERR_OR_NULL(ca->bdev))
         blkdev_put(ca->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 
     kfree(ca);
     module_put(THIS_MODULE);
 }
 
 static int cache_alloc(struct cache *ca)
 {
     size_t free;
     size_t btree_buckets;
     struct bucket *b;
     int ret = -ENOMEM;
     const char *err = NULL;
 
     __module_get(THIS_MODULE);
     kobject_init(&ca->kobj, &bch_cache_ktype);
 
     bio_init(&ca->journal.bio, NULL, ca->journal.bio.bi_inline_vecs, 8, 0);
 
     /*
      * when ca->sb.njournal_buckets is not zero, journal exists,
      * and in bch_journal_replay(), tree node may split,
      * so bucket of RESERVE_BTREE type is needed,
      * the worst situation is all journal buckets are valid journal,
      * and all the keys need to replay,
      * so the number of  RESERVE_BTREE type buckets should be as much
      * as journal buckets
      */
     btree_buckets = ca->sb.njournal_buckets ?: 8;
     free = roundup_pow_of_two(ca->sb.nbuckets) >> 10;
     if (!free) {
         ret = -EPERM;
         err = "ca->sb.nbuckets is too small";
         goto err_free;
     }
 
     if (!init_fifo(&ca->free[RESERVE_BTREE], btree_buckets,
                         GFP_KERNEL)) {
         err = "ca->free[RESERVE_BTREE] alloc failed";
         goto err_btree_alloc;
     }
 
     if (!init_fifo_exact(&ca->free[RESERVE_PRIO], prio_buckets(ca),
                             GFP_KERNEL)) {
         err = "ca->free[RESERVE_PRIO] alloc failed";
         goto err_prio_alloc;
     }
 
     if (!init_fifo(&ca->free[RESERVE_MOVINGGC], free, GFP_KERNEL)) {
         err = "ca->free[RESERVE_MOVINGGC] alloc failed";
         goto err_movinggc_alloc;
     }
 
     if (!init_fifo(&ca->free[RESERVE_NONE], free, GFP_KERNEL)) {
         err = "ca->free[RESERVE_NONE] alloc failed";
         goto err_none_alloc;
     }
 
     if (!init_fifo(&ca->free_inc, free << 2, GFP_KERNEL)) {
         err = "ca->free_inc alloc failed";
         goto err_free_inc_alloc;
     }
 
     if (!init_heap(&ca->heap, free << 3, GFP_KERNEL)) {
         err = "ca->heap alloc failed";
         goto err_heap_alloc;
     }
 
     ca->buckets = vzalloc(array_size(sizeof(struct bucket),
                   ca->sb.nbuckets));
     if (!ca->buckets) {
         err = "ca->buckets alloc failed";
         goto err_buckets_alloc;
     }
 
     ca->prio_buckets = kzalloc(array3_size(sizeof(uint64_t),
                    prio_buckets(ca), 2),
                    GFP_KERNEL);
     if (!ca->prio_buckets) {
         err = "ca->prio_buckets alloc failed";
         goto err_prio_buckets_alloc;
     }
 
     ca->disk_buckets = alloc_meta_bucket_pages(GFP_KERNEL, &ca->sb);
     if (!ca->disk_buckets) {
         err = "ca->disk_buckets alloc failed";
         goto err_disk_buckets_alloc;
     }
 
     ca->prio_last_buckets = ca->prio_buckets + prio_buckets(ca);
 
     for_each_bucket(b, ca)
         atomic_set(&b->pin, 0);
     return 0;
 
 err_disk_buckets_alloc:
     kfree(ca->prio_buckets);
 err_prio_buckets_alloc:
     vfree(ca->buckets);
 err_buckets_alloc:
     free_heap(&ca->heap);
 err_heap_alloc:
     free_fifo(&ca->free_inc);
 err_free_inc_alloc:
     free_fifo(&ca->free[RESERVE_NONE]);
 err_none_alloc:
     free_fifo(&ca->free[RESERVE_MOVINGGC]);
 err_movinggc_alloc:
     free_fifo(&ca->free[RESERVE_PRIO]);
 err_prio_alloc:
     free_fifo(&ca->free[RESERVE_BTREE]);
 err_btree_alloc:
 err_free:
     module_put(THIS_MODULE);
     if (err)
         pr_notice("error %pg: %s\n", ca->bdev, err);
     return ret;
 }
 
 static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
                 struct block_device *bdev, struct cache *ca)
 {
     const char *err = NULL; /* must be set for any error case */
     int ret = 0;
 
     memcpy(&ca->sb, sb, sizeof(struct cache_sb));
     ca->bdev = bdev;
     ca->bdev->bd_holder = ca;
     ca->sb_disk = sb_disk;
 
     if (bdev_max_discard_sectors((bdev)))
         ca->discard = CACHE_DISCARD(&ca->sb);
 
     ret = cache_alloc(ca);
     if (ret != 0) {
         /*
          * If we failed here, it means ca->kobj is not initialized yet,
          * kobject_put() won't be called and there is no chance to
          * call blkdev_put() to bdev in bch_cache_release(). So we
          * explicitly call blkdev_put() here.
          */
         blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
         if (ret == -ENOMEM)
             err = "cache_alloc(): -ENOMEM";
         else if (ret == -EPERM)
             err = "cache_alloc(): cache device is too small";
         else
             err = "cache_alloc(): unknown error";
         goto err;
     }
 
     if (kobject_add(&ca->kobj, bdev_kobj(bdev), "bcache")) {
         err = "error calling kobject_add";
         ret = -ENOMEM;
         goto out;
     }
 
     mutex_lock(&bch_register_lock);
     err = register_cache_set(ca);
     mutex_unlock(&bch_register_lock);
 
     if (err) {
         ret = -ENODEV;
         goto out;
     }
 
     pr_info("registered cache device %pg\n", ca->bdev);
 
 out:
     kobject_put(&ca->kobj);
 
 err:
     if (err)
         pr_notice("error %pg: %s\n", ca->bdev, err);
 
     return ret;
 }
 
 /* Global interfaces/init */
 
 static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
                    const char *buffer, size_t size);
 static ssize_t bch_pending_bdevs_cleanup(struct kobject *k,
                      struct kobj_attribute *attr,
                      const char *buffer, size_t size);
 
 kobj_attribute_write(register,      register_bcache);
 kobj_attribute_write(register_quiet,    register_bcache);
 kobj_attribute_write(pendings_cleanup,  bch_pending_bdevs_cleanup);
 
 static bool bch_is_open_backing(dev_t dev)
 {
     struct cache_set *c, *tc;
     struct cached_dev *dc, *t;
 
     list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
         list_for_each_entry_safe(dc, t, &c->cached_devs, list)
             if (dc->bdev->bd_dev == dev)
                 return true;
     list_for_each_entry_safe(dc, t, &uncached_devices, list)
         if (dc->bdev->bd_dev == dev)
             return true;
     return false;
 }
 
 static bool bch_is_open_cache(dev_t dev)
 {
     struct cache_set *c, *tc;
 
     list_for_each_entry_safe(c, tc, &bch_cache_sets, list) {
         struct cache *ca = c->cache;
 
         if (ca->bdev->bd_dev == dev)
             return true;
     }
 
     return false;
 }
 
 static bool bch_is_open(dev_t dev)
 {
     return bch_is_open_cache(dev) || bch_is_open_backing(dev);
 }
 
 struct async_reg_args {
     struct delayed_work reg_work;
     char *path;
     struct cache_sb *sb;
     struct cache_sb_disk *sb_disk;
     struct block_device *bdev;
 };
 
 static void register_bdev_worker(struct work_struct *work)
 {
     int fail = false;
     struct async_reg_args *args =
         container_of(work, struct async_reg_args, reg_work.work);
     struct cached_dev *dc;
 
     dc = kzalloc(sizeof(*dc), GFP_KERNEL);
     if (!dc) {
         fail = true;
         put_page(virt_to_page(args->sb_disk));
         blkdev_put(args->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
         goto out;
     }
 
     mutex_lock(&bch_register_lock);
     if (register_bdev(args->sb, args->sb_disk, args->bdev, dc) < 0)
         fail = true;
     mutex_unlock(&bch_register_lock);
 
 out:
     if (fail)
         pr_info("error %s: fail to register backing device\n",
             args->path);
     kfree(args->sb);
     kfree(args->path);
     kfree(args);
     module_put(THIS_MODULE);
 }
 
 static void register_cache_worker(struct work_struct *work)
 {
     int fail = false;
     struct async_reg_args *args =
         container_of(work, struct async_reg_args, reg_work.work);
     struct cache *ca;
 
     ca = kzalloc(sizeof(*ca), GFP_KERNEL);
     if (!ca) {
         fail = true;
         put_page(virt_to_page(args->sb_disk));
         blkdev_put(args->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
         goto out;
     }
 
     /* blkdev_put() will be called in bch_cache_release() */
     if (register_cache(args->sb, args->sb_disk, args->bdev, ca) != 0)
         fail = true;
 
 out:
     if (fail)
         pr_info("error %s: fail to register cache device\n",
             args->path);
     kfree(args->sb);
     kfree(args->path);
     kfree(args);
     module_put(THIS_MODULE);
 }
 
 static void register_device_async(struct async_reg_args *args)
 {
     if (SB_IS_BDEV(args->sb))
         INIT_DELAYED_WORK(&args->reg_work, register_bdev_worker);
     else
         INIT_DELAYED_WORK(&args->reg_work, register_cache_worker);
 
     /* 10 jiffies is enough for a delay */
     queue_delayed_work(system_wq, &args->reg_work, 10);
 }
 
 static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
                    const char *buffer, size_t size)
 {
     const char *err;
     char *path = NULL;
     struct cache_sb *sb;
     struct cache_sb_disk *sb_disk;
     struct block_device *bdev;
     ssize_t ret;
     bool async_registration = false;
 
 #ifdef CONFIG_BCACHE_ASYNC_REGISTRATION
     async_registration = true;
 #endif
 
     ret = -EBUSY;
     err = "failed to reference bcache module";
     if (!try_module_get(THIS_MODULE))
         goto out;
 
     /* For latest state of bcache_is_reboot */
     smp_mb();
     err = "bcache is in reboot";
     if (bcache_is_reboot)
         goto out_module_put;
 
     ret = -ENOMEM;
     err = "cannot allocate memory";
     path = kstrndup(buffer, size, GFP_KERNEL);
     if (!path)
         goto out_module_put;
 
     sb = kmalloc(sizeof(struct cache_sb), GFP_KERNEL);
     if (!sb)
         goto out_free_path;
 
     ret = -EINVAL;
     err = "failed to open device";
     bdev = blkdev_get_by_path(strim(path),
                   FMODE_READ|FMODE_WRITE|FMODE_EXCL,
                   sb);
     if (IS_ERR(bdev)) {
         if (bdev == ERR_PTR(-EBUSY)) {
             dev_t dev;
 
             mutex_lock(&bch_register_lock);
             if (lookup_bdev(strim(path), &dev) == 0 &&
                 bch_is_open(dev))
                 err = "device already registered";
             else
                 err = "device busy";
             mutex_unlock(&bch_register_lock);
             if (attr == &ksysfs_register_quiet)
                 goto done;
         }
         goto out_free_sb;
     }
 
     err = "failed to set blocksize";
     if (set_blocksize(bdev, 4096))
         goto out_blkdev_put;
 
     err = read_super(sb, bdev, &sb_disk);
     if (err)
         goto out_blkdev_put;
 
     err = "failed to register device";
 
     if (async_registration) {
         /* register in asynchronous way */
         struct async_reg_args *args =
             kzalloc(sizeof(struct async_reg_args), GFP_KERNEL);
 
         if (!args) {
             ret = -ENOMEM;
             err = "cannot allocate memory";
             goto out_put_sb_page;
         }
 
         args->path  = path;
         args->sb    = sb;
         args->sb_disk   = sb_disk;
         args->bdev  = bdev;
         register_device_async(args);
         /* No wait and returns to user space */
         goto async_done;
     }
 
     if (SB_IS_BDEV(sb)) {
         struct cached_dev *dc = kzalloc(sizeof(*dc), GFP_KERNEL);
 
         if (!dc) {
             ret = -ENOMEM;
             err = "cannot allocate memory";
             goto out_put_sb_page;
         }
 
         mutex_lock(&bch_register_lock);
         ret = register_bdev(sb, sb_disk, bdev, dc);
         mutex_unlock(&bch_register_lock);
         /* blkdev_put() will be called in cached_dev_free() */
         if (ret < 0)
             goto out_free_sb;
     } else {
         struct cache *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
 
         if (!ca) {
             ret = -ENOMEM;
             err = "cannot allocate memory";
             goto out_put_sb_page;
         }
 
         /* blkdev_put() will be called in bch_cache_release() */
         ret = register_cache(sb, sb_disk, bdev, ca);
         if (ret)
             goto out_free_sb;
     }
 
 done:
     kfree(sb);
     kfree(path);
     module_put(THIS_MODULE);
 async_done:
     return size;
 
 out_put_sb_page:
     put_page(virt_to_page(sb_disk));
 out_blkdev_put:
     blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 out_free_sb:
     kfree(sb);
 out_free_path:
     kfree(path);
     path = NULL;
 out_module_put:
     module_put(THIS_MODULE);
 out:
     pr_info("error %s: %s\n", path?path:"", err);
     return ret;
 }
 
 
 struct pdev {
     struct list_head list;
     struct cached_dev *dc;
 };
 
 static ssize_t bch_pending_bdevs_cleanup(struct kobject *k,
                      struct kobj_attribute *attr,
                      const char *buffer,
                      size_t size)
 {
     LIST_HEAD(pending_devs);
     ssize_t ret = size;
     struct cached_dev *dc, *tdc;
     struct pdev *pdev, *tpdev;
     struct cache_set *c, *tc;
 
     mutex_lock(&bch_register_lock);
     list_for_each_entry_safe(dc, tdc, &uncached_devices, list) {
         pdev = kmalloc(sizeof(struct pdev), GFP_KERNEL);
         if (!pdev)
             break;
         pdev->dc = dc;
         list_add(&pdev->list, &pending_devs);
     }
 
     list_for_each_entry_safe(pdev, tpdev, &pending_devs, list) {
         char *pdev_set_uuid = pdev->dc->sb.set_uuid;
         list_for_each_entry_safe(c, tc, &bch_cache_sets, list) {
             char *set_uuid = c->set_uuid;
 
             if (!memcmp(pdev_set_uuid, set_uuid, 16)) {
                 list_del(&pdev->list);
                 kfree(pdev);
                 break;
             }
         }
     }
     mutex_unlock(&bch_register_lock);
 
     list_for_each_entry_safe(pdev, tpdev, &pending_devs, list) {
         pr_info("delete pdev %p\n", pdev);
         list_del(&pdev->list);
         bcache_device_stop(&pdev->dc->disk);
         kfree(pdev);
     }
 
     return ret;
 }
 
 static int bcache_reboot(struct notifier_block *n, unsigned long code, void *x)
 {
     if (bcache_is_reboot)
         return NOTIFY_DONE;
 
     if (code == SYS_DOWN ||
         code == SYS_HALT ||
         code == SYS_POWER_OFF) {
         DEFINE_WAIT(wait);
         unsigned long start = jiffies;
         bool stopped = false;
 
         struct cache_set *c, *tc;
         struct cached_dev *dc, *tdc;
 
         mutex_lock(&bch_register_lock);
 
         if (bcache_is_reboot)
             goto out;
 
         /* New registration is rejected since now */
         bcache_is_reboot = true;
         /*
          * Make registering caller (if there is) on other CPU
          * core know bcache_is_reboot set to true earlier
          */
         smp_mb();
 
         if (list_empty(&bch_cache_sets) &&
             list_empty(&uncached_devices))
             goto out;
 
         mutex_unlock(&bch_register_lock);
 
         pr_info("Stopping all devices:\n");
 
         /*
          * The reason bch_register_lock is not held to call
          * bch_cache_set_stop() and bcache_device_stop() is to
          * avoid potential deadlock during reboot, because cache
          * set or bcache device stopping process will acquire
          * bch_register_lock too.
          *
          * We are safe here because bcache_is_reboot sets to
          * true already, register_bcache() will reject new
          * registration now. bcache_is_reboot also makes sure
          * bcache_reboot() won't be re-entered on by other thread,
          * so there is no race in following list iteration by
          * list_for_each_entry_safe().
          */
         list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
             bch_cache_set_stop(c);
 
         list_for_each_entry_safe(dc, tdc, &uncached_devices, list)
             bcache_device_stop(&dc->disk);
 
 
         /*
          * Give an early chance for other kthreads and
          * kworkers to stop themselves
          */
         schedule();
 
         /* What's a condition variable? */
         while (1) {
             long timeout = start + 10 * HZ - jiffies;
 
             mutex_lock(&bch_register_lock);
             stopped = list_empty(&bch_cache_sets) &&
                 list_empty(&uncached_devices);
 
             if (timeout < 0 || stopped)
                 break;
 
             prepare_to_wait(&unregister_wait, &wait,
                     TASK_UNINTERRUPTIBLE);
 
             mutex_unlock(&bch_register_lock);
             schedule_timeout(timeout);
         }
 
         finish_wait(&unregister_wait, &wait);
 
         if (stopped)
             pr_info("All devices stopped\n");
         else
             pr_notice("Timeout waiting for devices to be closed\n");
 out:
         mutex_unlock(&bch_register_lock);
     }
 
     return NOTIFY_DONE;
 }
 
 static struct notifier_block reboot = {
     .notifier_call  = bcache_reboot,
     .priority   = INT_MAX, /* before any real devices */
 };
 
 static void bcache_exit(void)
 {
     bch_debug_exit();
     bch_request_exit();
     if (bcache_kobj)
         kobject_put(bcache_kobj);
     if (bcache_wq)
         destroy_workqueue(bcache_wq);
     if (bch_journal_wq)
         destroy_workqueue(bch_journal_wq);
     if (bch_flush_wq)
         destroy_workqueue(bch_flush_wq);
     bch_btree_exit();
 
     if (bcache_major)
         unregister_blkdev(bcache_major, "bcache");
     unregister_reboot_notifier(&reboot);
     mutex_destroy(&bch_register_lock);
 }
 
 /* Check and fixup module parameters */
 static void check_module_parameters(void)
 {
     if (bch_cutoff_writeback_sync == 0)
         bch_cutoff_writeback_sync = CUTOFF_WRITEBACK_SYNC;
     else if (bch_cutoff_writeback_sync > CUTOFF_WRITEBACK_SYNC_MAX) {
         pr_warn("set bch_cutoff_writeback_sync (%u) to max value %u\n",
             bch_cutoff_writeback_sync, CUTOFF_WRITEBACK_SYNC_MAX);
         bch_cutoff_writeback_sync = CUTOFF_WRITEBACK_SYNC_MAX;
     }
 
     if (bch_cutoff_writeback == 0)
         bch_cutoff_writeback = CUTOFF_WRITEBACK;
     else if (bch_cutoff_writeback > CUTOFF_WRITEBACK_MAX) {
         pr_warn("set bch_cutoff_writeback (%u) to max value %u\n",
             bch_cutoff_writeback, CUTOFF_WRITEBACK_MAX);
         bch_cutoff_writeback = CUTOFF_WRITEBACK_MAX;
     }
 
     if (bch_cutoff_writeback > bch_cutoff_writeback_sync) {
         pr_warn("set bch_cutoff_writeback (%u) to %u\n",
             bch_cutoff_writeback, bch_cutoff_writeback_sync);
         bch_cutoff_writeback = bch_cutoff_writeback_sync;
     }
 }
 
 static int __init bcache_init(void)
 {
     static const struct attribute *files[] = {
         &ksysfs_register.attr,
         &ksysfs_register_quiet.attr,
         &ksysfs_pendings_cleanup.attr,
         NULL
     };
 
     check_module_parameters();
 
     mutex_init(&bch_register_lock);
     init_waitqueue_head(&unregister_wait);
     register_reboot_notifier(&reboot);
 
     bcache_major = register_blkdev(0, "bcache");
     if (bcache_major < 0) {
         unregister_reboot_notifier(&reboot);
         mutex_destroy(&bch_register_lock);
         return bcache_major;
     }
 
     if (bch_btree_init())
         goto err;
 
     bcache_wq = alloc_workqueue("bcache", WQ_MEM_RECLAIM, 0);
     if (!bcache_wq)
         goto err;
 
     /*
      * Let's not make this `WQ_MEM_RECLAIM` for the following reasons:
      *
      * 1. It used `system_wq` before which also does no memory reclaim.
      * 2. With `WQ_MEM_RECLAIM` desktop stalls, increased boot times, and
      *    reduced throughput can be observed.
      *
      * We still want to user our own queue to not congest the `system_wq`.
      */
     bch_flush_wq = alloc_workqueue("bch_flush", 0, 0);
     if (!bch_flush_wq)
         goto err;
 
     bch_journal_wq = alloc_workqueue("bch_journal", WQ_MEM_RECLAIM, 0);
     if (!bch_journal_wq)
         goto err;
 
     bcache_kobj = kobject_create_and_add("bcache", fs_kobj);
     if (!bcache_kobj)
         goto err;
 
     if (bch_request_init() ||
         sysfs_create_files(bcache_kobj, files))
         goto err;
 
     bch_debug_init();
     closure_debug_init();
 
     bcache_is_reboot = false;
 
     return 0;
 err:
     bcache_exit();
     return -ENOMEM;
 }
 
 /*
  * Module hooks
  */
 module_exit(bcache_exit);
 module_init(bcache_init);
 
 module_param(bch_cutoff_writeback, uint, 0);
 MODULE_PARM_DESC(bch_cutoff_writeback, "threshold to cutoff writeback");
 
 module_param(bch_cutoff_writeback_sync, uint, 0);
 MODULE_PARM_DESC(bch_cutoff_writeback_sync, "hard threshold to cutoff writeback");
 
 MODULE_DESCRIPTION("Bcache: a Linux block layer cache");
 MODULE_AUTHOR("Kent Overstreet <kent.overstreet@gmail.com>");
 MODULE_LICENSE("GPL");