Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2934 insertions, 0 deletions

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
new file mode 100644
index 0000000000..1e677af385
--- /dev/null
+++ b/drivers/md/bcache/super.c
@@ -0,0 +1,2934 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * bcache setup/teardown code, and some metadata io - read a superblock and
+ * figure out what to do with it.
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "extents.h"
+#include "request.h"
+#include "writeback.h"
+#include "features.h"
+
+#include <linux/blkdev.h>
+#include <linux/pagemap.h>
+#include <linux/debugfs.h>
+#include <linux/idr.h>
+#include <linux/kthread.h>
+#include <linux/workqueue.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/reboot.h>
+#include <linux/sysfs.h>
+
+unsigned int bch_cutoff_writeback;
+unsigned int bch_cutoff_writeback_sync;
+
+static const char bcache_magic[] = {
+	0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
+	0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81
+};
+
+static const char invalid_uuid[] = {
+	0xa0, 0x3e, 0xf8, 0xed, 0x3e, 0xe1, 0xb8, 0x78,
+	0xc8, 0x50, 0xfc, 0x5e, 0xcb, 0x16, 0xcd, 0x99
+};
+
+static struct kobject *bcache_kobj;
+struct mutex bch_register_lock;
+bool bcache_is_reboot;
+LIST_HEAD(bch_cache_sets);
+static LIST_HEAD(uncached_devices);
+
+static int bcache_major;
+static DEFINE_IDA(bcache_device_idx);
+static wait_queue_head_t unregister_wait;
+struct workqueue_struct *bcache_wq;
+struct workqueue_struct *bch_flush_wq;
+struct workqueue_struct *bch_journal_wq;
+
+
+#define BTREE_MAX_PAGES		(256 * 1024 / PAGE_SIZE)
+/* limitation of partitions number on single bcache device */
+#define BCACHE_MINORS		128
+/* limitation of bcache devices number on single system */
+#define BCACHE_DEVICE_IDX_MAX	((1U << MINORBITS)/BCACHE_MINORS)
+
+/* Superblock */
+
+static unsigned int get_bucket_size(struct cache_sb *sb, struct cache_sb_disk *s)
+{
+	unsigned int bucket_size = le16_to_cpu(s->bucket_size);
+
+	if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
+		if (bch_has_feature_large_bucket(sb)) {
+			unsigned int max, order;
+
+			max = sizeof(unsigned int) * BITS_PER_BYTE - 1;
+			order = le16_to_cpu(s->bucket_size);
+			/*
+			 * bcache tool will make sure the overflow won't
+			 * happen, an error message here is enough.
+			 */
+			if (order > max)
+				pr_err("Bucket size (1 << %u) overflows\n",
+					order);
+			bucket_size = 1 << order;
+		} else if (bch_has_feature_obso_large_bucket(sb)) {
+			bucket_size +=
+				le16_to_cpu(s->obso_bucket_size_hi) << 16;
+		}
+	}
+
+	return bucket_size;
+}
+
+static const char *read_super_common(struct cache_sb *sb,  struct block_device *bdev,
+				     struct cache_sb_disk *s)
+{
+	const char *err;
+	unsigned int i;
+
+	sb->first_bucket= le16_to_cpu(s->first_bucket);
+	sb->nbuckets	= le64_to_cpu(s->nbuckets);
+	sb->bucket_size	= get_bucket_size(sb, s);
+
+	sb->nr_in_set	= le16_to_cpu(s->nr_in_set);
+	sb->nr_this_dev	= le16_to_cpu(s->nr_this_dev);
+
+	err = "Too many journal buckets";
+	if (sb->keys > SB_JOURNAL_BUCKETS)
+		goto err;
+
+	err = "Too many buckets";
+	if (sb->nbuckets > LONG_MAX)
+		goto err;
+
+	err = "Not enough buckets";
+	if (sb->nbuckets < 1 << 7)
+		goto err;
+
+	err = "Bad block size (not power of 2)";
+	if (!is_power_of_2(sb->block_size))
+		goto err;
+
+	err = "Bad block size (larger than page size)";
+	if (sb->block_size > PAGE_SECTORS)
+		goto err;
+
+	err = "Bad bucket size (not power of 2)";
+	if (!is_power_of_2(sb->bucket_size))
+		goto err;
+
+	err = "Bad bucket size (smaller than page size)";
+	if (sb->bucket_size < PAGE_SECTORS)
+		goto err;
+
+	err = "Invalid superblock: device too small";
+	if (get_capacity(bdev->bd_disk) <
+	    sb->bucket_size * sb->nbuckets)
+		goto err;
+
+	err = "Bad UUID";
+	if (bch_is_zero(sb->set_uuid, 16))
+		goto err;
+
+	err = "Bad cache device number in set";
+	if (!sb->nr_in_set ||
+	    sb->nr_in_set <= sb->nr_this_dev ||
+	    sb->nr_in_set > MAX_CACHES_PER_SET)
+		goto err;
+
+	err = "Journal buckets not sequential";
+	for (i = 0; i < sb->keys; i++)
+		if (sb->d[i] != sb->first_bucket + i)
+			goto err;
+
+	err = "Too many journal buckets";
+	if (sb->first_bucket + sb->keys > sb->nbuckets)
+		goto err;
+
+	err = "Invalid superblock: first bucket comes before end of super";
+	if (sb->first_bucket * sb->bucket_size < 16)
+		goto err;
+
+	err = NULL;
+err:
+	return err;
+}
+
+
+static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
+			      struct cache_sb_disk **res)
+{
+	const char *err;
+	struct cache_sb_disk *s;
+	struct page *page;
+	unsigned int i;
+
+	page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
+				   SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
+	if (IS_ERR(page))
+		return "IO error";
+	s = page_address(page) + offset_in_page(SB_OFFSET);
+
+	sb->offset		= le64_to_cpu(s->offset);
+	sb->version		= le64_to_cpu(s->version);
+
+	memcpy(sb->magic,	s->magic, 16);
+	memcpy(sb->uuid,	s->uuid, 16);
+	memcpy(sb->set_uuid,	s->set_uuid, 16);
+	memcpy(sb->label,	s->label, SB_LABEL_SIZE);
+
+	sb->flags		= le64_to_cpu(s->flags);
+	sb->seq			= le64_to_cpu(s->seq);
+	sb->last_mount		= le32_to_cpu(s->last_mount);
+	sb->keys		= le16_to_cpu(s->keys);
+
+	for (i = 0; i < SB_JOURNAL_BUCKETS; i++)
+		sb->d[i] = le64_to_cpu(s->d[i]);
+
+	pr_debug("read sb version %llu, flags %llu, seq %llu, journal size %u\n",
+		 sb->version, sb->flags, sb->seq, sb->keys);
+
+	err = "Not a bcache superblock (bad offset)";
+	if (sb->offset != SB_SECTOR)
+		goto err;
+
+	err = "Not a bcache superblock (bad magic)";
+	if (memcmp(sb->magic, bcache_magic, 16))
+		goto err;
+
+	err = "Bad checksum";
+	if (s->csum != csum_set(s))
+		goto err;
+
+	err = "Bad UUID";
+	if (bch_is_zero(sb->uuid, 16))
+		goto err;
+
+	sb->block_size	= le16_to_cpu(s->block_size);
+
+	err = "Superblock block size smaller than device block size";
+	if (sb->block_size << 9 < bdev_logical_block_size(bdev))
+		goto err;
+
+	switch (sb->version) {
+	case BCACHE_SB_VERSION_BDEV:
+		sb->data_offset	= BDEV_DATA_START_DEFAULT;
+		break;
+	case BCACHE_SB_VERSION_BDEV_WITH_OFFSET:
+	case BCACHE_SB_VERSION_BDEV_WITH_FEATURES:
+		sb->data_offset	= le64_to_cpu(s->data_offset);
+
+		err = "Bad data offset";
+		if (sb->data_offset < BDEV_DATA_START_DEFAULT)
+			goto err;
+
+		break;
+	case BCACHE_SB_VERSION_CDEV:
+	case BCACHE_SB_VERSION_CDEV_WITH_UUID:
+		err = read_super_common(sb, bdev, s);
+		if (err)
+			goto err;
+		break;
+	case BCACHE_SB_VERSION_CDEV_WITH_FEATURES:
+		/*
+		 * Feature bits are needed in read_super_common(),
+		 * convert them firstly.
+		 */
+		sb->feature_compat = le64_to_cpu(s->feature_compat);
+		sb->feature_incompat = le64_to_cpu(s->feature_incompat);
+		sb->feature_ro_compat = le64_to_cpu(s->feature_ro_compat);
+
+		/* Check incompatible features */
+		err = "Unsupported compatible feature found";
+		if (bch_has_unknown_compat_features(sb))
+			goto err;
+
+		err = "Unsupported read-only compatible feature found";
+		if (bch_has_unknown_ro_compat_features(sb))
+			goto err;
+
+		err = "Unsupported incompatible feature found";
+		if (bch_has_unknown_incompat_features(sb))
+			goto err;
+
+		err = read_super_common(sb, bdev, s);
+		if (err)
+			goto err;
+		break;
+	default:
+		err = "Unsupported superblock version";
+		goto err;
+	}
+
+	sb->last_mount = (u32)ktime_get_real_seconds();
+	*res = s;
+	return NULL;
+err:
+	put_page(page);
+	return err;
+}
+
+static void write_bdev_super_endio(struct bio *bio)
+{
+	struct cached_dev *dc = bio->bi_private;
+
+	if (bio->bi_status)
+		bch_count_backing_io_errors(dc, bio);
+
+	closure_put(&dc->sb_write);
+}
+
+static void __write_super(struct cache_sb *sb, struct cache_sb_disk *out,
+		struct bio *bio)
+{
+	unsigned int i;
+
+	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_META;
+	bio->bi_iter.bi_sector	= SB_SECTOR;
+	__bio_add_page(bio, virt_to_page(out), SB_SIZE,
+			offset_in_page(out));
+
+	out->offset		= cpu_to_le64(sb->offset);
+
+	memcpy(out->uuid,	sb->uuid, 16);
+	memcpy(out->set_uuid,	sb->set_uuid, 16);
+	memcpy(out->label,	sb->label, SB_LABEL_SIZE);
+
+	out->flags		= cpu_to_le64(sb->flags);
+	out->seq		= cpu_to_le64(sb->seq);
+
+	out->last_mount		= cpu_to_le32(sb->last_mount);
+	out->first_bucket	= cpu_to_le16(sb->first_bucket);
+	out->keys		= cpu_to_le16(sb->keys);
+
+	for (i = 0; i < sb->keys; i++)
+		out->d[i] = cpu_to_le64(sb->d[i]);
+
+	if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
+		out->feature_compat    = cpu_to_le64(sb->feature_compat);
+		out->feature_incompat  = cpu_to_le64(sb->feature_incompat);
+		out->feature_ro_compat = cpu_to_le64(sb->feature_ro_compat);
+	}
+
+	out->version		= cpu_to_le64(sb->version);
+	out->csum = csum_set(out);
+
+	pr_debug("ver %llu, flags %llu, seq %llu\n",
+		 sb->version, sb->flags, sb->seq);
+
+	submit_bio(bio);
+}
+
+static void bch_write_bdev_super_unlock(struct closure *cl)
+{
+	struct cached_dev *dc = container_of(cl, struct cached_dev, sb_write);
+
+	up(&dc->sb_write_mutex);
+}
+
+void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent)
+{
+	struct closure *cl = &dc->sb_write;
+	struct bio *bio = &dc->sb_bio;
+
+	down(&dc->sb_write_mutex);
+	closure_init(cl, parent);
+
+	bio_init(bio, dc->bdev, dc->sb_bv, 1, 0);
+	bio->bi_end_io	= write_bdev_super_endio;
+	bio->bi_private = dc;
+
+	closure_get(cl);
+	/* I/O request sent to backing device */
+	__write_super(&dc->sb, dc->sb_disk, bio);
+
+	closure_return_with_destructor(cl, bch_write_bdev_super_unlock);
+}
+
+static void write_super_endio(struct bio *bio)
+{
+	struct cache *ca = bio->bi_private;
+
+	/* is_read = 0 */
+	bch_count_io_errors(ca, bio->bi_status, 0,
+			    "writing superblock");
+	closure_put(&ca->set->sb_write);
+}
+
+static void bcache_write_super_unlock(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, sb_write);
+
+	up(&c->sb_write_mutex);
+}
+
+void bcache_write_super(struct cache_set *c)
+{
+	struct closure *cl = &c->sb_write;
+	struct cache *ca = c->cache;
+	struct bio *bio = &ca->sb_bio;
+	unsigned int version = BCACHE_SB_VERSION_CDEV_WITH_UUID;
+
+	down(&c->sb_write_mutex);
+	closure_init(cl, &c->cl);
+
+	ca->sb.seq++;
+
+	if (ca->sb.version < version)
+		ca->sb.version = version;
+
+	bio_init(bio, ca->bdev, ca->sb_bv, 1, 0);
+	bio->bi_end_io	= write_super_endio;
+	bio->bi_private = ca;
+
+	closure_get(cl);
+	__write_super(&ca->sb, ca->sb_disk, bio);
+
+	closure_return_with_destructor(cl, bcache_write_super_unlock);
+}
+
+/* UUID io */
+
+static void uuid_endio(struct bio *bio)
+{
+	struct closure *cl = bio->bi_private;
+	struct cache_set *c = container_of(cl, struct cache_set, uuid_write);
+
+	cache_set_err_on(bio->bi_status, c, "accessing uuids");
+	bch_bbio_free(bio, c);
+	closure_put(cl);
+}
+
+static void uuid_io_unlock(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, uuid_write);
+
+	up(&c->uuid_write_mutex);
+}
+
+static void uuid_io(struct cache_set *c, blk_opf_t opf, struct bkey *k,
+		    struct closure *parent)
+{
+	struct closure *cl = &c->uuid_write;
+	struct uuid_entry *u;
+	unsigned int i;
+	char buf[80];
+
+	BUG_ON(!parent);
+	down(&c->uuid_write_mutex);
+	closure_init(cl, parent);
+
+	for (i = 0; i < KEY_PTRS(k); i++) {
+		struct bio *bio = bch_bbio_alloc(c);
+
+		bio->bi_opf = opf | REQ_SYNC | REQ_META;
+		bio->bi_iter.bi_size = KEY_SIZE(k) << 9;
+
+		bio->bi_end_io	= uuid_endio;
+		bio->bi_private = cl;
+		bch_bio_map(bio, c->uuids);
+
+		bch_submit_bbio(bio, c, k, i);
+
+		if ((opf & REQ_OP_MASK) != REQ_OP_WRITE)
+			break;
+	}
+
+	bch_extent_to_text(buf, sizeof(buf), k);
+	pr_debug("%s UUIDs at %s\n", (opf & REQ_OP_MASK) == REQ_OP_WRITE ?
+		 "wrote" : "read", buf);
+
+	for (u = c->uuids; u < c->uuids + c->nr_uuids; u++)
+		if (!bch_is_zero(u->uuid, 16))
+			pr_debug("Slot %zi: %pU: %s: 1st: %u last: %u inv: %u\n",
+				 u - c->uuids, u->uuid, u->label,
+				 u->first_reg, u->last_reg, u->invalidated);
+
+	closure_return_with_destructor(cl, uuid_io_unlock);
+}
+
+static char *uuid_read(struct cache_set *c, struct jset *j, struct closure *cl)
+{
+	struct bkey *k = &j->uuid_bucket;
+
+	if (__bch_btree_ptr_invalid(c, k))
+		return "bad uuid pointer";
+
+	bkey_copy(&c->uuid_bucket, k);
+	uuid_io(c, REQ_OP_READ, k, cl);
+
+	if (j->version < BCACHE_JSET_VERSION_UUIDv1) {
+		struct uuid_entry_v0	*u0 = (void *) c->uuids;
+		struct uuid_entry	*u1 = (void *) c->uuids;
+		int i;
+
+		closure_sync(cl);
+
+		/*
+		 * Since the new uuid entry is bigger than the old, we have to
+		 * convert starting at the highest memory address and work down
+		 * in order to do it in place
+		 */
+
+		for (i = c->nr_uuids - 1;
+		     i >= 0;
+		     --i) {
+			memcpy(u1[i].uuid,	u0[i].uuid, 16);
+			memcpy(u1[i].label,	u0[i].label, 32);
+
+			u1[i].first_reg		= u0[i].first_reg;
+			u1[i].last_reg		= u0[i].last_reg;
+			u1[i].invalidated	= u0[i].invalidated;
+
+			u1[i].flags	= 0;
+			u1[i].sectors	= 0;
+		}
+	}
+
+	return NULL;
+}
+
+static int __uuid_write(struct cache_set *c)
+{
+	BKEY_PADDED(key) k;
+	struct closure cl;
+	struct cache *ca = c->cache;
+	unsigned int size;
+
+	closure_init_stack(&cl);
+	lockdep_assert_held(&bch_register_lock);
+
+	if (bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, true))
+		return 1;
+
+	size =  meta_bucket_pages(&ca->sb) * PAGE_SECTORS;
+	SET_KEY_SIZE(&k.key, size);
+	uuid_io(c, REQ_OP_WRITE, &k.key, &cl);
+	closure_sync(&cl);
+
+	/* Only one bucket used for uuid write */
+	atomic_long_add(ca->sb.bucket_size, &ca->meta_sectors_written);
+
+	bkey_copy(&c->uuid_bucket, &k.key);
+	bkey_put(c, &k.key);
+	return 0;
+}
+
+int bch_uuid_write(struct cache_set *c)
+{
+	int ret = __uuid_write(c);
+
+	if (!ret)
+		bch_journal_meta(c, NULL);
+
+	return ret;
+}
+
+static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
+{
+	struct uuid_entry *u;
+
+	for (u = c->uuids;
+	     u < c->uuids + c->nr_uuids; u++)
+		if (!memcmp(u->uuid, uuid, 16))
+			return u;
+
+	return NULL;
+}
+
+static struct uuid_entry *uuid_find_empty(struct cache_set *c)
+{
+	static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+
+	return uuid_find(c, zero_uuid);
+}
+
+/*
+ * Bucket priorities/gens:
+ *
+ * For each bucket, we store on disk its
+ *   8 bit gen
+ *  16 bit priority
+ *
+ * See alloc.c for an explanation of the gen. The priority is used to implement
+ * lru (and in the future other) cache replacement policies; for most purposes
+ * it's just an opaque integer.
+ *
+ * The gens and the priorities don't have a whole lot to do with each other, and
+ * it's actually the gens that must be written out at specific times - it's no
+ * big deal if the priorities don't get written, if we lose them we just reuse
+ * buckets in suboptimal order.
+ *
+ * On disk they're stored in a packed array, and in as many buckets are required
+ * to fit them all. The buckets we use to store them form a list; the journal
+ * header points to the first bucket, the first bucket points to the second
+ * bucket, et cetera.
+ *
+ * This code is used by the allocation code; periodically (whenever it runs out
+ * of buckets to allocate from) the allocation code will invalidate some
+ * buckets, but it can't use those buckets until their new gens are safely on
+ * disk.
+ */
+
+static void prio_endio(struct bio *bio)
+{
+	struct cache *ca = bio->bi_private;
+
+	cache_set_err_on(bio->bi_status, ca->set, "accessing priorities");
+	bch_bbio_free(bio, ca->set);
+	closure_put(&ca->prio);
+}
+
+static void prio_io(struct cache *ca, uint64_t bucket, blk_opf_t opf)
+{
+	struct closure *cl = &ca->prio;
+	struct bio *bio = bch_bbio_alloc(ca->set);
+
+	closure_init_stack(cl);
+
+	bio->bi_iter.bi_sector	= bucket * ca->sb.bucket_size;
+	bio_set_dev(bio, ca->bdev);
+	bio->bi_iter.bi_size	= meta_bucket_bytes(&ca->sb);
+
+	bio->bi_end_io	= prio_endio;
+	bio->bi_private = ca;
+	bio->bi_opf = opf | REQ_SYNC | REQ_META;
+	bch_bio_map(bio, ca->disk_buckets);
+
+	closure_bio_submit(ca->set, bio, &ca->prio);
+	closure_sync(cl);
+}
+
+int bch_prio_write(struct cache *ca, bool wait)
+{
+	int i;
+	struct bucket *b;
+	struct closure cl;
+
+	pr_debug("free_prio=%zu, free_none=%zu, free_inc=%zu\n",
+		 fifo_used(&ca->free[RESERVE_PRIO]),
+		 fifo_used(&ca->free[RESERVE_NONE]),
+		 fifo_used(&ca->free_inc));
+
+	/*
+	 * Pre-check if there are enough free buckets. In the non-blocking
+	 * scenario it's better to fail early rather than starting to allocate
+	 * buckets and do a cleanup later in case of failure.
+	 */
+	if (!wait) {
+		size_t avail = fifo_used(&ca->free[RESERVE_PRIO]) +
+			       fifo_used(&ca->free[RESERVE_NONE]);
+		if (prio_buckets(ca) > avail)
+			return -ENOMEM;
+	}
+
+	closure_init_stack(&cl);
+
+	lockdep_assert_held(&ca->set->bucket_lock);
+
+	ca->disk_buckets->seq++;
+
+	atomic_long_add(ca->sb.bucket_size * prio_buckets(ca),
+			&ca->meta_sectors_written);
+
+	for (i = prio_buckets(ca) - 1; i >= 0; --i) {
+		long bucket;
+		struct prio_set *p = ca->disk_buckets;
+		struct bucket_disk *d = p->data;
+		struct bucket_disk *end = d + prios_per_bucket(ca);
+
+		for (b = ca->buckets + i * prios_per_bucket(ca);
+		     b < ca->buckets + ca->sb.nbuckets && d < end;
+		     b++, d++) {
+			d->prio = cpu_to_le16(b->prio);
+			d->gen = b->gen;
+		}
+
+		p->next_bucket	= ca->prio_buckets[i + 1];
+		p->magic	= pset_magic(&ca->sb);
+		p->csum		= bch_crc64(&p->magic, meta_bucket_bytes(&ca->sb) - 8);
+
+		bucket = bch_bucket_alloc(ca, RESERVE_PRIO, wait);
+		BUG_ON(bucket == -1);
+
+		mutex_unlock(&ca->set->bucket_lock);
+		prio_io(ca, bucket, REQ_OP_WRITE);
+		mutex_lock(&ca->set->bucket_lock);
+
+		ca->prio_buckets[i] = bucket;
+		atomic_dec_bug(&ca->buckets[bucket].pin);
+	}
+
+	mutex_unlock(&ca->set->bucket_lock);
+
+	bch_journal_meta(ca->set, &cl);
+	closure_sync(&cl);
+
+	mutex_lock(&ca->set->bucket_lock);
+
+	/*
+	 * Don't want the old priorities to get garbage collected until after we
+	 * finish writing the new ones, and they're journalled
+	 */
+	for (i = 0; i < prio_buckets(ca); i++) {
+		if (ca->prio_last_buckets[i])
+			__bch_bucket_free(ca,
+				&ca->buckets[ca->prio_last_buckets[i]]);
+
+		ca->prio_last_buckets[i] = ca->prio_buckets[i];
+	}
+	return 0;
+}
+
+static int prio_read(struct cache *ca, uint64_t bucket)
+{
+	struct prio_set *p = ca->disk_buckets;
+	struct bucket_disk *d = p->data + prios_per_bucket(ca), *end = d;
+	struct bucket *b;
+	unsigned int bucket_nr = 0;
+	int ret = -EIO;
+
+	for (b = ca->buckets;
+	     b < ca->buckets + ca->sb.nbuckets;
+	     b++, d++) {
+		if (d == end) {
+			ca->prio_buckets[bucket_nr] = bucket;
+			ca->prio_last_buckets[bucket_nr] = bucket;
+			bucket_nr++;
+
+			prio_io(ca, bucket, REQ_OP_READ);
+
+			if (p->csum !=
+			    bch_crc64(&p->magic, meta_bucket_bytes(&ca->sb) - 8)) {
+				pr_warn("bad csum reading priorities\n");
+				goto out;
+			}
+
+			if (p->magic != pset_magic(&ca->sb)) {
+				pr_warn("bad magic reading priorities\n");
+				goto out;
+			}
+
+			bucket = p->next_bucket;
+			d = p->data;
+		}
+
+		b->prio = le16_to_cpu(d->prio);
+		b->gen = b->last_gc = d->gen;
+	}
+
+	ret = 0;
+out:
+	return ret;
+}
+
+/* Bcache device */
+
+static int open_dev(struct 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_simple_remove(&bcache_device_idx,
+				  first_minor_to_idx(disk->first_minor));
+		put_disk(disk);
+	}
+
+	bioset_exit(&d->bio_split);
+	kvfree(d->full_dirty_stripes);
+	kvfree(d->stripe_sectors_dirty);
+
+	closure_debug_destroy(&d->cl);
+}
+
+static int bcache_device_init(struct bcache_device *d, unsigned int block_size,
+		sector_t sectors, struct block_device *cached_bdev,
+		const struct block_device_operations *ops)
+{
+	struct request_queue *q;
+	const size_t max_stripes = min_t(size_t, INT_MAX,
+					 SIZE_MAX / sizeof(atomic_t));
+	uint64_t n;
+	int idx;
+
+	if (!d->stripe_size)
+		d->stripe_size = 1 << 31;
+	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_simple_get(&bcache_device_idx, 0,
+				BCACHE_DEVICE_IDX_MAX, GFP_KERNEL);
+	if (idx < 0)
+		goto out_free_full_dirty_stripes;
+
+	if (bioset_init(&d->bio_split, 4, offsetof(struct bbio, bio),
+			BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER))
+		goto out_ida_remove;
+
+	d->disk = blk_alloc_disk(NUMA_NO_NODE);
+	if (!d->disk)
+		goto out_bioset_exit;
+
+	set_capacity(d->disk, sectors);
+	snprintf(d->disk->disk_name, DISK_NAME_LEN, "bcache%i", idx);
+
+	d->disk->major		= bcache_major;
+	d->disk->first_minor	= idx_to_first_minor(idx);
+	d->disk->minors		= BCACHE_MINORS;
+	d->disk->fops		= ops;
+	d->disk->private_data	= d;
+
+	q = d->disk->queue;
+	q->limits.max_hw_sectors	= UINT_MAX;
+	q->limits.max_sectors		= UINT_MAX;
+	q->limits.max_segment_size	= UINT_MAX;
+	q->limits.max_segments		= BIO_MAX_VECS;
+	blk_queue_max_discard_sectors(q, UINT_MAX);
+	q->limits.discard_granularity	= 512;
+	q->limits.io_min		= block_size;
+	q->limits.logical_block_size	= block_size;
+	q->limits.physical_block_size	= block_size;
+
+	if (q->limits.logical_block_size > PAGE_SIZE && cached_bdev) {
+		/*
+		 * This should only happen with BCACHE_SB_VERSION_BDEV.
+		 * Block/page size is checked for BCACHE_SB_VERSION_CDEV.
+		 */
+		pr_info("%s: sb/logical block size (%u) greater than page size (%lu) falling back to device logical block size (%u)\n",
+			d->disk->disk_name, q->limits.logical_block_size,
+			PAGE_SIZE, bdev_logical_block_size(cached_bdev));
+
+		/* This also adjusts physical block size/min io size if needed */
+		blk_queue_logical_block_size(q, bdev_logical_block_size(cached_bdev));
+	}
+
+	blk_queue_flag_set(QUEUE_FLAG_NONROT, d->disk->queue);
+
+	blk_queue_write_cache(q, true, true);
+
+	return 0;
+
+out_bioset_exit:
+	bioset_exit(&d->bio_split);
+out_ida_remove:
+	ida_simple_remove(&bcache_device_idx, idx);
+out_free_full_dirty_stripes:
+	kvfree(d->full_dirty_stripes);
+out_free_stripe_sectors_dirty:
+	kvfree(d->stripe_sectors_dirty);
+	return -ENOMEM;
+
+}
+
+/* Cached device */
+
+static void calc_cached_dev_sectors(struct cache_set *c)
+{
+	uint64_t sectors = 0;
+	struct cached_dev *dc;
+
+	list_for_each_entry(dc, &c->cached_devs, list)
+		sectors += bdev_nr_sectors(dc->bdev);
+
+	c->cached_dev_sectors = sectors;
+}
+
+#define BACKING_DEV_OFFLINE_TIMEOUT 5
+static int cached_dev_status_update(void *arg)
+{
+	struct cached_dev *dc = arg;
+	struct request_queue *q;
+
+	/*
+	 * If this delayed worker is stopping outside, directly quit here.
+	 * dc->io_disable might be set via sysfs interface, so check it
+	 * here too.
+	 */
+	while (!kthread_should_stop() && !dc->io_disable) {
+		q = bdev_get_queue(dc->bdev);
+		if (blk_queue_dying(q))
+			dc->offline_seconds++;
+		else
+			dc->offline_seconds = 0;
+
+		if (dc->offline_seconds >= BACKING_DEV_OFFLINE_TIMEOUT) {
+			pr_err("%pg: device offline for %d seconds\n",
+			       dc->bdev,
+			       BACKING_DEV_OFFLINE_TIMEOUT);
+			pr_err("%s: disable I/O request due to backing device offline\n",
+			       dc->disk.name);
+			dc->io_disable = true;
+			/* let others know earlier that io_disable is true */
+			smp_mb();
+			bcache_device_stop(&dc->disk);
+			break;
+		}
+		schedule_timeout_interruptible(HZ);
+	}
+
+	wait_for_kthread_stop();
+	return 0;
+}
+
+
+int bch_cached_dev_run(struct cached_dev *dc)
+{
+	int ret = 0;
+	struct bcache_device *d = &dc->disk;
+	char *buf = kmemdup_nul(dc->sb.label, SB_LABEL_SIZE, GFP_KERNEL);
+	char *env[] = {
+		"DRIVER=bcache",
+		kasprintf(GFP_KERNEL, "CACHED_UUID=%pU", dc->sb.uuid),
+		kasprintf(GFP_KERNEL, "CACHED_LABEL=%s", buf ? : ""),
+		NULL,
+	};
+
+	if (dc->io_disable) {
+		pr_err("I/O disabled on cached dev %pg\n", dc->bdev);
+		ret = -EIO;
+		goto out;
+	}
+
+	if (atomic_xchg(&dc->running, 1)) {
+		pr_info("cached dev %pg is running already\n", dc->bdev);
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (!d->c &&
+	    BDEV_STATE(&dc->sb) != BDEV_STATE_NONE) {
+		struct closure cl;
+
+		closure_init_stack(&cl);
+
+		SET_BDEV_STATE(&dc->sb, BDEV_STATE_STALE);
+		bch_write_bdev_super(dc, &cl);
+		closure_sync(&cl);
+	}
+
+	ret = add_disk(d->disk);
+	if (ret)
+		goto out;
+	bd_link_disk_holder(dc->bdev, dc->disk.disk);
+	/*
+	 * won't show up in the uevent file, use udevadm monitor -e instead
+	 * only class / kset properties are persistent
+	 */
+	kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env);
+
+	if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") ||
+	    sysfs_create_link(&disk_to_dev(d->disk)->kobj,
+			      &d->kobj, "bcache")) {
+		pr_err("Couldn't create bcache dev <-> disk sysfs symlinks\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	dc->status_update_thread = kthread_run(cached_dev_status_update,
+					       dc, "bcache_status_update");
+	if (IS_ERR(dc->status_update_thread)) {
+		pr_warn("failed to create bcache_status_update kthread, continue to run without monitoring backing device status\n");
+	}
+
+out:
+	kfree(env[1]);
+	kfree(env[2]);
+	kfree(buf);
+	return ret;
+}
+
+/*
+ * If BCACHE_DEV_RATE_DW_RUNNING is set, it means routine of the delayed
+ * work dc->writeback_rate_update is running. Wait until the routine
+ * quits (BCACHE_DEV_RATE_DW_RUNNING is clear), then continue to
+ * cancel it. If BCACHE_DEV_RATE_DW_RUNNING is not clear after time_out
+ * seconds, give up waiting here and continue to cancel it too.
+ */
+static void cancel_writeback_rate_update_dwork(struct cached_dev *dc)
+{
+	int time_out = WRITEBACK_RATE_UPDATE_SECS_MAX * HZ;
+
+	do {
+		if (!test_bit(BCACHE_DEV_RATE_DW_RUNNING,
+			      &dc->disk.flags))
+			break;
+		time_out--;
+		schedule_timeout_interruptible(1);
+	} while (time_out > 0);
+
+	if (time_out == 0)
+		pr_warn("give up waiting for dc->writeback_write_update to quit\n");
+
+	cancel_delayed_work_sync(&dc->writeback_rate_update);
+}
+
+static void cached_dev_detach_finish(struct work_struct *w)
+{
+	struct cached_dev *dc = container_of(w, struct cached_dev, detach);
+	struct cache_set *c = dc->disk.c;
+
+	BUG_ON(!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags));
+	BUG_ON(refcount_read(&dc->count));
+
+
+	if (test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
+		cancel_writeback_rate_update_dwork(dc);
+
+	if (!IS_ERR_OR_NULL(dc->writeback_thread)) {
+		kthread_stop(dc->writeback_thread);
+		dc->writeback_thread = NULL;
+	}
+
+	mutex_lock(&bch_register_lock);
+
+	bcache_device_detach(&dc->disk);
+	list_move(&dc->list, &uncached_devices);
+	calc_cached_dev_sectors(c);
+
+	clear_bit(BCACHE_DEV_DETACHING, &dc->disk.flags);
+	clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags);
+
+	mutex_unlock(&bch_register_lock);
+
+	pr_info("Caching disabled for %pg\n", dc->bdev);
+
+	/* Drop ref we took in cached_dev_detach() */
+	closure_put(&dc->disk.cl);
+}
+
+void bch_cached_dev_detach(struct cached_dev *dc)
+{
+	lockdep_assert_held(&bch_register_lock);
+
+	if (test_bit(BCACHE_DEV_CLOSING, &dc->disk.flags))
+		return;
+
+	if (test_and_set_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
+		return;
+
+	/*
+	 * Block the device from being closed and freed until we're finished
+	 * detaching
+	 */
+	closure_get(&dc->disk.cl);
+
+	bch_writeback_queue(dc);
+
+	cached_dev_put(dc);
+}
+
+int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
+			  uint8_t *set_uuid)
+{
+	uint32_t rtime = cpu_to_le32((u32)ktime_get_real_seconds());
+	struct uuid_entry *u;
+	struct cached_dev *exist_dc, *t;
+	int ret = 0;
+
+	if ((set_uuid && memcmp(set_uuid, c->set_uuid, 16)) ||
+	    (!set_uuid && memcmp(dc->sb.set_uuid, c->set_uuid, 16)))
+		return -ENOENT;
+
+	if (dc->disk.c) {
+		pr_err("Can't attach %pg: already attached\n", dc->bdev);
+		return -EINVAL;
+	}
+
+	if (test_bit(CACHE_SET_STOPPING, &c->flags)) {
+		pr_err("Can't attach %pg: shutting down\n", dc->bdev);
+		return -EINVAL;
+	}
+
+	if (dc->sb.block_size < c->cache->sb.block_size) {
+		/* Will die */
+		pr_err("Couldn't attach %pg: block size less than set's block size\n",
+		       dc->bdev);
+		return -EINVAL;
+	}
+
+	/* Check whether already attached */
+	list_for_each_entry_safe(exist_dc, t, &c->cached_devs, list) {
+		if (!memcmp(dc->sb.uuid, exist_dc->sb.uuid, 16)) {
+			pr_err("Tried to attach %pg but duplicate UUID already attached\n",
+				dc->bdev);
+
+			return -EINVAL;
+		}
+	}
+
+	u = uuid_find(c, dc->sb.uuid);
+
+	if (u &&
+	    (BDEV_STATE(&dc->sb) == BDEV_STATE_STALE ||
+	     BDEV_STATE(&dc->sb) == BDEV_STATE_NONE)) {
+		memcpy(u->uuid, invalid_uuid, 16);
+		u->invalidated = cpu_to_le32((u32)ktime_get_real_seconds());
+		u = NULL;
+	}
+
+	if (!u) {
+		if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
+			pr_err("Couldn't find uuid for %pg in set\n", dc->bdev);
+			return -ENOENT;
+		}
+
+		u = uuid_find_empty(c);
+		if (!u) {
+			pr_err("Not caching %pg, no room for UUID\n", dc->bdev);
+			return -EINVAL;
+		}
+	}
+
+	/*
+	 * Deadlocks since we're called via sysfs...
+	 * sysfs_remove_file(&dc->kobj, &sysfs_attach);
+	 */
+
+	if (bch_is_zero(u->uuid, 16)) {
+		struct closure cl;
+
+		closure_init_stack(&cl);
+
+		memcpy(u->uuid, dc->sb.uuid, 16);
+		memcpy(u->label, dc->sb.label, SB_LABEL_SIZE);
+		u->first_reg = u->last_reg = rtime;
+		bch_uuid_write(c);
+
+		memcpy(dc->sb.set_uuid, c->set_uuid, 16);
+		SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
+
+		bch_write_bdev_super(dc, &cl);
+		closure_sync(&cl);
+	} else {
+		u->last_reg = rtime;
+		bch_uuid_write(c);
+	}
+
+	bcache_device_attach(&dc->disk, c, u - c->uuids);
+	list_move(&dc->list, &c->cached_devs);
+	calc_cached_dev_sectors(c);
+
+	/*
+	 * dc->c must be set before dc->count != 0 - paired with the mb in
+	 * cached_dev_get()
+	 */
+	smp_wmb();
+	refcount_set(&dc->count, 1);
+
+	/* Block writeback thread, but spawn it */
+	down_write(&dc->writeback_lock);
+	if (bch_cached_dev_writeback_start(dc)) {
+		up_write(&dc->writeback_lock);
+		pr_err("Couldn't start writeback facilities for %s\n",
+		       dc->disk.disk->disk_name);
+		return -ENOMEM;
+	}
+
+	if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
+		atomic_set(&dc->has_dirty, 1);
+		bch_writeback_queue(dc);
+	}
+
+	bch_sectors_dirty_init(&dc->disk);
+
+	ret = bch_cached_dev_run(dc);
+	if (ret && (ret != -EBUSY)) {
+		up_write(&dc->writeback_lock);
+		/*
+		 * bch_register_lock is held, bcache_device_stop() is not
+		 * able to be directly called. The kthread and kworker
+		 * created previously in bch_cached_dev_writeback_start()
+		 * have to be stopped manually here.
+		 */
+		kthread_stop(dc->writeback_thread);
+		cancel_writeback_rate_update_dwork(dc);
+		pr_err("Couldn't run cached device %pg\n", dc->bdev);
+		return ret;
+	}
+
+	bcache_device_link(&dc->disk, c, "bdev");
+	atomic_inc(&c->attached_dev_nr);
+
+	if (bch_has_feature_obso_large_bucket(&(c->cache->sb))) {
+		pr_err("The obsoleted large bucket layout is unsupported, set the bcache device into read-only\n");
+		pr_err("Please update to the latest bcache-tools to create the cache device\n");
+		set_disk_ro(dc->disk.disk, 1);
+	}
+
+	/* Allow the writeback thread to proceed */
+	up_write(&dc->writeback_lock);
+
+	pr_info("Caching %pg as %s on set %pU\n",
+		dc->bdev,
+		dc->disk.disk->disk_name,
+		dc->disk.c->set_uuid);
+	return 0;
+}
+
+/* when dc->disk.kobj released */
+void bch_cached_dev_release(struct kobject *kobj)
+{
+	struct cached_dev *dc = container_of(kobj, struct cached_dev,
+					     disk.kobj);
+	kfree(dc);
+	module_put(THIS_MODULE);
+}
+
+static void cached_dev_free(struct closure *cl)
+{
+	struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
+
+	if (test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
+		cancel_writeback_rate_update_dwork(dc);
+
+	if (!IS_ERR_OR_NULL(dc->writeback_thread))
+		kthread_stop(dc->writeback_thread);
+	if (!IS_ERR_OR_NULL(dc->status_update_thread))
+		kthread_stop(dc->status_update_thread);
+
+	mutex_lock(&bch_register_lock);
+
+	if (atomic_read(&dc->running)) {
+		bd_unlink_disk_holder(dc->bdev, dc->disk.disk);
+		del_gendisk(dc->disk.disk);
+	}
+	bcache_device_free(&dc->disk);
+	list_del(&dc->list);
+
+	mutex_unlock(&bch_register_lock);
+
+	if (dc->sb_disk)
+		put_page(virt_to_page(dc->sb_disk));
+
+	if (!IS_ERR_OR_NULL(dc->bdev))
+		blkdev_put(dc->bdev, dc);
+
+	wake_up(&unregister_wait);
+
+	kobject_put(&dc->disk.kobj);
+}
+
+static void cached_dev_flush(struct closure *cl)
+{
+	struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
+	struct bcache_device *d = &dc->disk;
+
+	mutex_lock(&bch_register_lock);
+	bcache_device_unlink(d);
+	mutex_unlock(&bch_register_lock);
+
+	bch_cache_accounting_destroy(&dc->accounting);
+	kobject_del(&d->kobj);
+
+	continue_at(cl, cached_dev_free, system_wq);
+}
+
+static int cached_dev_init(struct cached_dev *dc, unsigned int block_size)
+{
+	int ret;
+	struct io *io;
+	struct request_queue *q = bdev_get_queue(dc->bdev);
+
+	__module_get(THIS_MODULE);
+	INIT_LIST_HEAD(&dc->list);
+	closure_init(&dc->disk.cl, NULL);
+	set_closure_fn(&dc->disk.cl, cached_dev_flush, system_wq);
+	kobject_init(&dc->disk.kobj, &bch_cached_dev_ktype);
+	INIT_WORK(&dc->detach, cached_dev_detach_finish);
+	sema_init(&dc->sb_write_mutex, 1);
+	INIT_LIST_HEAD(&dc->io_lru);
+	spin_lock_init(&dc->io_lock);
+	bch_cache_accounting_init(&dc->accounting, &dc->disk.cl);
+
+	dc->sequential_cutoff		= 4 << 20;
+
+	for (io = dc->io; io < dc->io + RECENT_IO; io++) {
+		list_add(&io->lru, &dc->io_lru);
+		hlist_add_head(&io->hash, dc->io_hash + RECENT_IO);
+	}
+
+	dc->disk.stripe_size = q->limits.io_opt >> 9;
+
+	if (dc->disk.stripe_size)
+		dc->partial_stripes_expensive =
+			q->limits.raid_partial_stripes_expensive;
+
+	ret = bcache_device_init(&dc->disk, block_size,
+			 bdev_nr_sectors(dc->bdev) - dc->sb.data_offset,
+			 dc->bdev, &bcache_cached_ops);
+	if (ret)
+		return ret;
+
+	blk_queue_io_opt(dc->disk.disk->queue,
+		max(queue_io_opt(dc->disk.disk->queue), queue_io_opt(q)));
+
+	atomic_set(&dc->io_errors, 0);
+	dc->io_disable = false;
+	dc->error_limit = DEFAULT_CACHED_DEV_ERROR_LIMIT;
+	/* default to auto */
+	dc->stop_when_cache_set_failed = BCH_CACHED_DEV_STOP_AUTO;
+
+	bch_cached_dev_request_init(dc);
+	bch_cached_dev_writeback_init(dc);
+	return 0;
+}
+
+/* Cached device - bcache superblock */
+
+static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
+				 struct block_device *bdev,
+				 struct cached_dev *dc)
+{
+	const char *err = "cannot allocate memory";
+	struct cache_set *c;
+	int ret = -ENOMEM;
+
+	memcpy(&dc->sb, sb, sizeof(struct cache_sb));
+	dc->bdev = bdev;
+	dc->sb_disk = sb_disk;
+
+	if (cached_dev_init(dc, sb->block_size << 9))
+		goto err;
+
+	err = "error creating kobject";
+	if (kobject_add(&dc->disk.kobj, bdev_kobj(bdev), "bcache"))
+		goto err;
+	if (bch_cache_accounting_add_kobjs(&dc->accounting, &dc->disk.kobj))
+		goto err;
+
+	pr_info("registered backing device %pg\n", dc->bdev);
+
+	list_add(&dc->list, &uncached_devices);
+	/* attach to a matched cache set if it exists */
+	list_for_each_entry(c, &bch_cache_sets, list)
+		bch_cached_dev_attach(dc, c, NULL);
+
+	if (BDEV_STATE(&dc->sb) == BDEV_STATE_NONE ||
+	    BDEV_STATE(&dc->sb) == BDEV_STATE_STALE) {
+		err = "failed to run cached device";
+		ret = bch_cached_dev_run(dc);
+		if (ret)
+			goto err;
+	}
+
+	return 0;
+err:
+	pr_notice("error %pg: %s\n", dc->bdev, err);
+	bcache_device_stop(&dc->disk);
+	return ret;
+}
+
+/* Flash only volumes */
+
+/* When d->kobj released */
+void bch_flash_dev_release(struct kobject *kobj)
+{
+	struct bcache_device *d = container_of(kobj, struct bcache_device,
+					       kobj);
+	kfree(d);
+}
+
+static void flash_dev_free(struct closure *cl)
+{
+	struct bcache_device *d = container_of(cl, struct bcache_device, cl);
+
+	mutex_lock(&bch_register_lock);
+	atomic_long_sub(bcache_dev_sectors_dirty(d),
+			&d->c->flash_dev_dirty_sectors);
+	del_gendisk(d->disk);
+	bcache_device_free(d);
+	mutex_unlock(&bch_register_lock);
+	kobject_put(&d->kobj);
+}
+
+static void flash_dev_flush(struct closure *cl)
+{
+	struct bcache_device *d = container_of(cl, struct bcache_device, cl);
+
+	mutex_lock(&bch_register_lock);
+	bcache_device_unlink(d);
+	mutex_unlock(&bch_register_lock);
+	kobject_del(&d->kobj);
+	continue_at(cl, flash_dev_free, system_wq);
+}
+
+static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
+{
+	int err = -ENOMEM;
+	struct bcache_device *d = kzalloc(sizeof(struct bcache_device),
+					  GFP_KERNEL);
+	if (!d)
+		goto err_ret;
+
+	closure_init(&d->cl, NULL);
+	set_closure_fn(&d->cl, flash_dev_flush, system_wq);
+
+	kobject_init(&d->kobj, &bch_flash_dev_ktype);
+
+	if (bcache_device_init(d, block_bytes(c->cache), u->sectors,
+			NULL, &bcache_flash_ops))
+		goto err;
+
+	bcache_device_attach(d, c, u - c->uuids);
+	bch_sectors_dirty_init(d);
+	bch_flash_dev_request_init(d);
+	err = add_disk(d->disk);
+	if (err)
+		goto err;
+
+	err = kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache");
+	if (err)
+		goto err;
+
+	bcache_device_link(d, c, "volume");
+
+	if (bch_has_feature_obso_large_bucket(&c->cache->sb)) {
+		pr_err("The obsoleted large bucket layout is unsupported, set the bcache device into read-only\n");
+		pr_err("Please update to the latest bcache-tools to create the cache device\n");
+		set_disk_ro(d->disk, 1);
+	}
+
+	return 0;
+err:
+	kobject_put(&d->kobj);
+err_ret:
+	return err;
+}
+
+static int flash_devs_run(struct cache_set *c)
+{
+	int ret = 0;
+	struct uuid_entry *u;
+
+	for (u = c->uuids;
+	     u < c->uuids + c->nr_uuids && !ret;
+	     u++)
+		if (UUID_FLASH_ONLY(u))
+			ret = flash_dev_run(c, u);
+
+	return ret;
+}
+
+int bch_flash_dev_create(struct cache_set *c, uint64_t size)
+{
+	struct uuid_entry *u;
+
+	if (test_bit(CACHE_SET_STOPPING, &c->flags))
+		return -EINTR;
+
+	if (!test_bit(CACHE_SET_RUNNING, &c->flags))
+		return -EPERM;
+
+	u = uuid_find_empty(c);
+	if (!u) {
+		pr_err("Can't create volume, no room for UUID\n");
+		return -EINVAL;
+	}
+
+	get_random_bytes(u->uuid, 16);
+	memset(u->label, 0, 32);
+	u->first_reg = u->last_reg = cpu_to_le32((u32)ktime_get_real_seconds());
+
+	SET_UUID_FLASH_ONLY(u, 1);
+	u->sectors = size >> 9;
+
+	bch_uuid_write(c);
+
+	return flash_dev_run(c, u);
+}
+
+bool bch_cached_dev_error(struct cached_dev *dc)
+{
+	if (!dc || test_bit(BCACHE_DEV_CLOSING, &dc->disk.flags))
+		return false;
+
+	dc->io_disable = true;
+	/* make others know io_disable is true earlier */
+	smp_mb();
+
+	pr_err("stop %s: too many IO errors on backing device %pg\n",
+	       dc->disk.disk->disk_name, dc->bdev);
+
+	bcache_device_stop(&dc->disk);
+	return true;
+}
+
+/* Cache set */
+
+__printf(2, 3)
+bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	if (c->on_error != ON_ERROR_PANIC &&
+	    test_bit(CACHE_SET_STOPPING, &c->flags))
+		return false;
+
+	if (test_and_set_bit(CACHE_SET_IO_DISABLE, &c->flags))
+		pr_info("CACHE_SET_IO_DISABLE already set\n");
+
+	/*
+	 * XXX: we can be called from atomic context
+	 * acquire_console_sem();
+	 */
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	pr_err("error on %pU: %pV, disabling caching\n",
+	       c->set_uuid, &vaf);
+
+	va_end(args);
+
+	if (c->on_error == ON_ERROR_PANIC)
+		panic("panic forced after error\n");
+
+	bch_cache_set_unregister(c);
+	return true;
+}
+
+/* When c->kobj released */
+void bch_cache_set_release(struct kobject *kobj)
+{
+	struct cache_set *c = container_of(kobj, struct cache_set, kobj);
+
+	kfree(c);
+	module_put(THIS_MODULE);
+}
+
+static void cache_set_free(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, cl);
+	struct cache *ca;
+
+	debugfs_remove(c->debug);
+
+	bch_open_buckets_free(c);
+	bch_btree_cache_free(c);
+	bch_journal_free(c);
+
+	mutex_lock(&bch_register_lock);
+	bch_bset_sort_state_free(&c->sort);
+	free_pages((unsigned long) c->uuids, ilog2(meta_bucket_pages(&c->cache->sb)));
+
+	ca = c->cache;
+	if (ca) {
+		ca->set = NULL;
+		c->cache = NULL;
+		kobject_put(&ca->kobj);
+	}
+
+
+	if (c->moving_gc_wq)
+		destroy_workqueue(c->moving_gc_wq);
+	bioset_exit(&c->bio_split);
+	mempool_exit(&c->fill_iter);
+	mempool_exit(&c->bio_meta);
+	mempool_exit(&c->search);
+	kfree(c->devices);
+
+	list_del(&c->list);
+	mutex_unlock(&bch_register_lock);
+
+	pr_info("Cache set %pU unregistered\n", c->set_uuid);
+	wake_up(&unregister_wait);
+
+	closure_debug_destroy(&c->cl);
+	kobject_put(&c->kobj);
+}
+
+static void cache_set_flush(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, caching);
+	struct cache *ca = c->cache;
+	struct btree *b;
+
+	bch_cache_accounting_destroy(&c->accounting);
+
+	kobject_put(&c->internal);
+	kobject_del(&c->kobj);
+
+	if (!IS_ERR_OR_NULL(c->gc_thread))
+		kthread_stop(c->gc_thread);
+
+	if (!IS_ERR(c->root))
+		list_add(&c->root->list, &c->btree_cache);
+
+	/*
+	 * Avoid flushing cached nodes if cache set is retiring
+	 * due to too many I/O errors detected.
+	 */
+	if (!test_bit(CACHE_SET_IO_DISABLE, &c->flags))
+		list_for_each_entry(b, &c->btree_cache, list) {
+			mutex_lock(&b->write_lock);
+			if (btree_node_dirty(b))
+				__bch_btree_node_write(b, NULL);
+			mutex_unlock(&b->write_lock);
+		}
+
+	if (ca->alloc_thread)
+		kthread_stop(ca->alloc_thread);
+
+	if (c->journal.cur) {
+		cancel_delayed_work_sync(&c->journal.work);
+		/* flush last journal entry if needed */
+		c->journal.work.work.func(&c->journal.work.work);
+	}
+
+	closure_return(cl);
+}
+
+/*
+ * This function is only called when CACHE_SET_IO_DISABLE is set, which means
+ * cache set is unregistering due to too many I/O errors. In this condition,
+ * the bcache device might be stopped, it depends on stop_when_cache_set_failed
+ * value and whether the broken cache has dirty data:
+ *
+ * dc->stop_when_cache_set_failed    dc->has_dirty   stop bcache device
+ *  BCH_CACHED_STOP_AUTO               0               NO
+ *  BCH_CACHED_STOP_AUTO               1               YES
+ *  BCH_CACHED_DEV_STOP_ALWAYS         0               YES
+ *  BCH_CACHED_DEV_STOP_ALWAYS         1               YES
+ *
+ * The expected behavior is, if stop_when_cache_set_failed is configured to
+ * "auto" via sysfs interface, the bcache device will not be stopped if the
+ * backing device is clean on the broken cache device.
+ */
+static void conditional_stop_bcache_device(struct cache_set *c,
+					   struct bcache_device *d,
+					   struct cached_dev *dc)
+{
+	if (dc->stop_when_cache_set_failed == BCH_CACHED_DEV_STOP_ALWAYS) {
+		pr_warn("stop_when_cache_set_failed of %s is \"always\", stop it for failed cache set %pU.\n",
+			d->disk->disk_name, c->set_uuid);
+		bcache_device_stop(d);
+	} else if (atomic_read(&dc->has_dirty)) {
+		/*
+		 * dc->stop_when_cache_set_failed == BCH_CACHED_STOP_AUTO
+		 * and dc->has_dirty == 1
+		 */
+		pr_warn("stop_when_cache_set_failed of %s is \"auto\" and cache is dirty, stop it to avoid potential data corruption.\n",
+			d->disk->disk_name);
+		/*
+		 * There might be a small time gap that cache set is
+		 * released but bcache device is not. Inside this time
+		 * gap, regular I/O requests will directly go into
+		 * backing device as no cache set attached to. This
+		 * behavior may also introduce potential inconsistence
+		 * data in writeback mode while cache is dirty.
+		 * Therefore before calling bcache_device_stop() due
+		 * to a broken cache device, dc->io_disable should be
+		 * explicitly set to true.
+		 */
+		dc->io_disable = true;
+		/* make others know io_disable is true earlier */
+		smp_mb();
+		bcache_device_stop(d);
+	} else {
+		/*
+		 * dc->stop_when_cache_set_failed == BCH_CACHED_STOP_AUTO
+		 * and dc->has_dirty == 0
+		 */
+		pr_warn("stop_when_cache_set_failed of %s is \"auto\" and cache is clean, keep it alive.\n",
+			d->disk->disk_name);
+	}
+}
+
+static void __cache_set_unregister(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, caching);
+	struct cached_dev *dc;
+	struct bcache_device *d;
+	size_t i;
+
+	mutex_lock(&bch_register_lock);
+
+	for (i = 0; i < c->devices_max_used; i++) {
+		d = c->devices[i];
+		if (!d)
+			continue;
+
+		if (!UUID_FLASH_ONLY(&c->uuids[i]) &&
+		    test_bit(CACHE_SET_UNREGISTERING, &c->flags)) {
+			dc = container_of(d, struct cached_dev, disk);
+			bch_cached_dev_detach(dc);
+			if (test_bit(CACHE_SET_IO_DISABLE, &c->flags))
+				conditional_stop_bcache_device(c, d, dc);
+		} else {
+			bcache_device_stop(d);
+		}
+	}
+
+	mutex_unlock(&bch_register_lock);
+
+	continue_at(cl, cache_set_flush, system_wq);
+}
+
+void bch_cache_set_stop(struct cache_set *c)
+{
+	if (!test_and_set_bit(CACHE_SET_STOPPING, &c->flags))
+		/* closure_fn set to __cache_set_unregister() */
+		closure_queue(&c->caching);
+}
+
+void bch_cache_set_unregister(struct cache_set *c)
+{
+	set_bit(CACHE_SET_UNREGISTERING, &c->flags);
+	bch_cache_set_stop(c);
+}
+
+#define alloc_meta_bucket_pages(gfp, sb)		\
+	((void *) __get_free_pages(__GFP_ZERO|__GFP_COMP|gfp, ilog2(meta_bucket_pages(sb))))
+
+struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
+{
+	int iter_size;
+	struct cache *ca = container_of(sb, struct cache, sb);
+	struct cache_set *c = kzalloc(sizeof(struct cache_set), GFP_KERNEL);
+
+	if (!c)
+		return NULL;
+
+	__module_get(THIS_MODULE);
+	closure_init(&c->cl, NULL);
+	set_closure_fn(&c->cl, cache_set_free, system_wq);
+
+	closure_init(&c->caching, &c->cl);
+	set_closure_fn(&c->caching, __cache_set_unregister, system_wq);
+
+	/* Maybe create continue_at_noreturn() and use it here? */
+	closure_set_stopped(&c->cl);
+	closure_put(&c->cl);
+
+	kobject_init(&c->kobj, &bch_cache_set_ktype);
+	kobject_init(&c->internal, &bch_cache_set_internal_ktype);
+
+	bch_cache_accounting_init(&c->accounting, &c->cl);
+
+	memcpy(c->set_uuid, sb->set_uuid, 16);
+
+	c->cache		= ca;
+	c->cache->set		= c;
+	c->bucket_bits		= ilog2(sb->bucket_size);
+	c->block_bits		= ilog2(sb->block_size);
+	c->nr_uuids		= meta_bucket_bytes(sb) / sizeof(struct uuid_entry);
+	c->devices_max_used	= 0;
+	atomic_set(&c->attached_dev_nr, 0);
+	c->btree_pages		= meta_bucket_pages(sb);
+	if (c->btree_pages > BTREE_MAX_PAGES)
+		c->btree_pages = max_t(int, c->btree_pages / 4,
+				       BTREE_MAX_PAGES);
+
+	sema_init(&c->sb_write_mutex, 1);
+	mutex_init(&c->bucket_lock);
+	init_waitqueue_head(&c->btree_cache_wait);
+	spin_lock_init(&c->btree_cannibalize_lock);
+	init_waitqueue_head(&c->bucket_wait);
+	init_waitqueue_head(&c->gc_wait);
+	sema_init(&c->uuid_write_mutex, 1);
+
+	spin_lock_init(&c->btree_gc_time.lock);
+	spin_lock_init(&c->btree_split_time.lock);
+	spin_lock_init(&c->btree_read_time.lock);
+
+	bch_moving_init_cache_set(c);
+
+	INIT_LIST_HEAD(&c->list);
+	INIT_LIST_HEAD(&c->cached_devs);
+	INIT_LIST_HEAD(&c->btree_cache);
+	INIT_LIST_HEAD(&c->btree_cache_freeable);
+	INIT_LIST_HEAD(&c->btree_cache_freed);
+	INIT_LIST_HEAD(&c->data_buckets);
+
+	iter_size = ((meta_bucket_pages(sb) * PAGE_SECTORS) / sb->block_size + 1) *
+		sizeof(struct btree_iter_set);
+
+	c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL);
+	if (!c->devices)
+		goto err;
+
+	if (mempool_init_slab_pool(&c->search, 32, bch_search_cache))
+		goto err;
+
+	if (mempool_init_kmalloc_pool(&c->bio_meta, 2,
+			sizeof(struct bbio) +
+			sizeof(struct bio_vec) * meta_bucket_pages(sb)))
+		goto err;
+
+	if (mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size))
+		goto err;
+
+	if (bioset_init(&c->bio_split, 4, offsetof(struct bbio, bio),
+			BIOSET_NEED_RESCUER))
+		goto err;
+
+	c->uuids = alloc_meta_bucket_pages(GFP_KERNEL, sb);
+	if (!c->uuids)
+		goto err;
+
+	c->moving_gc_wq = alloc_workqueue("bcache_gc", WQ_MEM_RECLAIM, 0);
+	if (!c->moving_gc_wq)
+		goto err;
+
+	if (bch_journal_alloc(c))
+		goto err;
+
+	if (bch_btree_cache_alloc(c))
+		goto err;
+
+	if (bch_open_buckets_alloc(c))
+		goto err;
+
+	if (bch_bset_sort_state_init(&c->sort, ilog2(c->btree_pages)))
+		goto err;
+
+	c->congested_read_threshold_us	= 2000;
+	c->congested_write_threshold_us	= 20000;
+	c->error_limit	= DEFAULT_IO_ERROR_LIMIT;
+	c->idle_max_writeback_rate_enabled = 1;
+	WARN_ON(test_and_clear_bit(CACHE_SET_IO_DISABLE, &c->flags));
+
+	return c;
+err:
+	bch_cache_set_unregister(c);
+	return NULL;
+}
+
+static int run_cache_set(struct cache_set *c)
+{
+	const char *err = "cannot allocate memory";
+	struct cached_dev *dc, *t;
+	struct cache *ca = c->cache;
+	struct closure cl;
+	LIST_HEAD(journal);
+	struct journal_replay *l;
+
+	closure_init_stack(&cl);
+
+	c->nbuckets = ca->sb.nbuckets;
+	set_gc_sectors(c);
+
+	if (CACHE_SYNC(&c->cache->sb)) {
+		struct bkey *k;
+		struct jset *j;
+
+		err = "cannot allocate memory for journal";
+		if (bch_journal_read(c, &journal))
+			goto err;
+
+		pr_debug("btree_journal_read() done\n");
+
+		err = "no journal entries found";
+		if (list_empty(&journal))
+			goto err;
+
+		j = &list_entry(journal.prev, struct journal_replay, list)->j;
+
+		err = "IO error reading priorities";
+		if (prio_read(ca, j->prio_bucket[ca->sb.nr_this_dev]))
+			goto err;
+
+		/*
+		 * If prio_read() fails it'll call cache_set_error and we'll
+		 * tear everything down right away, but if we perhaps checked
+		 * sooner we could avoid journal replay.
+		 */
+
+		k = &j->btree_root;
+
+		err = "bad btree root";
+		if (__bch_btree_ptr_invalid(c, k))
+			goto err;
+
+		err = "error reading btree root";
+		c->root = bch_btree_node_get(c, NULL, k,
+					     j->btree_level,
+					     true, NULL);
+		if (IS_ERR(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)
+		put_page(virt_to_page(ca->sb_disk));
+
+	if (!IS_ERR_OR_NULL(ca->bdev))
+		blkdev_put(ca->bdev, ca);
+
+	kfree(ca);
+	module_put(THIS_MODULE);
+}
+
+static int cache_alloc(struct cache *ca)
+{
+	size_t free;
+	size_t btree_buckets;
+	struct bucket *b;
+	int ret = -ENOMEM;
+	const char *err = NULL;
+
+	__module_get(THIS_MODULE);
+	kobject_init(&ca->kobj, &bch_cache_ktype);
+
+	bio_init(&ca->journal.bio, NULL, ca->journal.bio.bi_inline_vecs, 8, 0);
+
+	/*
+	 * when ca->sb.njournal_buckets is not zero, journal exists,
+	 * and in bch_journal_replay(), tree node may split,
+	 * so bucket of RESERVE_BTREE type is needed,
+	 * the worst situation is all journal buckets are valid journal,
+	 * and all the keys need to replay,
+	 * so the number of  RESERVE_BTREE type buckets should be as much
+	 * as journal buckets
+	 */
+	btree_buckets = ca->sb.njournal_buckets ?: 8;
+	free = roundup_pow_of_two(ca->sb.nbuckets) >> 10;
+	if (!free) {
+		ret = -EPERM;
+		err = "ca->sb.nbuckets is too small";
+		goto err_free;
+	}
+
+	if (!init_fifo(&ca->free[RESERVE_BTREE], btree_buckets,
+						GFP_KERNEL)) {
+		err = "ca->free[RESERVE_BTREE] alloc failed";
+		goto err_btree_alloc;
+	}
+
+	if (!init_fifo_exact(&ca->free[RESERVE_PRIO], prio_buckets(ca),
+							GFP_KERNEL)) {
+		err = "ca->free[RESERVE_PRIO] alloc failed";
+		goto err_prio_alloc;
+	}
+
+	if (!init_fifo(&ca->free[RESERVE_MOVINGGC], free, GFP_KERNEL)) {
+		err = "ca->free[RESERVE_MOVINGGC] alloc failed";
+		goto err_movinggc_alloc;
+	}
+
+	if (!init_fifo(&ca->free[RESERVE_NONE], free, GFP_KERNEL)) {
+		err = "ca->free[RESERVE_NONE] alloc failed";
+		goto err_none_alloc;
+	}
+
+	if (!init_fifo(&ca->free_inc, free << 2, GFP_KERNEL)) {
+		err = "ca->free_inc alloc failed";
+		goto err_free_inc_alloc;
+	}
+
+	if (!init_heap(&ca->heap, free << 3, GFP_KERNEL)) {
+		err = "ca->heap alloc failed";
+		goto err_heap_alloc;
+	}
+
+	ca->buckets = vzalloc(array_size(sizeof(struct bucket),
+			      ca->sb.nbuckets));
+	if (!ca->buckets) {
+		err = "ca->buckets alloc failed";
+		goto err_buckets_alloc;
+	}
+
+	ca->prio_buckets = kzalloc(array3_size(sizeof(uint64_t),
+				   prio_buckets(ca), 2),
+				   GFP_KERNEL);
+	if (!ca->prio_buckets) {
+		err = "ca->prio_buckets alloc failed";
+		goto err_prio_buckets_alloc;
+	}
+
+	ca->disk_buckets = alloc_meta_bucket_pages(GFP_KERNEL, &ca->sb);
+	if (!ca->disk_buckets) {
+		err = "ca->disk_buckets alloc failed";
+		goto err_disk_buckets_alloc;
+	}
+
+	ca->prio_last_buckets = ca->prio_buckets + prio_buckets(ca);
+
+	for_each_bucket(b, ca)
+		atomic_set(&b->pin, 0);
+	return 0;
+
+err_disk_buckets_alloc:
+	kfree(ca->prio_buckets);
+err_prio_buckets_alloc:
+	vfree(ca->buckets);
+err_buckets_alloc:
+	free_heap(&ca->heap);
+err_heap_alloc:
+	free_fifo(&ca->free_inc);
+err_free_inc_alloc:
+	free_fifo(&ca->free[RESERVE_NONE]);
+err_none_alloc:
+	free_fifo(&ca->free[RESERVE_MOVINGGC]);
+err_movinggc_alloc:
+	free_fifo(&ca->free[RESERVE_PRIO]);
+err_prio_alloc:
+	free_fifo(&ca->free[RESERVE_BTREE]);
+err_btree_alloc:
+err_free:
+	module_put(THIS_MODULE);
+	if (err)
+		pr_notice("error %pg: %s\n", ca->bdev, err);
+	return ret;
+}
+
+static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
+				struct block_device *bdev, struct cache *ca)
+{
+	const char *err = NULL; /* must be set for any error case */
+	int ret = 0;
+
+	memcpy(&ca->sb, sb, sizeof(struct cache_sb));
+	ca->bdev = bdev;
+	ca->sb_disk = sb_disk;
+
+	if (bdev_max_discard_sectors((bdev)))
+		ca->discard = CACHE_DISCARD(&ca->sb);
+
+	ret = cache_alloc(ca);
+	if (ret != 0) {
+		/*
+		 * If we failed here, it means ca->kobj is not initialized yet,
+		 * kobject_put() won't be called and there is no chance to
+		 * call blkdev_put() to bdev in bch_cache_release(). So we
+		 * explicitly call blkdev_put() here.
+		 */
+		blkdev_put(bdev, ca);
+		if (ret == -ENOMEM)
+			err = "cache_alloc(): -ENOMEM";
+		else if (ret == -EPERM)
+			err = "cache_alloc(): cache device is too small";
+		else
+			err = "cache_alloc(): unknown error";
+		goto err;
+	}
+
+	if (kobject_add(&ca->kobj, bdev_kobj(bdev), "bcache")) {
+		err = "error calling kobject_add";
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&bch_register_lock);
+	err = register_cache_set(ca);
+	mutex_unlock(&bch_register_lock);
+
+	if (err) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	pr_info("registered cache device %pg\n", ca->bdev);
+
+out:
+	kobject_put(&ca->kobj);
+
+err:
+	if (err)
+		pr_notice("error %pg: %s\n", ca->bdev, err);
+
+	return ret;
+}
+
+/* Global interfaces/init */
+
+static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
+			       const char *buffer, size_t size);
+static ssize_t bch_pending_bdevs_cleanup(struct kobject *k,
+					 struct kobj_attribute *attr,
+					 const char *buffer, size_t size);
+
+kobj_attribute_write(register,		register_bcache);
+kobj_attribute_write(register_quiet,	register_bcache);
+kobj_attribute_write(pendings_cleanup,	bch_pending_bdevs_cleanup);
+
+static bool bch_is_open_backing(dev_t dev)
+{
+	struct cache_set *c, *tc;
+	struct cached_dev *dc, *t;
+
+	list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
+		list_for_each_entry_safe(dc, t, &c->cached_devs, list)
+			if (dc->bdev->bd_dev == dev)
+				return true;
+	list_for_each_entry_safe(dc, t, &uncached_devices, list)
+		if (dc->bdev->bd_dev == dev)
+			return true;
+	return false;
+}
+
+static bool bch_is_open_cache(dev_t dev)
+{
+	struct cache_set *c, *tc;
+
+	list_for_each_entry_safe(c, tc, &bch_cache_sets, list) {
+		struct cache *ca = c->cache;
+
+		if (ca->bdev->bd_dev == dev)
+			return true;
+	}
+
+	return false;
+}
+
+static bool bch_is_open(dev_t dev)
+{
+	return bch_is_open_cache(dev) || bch_is_open_backing(dev);
+}
+
+struct async_reg_args {
+	struct delayed_work reg_work;
+	char *path;
+	struct cache_sb *sb;
+	struct cache_sb_disk *sb_disk;
+	struct block_device *bdev;
+	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, 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, 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_wq, &args->reg_work, 10);
+}
+
+static void *alloc_holder_object(struct cache_sb *sb)
+{
+	if (SB_IS_BDEV(sb))
+		return kzalloc(sizeof(struct cached_dev), GFP_KERNEL);
+	return kzalloc(sizeof(struct cache), GFP_KERNEL);
+}
+
+static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
+			       const char *buffer, size_t size)
+{
+	const char *err;
+	char *path = NULL;
+	struct cache_sb *sb;
+	struct cache_sb_disk *sb_disk;
+	struct block_device *bdev, *bdev2;
+	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(sizeof(struct cache_sb), GFP_KERNEL);
+	if (!sb)
+		goto out_free_path;
+
+	ret = -EINVAL;
+	err = "failed to open device";
+	bdev = blkdev_get_by_path(strim(path), BLK_OPEN_READ, NULL, NULL);
+	if (IS_ERR(bdev))
+		goto out_free_sb;
+
+	err = "failed to set blocksize";
+	if (set_blocksize(bdev, 4096))
+		goto out_blkdev_put;
+
+	err = read_super(sb, bdev, &sb_disk);
+	if (err)
+		goto out_blkdev_put;
+
+	holder = alloc_holder_object(sb);
+	if (!holder) {
+		ret = -ENOMEM;
+		err = "cannot allocate memory";
+		goto out_put_sb_page;
+	}
+
+	/* Now reopen in exclusive mode with proper holder */
+	bdev2 = blkdev_get_by_dev(bdev->bd_dev, BLK_OPEN_READ | BLK_OPEN_WRITE,
+				  holder, NULL);
+	blkdev_put(bdev, NULL);
+	bdev = bdev2;
+	if (IS_ERR(bdev)) {
+		ret = PTR_ERR(bdev);
+		bdev = 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(sizeof(struct async_reg_args), GFP_KERNEL);
+
+		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	= bdev;
+		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, 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, 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_page:
+	put_page(virt_to_page(sb_disk));
+out_blkdev_put:
+	if (bdev)
+		blkdev_put(bdev, holder);
+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(sizeof(struct pdev), GFP_KERNEL);
+		if (!pdev)
+			break;
+		pdev->dc = dc;
+		list_add(&pdev->list, &pending_devs);
+	}
+
+	list_for_each_entry_safe(pdev, tpdev, &pending_devs, list) {
+		char *pdev_set_uuid = pdev->dc->sb.set_uuid;
+		list_for_each_entry_safe(c, tc, &bch_cache_sets, list) {
+			char *set_uuid = c->set_uuid;
+
+			if (!memcmp(pdev_set_uuid, set_uuid, 16)) {
+				list_del(&pdev->list);
+				kfree(pdev);
+				break;
+			}
+		}
+	}
+	mutex_unlock(&bch_register_lock);
+
+	list_for_each_entry_safe(pdev, tpdev, &pending_devs, list) {
+		pr_info("delete pdev %p\n", pdev);
+		list_del(&pdev->list);
+		bcache_device_stop(&pdev->dc->disk);
+		kfree(pdev);
+	}
+
+	return ret;
+}
+
+static int bcache_reboot(struct notifier_block *n, unsigned long code, void *x)
+{
+	if (bcache_is_reboot)
+		return NOTIFY_DONE;
+
+	if (code == SYS_DOWN ||
+	    code == SYS_HALT ||
+	    code == SYS_POWER_OFF) {
+		DEFINE_WAIT(wait);
+		unsigned long start = jiffies;
+		bool stopped = false;
+
+		struct cache_set *c, *tc;
+		struct cached_dev *dc, *tdc;
+
+		mutex_lock(&bch_register_lock);
+
+		if (bcache_is_reboot)
+			goto out;
+
+		/* New registration is rejected since now */
+		bcache_is_reboot = true;
+		/*
+		 * Make registering caller (if there is) on other CPU
+		 * core know bcache_is_reboot set to true earlier
+		 */
+		smp_mb();
+
+		if (list_empty(&bch_cache_sets) &&
+		    list_empty(&uncached_devices))
+			goto out;
+
+		mutex_unlock(&bch_register_lock);
+
+		pr_info("Stopping all devices:\n");
+
+		/*
+		 * The reason bch_register_lock is not held to call
+		 * bch_cache_set_stop() and bcache_device_stop() is to
+		 * avoid potential deadlock during reboot, because cache
+		 * set or bcache device stopping process will acquire
+		 * bch_register_lock too.
+		 *
+		 * We are safe here because bcache_is_reboot sets to
+		 * true already, register_bcache() will reject new
+		 * registration now. bcache_is_reboot also makes sure
+		 * bcache_reboot() won't be re-entered on by other thread,
+		 * so there is no race in following list iteration by
+		 * list_for_each_entry_safe().
+		 */
+		list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
+			bch_cache_set_stop(c);
+
+		list_for_each_entry_safe(dc, tdc, &uncached_devices, list)
+			bcache_device_stop(&dc->disk);
+
+
+		/*
+		 * Give an early chance for other kthreads and
+		 * kworkers to stop themselves
+		 */
+		schedule();
+
+		/* What's a condition variable? */
+		while (1) {
+			long timeout = start + 10 * HZ - jiffies;
+
+			mutex_lock(&bch_register_lock);
+			stopped = list_empty(&bch_cache_sets) &&
+				list_empty(&uncached_devices);
+
+			if (timeout < 0 || stopped)
+				break;
+
+			prepare_to_wait(&unregister_wait, &wait,
+					TASK_UNINTERRUPTIBLE);
+
+			mutex_unlock(&bch_register_lock);
+			schedule_timeout(timeout);
+		}
+
+		finish_wait(&unregister_wait, &wait);
+
+		if (stopped)
+			pr_info("All devices stopped\n");
+		else
+			pr_notice("Timeout waiting for devices to be closed\n");
+out:
+		mutex_unlock(&bch_register_lock);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block reboot = {
+	.notifier_call	= bcache_reboot,
+	.priority	= INT_MAX, /* before any real devices */
+};
+
+static void bcache_exit(void)
+{
+	bch_debug_exit();
+	bch_request_exit();
+	if (bcache_kobj)
+		kobject_put(bcache_kobj);
+	if (bcache_wq)
+		destroy_workqueue(bcache_wq);
+	if (bch_journal_wq)
+		destroy_workqueue(bch_journal_wq);
+	if (bch_flush_wq)
+		destroy_workqueue(bch_flush_wq);
+	bch_btree_exit();
+
+	if (bcache_major)
+		unregister_blkdev(bcache_major, "bcache");
+	unregister_reboot_notifier(&reboot);
+	mutex_destroy(&bch_register_lock);
+}
+
+/* Check and fixup module parameters */
+static void check_module_parameters(void)
+{
+	if (bch_cutoff_writeback_sync == 0)
+		bch_cutoff_writeback_sync = CUTOFF_WRITEBACK_SYNC;
+	else if (bch_cutoff_writeback_sync > CUTOFF_WRITEBACK_SYNC_MAX) {
+		pr_warn("set bch_cutoff_writeback_sync (%u) to max value %u\n",
+			bch_cutoff_writeback_sync, CUTOFF_WRITEBACK_SYNC_MAX);
+		bch_cutoff_writeback_sync = CUTOFF_WRITEBACK_SYNC_MAX;
+	}
+
+	if (bch_cutoff_writeback == 0)
+		bch_cutoff_writeback = CUTOFF_WRITEBACK;
+	else if (bch_cutoff_writeback > CUTOFF_WRITEBACK_MAX) {
+		pr_warn("set bch_cutoff_writeback (%u) to max value %u\n",
+			bch_cutoff_writeback, CUTOFF_WRITEBACK_MAX);
+		bch_cutoff_writeback = CUTOFF_WRITEBACK_MAX;
+	}
+
+	if (bch_cutoff_writeback > bch_cutoff_writeback_sync) {
+		pr_warn("set bch_cutoff_writeback (%u) to %u\n",
+			bch_cutoff_writeback, bch_cutoff_writeback_sync);
+		bch_cutoff_writeback = bch_cutoff_writeback_sync;
+	}
+}
+
+static int __init bcache_init(void)
+{
+	static const struct attribute *files[] = {
+		&ksysfs_register.attr,
+		&ksysfs_register_quiet.attr,
+		&ksysfs_pendings_cleanup.attr,
+		NULL
+	};
+
+	check_module_parameters();
+
+	mutex_init(&bch_register_lock);
+	init_waitqueue_head(&unregister_wait);
+	register_reboot_notifier(&reboot);
+
+	bcache_major = register_blkdev(0, "bcache");
+	if (bcache_major < 0) {
+		unregister_reboot_notifier(&reboot);
+		mutex_destroy(&bch_register_lock);
+		return bcache_major;
+	}
+
+	if (bch_btree_init())
+		goto err;
+
+	bcache_wq = alloc_workqueue("bcache", WQ_MEM_RECLAIM, 0);
+	if (!bcache_wq)
+		goto err;
+
+	/*
+	 * Let's not make this `WQ_MEM_RECLAIM` for the following reasons:
+	 *
+	 * 1. It used `system_wq` before which also does no memory reclaim.
+	 * 2. With `WQ_MEM_RECLAIM` desktop stalls, increased boot times, and
+	 *    reduced throughput can be observed.
+	 *
+	 * We still want to user our own queue to not congest the `system_wq`.
+	 */
+	bch_flush_wq = alloc_workqueue("bch_flush", 0, 0);
+	if (!bch_flush_wq)
+		goto err;
+
+	bch_journal_wq = alloc_workqueue("bch_journal", WQ_MEM_RECLAIM, 0);
+	if (!bch_journal_wq)
+		goto err;
+
+	bcache_kobj = kobject_create_and_add("bcache", fs_kobj);
+	if (!bcache_kobj)
+		goto err;
+
+	if (bch_request_init() ||
+	    sysfs_create_files(bcache_kobj, files))
+		goto err;
+
+	bch_debug_init();
+	closure_debug_init();
+
+	bcache_is_reboot = false;
+
+	return 0;
+err:
+	bcache_exit();
+	return -ENOMEM;
+}
+
+/*
+ * Module hooks
+ */
+module_exit(bcache_exit);
+module_init(bcache_init);
+
+module_param(bch_cutoff_writeback, uint, 0);
+MODULE_PARM_DESC(bch_cutoff_writeback, "threshold to cutoff writeback");
+
+module_param(bch_cutoff_writeback_sync, uint, 0);
+MODULE_PARM_DESC(bch_cutoff_writeback_sync, "hard threshold to cutoff writeback");
+
+MODULE_DESCRIPTION("Bcache: a Linux block layer cache");
+MODULE_AUTHOR("Kent Overstreet <kent.overstreet@gmail.com>");
+MODULE_LICENSE("GPL");