// 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 folio *folio;
        unsigned int i;

        folio = mapping_read_folio_gfp(bdev->bd_mapping,
                        SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
        if (IS_ERR(folio))
                return "IO error";
        s = folio_address(folio) + offset_in_folio(folio, 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:
        folio_put(folio);
        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_virt_nofail(bio, out, SB_SIZE);

        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 CLOSURE_CALLBACK(bch_write_bdev_super_unlock)
{
        closure_type(dc, 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 CLOSURE_CALLBACK(bcache_write_super_unlock)
{
        closure_type(c, 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 CLOSURE_CALLBACK(uuid_io_unlock)
{
        closure_type(c, 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] __nonstring =
                { 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 gendisk *disk, blk_mode_t mode)
{
        struct bcache_device *d = 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)
{
        struct bcache_device *d = b->private_data;

        closure_put(&d->cl);
}

static int ioctl_dev(struct block_device *b, blk_mode_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_free(&bcache_device_idx,
                         first_minor_to_idx(disk->first_minor));
                put_disk(disk);
        }

        bioset_exit(&d->bio_split);
        bioset_exit(&d->bio_detached);
        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)
{
        const size_t max_stripes = min_t(size_t, INT_MAX,
                                         SIZE_MAX / sizeof(atomic_t));
        struct queue_limits lim = {
                .max_hw_sectors         = UINT_MAX,
                .max_sectors            = UINT_MAX,
                .max_segment_size       = UINT_MAX,
                .max_segments           = BIO_MAX_VECS,
                .max_hw_discard_sectors = UINT_MAX,
                .io_min                 = block_size,
                .logical_block_size     = block_size,
                .physical_block_size    = block_size,
                .features               = BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA,
        };
        uint64_t n;
        int idx;

        if (cached_bdev) {
                d->stripe_size = bdev_io_opt(cached_bdev) >> SECTOR_SHIFT;
                lim.io_opt = umax(block_size, bdev_io_opt(cached_bdev));
        }
        if (!d->stripe_size)
                d->stripe_size = 1 << 31;
        else if (d->stripe_size < BCH_MIN_STRIPE_SZ)
                d->stripe_size = roundup(BCH_MIN_STRIPE_SZ, d->stripe_size);

        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_alloc_max(&bcache_device_idx, BCACHE_DEVICE_IDX_MAX - 1,
                            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;

        if (bioset_init(&d->bio_detached, 4,
                        offsetof(struct detached_dev_io_private, bio),
                        BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER))
                goto out_bioset_split_exit;

        if (lim.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("bcache%i: sb/logical block size (%u) greater than page size (%lu) falling back to device logical block size (%u)\n",
                        idx, lim.logical_block_size,
                        PAGE_SIZE, bdev_logical_block_size(cached_bdev));

                /* This also adjusts physical block size/min io size if needed */
                lim.logical_block_size = bdev_logical_block_size(cached_bdev);
        }

        d->disk = blk_alloc_disk(&lim, NUMA_NO_NODE);
        if (IS_ERR(d->disk))
                goto out_bioset_detach_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;
        return 0;

out_bioset_detach_exit:
        bioset_exit(&d->bio_detached);
out_bioset_split_exit:
        bioset_exit(&d->bio_split);
out_ida_remove:
        ida_free(&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 CLOSURE_CALLBACK(cached_dev_free)
{
        closure_type(dc, 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)
                folio_put(virt_to_folio(dc->sb_disk));

        if (dc->bdev_file)
                fput(dc->bdev_file);

        wake_up(&unregister_wait);

        kobject_put(&dc->disk.kobj);
}

static CLOSURE_CALLBACK(cached_dev_flush)
{
        closure_type(dc, 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_percpu_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_percpu_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);
        }

        if (bdev_io_opt(dc->bdev))
                dc->partial_stripes_expensive = !!(q->limits.features &
                        BLK_FEAT_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;

        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 file *bdev_file,
                                 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_file = bdev_file;
        dc->bdev = file_bdev(bdev_file);
        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(dc->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 CLOSURE_CALLBACK(flash_dev_free)
{
        closure_type(d, 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 CLOSURE_CALLBACK(flash_dev_flush)
{
        closure_type(d, 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_percpu_wq);
}

static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
{
        int err = -ENOMEM;
        struct bcache_device *d = kzalloc_obj(struct bcache_device);
        if (!d)
                goto err_ret;

        closure_init(&d->cl, NULL);
        set_closure_fn(&d->cl, flash_dev_flush, system_percpu_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 CLOSURE_CALLBACK(cache_set_free)
{
        closure_type(c, 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 CLOSURE_CALLBACK(cache_set_flush)
{
        closure_type(c, 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 the register_cache_set() call to bch_cache_set_alloc() failed,
         * ca has not been assigned a value and return error.
         * So we need check ca is not NULL during bch_cache_set_unregister().
         */
        if (ca && 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 CLOSURE_CALLBACK(__cache_set_unregister)
{
        closure_type(c, 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_percpu_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_obj(struct cache_set);

        if (!c)
                return NULL;

        __module_get(THIS_MODULE);
        closure_init(&c->cl, NULL);
        set_closure_fn(&c->cl, cache_set_free, system_percpu_wq);

        closure_init(&c->caching, &c->cl);
        set_closure_fn(&c->caching, __cache_set_unregister, system_percpu_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 = sizeof(struct btree_iter) +
                    ((meta_bucket_pages(sb) * PAGE_SECTORS) / sb->block_size) *
                            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 | WQ_PERCPU, 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(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(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)
                folio_put(virt_to_folio(ca->sb_disk));

        if (ca->bdev_file)
                fput(ca->bdev_file);

        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_inline(&ca->journal.bio, NULL, 8, 0);

        /*
         * When the cache disk is first registered, ca->sb.njournal_buckets
         * is zero, and it is assigned in run_cache_set().
         *
         * When ca->sb.njournal_buckets is not zero, journal exists,
         * and in bch_journal_replay(), tree node may split.
         * 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.
         *
         * If the number of RESERVE_BTREE type buckets is too few, the
         * bch_allocator_thread() may hang up and unable to allocate
         * bucket. The situation is roughly as follows:
         *
         * 1. In bch_data_insert_keys(), if the operation is not op->replace,
         *    it will call the bch_journal(), which increments the journal_ref
         *    counter. This counter is only decremented after bch_btree_insert
         *    completes.
         *
         * 2. When calling bch_btree_insert, if the btree needs to split,
         *    it will call btree_split() and btree_check_reserve() to check
         *    whether there are enough reserved buckets in the RESERVE_BTREE
         *    slot. If not enough, bcache_btree_root() will repeatedly retry.
         *
         * 3. Normally, the bch_allocator_thread is responsible for filling
         *    the reservation slots from the free_inc bucket list. When the
         *    free_inc bucket list is exhausted, the bch_allocator_thread
         *    will call invalidate_buckets() until free_inc is refilled.
         *    Then bch_allocator_thread calls bch_prio_write() once. and
         *    bch_prio_write() will call bch_journal_meta() and waits for
         *    the journal write to complete.
         *
         * 4. During journal_write, journal_write_unlocked() is be called.
         *    If journal full occurs, journal_reclaim() and btree_flush_write()
         *    will be called sequentially, then retry journal_write.
         *
         * 5. When 2 and 4 occur together, IO will hung up and cannot recover.
         *
         * Therefore, reserve more RESERVE_BTREE type buckets.
         */
        btree_buckets = clamp_t(size_t, ca->sb.nbuckets >> 7,
                                32, SB_JOURNAL_BUCKETS);
        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 file *bdev_file,
                                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_file = bdev_file;
        ca->bdev = file_bdev(bdev_file);
        ca->sb_disk = sb_disk;

        ret = cache_alloc(ca);
        if (ret != 0) {
                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";
                pr_notice("error %pg: %s\n", file_bdev(bdev_file), err);
                /*
                 * 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 fput() to bdev in bch_cache_release(). So
                 * we explicitly call fput() on the block device here.
                 */
                fput(bdev_file);
                return ret;
        }

        if (kobject_add(&ca->kobj, bdev_kobj(file_bdev(bdev_file)), "bcache")) {
                pr_notice("error %pg: error calling kobject_add\n",
                          file_bdev(bdev_file));
                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", file_bdev(ca->bdev_file));

out:
        kobject_put(&ca->kobj);
        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 file *bdev_file;
        void *holder;
};

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);

        mutex_lock(&bch_register_lock);
        if (register_bdev(args->sb, args->sb_disk, args->bdev_file,
                          args->holder) < 0)
                fail = true;
        mutex_unlock(&bch_register_lock);

        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);

        /* blkdev_put() will be called in bch_cache_release() */
        if (register_cache(args->sb, args->sb_disk, args->bdev_file,
                           args->holder))
                fail = true;

        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_percpu_wq, &args->reg_work, 10);
}

static void *alloc_holder_object(struct cache_sb *sb)
{
        if (SB_IS_BDEV(sb))
                return kzalloc_obj(struct cached_dev);
        return kzalloc_obj(struct cache);
}

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 file *bdev_file, *bdev_file2;
        void *holder = NULL;
        ssize_t ret;
        bool async_registration = false;
        bool quiet = 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_obj(struct cache_sb);
        if (!sb)
                goto out_free_path;

        ret = -EINVAL;
        err = "failed to open device";
        bdev_file = bdev_file_open_by_path(strim(path), BLK_OPEN_READ, NULL, NULL);
        if (IS_ERR(bdev_file))
                goto out_free_sb;

        err = read_super(sb, file_bdev(bdev_file), &sb_disk);
        if (err)
                goto out_blkdev_put;

        holder = alloc_holder_object(sb);
        if (!holder) {
                ret = -ENOMEM;
                err = "cannot allocate memory";
                goto out_put_sb_folio;
        }

        /* Now reopen in exclusive mode with proper holder */
        bdev_file2 = bdev_file_open_by_dev(file_bdev(bdev_file)->bd_dev,
                        BLK_OPEN_READ | BLK_OPEN_WRITE, holder, NULL);
        fput(bdev_file);
        bdev_file = bdev_file2;
        if (IS_ERR(bdev_file)) {
                ret = PTR_ERR(bdev_file);
                bdev_file = NULL;
                if (ret == -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) {
                                quiet = true;
                                ret = size;
                        }
                }
                goto out_free_holder;
        }

        err = "failed to register device";

        if (async_registration) {
                /* register in asynchronous way */
                struct async_reg_args *args =
                        kzalloc_obj(struct async_reg_args);

                if (!args) {
                        ret = -ENOMEM;
                        err = "cannot allocate memory";
                        goto out_free_holder;
                }

                args->path      = path;
                args->sb        = sb;
                args->sb_disk   = sb_disk;
                args->bdev_file = bdev_file;
                args->holder    = holder;
                register_device_async(args);
                /* No wait and returns to user space */
                goto async_done;
        }

        if (SB_IS_BDEV(sb)) {
                mutex_lock(&bch_register_lock);
                ret = register_bdev(sb, sb_disk, bdev_file, holder);
                mutex_unlock(&bch_register_lock);
                /* blkdev_put() will be called in cached_dev_free() */
                if (ret < 0)
                        goto out_free_sb;
        } else {
                /* blkdev_put() will be called in bch_cache_release() */
                ret = register_cache(sb, sb_disk, bdev_file, holder);
                if (ret)
                        goto out_free_sb;
        }

        kfree(sb);
        kfree(path);
        module_put(THIS_MODULE);
async_done:
        return size;

out_free_holder:
        kfree(holder);
out_put_sb_folio:
        folio_put(virt_to_folio(sb_disk));
out_blkdev_put:
        if (bdev_file)
                fput(bdev_file);
out_free_sb:
        kfree(sb);
out_free_path:
        kfree(path);
        path = NULL;
out_module_put:
        module_put(THIS_MODULE);
out:
        if (!quiet)
                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_obj(struct pdev);
                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 | WQ_PERCPU, 0);
        if (!bcache_wq)
                goto err;

        /*
         * Let's not make this `WQ_MEM_RECLAIM` for the following reasons:
         *
         * 1. It used `system_percpu_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_percpu_wq`.
         */
        bch_flush_wq = alloc_workqueue("bch_flush", WQ_PERCPU, 0);
        if (!bch_flush_wq)
                goto err;

        bch_journal_wq = alloc_workqueue("bch_journal",
                                         WQ_MEM_RECLAIM | WQ_PERCPU, 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();

        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");