[sfrench/cifs-2.6.git] / fs / btrfs / disk-io.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/radix-tree.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h>
#include <linux/workqueue.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/migrate.h>
#include <linux/ratelimit.h>
#include <linux/uuid.h>
#include <linux/semaphore.h>
#include <linux/error-injection.h>
#include <linux/crc32c.h>
#include <linux/sched/mm.h>
#include <asm/unaligned.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "volumes.h"
#include "print-tree.h"
#include "locking.h"
#include "tree-log.h"
#include "free-space-cache.h"
#include "free-space-tree.h"
#include "inode-map.h"
#include "check-integrity.h"
#include "rcu-string.h"
#include "dev-replace.h"
#include "raid56.h"
#include "sysfs.h"
#include "qgroup.h"
#include "compression.h"
#include "tree-checker.h"
#include "ref-verify.h"

#define BTRFS_SUPER_FLAG_SUPP   (BTRFS_HEADER_FLAG_WRITTEN |\
                                 BTRFS_HEADER_FLAG_RELOC |\
                                 BTRFS_SUPER_FLAG_ERROR |\
                                 BTRFS_SUPER_FLAG_SEEDING |\
                                 BTRFS_SUPER_FLAG_METADUMP |\
                                 BTRFS_SUPER_FLAG_METADUMP_V2)

static const struct extent_io_ops btree_extent_io_ops;
static void end_workqueue_fn(struct btrfs_work *work);
static void btrfs_destroy_ordered_extents(struct btrfs_root *root);
static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
                                      struct btrfs_fs_info *fs_info);
static void btrfs_destroy_delalloc_inodes(struct btrfs_root *root);
static int btrfs_destroy_marked_extents(struct btrfs_fs_info *fs_info,
                                        struct extent_io_tree *dirty_pages,
                                        int mark);
static int btrfs_destroy_pinned_extent(struct btrfs_fs_info *fs_info,
                                       struct extent_io_tree *pinned_extents);
static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info);
static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info);

/*
 * btrfs_end_io_wq structs are used to do processing in task context when an IO
 * is complete.  This is used during reads to verify checksums, and it is used
 * by writes to insert metadata for new file extents after IO is complete.
 */
struct btrfs_end_io_wq {
        struct bio *bio;
        bio_end_io_t *end_io;
        void *private;
        struct btrfs_fs_info *info;
        blk_status_t status;
        enum btrfs_wq_endio_type metadata;
        struct btrfs_work work;
};

static struct kmem_cache *btrfs_end_io_wq_cache;

int __init btrfs_end_io_wq_init(void)
{
        btrfs_end_io_wq_cache = kmem_cache_create("btrfs_end_io_wq",
                                        sizeof(struct btrfs_end_io_wq),
                                        0,
                                        SLAB_MEM_SPREAD,
                                        NULL);
        if (!btrfs_end_io_wq_cache)
                return -ENOMEM;
        return 0;
}

void __cold btrfs_end_io_wq_exit(void)
{
        kmem_cache_destroy(btrfs_end_io_wq_cache);
}

/*
 * async submit bios are used to offload expensive checksumming
 * onto the worker threads.  They checksum file and metadata bios
 * just before they are sent down the IO stack.
 */
struct async_submit_bio {
        void *private_data;
        struct bio *bio;
        extent_submit_bio_start_t *submit_bio_start;
        int mirror_num;
        /*
         * bio_offset is optional, can be used if the pages in the bio
         * can't tell us where in the file the bio should go
         */
        u64 bio_offset;
        struct btrfs_work work;
        blk_status_t status;
};

/*
 * Lockdep class keys for extent_buffer->lock's in this root.  For a given
 * eb, the lockdep key is determined by the btrfs_root it belongs to and
 * the level the eb occupies in the tree.
 *
 * Different roots are used for different purposes and may nest inside each
 * other and they require separate keysets.  As lockdep keys should be
 * static, assign keysets according to the purpose of the root as indicated
 * by btrfs_root->root_key.objectid.  This ensures that all special purpose
 * roots have separate keysets.
 *
 * Lock-nesting across peer nodes is always done with the immediate parent
 * node locked thus preventing deadlock.  As lockdep doesn't know this, use
 * subclass to avoid triggering lockdep warning in such cases.
 *
 * The key is set by the readpage_end_io_hook after the buffer has passed
 * csum validation but before the pages are unlocked.  It is also set by
 * btrfs_init_new_buffer on freshly allocated blocks.
 *
 * We also add a check to make sure the highest level of the tree is the
 * same as our lockdep setup here.  If BTRFS_MAX_LEVEL changes, this code
 * needs update as well.
 */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
# if BTRFS_MAX_LEVEL != 8
#  error
# endif

static struct btrfs_lockdep_keyset {
        u64                     id;             /* root objectid */
        const char              *name_stem;     /* lock name stem */
        char                    names[BTRFS_MAX_LEVEL + 1][20];
        struct lock_class_key   keys[BTRFS_MAX_LEVEL + 1];
} btrfs_lockdep_keysets[] = {
        { .id = BTRFS_ROOT_TREE_OBJECTID,       .name_stem = "root"     },
        { .id = BTRFS_EXTENT_TREE_OBJECTID,     .name_stem = "extent"   },
        { .id = BTRFS_CHUNK_TREE_OBJECTID,      .name_stem = "chunk"    },
        { .id = BTRFS_DEV_TREE_OBJECTID,        .name_stem = "dev"      },
        { .id = BTRFS_FS_TREE_OBJECTID,         .name_stem = "fs"       },
        { .id = BTRFS_CSUM_TREE_OBJECTID,       .name_stem = "csum"     },
        { .id = BTRFS_QUOTA_TREE_OBJECTID,      .name_stem = "quota"    },
        { .id = BTRFS_TREE_LOG_OBJECTID,        .name_stem = "log"      },
        { .id = BTRFS_TREE_RELOC_OBJECTID,      .name_stem = "treloc"   },
        { .id = BTRFS_DATA_RELOC_TREE_OBJECTID, .name_stem = "dreloc"   },
        { .id = BTRFS_UUID_TREE_OBJECTID,       .name_stem = "uuid"     },
        { .id = BTRFS_FREE_SPACE_TREE_OBJECTID, .name_stem = "free-space" },
        { .id = 0,                              .name_stem = "tree"     },
};

void __init btrfs_init_lockdep(void)
{
        int i, j;

        /* initialize lockdep class names */
        for (i = 0; i < ARRAY_SIZE(btrfs_lockdep_keysets); i++) {
                struct btrfs_lockdep_keyset *ks = &btrfs_lockdep_keysets[i];

                for (j = 0; j < ARRAY_SIZE(ks->names); j++)
                        snprintf(ks->names[j], sizeof(ks->names[j]),
                                 "btrfs-%s-%02d", ks->name_stem, j);
        }
}

void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb,
                                    int level)
{
        struct btrfs_lockdep_keyset *ks;

        BUG_ON(level >= ARRAY_SIZE(ks->keys));

        /* find the matching keyset, id 0 is the default entry */
        for (ks = btrfs_lockdep_keysets; ks->id; ks++)
                if (ks->id == objectid)
                        break;

        lockdep_set_class_and_name(&eb->lock,
                                   &ks->keys[level], ks->names[level]);
}

#endif

/*
 * extents on the btree inode are pretty simple, there's one extent
 * that covers the entire device
 */
struct extent_map *btree_get_extent(struct btrfs_inode *inode,
                struct page *page, size_t pg_offset, u64 start, u64 len,
                int create)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct extent_map_tree *em_tree = &inode->extent_tree;
        struct extent_map *em;
        int ret;

        read_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, len);
        if (em) {
                em->bdev = fs_info->fs_devices->latest_bdev;
                read_unlock(&em_tree->lock);
                goto out;
        }
        read_unlock(&em_tree->lock);

        em = alloc_extent_map();
        if (!em) {
                em = ERR_PTR(-ENOMEM);
                goto out;
        }
        em->start = 0;
        em->len = (u64)-1;
        em->block_len = (u64)-1;
        em->block_start = 0;
        em->bdev = fs_info->fs_devices->latest_bdev;

        write_lock(&em_tree->lock);
        ret = add_extent_mapping(em_tree, em, 0);
        if (ret == -EEXIST) {
                free_extent_map(em);
                em = lookup_extent_mapping(em_tree, start, len);
                if (!em)
                        em = ERR_PTR(-EIO);
        } else if (ret) {
                free_extent_map(em);
                em = ERR_PTR(ret);
        }
        write_unlock(&em_tree->lock);

out:
        return em;
}

u32 btrfs_csum_data(const char *data, u32 seed, size_t len)
{
        return crc32c(seed, data, len);
}

void btrfs_csum_final(u32 crc, u8 *result)
{
        put_unaligned_le32(~crc, result);
}

/*
 * Compute the csum of a btree block and store the result to provided buffer.
 *
 * Returns error if the extent buffer cannot be mapped.
 */
static int csum_tree_block(struct extent_buffer *buf, u8 *result)
{
        unsigned long len;
        unsigned long cur_len;
        unsigned long offset = BTRFS_CSUM_SIZE;
        char *kaddr;
        unsigned long map_start;
        unsigned long map_len;
        int err;
        u32 crc = ~(u32)0;

        len = buf->len - offset;
        while (len > 0) {
                /*
                 * Note: we don't need to check for the err == 1 case here, as
                 * with the given combination of 'start = BTRFS_CSUM_SIZE (32)'
                 * and 'min_len = 32' and the currently implemented mapping
                 * algorithm we cannot cross a page boundary.
                 */
                err = map_private_extent_buffer(buf, offset, 32,
                                        &kaddr, &map_start, &map_len);
                if (WARN_ON(err))
                        return err;
                cur_len = min(len, map_len - (offset - map_start));
                crc = btrfs_csum_data(kaddr + offset - map_start,
                                      crc, cur_len);
                len -= cur_len;
                offset += cur_len;
        }
        memset(result, 0, BTRFS_CSUM_SIZE);

        btrfs_csum_final(crc, result);

        return 0;
}

/*
 * we can't consider a given block up to date unless the transid of the
 * block matches the transid in the parent node's pointer.  This is how we
 * detect blocks that either didn't get written at all or got written
 * in the wrong place.
 */
static int verify_parent_transid(struct extent_io_tree *io_tree,
                                 struct extent_buffer *eb, u64 parent_transid,
                                 int atomic)
{
        struct extent_state *cached_state = NULL;
        int ret;
        bool need_lock = (current->journal_info == BTRFS_SEND_TRANS_STUB);

        if (!parent_transid || btrfs_header_generation(eb) == parent_transid)
                return 0;

        if (atomic)
                return -EAGAIN;

        if (need_lock) {
                btrfs_tree_read_lock(eb);
                btrfs_set_lock_blocking_read(eb);
        }

        lock_extent_bits(io_tree, eb->start, eb->start + eb->len - 1,
                         &cached_state);
        if (extent_buffer_uptodate(eb) &&
            btrfs_header_generation(eb) == parent_transid) {
                ret = 0;
                goto out;
        }
        btrfs_err_rl(eb->fs_info,
                "parent transid verify failed on %llu wanted %llu found %llu",
                        eb->start,
                        parent_transid, btrfs_header_generation(eb));
        ret = 1;

        /*
         * Things reading via commit roots that don't have normal protection,
         * like send, can have a really old block in cache that may point at a
         * block that has been freed and re-allocated.  So don't clear uptodate
         * if we find an eb that is under IO (dirty/writeback) because we could
         * end up reading in the stale data and then writing it back out and
         * making everybody very sad.
         */
        if (!extent_buffer_under_io(eb))
                clear_extent_buffer_uptodate(eb);
out:
        unlock_extent_cached(io_tree, eb->start, eb->start + eb->len - 1,
                             &cached_state);
        if (need_lock)
                btrfs_tree_read_unlock_blocking(eb);
        return ret;
}

static bool btrfs_supported_super_csum(u16 csum_type)
{
        switch (csum_type) {
        case BTRFS_CSUM_TYPE_CRC32:
                return true;
        default:
                return false;
        }
}

/*
 * Return 0 if the superblock checksum type matches the checksum value of that
 * algorithm. Pass the raw disk superblock data.
 */
static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
                                  char *raw_disk_sb)
{
        struct btrfs_super_block *disk_sb =
                (struct btrfs_super_block *)raw_disk_sb;
        u32 crc = ~(u32)0;
        char result[BTRFS_CSUM_SIZE];

        /*
         * The super_block structure does not span the whole
         * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space is
         * filled with zeros and is included in the checksum.
         */
        crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,
                              crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
        btrfs_csum_final(crc, result);

        if (memcmp(disk_sb->csum, result, btrfs_super_csum_size(disk_sb)))
                return 1;

        return 0;
}

int btrfs_verify_level_key(struct extent_buffer *eb, int level,
                           struct btrfs_key *first_key, u64 parent_transid)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        int found_level;
        struct btrfs_key found_key;
        int ret;

        found_level = btrfs_header_level(eb);
        if (found_level != level) {
                WARN(IS_ENABLED(CONFIG_BTRFS_DEBUG),
                     KERN_ERR "BTRFS: tree level check failed\n");
                btrfs_err(fs_info,
"tree level mismatch detected, bytenr=%llu level expected=%u has=%u",
                          eb->start, level, found_level);
                return -EIO;
        }

        if (!first_key)
                return 0;

        /*
         * For live tree block (new tree blocks in current transaction),
         * we need proper lock context to avoid race, which is impossible here.
         * So we only checks tree blocks which is read from disk, whose
         * generation <= fs_info->last_trans_committed.
         */
        if (btrfs_header_generation(eb) > fs_info->last_trans_committed)
                return 0;
        if (found_level)
                btrfs_node_key_to_cpu(eb, &found_key, 0);
        else
                btrfs_item_key_to_cpu(eb, &found_key, 0);
        ret = btrfs_comp_cpu_keys(first_key, &found_key);

        if (ret) {
                WARN(IS_ENABLED(CONFIG_BTRFS_DEBUG),
                     KERN_ERR "BTRFS: tree first key check failed\n");
                btrfs_err(fs_info,
"tree first key mismatch detected, bytenr=%llu parent_transid=%llu key expected=(%llu,%u,%llu) has=(%llu,%u,%llu)",
                          eb->start, parent_transid, first_key->objectid,
                          first_key->type, first_key->offset,
                          found_key.objectid, found_key.type,
                          found_key.offset);
        }
        return ret;
}

/*
 * helper to read a given tree block, doing retries as required when
 * the checksums don't match and we have alternate mirrors to try.
 *
 * @parent_transid:     expected transid, skip check if 0
 * @level:              expected level, mandatory check
 * @first_key:          expected key of first slot, skip check if NULL
 */
static int btree_read_extent_buffer_pages(struct extent_buffer *eb,
                                          u64 parent_transid, int level,
                                          struct btrfs_key *first_key)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        struct extent_io_tree *io_tree;
        int failed = 0;
        int ret;
        int num_copies = 0;
        int mirror_num = 0;
        int failed_mirror = 0;

        io_tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
        while (1) {
                clear_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
                ret = read_extent_buffer_pages(eb, WAIT_COMPLETE, mirror_num);
                if (!ret) {
                        if (verify_parent_transid(io_tree, eb,
                                                   parent_transid, 0))
                                ret = -EIO;
                        else if (btrfs_verify_level_key(eb, level,
                                                first_key, parent_transid))
                                ret = -EUCLEAN;
                        else
                                break;
                }

                num_copies = btrfs_num_copies(fs_info,
                                              eb->start, eb->len);
                if (num_copies == 1)
                        break;

                if (!failed_mirror) {
                        failed = 1;
                        failed_mirror = eb->read_mirror;
                }

                mirror_num++;
                if (mirror_num == failed_mirror)
                        mirror_num++;

                if (mirror_num > num_copies)
                        break;
        }

        if (failed && !ret && failed_mirror)
                btrfs_repair_eb_io_failure(eb, failed_mirror);

        return ret;
}

/*
 * checksum a dirty tree block before IO.  This has extra checks to make sure
 * we only fill in the checksum field in the first page of a multi-page block
 */

static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
{
        u64 start = page_offset(page);
        u64 found_start;
        u8 result[BTRFS_CSUM_SIZE];
        u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
        struct extent_buffer *eb;
        int ret;

        eb = (struct extent_buffer *)page->private;
        if (page != eb->pages[0])
                return 0;

        found_start = btrfs_header_bytenr(eb);
        /*
         * Please do not consolidate these warnings into a single if.
         * It is useful to know what went wrong.
         */
        if (WARN_ON(found_start != start))
                return -EUCLEAN;
        if (WARN_ON(!PageUptodate(page)))
                return -EUCLEAN;

        ASSERT(memcmp_extent_buffer(eb, fs_info->fs_devices->metadata_uuid,
                        btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);

        if (csum_tree_block(eb, result))
                return -EINVAL;

        if (btrfs_header_level(eb))
                ret = btrfs_check_node(eb);
        else
                ret = btrfs_check_leaf_full(eb);

        if (ret < 0) {
                btrfs_err(fs_info,
                "block=%llu write time tree block corruption detected",
                          eb->start);
                return ret;
        }
        write_extent_buffer(eb, result, 0, csum_size);

        return 0;
}

static int check_tree_block_fsid(struct extent_buffer *eb)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
        u8 fsid[BTRFS_FSID_SIZE];
        int ret = 1;

        read_extent_buffer(eb, fsid, btrfs_header_fsid(), BTRFS_FSID_SIZE);
        while (fs_devices) {
                u8 *metadata_uuid;

                /*
                 * Checking the incompat flag is only valid for the current
                 * fs. For seed devices it's forbidden to have their uuid
                 * changed so reading ->fsid in this case is fine
                 */
                if (fs_devices == fs_info->fs_devices &&
                    btrfs_fs_incompat(fs_info, METADATA_UUID))
                        metadata_uuid = fs_devices->metadata_uuid;
                else
                        metadata_uuid = fs_devices->fsid;

                if (!memcmp(fsid, metadata_uuid, BTRFS_FSID_SIZE)) {
                        ret = 0;
                        break;
                }
                fs_devices = fs_devices->seed;
        }
        return ret;
}

static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
                                      u64 phy_offset, struct page *page,
                                      u64 start, u64 end, int mirror)
{
        u64 found_start;
        int found_level;
        struct extent_buffer *eb;
        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
        int ret = 0;
        u8 result[BTRFS_CSUM_SIZE];
        int reads_done;

        if (!page->private)
                goto out;

        eb = (struct extent_buffer *)page->private;

        /* the pending IO might have been the only thing that kept this buffer
         * in memory.  Make sure we have a ref for all this other checks
         */
        extent_buffer_get(eb);

        reads_done = atomic_dec_and_test(&eb->io_pages);
        if (!reads_done)
                goto err;

        eb->read_mirror = mirror;
        if (test_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags)) {
                ret = -EIO;
                goto err;
        }

        found_start = btrfs_header_bytenr(eb);
        if (found_start != eb->start) {
                btrfs_err_rl(fs_info, "bad tree block start, want %llu have %llu",
                             eb->start, found_start);
                ret = -EIO;
                goto err;
        }
        if (check_tree_block_fsid(eb)) {
                btrfs_err_rl(fs_info, "bad fsid on block %llu",
                             eb->start);
                ret = -EIO;
                goto err;
        }
        found_level = btrfs_header_level(eb);
        if (found_level >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "bad tree block level %d on %llu",
                          (int)btrfs_header_level(eb), eb->start);
                ret = -EIO;
                goto err;
        }

        btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb),
                                       eb, found_level);

        ret = csum_tree_block(eb, result);
        if (ret)
                goto err;

        if (memcmp_extent_buffer(eb, result, 0, csum_size)) {
                u32 val;
                u32 found = 0;

                memcpy(&found, result, csum_size);

                read_extent_buffer(eb, &val, 0, csum_size);
                btrfs_warn_rl(fs_info,
                "%s checksum verify failed on %llu wanted %x found %x level %d",
                              fs_info->sb->s_id, eb->start,
                              val, found, btrfs_header_level(eb));
                ret = -EUCLEAN;
                goto err;
        }

        /*
         * If this is a leaf block and it is corrupt, set the corrupt bit so
         * that we don't try and read the other copies of this block, just
         * return -EIO.
         */
        if (found_level == 0 && btrfs_check_leaf_full(eb)) {
                set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
                ret = -EIO;
        }

        if (found_level > 0 && btrfs_check_node(eb))
                ret = -EIO;

        if (!ret)
                set_extent_buffer_uptodate(eb);
        else
                btrfs_err(fs_info,
                          "block=%llu read time tree block corruption detected",
                          eb->start);
err:
        if (reads_done &&
            test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
                btree_readahead_hook(eb, ret);

        if (ret) {
                /*
                 * our io error hook is going to dec the io pages
                 * again, we have to make sure it has something
                 * to decrement
                 */
                atomic_inc(&eb->io_pages);
                clear_extent_buffer_uptodate(eb);
        }
        free_extent_buffer(eb);
out:
        return ret;
}

static void end_workqueue_bio(struct bio *bio)
{
        struct btrfs_end_io_wq *end_io_wq = bio->bi_private;
        struct btrfs_fs_info *fs_info;
        struct btrfs_workqueue *wq;
        btrfs_work_func_t func;

        fs_info = end_io_wq->info;
        end_io_wq->status = bio->bi_status;

        if (bio_op(bio) == REQ_OP_WRITE) {
                if (end_io_wq->metadata == BTRFS_WQ_ENDIO_METADATA) {
                        wq = fs_info->endio_meta_write_workers;
                        func = btrfs_endio_meta_write_helper;
                } else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_FREE_SPACE) {
                        wq = fs_info->endio_freespace_worker;
                        func = btrfs_freespace_write_helper;
                } else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_RAID56) {
                        wq = fs_info->endio_raid56_workers;
                        func = btrfs_endio_raid56_helper;
                } else {
                        wq = fs_info->endio_write_workers;
                        func = btrfs_endio_write_helper;
                }
        } else {
                if (unlikely(end_io_wq->metadata ==
                             BTRFS_WQ_ENDIO_DIO_REPAIR)) {
                        wq = fs_info->endio_repair_workers;
                        func = btrfs_endio_repair_helper;
                } else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_RAID56) {
                        wq = fs_info->endio_raid56_workers;
                        func = btrfs_endio_raid56_helper;
                } else if (end_io_wq->metadata) {
                        wq = fs_info->endio_meta_workers;
                        func = btrfs_endio_meta_helper;
                } else {
                        wq = fs_info->endio_workers;
                        func = btrfs_endio_helper;
                }
        }

        btrfs_init_work(&end_io_wq->work, func, end_workqueue_fn, NULL, NULL);
        btrfs_queue_work(wq, &end_io_wq->work);
}

blk_status_t btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
                        enum btrfs_wq_endio_type metadata)
{
        struct btrfs_end_io_wq *end_io_wq;

        end_io_wq = kmem_cache_alloc(btrfs_end_io_wq_cache, GFP_NOFS);
        if (!end_io_wq)
                return BLK_STS_RESOURCE;

        end_io_wq->private = bio->bi_private;
        end_io_wq->end_io = bio->bi_end_io;
        end_io_wq->info = info;
        end_io_wq->status = 0;
        end_io_wq->bio = bio;
        end_io_wq->metadata = metadata;

        bio->bi_private = end_io_wq;
        bio->bi_end_io = end_workqueue_bio;
        return 0;
}

static void run_one_async_start(struct btrfs_work *work)
{
        struct async_submit_bio *async;
        blk_status_t ret;

        async = container_of(work, struct  async_submit_bio, work);
        ret = async->submit_bio_start(async->private_data, async->bio,
                                      async->bio_offset);
        if (ret)
                async->status = ret;
}

/*
 * In order to insert checksums into the metadata in large chunks, we wait
 * until bio submission time.   All the pages in the bio are checksummed and
 * sums are attached onto the ordered extent record.
 *
 * At IO completion time the csums attached on the ordered extent record are
 * inserted into the tree.
 */
static void run_one_async_done(struct btrfs_work *work)
{
        struct async_submit_bio *async;
        struct inode *inode;
        blk_status_t ret;

        async = container_of(work, struct  async_submit_bio, work);
        inode = async->private_data;

        /* If an error occurred we just want to clean up the bio and move on */
        if (async->status) {
                async->bio->bi_status = async->status;
                bio_endio(async->bio);
                return;
        }

        ret = btrfs_map_bio(btrfs_sb(inode->i_sb), async->bio,
                        async->mirror_num, 1);
        if (ret) {
                async->bio->bi_status = ret;
                bio_endio(async->bio);
        }
}

static void run_one_async_free(struct btrfs_work *work)
{
        struct async_submit_bio *async;

        async = container_of(work, struct  async_submit_bio, work);
        kfree(async);
}

blk_status_t btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
                                 int mirror_num, unsigned long bio_flags,
                                 u64 bio_offset, void *private_data,
                                 extent_submit_bio_start_t *submit_bio_start)
{
        struct async_submit_bio *async;

        async = kmalloc(sizeof(*async), GFP_NOFS);
        if (!async)
                return BLK_STS_RESOURCE;

        async->private_data = private_data;
        async->bio = bio;
        async->mirror_num = mirror_num;
        async->submit_bio_start = submit_bio_start;

        btrfs_init_work(&async->work, btrfs_worker_helper, run_one_async_start,
                        run_one_async_done, run_one_async_free);

        async->bio_offset = bio_offset;

        async->status = 0;

        if (op_is_sync(bio->bi_opf))
                btrfs_set_work_high_priority(&async->work);

        btrfs_queue_work(fs_info->workers, &async->work);
        return 0;
}

static blk_status_t btree_csum_one_bio(struct bio *bio)
{
        struct bio_vec *bvec;
        struct btrfs_root *root;
        int ret = 0;
        struct bvec_iter_all iter_all;

        ASSERT(!bio_flagged(bio, BIO_CLONED));
        bio_for_each_segment_all(bvec, bio, iter_all) {
                root = BTRFS_I(bvec->bv_page->mapping->host)->root;
                ret = csum_dirty_buffer(root->fs_info, bvec->bv_page);
                if (ret)
                        break;
        }

        return errno_to_blk_status(ret);
}

static blk_status_t btree_submit_bio_start(void *private_data, struct bio *bio,
                                             u64 bio_offset)
{
        /*
         * when we're called for a write, we're already in the async
         * submission context.  Just jump into btrfs_map_bio
         */
        return btree_csum_one_bio(bio);
}

static int check_async_write(struct btrfs_fs_info *fs_info,
                             struct btrfs_inode *bi)
{
        if (atomic_read(&bi->sync_writers))
                return 0;
        if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags))
                return 0;
        return 1;
}

static blk_status_t btree_submit_bio_hook(struct inode *inode, struct bio *bio,
                                          int mirror_num,
                                          unsigned long bio_flags)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        int async = check_async_write(fs_info, BTRFS_I(inode));
        blk_status_t ret;

        if (bio_op(bio) != REQ_OP_WRITE) {
                /*
                 * called for a read, do the setup so that checksum validation
                 * can happen in the async kernel threads
                 */
                ret = btrfs_bio_wq_end_io(fs_info, bio,
                                          BTRFS_WQ_ENDIO_METADATA);
                if (ret)
                        goto out_w_error;
                ret = btrfs_map_bio(fs_info, bio, mirror_num, 0);
        } else if (!async) {
                ret = btree_csum_one_bio(bio);
                if (ret)
                        goto out_w_error;
                ret = btrfs_map_bio(fs_info, bio, mirror_num, 0);
        } else {
                /*
                 * kthread helpers are used to submit writes so that
                 * checksumming can happen in parallel across all CPUs
                 */
                ret = btrfs_wq_submit_bio(fs_info, bio, mirror_num, 0,
                                          0, inode, btree_submit_bio_start);
        }

        if (ret)
                goto out_w_error;
        return 0;

out_w_error:
        bio->bi_status = ret;
        bio_endio(bio);
        return ret;
}

#ifdef CONFIG_MIGRATION
static int btree_migratepage(struct address_space *mapping,
                        struct page *newpage, struct page *page,
                        enum migrate_mode mode)
{
        /*
         * we can't safely write a btree page from here,
         * we haven't done the locking hook
         */
        if (PageDirty(page))
                return -EAGAIN;
        /*
         * Buffers may be managed in a filesystem specific way.
         * We must have no buffers or drop them.
         */
        if (page_has_private(page) &&
            !try_to_release_page(page, GFP_KERNEL))
                return -EAGAIN;
        return migrate_page(mapping, newpage, page, mode);
}
#endif


static int btree_writepages(struct address_space *mapping,
                            struct writeback_control *wbc)
{
        struct btrfs_fs_info *fs_info;
        int ret;

        if (wbc->sync_mode == WB_SYNC_NONE) {

                if (wbc->for_kupdate)
                        return 0;

                fs_info = BTRFS_I(mapping->host)->root->fs_info;
                /* this is a bit racy, but that's ok */
                ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
                                             BTRFS_DIRTY_METADATA_THRESH,
                                             fs_info->dirty_metadata_batch);
                if (ret < 0)
                        return 0;
        }
        return btree_write_cache_pages(mapping, wbc);
}

static int btree_readpage(struct file *file, struct page *page)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_read_full_page(tree, page, btree_get_extent, 0);
}

static int btree_releasepage(struct page *page, gfp_t gfp_flags)
{
        if (PageWriteback(page) || PageDirty(page))
                return 0;

        return try_release_extent_buffer(page);
}

static void btree_invalidatepage(struct page *page, unsigned int offset,
                                 unsigned int length)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        extent_invalidatepage(tree, page, offset);
        btree_releasepage(page, GFP_NOFS);
        if (PagePrivate(page)) {
                btrfs_warn(BTRFS_I(page->mapping->host)->root->fs_info,
                           "page private not zero on page %llu",
                           (unsigned long long)page_offset(page));
                ClearPagePrivate(page);
                set_page_private(page, 0);
                put_page(page);
        }
}

static int btree_set_page_dirty(struct page *page)
{
#ifdef DEBUG
        struct extent_buffer *eb;

        BUG_ON(!PagePrivate(page));
        eb = (struct extent_buffer *)page->private;
        BUG_ON(!eb);
        BUG_ON(!test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
        BUG_ON(!atomic_read(&eb->refs));
        btrfs_assert_tree_locked(eb);
#endif
        return __set_page_dirty_nobuffers(page);
}

static const struct address_space_operations btree_aops = {
        .readpage       = btree_readpage,
        .writepages     = btree_writepages,
        .releasepage    = btree_releasepage,
        .invalidatepage = btree_invalidatepage,
#ifdef CONFIG_MIGRATION
        .migratepage    = btree_migratepage,
#endif
        .set_page_dirty = btree_set_page_dirty,
};

void readahead_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr)
{
        struct extent_buffer *buf = NULL;
        int ret;

        buf = btrfs_find_create_tree_block(fs_info, bytenr);
        if (IS_ERR(buf))
                return;

        ret = read_extent_buffer_pages(buf, WAIT_NONE, 0);
        if (ret < 0)
                free_extent_buffer_stale(buf);
        else
                free_extent_buffer(buf);
}

int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr,
                         int mirror_num, struct extent_buffer **eb)
{
        struct extent_buffer *buf = NULL;
        int ret;

        buf = btrfs_find_create_tree_block(fs_info, bytenr);
        if (IS_ERR(buf))
                return 0;

        set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);

        ret = read_extent_buffer_pages(buf, WAIT_PAGE_LOCK, mirror_num);
        if (ret) {
                free_extent_buffer_stale(buf);
                return ret;
        }

        if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) {
                free_extent_buffer_stale(buf);
                return -EIO;
        } else if (extent_buffer_uptodate(buf)) {
                *eb = buf;
        } else {
                free_extent_buffer(buf);
        }
        return 0;
}

struct extent_buffer *btrfs_find_create_tree_block(
                                                struct btrfs_fs_info *fs_info,
                                                u64 bytenr)
{
        if (btrfs_is_testing(fs_info))
                return alloc_test_extent_buffer(fs_info, bytenr);
        return alloc_extent_buffer(fs_info, bytenr);
}

/*
 * Read tree block at logical address @bytenr and do variant basic but critical
 * verification.
 *
 * @parent_transid:     expected transid of this tree block, skip check if 0
 * @level:              expected level, mandatory check
 * @first_key:          expected key in slot 0, skip check if NULL
 */
struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
                                      u64 parent_transid, int level,
                                      struct btrfs_key *first_key)
{
        struct extent_buffer *buf = NULL;
        int ret;

        buf = btrfs_find_create_tree_block(fs_info, bytenr);
        if (IS_ERR(buf))
                return buf;

        ret = btree_read_extent_buffer_pages(buf, parent_transid,
                                             level, first_key);
        if (ret) {
                free_extent_buffer_stale(buf);
                return ERR_PTR(ret);
        }
        return buf;

}

void btrfs_clean_tree_block(struct extent_buffer *buf)
{
        struct btrfs_fs_info *fs_info = buf->fs_info;
        if (btrfs_header_generation(buf) ==
            fs_info->running_transaction->transid) {
                btrfs_assert_tree_locked(buf);

                if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &buf->bflags)) {
                        percpu_counter_add_batch(&fs_info->dirty_metadata_bytes,
                                                 -buf->len,
                                                 fs_info->dirty_metadata_batch);
                        /* ugh, clear_extent_buffer_dirty needs to lock the page */
                        btrfs_set_lock_blocking_write(buf);
                        clear_extent_buffer_dirty(buf);
                }
        }
}

static struct btrfs_subvolume_writers *btrfs_alloc_subvolume_writers(void)
{
        struct btrfs_subvolume_writers *writers;
        int ret;

        writers = kmalloc(sizeof(*writers), GFP_NOFS);
        if (!writers)
                return ERR_PTR(-ENOMEM);

        ret = percpu_counter_init(&writers->counter, 0, GFP_NOFS);
        if (ret < 0) {
                kfree(writers);
                return ERR_PTR(ret);
        }

        init_waitqueue_head(&writers->wait);
        return writers;
}

static void
btrfs_free_subvolume_writers(struct btrfs_subvolume_writers *writers)
{
        percpu_counter_destroy(&writers->counter);
        kfree(writers);
}

static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
                         u64 objectid)
{
        bool dummy = test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state);
        root->node = NULL;
        root->commit_root = NULL;
        root->state = 0;
        root->orphan_cleanup_state = 0;

        root->last_trans = 0;
        root->highest_objectid = 0;
        root->nr_delalloc_inodes = 0;
        root->nr_ordered_extents = 0;
        root->inode_tree = RB_ROOT;
        INIT_RADIX_TREE(&root->delayed_nodes_tree, GFP_ATOMIC);
        root->block_rsv = NULL;

        INIT_LIST_HEAD(&root->dirty_list);
        INIT_LIST_HEAD(&root->root_list);
        INIT_LIST_HEAD(&root->delalloc_inodes);
        INIT_LIST_HEAD(&root->delalloc_root);
        INIT_LIST_HEAD(&root->ordered_extents);
        INIT_LIST_HEAD(&root->ordered_root);
        INIT_LIST_HEAD(&root->reloc_dirty_list);
        INIT_LIST_HEAD(&root->logged_list[0]);
        INIT_LIST_HEAD(&root->logged_list[1]);
        spin_lock_init(&root->inode_lock);
        spin_lock_init(&root->delalloc_lock);
        spin_lock_init(&root->ordered_extent_lock);
        spin_lock_init(&root->accounting_lock);
        spin_lock_init(&root->log_extents_lock[0]);
        spin_lock_init(&root->log_extents_lock[1]);
        spin_lock_init(&root->qgroup_meta_rsv_lock);
        mutex_init(&root->objectid_mutex);
        mutex_init(&root->log_mutex);
        mutex_init(&root->ordered_extent_mutex);
        mutex_init(&root->delalloc_mutex);
        init_waitqueue_head(&root->log_writer_wait);
        init_waitqueue_head(&root->log_commit_wait[0]);
        init_waitqueue_head(&root->log_commit_wait[1]);
        INIT_LIST_HEAD(&root->log_ctxs[0]);
        INIT_LIST_HEAD(&root->log_ctxs[1]);
        atomic_set(&root->log_commit[0], 0);
        atomic_set(&root->log_commit[1], 0);
        atomic_set(&root->log_writers, 0);
        atomic_set(&root->log_batch, 0);
        refcount_set(&root->refs, 1);
        atomic_set(&root->will_be_snapshotted, 0);
        atomic_set(&root->snapshot_force_cow, 0);
        atomic_set(&root->nr_swapfiles, 0);
        root->log_transid = 0;
        root->log_transid_committed = -1;
        root->last_log_commit = 0;
        if (!dummy)
                extent_io_tree_init(fs_info, &root->dirty_log_pages,
                                    IO_TREE_ROOT_DIRTY_LOG_PAGES, NULL);

        memset(&root->root_key, 0, sizeof(root->root_key));
        memset(&root->root_item, 0, sizeof(root->root_item));
        memset(&root->defrag_progress, 0, sizeof(root->defrag_progress));
        if (!dummy)
                root->defrag_trans_start = fs_info->generation;
        else
                root->defrag_trans_start = 0;
        root->root_key.objectid = objectid;
        root->anon_dev = 0;

        spin_lock_init(&root->root_item_lock);
        btrfs_qgroup_init_swapped_blocks(&root->swapped_blocks);
}

static struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info,
                gfp_t flags)
{
        struct btrfs_root *root = kzalloc(sizeof(*root), flags);
        if (root)
                root->fs_info = fs_info;
        return root;
}

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
/* Should only be used by the testing infrastructure */
struct btrfs_root *btrfs_alloc_dummy_root(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;

        if (!fs_info)
                return ERR_PTR(-EINVAL);

        root = btrfs_alloc_root(fs_info, GFP_KERNEL);
        if (!root)
                return ERR_PTR(-ENOMEM);

        /* We don't use the stripesize in selftest, set it as sectorsize */
        __setup_root(root, fs_info, BTRFS_ROOT_TREE_OBJECTID);
        root->alloc_bytenr = 0;

        return root;
}
#endif

struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
                                     u64 objectid)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct extent_buffer *leaf;
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *root;
        struct btrfs_key key;
        unsigned int nofs_flag;
        int ret = 0;
        uuid_le uuid = NULL_UUID_LE;

        /*
         * We're holding a transaction handle, so use a NOFS memory allocation
         * context to avoid deadlock if reclaim happens.
         */
        nofs_flag = memalloc_nofs_save();
        root = btrfs_alloc_root(fs_info, GFP_KERNEL);
        memalloc_nofs_restore(nofs_flag);
        if (!root)
                return ERR_PTR(-ENOMEM);

        __setup_root(root, fs_info, objectid);
        root->root_key.objectid = objectid;
        root->root_key.type = BTRFS_ROOT_ITEM_KEY;
        root->root_key.offset = 0;

        leaf = btrfs_alloc_tree_block(trans, root, 0, objectid, NULL, 0, 0, 0);
        if (IS_ERR(leaf)) {
                ret = PTR_ERR(leaf);
                leaf = NULL;
                goto fail;
        }

        root->node = leaf;
        btrfs_mark_buffer_dirty(leaf);

        root->commit_root = btrfs_root_node(root);
        set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);

        root->root_item.flags = 0;
        root->root_item.byte_limit = 0;
        btrfs_set_root_bytenr(&root->root_item, leaf->start);
        btrfs_set_root_generation(&root->root_item, trans->transid);
        btrfs_set_root_level(&root->root_item, 0);
        btrfs_set_root_refs(&root->root_item, 1);
        btrfs_set_root_used(&root->root_item, leaf->len);
        btrfs_set_root_last_snapshot(&root->root_item, 0);
        btrfs_set_root_dirid(&root->root_item, 0);
        if (is_fstree(objectid))
                uuid_le_gen(&uuid);
        memcpy(root->root_item.uuid, uuid.b, BTRFS_UUID_SIZE);
        root->root_item.drop_level = 0;

        key.objectid = objectid;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_insert_root(trans, tree_root, &key, &root->root_item);
        if (ret)
                goto fail;

        btrfs_tree_unlock(leaf);

        return root;

fail:
        if (leaf) {
                btrfs_tree_unlock(leaf);
                free_extent_buffer(root->commit_root);
                free_extent_buffer(leaf);
        }
        kfree(root);

        return ERR_PTR(ret);
}

static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
                                         struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;
        struct extent_buffer *leaf;

        root = btrfs_alloc_root(fs_info, GFP_NOFS);
        if (!root)
                return ERR_PTR(-ENOMEM);

        __setup_root(root, fs_info, BTRFS_TREE_LOG_OBJECTID);

        root->root_key.objectid = BTRFS_TREE_LOG_OBJECTID;
        root->root_key.type = BTRFS_ROOT_ITEM_KEY;
        root->root_key.offset = BTRFS_TREE_LOG_OBJECTID;

        /*
         * DON'T set REF_COWS for log trees
         *
         * log trees do not get reference counted because they go away
         * before a real commit is actually done.  They do store pointers
         * to file data extents, and those reference counts still get
         * updated (along with back refs to the log tree).
         */

        leaf = btrfs_alloc_tree_block(trans, root, 0, BTRFS_TREE_LOG_OBJECTID,
                        NULL, 0, 0, 0);
        if (IS_ERR(leaf)) {
                kfree(root);
                return ERR_CAST(leaf);
        }

        root->node = leaf;

        btrfs_mark_buffer_dirty(root->node);
        btrfs_tree_unlock(root->node);
        return root;
}

int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
                             struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *log_root;

        log_root = alloc_log_tree(trans, fs_info);
        if (IS_ERR(log_root))
                return PTR_ERR(log_root);
        WARN_ON(fs_info->log_root_tree);
        fs_info->log_root_tree = log_root;
        return 0;
}

int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_root *log_root;
        struct btrfs_inode_item *inode_item;

        log_root = alloc_log_tree(trans, fs_info);
        if (IS_ERR(log_root))
                return PTR_ERR(log_root);

        log_root->last_trans = trans->transid;
        log_root->root_key.offset = root->root_key.objectid;

        inode_item = &log_root->root_item.inode;
        btrfs_set_stack_inode_generation(inode_item, 1);
        btrfs_set_stack_inode_size(inode_item, 3);
        btrfs_set_stack_inode_nlink(inode_item, 1);
        btrfs_set_stack_inode_nbytes(inode_item,
                                     fs_info->nodesize);
        btrfs_set_stack_inode_mode(inode_item, S_IFDIR | 0755);

        btrfs_set_root_node(&log_root->root_item, log_root->node);

        WARN_ON(root->log_root);
        root->log_root = log_root;
        root->log_transid = 0;
        root->log_transid_committed = -1;
        root->last_log_commit = 0;
        return 0;
}

static struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
                                               struct btrfs_key *key)
{
        struct btrfs_root *root;
        struct btrfs_fs_info *fs_info = tree_root->fs_info;
        struct btrfs_path *path;
        u64 generation;
        int ret;
        int level;

        path = btrfs_alloc_path();
        if (!path)
                return ERR_PTR(-ENOMEM);

        root = btrfs_alloc_root(fs_info, GFP_NOFS);
        if (!root) {
                ret = -ENOMEM;
                goto alloc_fail;
        }

        __setup_root(root, fs_info, key->objectid);

        ret = btrfs_find_root(tree_root, key, path,
                              &root->root_item, &root->root_key);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto find_fail;
        }

        generation = btrfs_root_generation(&root->root_item);
        level = btrfs_root_level(&root->root_item);
        root->node = read_tree_block(fs_info,
                                     btrfs_root_bytenr(&root->root_item),
                                     generation, level, NULL);
        if (IS_ERR(root->node)) {
                ret = PTR_ERR(root->node);
                goto find_fail;
        } else if (!btrfs_buffer_uptodate(root->node, generation, 0)) {
                ret = -EIO;
                free_extent_buffer(root->node);
                goto find_fail;
        }
        root->commit_root = btrfs_root_node(root);
out:
        btrfs_free_path(path);
        return root;

find_fail:
        kfree(root);
alloc_fail:
        root = ERR_PTR(ret);
        goto out;
}

struct btrfs_root *btrfs_read_fs_root(struct btrfs_root *tree_root,
                                      struct btrfs_key *location)
{
        struct btrfs_root *root;

        root = btrfs_read_tree_root(tree_root, location);
        if (IS_ERR(root))
                return root;

        if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
                set_bit(BTRFS_ROOT_REF_COWS, &root->state);
                btrfs_check_and_init_root_item(&root->root_item);
        }

        return root;
}

int btrfs_init_fs_root(struct btrfs_root *root)
{
        int ret;
        struct btrfs_subvolume_writers *writers;

        root->free_ino_ctl = kzalloc(sizeof(*root->free_ino_ctl), GFP_NOFS);
        root->free_ino_pinned = kzalloc(sizeof(*root->free_ino_pinned),
                                        GFP_NOFS);
        if (!root->free_ino_pinned || !root->free_ino_ctl) {
                ret = -ENOMEM;
                goto fail;
        }

        writers = btrfs_alloc_subvolume_writers();
        if (IS_ERR(writers)) {
                ret = PTR_ERR(writers);
                goto fail;
        }
        root->subv_writers = writers;

        btrfs_init_free_ino_ctl(root);
        spin_lock_init(&root->ino_cache_lock);
        init_waitqueue_head(&root->ino_cache_wait);

        ret = get_anon_bdev(&root->anon_dev);
        if (ret)
                goto fail;

        mutex_lock(&root->objectid_mutex);
        ret = btrfs_find_highest_objectid(root,
                                        &root->highest_objectid);
        if (ret) {
                mutex_unlock(&root->objectid_mutex);
                goto fail;
        }

        ASSERT(root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);

        mutex_unlock(&root->objectid_mutex);

        return 0;
fail:
        /* The caller is responsible to call btrfs_free_fs_root */
        return ret;
}

struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
                                        u64 root_id)
{
        struct btrfs_root *root;

        spin_lock(&fs_info->fs_roots_radix_lock);
        root = radix_tree_lookup(&fs_info->fs_roots_radix,
                                 (unsigned long)root_id);
        spin_unlock(&fs_info->fs_roots_radix_lock);
        return root;
}

int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
                         struct btrfs_root *root)
{
        int ret;

        ret = radix_tree_preload(GFP_NOFS);
        if (ret)
                return ret;

        spin_lock(&fs_info->fs_roots_radix_lock);
        ret = radix_tree_insert(&fs_info->fs_roots_radix,
                                (unsigned long)root->root_key.objectid,
                                root);
        if (ret == 0)
                set_bit(BTRFS_ROOT_IN_RADIX, &root->state);
        spin_unlock(&fs_info->fs_roots_radix_lock);
        radix_tree_preload_end();

        return ret;
}

struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
                                     struct btrfs_key *location,
                                     bool check_ref)
{
        struct btrfs_root *root;
        struct btrfs_path *path;
        struct btrfs_key key;
        int ret;

        if (location->objectid == BTRFS_ROOT_TREE_OBJECTID)
                return fs_info->tree_root;
        if (location->objectid == BTRFS_EXTENT_TREE_OBJECTID)
                return fs_info->extent_root;
        if (location->objectid == BTRFS_CHUNK_TREE_OBJECTID)
                return fs_info->chunk_root;
        if (location->objectid == BTRFS_DEV_TREE_OBJECTID)
                return fs_info->dev_root;
        if (location->objectid == BTRFS_CSUM_TREE_OBJECTID)
                return fs_info->csum_root;
        if (location->objectid == BTRFS_QUOTA_TREE_OBJECTID)
                return fs_info->quota_root ? fs_info->quota_root :
                                             ERR_PTR(-ENOENT);
        if (location->objectid == BTRFS_UUID_TREE_OBJECTID)
                return fs_info->uuid_root ? fs_info->uuid_root :
                                            ERR_PTR(-ENOENT);
        if (location->objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
                return fs_info->free_space_root ? fs_info->free_space_root :
                                                  ERR_PTR(-ENOENT);
again:
        root = btrfs_lookup_fs_root(fs_info, location->objectid);
        if (root) {
                if (check_ref && btrfs_root_refs(&root->root_item) == 0)
                        return ERR_PTR(-ENOENT);
                return root;
        }

        root = btrfs_read_fs_root(fs_info->tree_root, location);
        if (IS_ERR(root))
                return root;

        if (check_ref && btrfs_root_refs(&root->root_item) == 0) {
                ret = -ENOENT;
                goto fail;
        }

        ret = btrfs_init_fs_root(root);
        if (ret)
                goto fail;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto fail;
        }
        key.objectid = BTRFS_ORPHAN_OBJECTID;
        key.type = BTRFS_ORPHAN_ITEM_KEY;
        key.offset = location->objectid;

        ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
        btrfs_free_path(path);
        if (ret < 0)
                goto fail;
        if (ret == 0)
                set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);

        ret = btrfs_insert_fs_root(fs_info, root);
        if (ret) {
                if (ret == -EEXIST) {
                        btrfs_free_fs_root(root);
                        goto again;
                }
                goto fail;
        }
        return root;
fail:
        btrfs_free_fs_root(root);
        return ERR_PTR(ret);
}

static int btrfs_congested_fn(void *congested_data, int bdi_bits)
{
        struct btrfs_fs_info *info = (struct btrfs_fs_info *)congested_data;
        int ret = 0;
        struct btrfs_device *device;
        struct backing_dev_info *bdi;

        rcu_read_lock();
        list_for_each_entry_rcu(device, &info->fs_devices->devices, dev_list) {
                if (!device->bdev)
                        continue;
                bdi = device->bdev->bd_bdi;
                if (bdi_congested(bdi, bdi_bits)) {
                        ret = 1;
                        break;
                }
        }
        rcu_read_unlock();
        return ret;
}

/*
 * called by the kthread helper functions to finally call the bio end_io
 * functions.  This is where read checksum verification actually happens
 */
static void end_workqueue_fn(struct btrfs_work *work)
{
        struct bio *bio;
        struct btrfs_end_io_wq *end_io_wq;

        end_io_wq = container_of(work, struct btrfs_end_io_wq, work);
        bio = end_io_wq->bio;

        bio->bi_status = end_io_wq->status;
        bio->bi_private = end_io_wq->private;
        bio->bi_end_io = end_io_wq->end_io;
        kmem_cache_free(btrfs_end_io_wq_cache, end_io_wq);
        bio_endio(bio);
}

static int cleaner_kthread(void *arg)
{
        struct btrfs_root *root = arg;
        struct btrfs_fs_info *fs_info = root->fs_info;
        int again;

        while (1) {
                again = 0;

                set_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags);

                /* Make the cleaner go to sleep early. */
                if (btrfs_need_cleaner_sleep(fs_info))
                        goto sleep;

                /*
                 * Do not do anything if we might cause open_ctree() to block
                 * before we have finished mounting the filesystem.
                 */
                if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
                        goto sleep;

                if (!mutex_trylock(&fs_info->cleaner_mutex))
                        goto sleep;

                /*
                 * Avoid the problem that we change the status of the fs
                 * during the above check and trylock.
                 */
                if (btrfs_need_cleaner_sleep(fs_info)) {
                        mutex_unlock(&fs_info->cleaner_mutex);
                        goto sleep;
                }

                btrfs_run_delayed_iputs(fs_info);

                again = btrfs_clean_one_deleted_snapshot(root);
                mutex_unlock(&fs_info->cleaner_mutex);

                /*
                 * The defragger has dealt with the R/O remount and umount,
                 * needn't do anything special here.
                 */
                btrfs_run_defrag_inodes(fs_info);

                /*
                 * Acquires fs_info->delete_unused_bgs_mutex to avoid racing
                 * with relocation (btrfs_relocate_chunk) and relocation
                 * acquires fs_info->cleaner_mutex (btrfs_relocate_block_group)
                 * after acquiring fs_info->delete_unused_bgs_mutex. So we
                 * can't hold, nor need to, fs_info->cleaner_mutex when deleting
                 * unused block groups.
                 */
                btrfs_delete_unused_bgs(fs_info);
sleep:
                clear_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags);
                if (kthread_should_park())
                        kthread_parkme();
                if (kthread_should_stop())
                        return 0;
                if (!again) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        schedule();
                        __set_current_state(TASK_RUNNING);
                }
        }
}

static int transaction_kthread(void *arg)
{
        struct btrfs_root *root = arg;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_trans_handle *trans;
        struct btrfs_transaction *cur;
        u64 transid;
        time64_t now;
        unsigned long delay;
        bool cannot_commit;

        do {
                cannot_commit = false;
                delay = HZ * fs_info->commit_interval;
                mutex_lock(&fs_info->transaction_kthread_mutex);

                spin_lock(&fs_info->trans_lock);
                cur = fs_info->running_transaction;
                if (!cur) {
                        spin_unlock(&fs_info->trans_lock);
                        goto sleep;
                }

                now = ktime_get_seconds();
                if (cur->state < TRANS_STATE_BLOCKED &&
                    !test_bit(BTRFS_FS_NEED_ASYNC_COMMIT, &fs_info->flags) &&
                    (now < cur->start_time ||
                     now - cur->start_time < fs_info->commit_interval)) {
                        spin_unlock(&fs_info->trans_lock);
                        delay = HZ * 5;
                        goto sleep;
                }
                transid = cur->transid;
                spin_unlock(&fs_info->trans_lock);

                /* If the file system is aborted, this will always fail. */
                trans = btrfs_attach_transaction(root);
                if (IS_ERR(trans)) {
                        if (PTR_ERR(trans) != -ENOENT)
                                cannot_commit = true;
                        goto sleep;
                }
                if (transid == trans->transid) {
                        btrfs_commit_transaction(trans);
                } else {
                        btrfs_end_transaction(trans);
                }
sleep:
                wake_up_process(fs_info->cleaner_kthread);
                mutex_unlock(&fs_info->transaction_kthread_mutex);

                if (unlikely(test_bit(BTRFS_FS_STATE_ERROR,
                                      &fs_info->fs_state)))
                        btrfs_cleanup_transaction(fs_info);
                if (!kthread_should_stop() &&
                                (!btrfs_transaction_blocked(fs_info) ||
                                 cannot_commit))
                        schedule_timeout_interruptible(delay);
        } while (!kthread_should_stop());
        return 0;
}

/*
 * this will find the highest generation in the array of
 * root backups.  The index of the highest array is returned,
 * or -1 if we can't find anything.
 *
 * We check to make sure the array is valid by comparing the
 * generation of the latest  root in the array with the generation
 * in the super block.  If they don't match we pitch it.
 */
static int find_newest_super_backup(struct btrfs_fs_info *info, u64 newest_gen)
{
        u64 cur;
        int newest_index = -1;
        struct btrfs_root_backup *root_backup;
        int i;

        for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; i++) {
                root_backup = info->super_copy->super_roots + i;
                cur = btrfs_backup_tree_root_gen(root_backup);
                if (cur == newest_gen)
                        newest_index = i;
        }

        /* check to see if we actually wrapped around */
        if (newest_index == BTRFS_NUM_BACKUP_ROOTS - 1) {
                root_backup = info->super_copy->super_roots;
                cur = btrfs_backup_tree_root_gen(root_backup);
                if (cur == newest_gen)
                        newest_index = 0;
        }
        return newest_index;
}


/*
 * find the oldest backup so we know where to store new entries
 * in the backup array.  This will set the backup_root_index
 * field in the fs_info struct
 */
static void find_oldest_super_backup(struct btrfs_fs_info *info,
                                     u64 newest_gen)
{
        int newest_index = -1;

        newest_index = find_newest_super_backup(info, newest_gen);
        /* if there was garbage in there, just move along */
        if (newest_index == -1) {
                info->backup_root_index = 0;
        } else {
                info->backup_root_index = (newest_index + 1) % BTRFS_NUM_BACKUP_ROOTS;
        }
}

/*
 * copy all the root pointers into the super backup array.
 * this will bump the backup pointer by one when it is
 * done
 */
static void backup_super_roots(struct btrfs_fs_info *info)
{
        int next_backup;
        struct btrfs_root_backup *root_backup;
        int last_backup;

        next_backup = info->backup_root_index;
        last_backup = (next_backup + BTRFS_NUM_BACKUP_ROOTS - 1) %
                BTRFS_NUM_BACKUP_ROOTS;

        /*
         * just overwrite the last backup if we're at the same generation
         * this happens only at umount
         */
        root_backup = info->super_for_commit->super_roots + last_backup;
        if (btrfs_backup_tree_root_gen(root_backup) ==
            btrfs_header_generation(info->tree_root->node))
                next_backup = last_backup;

        root_backup = info->super_for_commit->super_roots + next_backup;

        /*
         * make sure all of our padding and empty slots get zero filled
         * regardless of which ones we use today
         */
        memset(root_backup, 0, sizeof(*root_backup));

        info->backup_root_index = (next_backup + 1) % BTRFS_NUM_BACKUP_ROOTS;

        btrfs_set_backup_tree_root(root_backup, info->tree_root->node->start);
        btrfs_set_backup_tree_root_gen(root_backup,
                               btrfs_header_generation(info->tree_root->node));

        btrfs_set_backup_tree_root_level(root_backup,
                               btrfs_header_level(info->tree_root->node));

        btrfs_set_backup_chunk_root(root_backup, info->chunk_root->node->start);
        btrfs_set_backup_chunk_root_gen(root_backup,
                               btrfs_header_generation(info->chunk_root->node));
        btrfs_set_backup_chunk_root_level(root_backup,
                               btrfs_header_level(info->chunk_root->node));

        btrfs_set_backup_extent_root(root_backup, info->extent_root->node->start);
        btrfs_set_backup_extent_root_gen(root_backup,
                               btrfs_header_generation(info->extent_root->node));
        btrfs_set_backup_extent_root_level(root_backup,
                               btrfs_header_level(info->extent_root->node));

        /*
         * we might commit during log recovery, which happens before we set
         * the fs_root.  Make sure it is valid before we fill it in.
         */
        if (info->fs_root && info->fs_root->node) {
                btrfs_set_backup_fs_root(root_backup,
                                         info->fs_root->node->start);
                btrfs_set_backup_fs_root_gen(root_backup,
                               btrfs_header_generation(info->fs_root->node));
                btrfs_set_backup_fs_root_level(root_backup,
                               btrfs_header_level(info->fs_root->node));
        }

        btrfs_set_backup_dev_root(root_backup, info->dev_root->node->start);
        btrfs_set_backup_dev_root_gen(root_backup,
                               btrfs_header_generation(info->dev_root->node));
        btrfs_set_backup_dev_root_level(root_backup,
                                       btrfs_header_level(info->dev_root->node));

        btrfs_set_backup_csum_root(root_backup, info->csum_root->node->start);
        btrfs_set_backup_csum_root_gen(root_backup,
                               btrfs_header_generation(info->csum_root->node));
        btrfs_set_backup_csum_root_level(root_backup,
                               btrfs_header_level(info->csum_root->node));

        btrfs_set_backup_total_bytes(root_backup,
                             btrfs_super_total_bytes(info->super_copy));
        btrfs_set_backup_bytes_used(root_backup,
                             btrfs_super_bytes_used(info->super_copy));
        btrfs_set_backup_num_devices(root_backup,
                             btrfs_super_num_devices(info->super_copy));

        /*
         * if we don't copy this out to the super_copy, it won't get remembered
         * for the next commit
         */
        memcpy(&info->super_copy->super_roots,
               &info->super_for_commit->super_roots,
               sizeof(*root_backup) * BTRFS_NUM_BACKUP_ROOTS);
}

/*
 * this copies info out of the root backup array and back into
 * the in-memory super block.  It is meant to help iterate through
 * the array, so you send it the number of backups you've already
 * tried and the last backup index you used.
 *
 * this returns -1 when it has tried all the backups
 */
static noinline int next_root_backup(struct btrfs_fs_info *info,
                                     struct btrfs_super_block *super,
                                     int *num_backups_tried, int *backup_index)
{
        struct btrfs_root_backup *root_backup;
        int newest = *backup_index;

        if (*num_backups_tried == 0) {
                u64 gen = btrfs_super_generation(super);

                newest = find_newest_super_backup(info, gen);
                if (newest == -1)
                        return -1;

                *backup_index = newest;
                *num_backups_tried = 1;
        } else if (*num_backups_tried == BTRFS_NUM_BACKUP_ROOTS) {
                /* we've tried all the backups, all done */
                return -1;
        } else {
                /* jump to the next oldest backup */
                newest = (*backup_index + BTRFS_NUM_BACKUP_ROOTS - 1) %
                        BTRFS_NUM_BACKUP_ROOTS;
                *backup_index = newest;
                *num_backups_tried += 1;
        }
        root_backup = super->super_roots + newest;

        btrfs_set_super_generation(super,
                                   btrfs_backup_tree_root_gen(root_backup));
        btrfs_set_super_root(super, btrfs_backup_tree_root(root_backup));
        btrfs_set_super_root_level(super,
                                   btrfs_backup_tree_root_level(root_backup));
        btrfs_set_super_bytes_used(super, btrfs_backup_bytes_used(root_backup));

        /*
         * fixme: the total bytes and num_devices need to match or we should
         * need a fsck
         */
        btrfs_set_super_total_bytes(super, btrfs_backup_total_bytes(root_backup));
        btrfs_set_super_num_devices(super, btrfs_backup_num_devices(root_backup));
        return 0;
}

/* helper to cleanup workers */
static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
{
        btrfs_destroy_workqueue(fs_info->fixup_workers);
        btrfs_destroy_workqueue(fs_info->delalloc_workers);
        btrfs_destroy_workqueue(fs_info->workers);
        btrfs_destroy_workqueue(fs_info->endio_workers);
        btrfs_destroy_workqueue(fs_info->endio_raid56_workers);
        btrfs_destroy_workqueue(fs_info->endio_repair_workers);
        btrfs_destroy_workqueue(fs_info->rmw_workers);
        btrfs_destroy_workqueue(fs_info->endio_write_workers);
        btrfs_destroy_workqueue(fs_info->endio_freespace_worker);
        btrfs_destroy_workqueue(fs_info->submit_workers);
        btrfs_destroy_workqueue(fs_info->delayed_workers);
        btrfs_destroy_workqueue(fs_info->caching_workers);
        btrfs_destroy_workqueue(fs_info->readahead_workers);
        btrfs_destroy_workqueue(fs_info->flush_workers);
        btrfs_destroy_workqueue(fs_info->qgroup_rescan_workers);
        btrfs_destroy_workqueue(fs_info->extent_workers);
        /*
         * Now that all other work queues are destroyed, we can safely destroy
         * the queues used for metadata I/O, since tasks from those other work
         * queues can do metadata I/O operations.
         */
        btrfs_destroy_workqueue(fs_info->endio_meta_workers);
        btrfs_destroy_workqueue(fs_info->endio_meta_write_workers);
}

static void free_root_extent_buffers(struct btrfs_root *root)
{
        if (root) {
                free_extent_buffer(root->node);
                free_extent_buffer(root->commit_root);
                root->node = NULL;
                root->commit_root = NULL;
        }
}

/* helper to cleanup tree roots */
static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
{
        free_root_extent_buffers(info->tree_root);

        free_root_extent_buffers(info->dev_root);
        free_root_extent_buffers(info->extent_root);
        free_root_extent_buffers(info->csum_root);
        free_root_extent_buffers(info->quota_root);
        free_root_extent_buffers(info->uuid_root);
        if (chunk_root)
                free_root_extent_buffers(info->chunk_root);
        free_root_extent_buffers(info->free_space_root);
}

void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info)
{
        int ret;
        struct btrfs_root *gang[8];
        int i;

        while (!list_empty(&fs_info->dead_roots)) {
                gang[0] = list_entry(fs_info->dead_roots.next,
                                     struct btrfs_root, root_list);
                list_del(&gang[0]->root_list);

                if (test_bit(BTRFS_ROOT_IN_RADIX, &gang[0]->state)) {
                        btrfs_drop_and_free_fs_root(fs_info, gang[0]);
                } else {
                        free_extent_buffer(gang[0]->node);
                        free_extent_buffer(gang[0]->commit_root);
                        btrfs_put_fs_root(gang[0]);
                }
        }

        while (1) {
                ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
                                             (void **)gang, 0,
                                             ARRAY_SIZE(gang));
                if (!ret)
                        break;
                for (i = 0; i < ret; i++)
                        btrfs_drop_and_free_fs_root(fs_info, gang[i]);
        }

        if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
                btrfs_free_log_root_tree(NULL, fs_info);
                btrfs_destroy_pinned_extent(fs_info, fs_info->pinned_extents);
        }
}

static void btrfs_init_scrub(struct btrfs_fs_info *fs_info)
{
        mutex_init(&fs_info->scrub_lock);
        atomic_set(&fs_info->scrubs_running, 0);
        atomic_set(&fs_info->scrub_pause_req, 0);
        atomic_set(&fs_info->scrubs_paused, 0);
        atomic_set(&fs_info->scrub_cancel_req, 0);
        init_waitqueue_head(&fs_info->scrub_pause_wait);
        refcount_set(&fs_info->scrub_workers_refcnt, 0);
}

static void btrfs_init_balance(struct btrfs_fs_info *fs_info)
{
        spin_lock_init(&fs_info->balance_lock);
        mutex_init(&fs_info->balance_mutex);
        atomic_set(&fs_info->balance_pause_req, 0);
        atomic_set(&fs_info->balance_cancel_req, 0);
        fs_info->balance_ctl = NULL;
        init_waitqueue_head(&fs_info->balance_wait_q);
}

static void btrfs_init_btree_inode(struct btrfs_fs_info *fs_info)
{
        struct inode *inode = fs_info->btree_inode;

        inode->i_ino = BTRFS_BTREE_INODE_OBJECTID;
        set_nlink(inode, 1);
        /*
         * we set the i_size on the btree inode to the max possible int.
         * the real end of the address space is determined by all of
         * the devices in the system
         */
        inode->i_size = OFFSET_MAX;
        inode->i_mapping->a_ops = &btree_aops;

        RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
        extent_io_tree_init(fs_info, &BTRFS_I(inode)->io_tree,
                            IO_TREE_INODE_IO, inode);
        BTRFS_I(inode)->io_tree.track_uptodate = false;
        extent_map_tree_init(&BTRFS_I(inode)->extent_tree);

        BTRFS_I(inode)->io_tree.ops = &btree_extent_io_ops;

        BTRFS_I(inode)->root = fs_info->tree_root;
        memset(&BTRFS_I(inode)->location, 0, sizeof(struct btrfs_key));
        set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
        btrfs_insert_inode_hash(inode);
}

static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info)
{
        mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount);
        init_rwsem(&fs_info->dev_replace.rwsem);
        init_waitqueue_head(&fs_info->dev_replace.replace_wait);
}

static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info)
{
        spin_lock_init(&fs_info->qgroup_lock);
        mutex_init(&fs_info->qgroup_ioctl_lock);
        fs_info->qgroup_tree = RB_ROOT;
        INIT_LIST_HEAD(&fs_info->dirty_qgroups);
        fs_info->qgroup_seq = 1;
        fs_info->qgroup_ulist = NULL;
        fs_info->qgroup_rescan_running = false;
        mutex_init(&fs_info->qgroup_rescan_lock);
}

static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
                struct btrfs_fs_devices *fs_devices)
{
        u32 max_active = fs_info->thread_pool_size;
        unsigned int flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND;

        fs_info->workers =
                btrfs_alloc_workqueue(fs_info, "worker",
                                      flags | WQ_HIGHPRI, max_active, 16);

        fs_info->delalloc_workers =
                btrfs_alloc_workqueue(fs_info, "delalloc",
                                      flags, max_active, 2);

        fs_info->flush_workers =
                btrfs_alloc_workqueue(fs_info, "flush_delalloc",
                                      flags, max_active, 0);

        fs_info->caching_workers =
                btrfs_alloc_workqueue(fs_info, "cache", flags, max_active, 0);

        /*
         * a higher idle thresh on the submit workers makes it much more
         * likely that bios will be send down in a sane order to the
         * devices
         */
        fs_info->submit_workers =
                btrfs_alloc_workqueue(fs_info, "submit", flags,
                                      min_t(u64, fs_devices->num_devices,
                                            max_active), 64);

        fs_info->fixup_workers =
                btrfs_alloc_workqueue(fs_info, "fixup", flags, 1, 0);

        /*
         * endios are largely parallel and should have a very
         * low idle thresh
         */
        fs_info->endio_workers =
                btrfs_alloc_workqueue(fs_info, "endio", flags, max_active, 4);
        fs_info->endio_meta_workers =
                btrfs_alloc_workqueue(fs_info, "endio-meta", flags,
                                      max_active, 4);
        fs_info->endio_meta_write_workers =
                btrfs_alloc_workqueue(fs_info, "endio-meta-write", flags,
                                      max_active, 2);
        fs_info->endio_raid56_workers =
                btrfs_alloc_workqueue(fs_info, "endio-raid56", flags,
                                      max_active, 4);
        fs_info->endio_repair_workers =
                btrfs_alloc_workqueue(fs_info, "endio-repair", flags, 1, 0);
        fs_info->rmw_workers =
                btrfs_alloc_workqueue(fs_info, "rmw", flags, max_active, 2);
        fs_info->endio_write_workers =
                btrfs_alloc_workqueue(fs_info, "endio-write", flags,
                                      max_active, 2);
        fs_info->endio_freespace_worker =
                btrfs_alloc_workqueue(fs_info, "freespace-write", flags,
                                      max_active, 0);
        fs_info->delayed_workers =
                btrfs_alloc_workqueue(fs_info, "delayed-meta", flags,
                                      max_active, 0);
        fs_info->readahead_workers =
                btrfs_alloc_workqueue(fs_info, "readahead", flags,
                                      max_active, 2);
        fs_info->qgroup_rescan_workers =
                btrfs_alloc_workqueue(fs_info, "qgroup-rescan", flags, 1, 0);
        fs_info->extent_workers =
                btrfs_alloc_workqueue(fs_info, "extent-refs", flags,
                                      min_t(u64, fs_devices->num_devices,
                                            max_active), 8);

        if (!(fs_info->workers && fs_info->delalloc_workers &&
              fs_info->submit_workers && fs_info->flush_workers &&
              fs_info->endio_workers && fs_info->endio_meta_workers &&
              fs_info->endio_meta_write_workers &&
              fs_info->endio_repair_workers &&
              fs_info->endio_write_workers && fs_info->endio_raid56_workers &&
              fs_info->endio_freespace_worker && fs_info->rmw_workers &&
              fs_info->caching_workers && fs_info->readahead_workers &&
              fs_info->fixup_workers && fs_info->delayed_workers &&
              fs_info->extent_workers &&
              fs_info->qgroup_rescan_workers)) {
                return -ENOMEM;
        }

        return 0;
}

static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
                            struct btrfs_fs_devices *fs_devices)
{
        int ret;
        struct btrfs_root *log_tree_root;
        struct btrfs_super_block *disk_super = fs_info->super_copy;
        u64 bytenr = btrfs_super_log_root(disk_super);
        int level = btrfs_super_log_root_level(disk_super);

        if (fs_devices->rw_devices == 0) {
                btrfs_warn(fs_info, "log replay required on RO media");
                return -EIO;
        }

        log_tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
        if (!log_tree_root)
                return -ENOMEM;

        __setup_root(log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);

        log_tree_root->node = read_tree_block(fs_info, bytenr,
                                              fs_info->generation + 1,
                                              level, NULL);
        if (IS_ERR(log_tree_root->node)) {
                btrfs_warn(fs_info, "failed to read log tree");
                ret = PTR_ERR(log_tree_root->node);
                kfree(log_tree_root);
                return ret;
        } else if (!extent_buffer_uptodate(log_tree_root->node)) {
                btrfs_err(fs_info, "failed to read log tree");
                free_extent_buffer(log_tree_root->node);
                kfree(log_tree_root);
                return -EIO;
        }
        /* returns with log_tree_root freed on success */
        ret = btrfs_recover_log_trees(log_tree_root);
        if (ret) {
                btrfs_handle_fs_error(fs_info, ret,
                                      "Failed to recover log tree");
                free_extent_buffer(log_tree_root->node);
                kfree(log_tree_root);
                return ret;
        }

        if (sb_rdonly(fs_info->sb)) {
                ret = btrfs_commit_super(fs_info);
                if (ret)
                        return ret;
        }

        return 0;
}

static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *root;
        struct btrfs_key location;
        int ret;

        BUG_ON(!fs_info->tree_root);

        location.objectid = BTRFS_EXTENT_TREE_OBJECTID;
        location.type = BTRFS_ROOT_ITEM_KEY;
        location.offset = 0;

        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                ret = PTR_ERR(root);
                goto out;
        }
        set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
        fs_info->extent_root = root;

        location.objectid = BTRFS_DEV_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                ret = PTR_ERR(root);
                goto out;
        }
        set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
        fs_info->dev_root = root;
        btrfs_init_devices_late(fs_info);

        location.objectid = BTRFS_CSUM_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                ret = PTR_ERR(root);
                goto out;
        }
        set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
        fs_info->csum_root = root;

        location.objectid = BTRFS_QUOTA_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (!IS_ERR(root)) {
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
                fs_info->quota_root = root;
        }

        location.objectid = BTRFS_UUID_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                ret = PTR_ERR(root);
                if (ret != -ENOENT)
                        goto out;
        } else {
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                fs_info->uuid_root = root;
        }

        if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                location.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID;
                root = btrfs_read_tree_root(tree_root, &location);
                if (IS_ERR(root)) {
                        ret = PTR_ERR(root);
                        goto out;
                }
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                fs_info->free_space_root = root;
        }

        return 0;
out:
        btrfs_warn(fs_info, "failed to read root (objectid=%llu): %d",
                   location.objectid, ret);
        return ret;
}

/*
 * Real super block validation
 * NOTE: super csum type and incompat features will not be checked here.
 *
 * @sb:         super block to check
 * @mirror_num: the super block number to check its bytenr:
 *              0       the primary (1st) sb
 *              1, 2    2nd and 3rd backup copy
 *             -1       skip bytenr check
 */
static int validate_super(struct btrfs_fs_info *fs_info,
                            struct btrfs_super_block *sb, int mirror_num)
{
        u64 nodesize = btrfs_super_nodesize(sb);
        u64 sectorsize = btrfs_super_sectorsize(sb);
        int ret = 0;

        if (btrfs_super_magic(sb) != BTRFS_MAGIC) {
                btrfs_err(fs_info, "no valid FS found");
                ret = -EINVAL;
        }
        if (btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP) {
                btrfs_err(fs_info, "unrecognized or unsupported super flag: %llu",
                                btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
                ret = -EINVAL;
        }
        if (btrfs_super_root_level(sb) >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "tree_root level too big: %d >= %d",
                                btrfs_super_root_level(sb), BTRFS_MAX_LEVEL);
                ret = -EINVAL;
        }
        if (btrfs_super_chunk_root_level(sb) >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "chunk_root level too big: %d >= %d",
                                btrfs_super_chunk_root_level(sb), BTRFS_MAX_LEVEL);
                ret = -EINVAL;
        }
        if (btrfs_super_log_root_level(sb) >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "log_root level too big: %d >= %d",
                                btrfs_super_log_root_level(sb), BTRFS_MAX_LEVEL);
                ret = -EINVAL;
        }

        /*
         * Check sectorsize and nodesize first, other check will need it.
         * Check all possible sectorsize(4K, 8K, 16K, 32K, 64K) here.
         */
        if (!is_power_of_2(sectorsize) || sectorsize < 4096 ||
            sectorsize > BTRFS_MAX_METADATA_BLOCKSIZE) {
                btrfs_err(fs_info, "invalid sectorsize %llu", sectorsize);
                ret = -EINVAL;
        }
        /* Only PAGE SIZE is supported yet */
        if (sectorsize != PAGE_SIZE) {
                btrfs_err(fs_info,
                        "sectorsize %llu not supported yet, only support %lu",
                        sectorsize, PAGE_SIZE);
                ret = -EINVAL;
        }
        if (!is_power_of_2(nodesize) || nodesize < sectorsize ||
            nodesize > BTRFS_MAX_METADATA_BLOCKSIZE) {
                btrfs_err(fs_info, "invalid nodesize %llu", nodesize);
                ret = -EINVAL;
        }
        if (nodesize != le32_to_cpu(sb->__unused_leafsize)) {
                btrfs_err(fs_info, "invalid leafsize %u, should be %llu",
                          le32_to_cpu(sb->__unused_leafsize), nodesize);
                ret = -EINVAL;
        }

        /* Root alignment check */
        if (!IS_ALIGNED(btrfs_super_root(sb), sectorsize)) {
                btrfs_warn(fs_info, "tree_root block unaligned: %llu",
                           btrfs_super_root(sb));
                ret = -EINVAL;
        }
        if (!IS_ALIGNED(btrfs_super_chunk_root(sb), sectorsize)) {
                btrfs_warn(fs_info, "chunk_root block unaligned: %llu",
                           btrfs_super_chunk_root(sb));
                ret = -EINVAL;
        }
        if (!IS_ALIGNED(btrfs_super_log_root(sb), sectorsize)) {
                btrfs_warn(fs_info, "log_root block unaligned: %llu",
                           btrfs_super_log_root(sb));
                ret = -EINVAL;
        }

        if (memcmp(fs_info->fs_devices->metadata_uuid, sb->dev_item.fsid,
                   BTRFS_FSID_SIZE) != 0) {
                btrfs_err(fs_info,
                        "dev_item UUID does not match metadata fsid: %pU != %pU",
                        fs_info->fs_devices->metadata_uuid, sb->dev_item.fsid);
                ret = -EINVAL;
        }

        /*
         * Hint to catch really bogus numbers, bitflips or so, more exact checks are
         * done later
         */
        if (btrfs_super_bytes_used(sb) < 6 * btrfs_super_nodesize(sb)) {
                btrfs_err(fs_info, "bytes_used is too small %llu",
                          btrfs_super_bytes_used(sb));
                ret = -EINVAL;
        }
        if (!is_power_of_2(btrfs_super_stripesize(sb))) {
                btrfs_err(fs_info, "invalid stripesize %u",
                          btrfs_super_stripesize(sb));
                ret = -EINVAL;
        }
        if (btrfs_super_num_devices(sb) > (1UL << 31))
                btrfs_warn(fs_info, "suspicious number of devices: %llu",
                           btrfs_super_num_devices(sb));
        if (btrfs_super_num_devices(sb) == 0) {
                btrfs_err(fs_info, "number of devices is 0");
                ret = -EINVAL;
        }

        if (mirror_num >= 0 &&
            btrfs_super_bytenr(sb) != btrfs_sb_offset(mirror_num)) {
                btrfs_err(fs_info, "super offset mismatch %llu != %u",
                          btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
                ret = -EINVAL;
        }

        /*
         * Obvious sys_chunk_array corruptions, it must hold at least one key
         * and one chunk
         */
        if (btrfs_super_sys_array_size(sb) > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
                btrfs_err(fs_info, "system chunk array too big %u > %u",
                          btrfs_super_sys_array_size(sb),
                          BTRFS_SYSTEM_CHUNK_ARRAY_SIZE);
                ret = -EINVAL;
        }
        if (btrfs_super_sys_array_size(sb) < sizeof(struct btrfs_disk_key)
                        + sizeof(struct btrfs_chunk)) {
                btrfs_err(fs_info, "system chunk array too small %u < %zu",
                          btrfs_super_sys_array_size(sb),
                          sizeof(struct btrfs_disk_key)
                          + sizeof(struct btrfs_chunk));
                ret = -EINVAL;
        }

        /*
         * The generation is a global counter, we'll trust it more than the others
         * but it's still possible that it's the one that's wrong.
         */
        if (btrfs_super_generation(sb) < btrfs_super_chunk_root_generation(sb))
                btrfs_warn(fs_info,
                        "suspicious: generation < chunk_root_generation: %llu < %llu",
                        btrfs_super_generation(sb),
                        btrfs_super_chunk_root_generation(sb));
        if (btrfs_super_generation(sb) < btrfs_super_cache_generation(sb)
            && btrfs_super_cache_generation(sb) != (u64)-1)
                btrfs_warn(fs_info,
                        "suspicious: generation < cache_generation: %llu < %llu",
                        btrfs_super_generation(sb),
                        btrfs_super_cache_generation(sb));

        return ret;
}

/*
 * Validation of super block at mount time.
 * Some checks already done early at mount time, like csum type and incompat
 * flags will be skipped.
 */
static int btrfs_validate_mount_super(struct btrfs_fs_info *fs_info)
{
        return validate_super(fs_info, fs_info->super_copy, 0);
}

/*
 * Validation of super block at write time.
 * Some checks like bytenr check will be skipped as their values will be
 * overwritten soon.
 * Extra checks like csum type and incompat flags will be done here.
 */
static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
                                      struct btrfs_super_block *sb)
{
        int ret;

        ret = validate_super(fs_info, sb, -1);
        if (ret < 0)
                goto out;
        if (!btrfs_supported_super_csum(btrfs_super_csum_type(sb))) {
                ret = -EUCLEAN;
                btrfs_err(fs_info, "invalid csum type, has %u want %u",
                          btrfs_super_csum_type(sb), BTRFS_CSUM_TYPE_CRC32);
                goto out;
        }
        if (btrfs_super_incompat_flags(sb) & ~BTRFS_FEATURE_INCOMPAT_SUPP) {
                ret = -EUCLEAN;
                btrfs_err(fs_info,
                "invalid incompat flags, has 0x%llx valid mask 0x%llx",
                          btrfs_super_incompat_flags(sb),
                          (unsigned long long)BTRFS_FEATURE_INCOMPAT_SUPP);
                goto out;
        }
out:
        if (ret < 0)
                btrfs_err(fs_info,
                "super block corruption detected before writing it to disk");
        return ret;
}

int open_ctree(struct super_block *sb,
               struct btrfs_fs_devices *fs_devices,
               char *options)
{
        u32 sectorsize;
        u32 nodesize;
        u32 stripesize;
        u64 generation;
        u64 features;
        u16 csum_type;
        struct btrfs_key location;
        struct buffer_head *bh;
        struct btrfs_super_block *disk_super;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *tree_root;
        struct btrfs_root *chunk_root;
        int ret;
        int err = -EINVAL;
        int num_backups_tried = 0;
        int backup_index = 0;
        int clear_free_space_tree = 0;
        int level;

        tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
        chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
        if (!tree_root || !chunk_root) {
                err = -ENOMEM;
                goto fail;
        }

        ret = init_srcu_struct(&fs_info->subvol_srcu);
        if (ret) {
                err = ret;
                goto fail;
        }

        ret = percpu_counter_init(&fs_info->dio_bytes, 0, GFP_KERNEL);
        if (ret) {
                err = ret;
                goto fail_srcu;
        }

        ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0, GFP_KERNEL);
        if (ret) {
                err = ret;
                goto fail_dio_bytes;
        }
        fs_info->dirty_metadata_batch = PAGE_SIZE *
                                        (1 + ilog2(nr_cpu_ids));

        ret = percpu_counter_init(&fs_info->delalloc_bytes, 0, GFP_KERNEL);
        if (ret) {
                err = ret;
                goto fail_dirty_metadata_bytes;
        }

        ret = percpu_counter_init(&fs_info->dev_replace.bio_counter, 0,
                        GFP_KERNEL);
        if (ret) {
                err = ret;
                goto fail_delalloc_bytes;
        }

        INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
        INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
        INIT_LIST_HEAD(&fs_info->trans_list);
        INIT_LIST_HEAD(&fs_info->dead_roots);
        INIT_LIST_HEAD(&fs_info->delayed_iputs);
        INIT_LIST_HEAD(&fs_info->delalloc_roots);
        INIT_LIST_HEAD(&fs_info->caching_block_groups);
        INIT_LIST_HEAD(&fs_info->pending_raid_kobjs);
        spin_lock_init(&fs_info->pending_raid_kobjs_lock);
        spin_lock_init(&fs_info->delalloc_root_lock);
        spin_lock_init(&fs_info->trans_lock);
        spin_lock_init(&fs_info->fs_roots_radix_lock);
        spin_lock_init(&fs_info->delayed_iput_lock);
        spin_lock_init(&fs_info->defrag_inodes_lock);
        spin_lock_init(&fs_info->tree_mod_seq_lock);
        spin_lock_init(&fs_info->super_lock);
        spin_lock_init(&fs_info->buffer_lock);
        spin_lock_init(&fs_info->unused_bgs_lock);
        rwlock_init(&fs_info->tree_mod_log_lock);
        mutex_init(&fs_info->unused_bg_unpin_mutex);
        mutex_init(&fs_info->delete_unused_bgs_mutex);
        mutex_init(&fs_info->reloc_mutex);
        mutex_init(&fs_info->delalloc_root_mutex);
        seqlock_init(&fs_info->profiles_lock);

        INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);
        INIT_LIST_HEAD(&fs_info->space_info);
        INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
        INIT_LIST_HEAD(&fs_info->unused_bgs);
        extent_map_tree_init(&fs_info->mapping_tree);
        btrfs_init_block_rsv(&fs_info->global_block_rsv,
                             BTRFS_BLOCK_RSV_GLOBAL);
        btrfs_init_block_rsv(&fs_info->trans_block_rsv, BTRFS_BLOCK_RSV_TRANS);
        btrfs_init_block_rsv(&fs_info->chunk_block_rsv, BTRFS_BLOCK_RSV_CHUNK);
        btrfs_init_block_rsv(&fs_info->empty_block_rsv, BTRFS_BLOCK_RSV_EMPTY);
        btrfs_init_block_rsv(&fs_info->delayed_block_rsv,
                             BTRFS_BLOCK_RSV_DELOPS);
        btrfs_init_block_rsv(&fs_info->delayed_refs_rsv,
                             BTRFS_BLOCK_RSV_DELREFS);

        atomic_set(&fs_info->async_delalloc_pages, 0);
        atomic_set(&fs_info->defrag_running, 0);
        atomic_set(&fs_info->reada_works_cnt, 0);
        atomic_set(&fs_info->nr_delayed_iputs, 0);
        atomic64_set(&fs_info->tree_mod_seq, 0);
        fs_info->sb = sb;
        fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE;
        fs_info->metadata_ratio = 0;
        fs_info->defrag_inodes = RB_ROOT;
        atomic64_set(&fs_info->free_chunk_space, 0);
        fs_info->tree_mod_log = RB_ROOT;
        fs_info->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
        fs_info->avg_delayed_ref_runtime = NSEC_PER_SEC >> 6; /* div by 64 */
        /* readahead state */
        INIT_RADIX_TREE(&fs_info->reada_tree, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
        spin_lock_init(&fs_info->reada_lock);
        btrfs_init_ref_verify(fs_info);

        fs_info->thread_pool_size = min_t(unsigned long,
                                          num_online_cpus() + 2, 8);

        INIT_LIST_HEAD(&fs_info->ordered_roots);
        spin_lock_init(&fs_info->ordered_root_lock);

        fs_info->btree_inode = new_inode(sb);
        if (!fs_info->btree_inode) {
                err = -ENOMEM;
                goto fail_bio_counter;
        }
        mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);

        fs_info->delayed_root = kmalloc(sizeof(struct btrfs_delayed_root),
                                        GFP_KERNEL);
        if (!fs_info->delayed_root) {
                err = -ENOMEM;
                goto fail_iput;
        }
        btrfs_init_delayed_root(fs_info->delayed_root);

        btrfs_init_scrub(fs_info);
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        fs_info->check_integrity_print_mask = 0;
#endif
        btrfs_init_balance(fs_info);
        btrfs_init_async_reclaim_work(&fs_info->async_reclaim_work);

        sb->s_blocksize = BTRFS_BDEV_BLOCKSIZE;
        sb->s_blocksize_bits = blksize_bits(BTRFS_BDEV_BLOCKSIZE);

        btrfs_init_btree_inode(fs_info);

        spin_lock_init(&fs_info->block_group_cache_lock);
        fs_info->block_group_cache_tree = RB_ROOT;
        fs_info->first_logical_byte = (u64)-1;

        extent_io_tree_init(fs_info, &fs_info->freed_extents[0],
                            IO_TREE_FS_INFO_FREED_EXTENTS0, NULL);
        extent_io_tree_init(fs_info, &fs_info->freed_extents[1],
                            IO_TREE_FS_INFO_FREED_EXTENTS1, NULL);
        fs_info->pinned_extents = &fs_info->freed_extents[0];
        set_bit(BTRFS_FS_BARRIER, &fs_info->flags);

        mutex_init(&fs_info->ordered_operations_mutex);
        mutex_init(&fs_info->tree_log_mutex);
        mutex_init(&fs_info->chunk_mutex);
        mutex_init(&fs_info->transaction_kthread_mutex);
        mutex_init(&fs_info->cleaner_mutex);
        mutex_init(&fs_info->ro_block_group_mutex);
        init_rwsem(&fs_info->commit_root_sem);
        init_rwsem(&fs_info->cleanup_work_sem);
        init_rwsem(&fs_info->subvol_sem);
        sema_init(&fs_info->uuid_tree_rescan_sem, 1);

        btrfs_init_dev_replace_locks(fs_info);
        btrfs_init_qgroup(fs_info);

        btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
        btrfs_init_free_cluster(&fs_info->data_alloc_cluster);

        init_waitqueue_head(&fs_info->transaction_throttle);
        init_waitqueue_head(&fs_info->transaction_wait);
        init_waitqueue_head(&fs_info->transaction_blocked_wait);
        init_waitqueue_head(&fs_info->async_submit_wait);
        init_waitqueue_head(&fs_info->delayed_iputs_wait);

        /* Usable values until the real ones are cached from the superblock */
        fs_info->nodesize = 4096;
        fs_info->sectorsize = 4096;
        fs_info->stripesize = 4096;

        spin_lock_init(&fs_info->swapfile_pins_lock);
        fs_info->swapfile_pins = RB_ROOT;

        ret = btrfs_alloc_stripe_hash_table(fs_info);
        if (ret) {
                err = ret;
                goto fail_alloc;
        }

        __setup_root(tree_root, fs_info, BTRFS_ROOT_TREE_OBJECTID);

        invalidate_bdev(fs_devices->latest_bdev);

        /*
         * Read super block and check the signature bytes only
         */
        bh = btrfs_read_dev_super(fs_devices->latest_bdev);
        if (IS_ERR(bh)) {
                err = PTR_ERR(bh);
                goto fail_alloc;
        }

        /*
         * Verify the type first, if that or the the checksum value are
         * corrupted, we'll find out
         */
        csum_type = btrfs_super_csum_type((struct btrfs_super_block *)bh->b_data);
        if (!btrfs_supported_super_csum(csum_type)) {
                btrfs_err(fs_info, "unsupported checksum algorithm: %u",
                          csum_type);
                err = -EINVAL;
                brelse(bh);
                goto fail_alloc;
        }

        /*
         * We want to check superblock checksum, the type is stored inside.
         * Pass the whole disk block of size BTRFS_SUPER_INFO_SIZE (4k).
         */
        if (btrfs_check_super_csum(fs_info, bh->b_data)) {
                btrfs_err(fs_info, "superblock checksum mismatch");
                err = -EINVAL;
                brelse(bh);
                goto fail_alloc;
        }

        /*
         * super_copy is zeroed at allocation time and we never touch the
         * following bytes up to INFO_SIZE, the checksum is calculated from
         * the whole block of INFO_SIZE
         */
        memcpy(fs_info->super_copy, bh->b_data, sizeof(*fs_info->super_copy));
        brelse(bh);

        disk_super = fs_info->super_copy;

        ASSERT(!memcmp(fs_info->fs_devices->fsid, fs_info->super_copy->fsid,
                       BTRFS_FSID_SIZE));

        if (btrfs_fs_incompat(fs_info, METADATA_UUID)) {
                ASSERT(!memcmp(fs_info->fs_devices->metadata_uuid,
                                fs_info->super_copy->metadata_uuid,
                                BTRFS_FSID_SIZE));
        }

        features = btrfs_super_flags(disk_super);
        if (features & BTRFS_SUPER_FLAG_CHANGING_FSID_V2) {
                features &= ~BTRFS_SUPER_FLAG_CHANGING_FSID_V2;
                btrfs_set_super_flags(disk_super, features);
                btrfs_info(fs_info,
                        "found metadata UUID change in progress flag, clearing");
        }

        memcpy(fs_info->super_for_commit, fs_info->super_copy,
               sizeof(*fs_info->super_for_commit));

        ret = btrfs_validate_mount_super(fs_info);
        if (ret) {
                btrfs_err(fs_info, "superblock contains fatal errors");
                err = -EINVAL;
                goto fail_alloc;
        }

        if (!btrfs_super_root(disk_super))
                goto fail_alloc;

        /* check FS state, whether FS is broken. */
        if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)
                set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);

        /*
         * run through our array of backup supers and setup
         * our ring pointer to the oldest one
         */
        generation = btrfs_super_generation(disk_super);
        find_oldest_super_backup(fs_info, generation);

        /*
         * In the long term, we'll store the compression type in the super
         * block, and it'll be used for per file compression control.
         */
        fs_info->compress_type = BTRFS_COMPRESS_ZLIB;

        ret = btrfs_parse_options(fs_info, options, sb->s_flags);
        if (ret) {
                err = ret;
                goto fail_alloc;
        }

        features = btrfs_super_incompat_flags(disk_super) &
                ~BTRFS_FEATURE_INCOMPAT_SUPP;
        if (features) {
                btrfs_err(fs_info,
                    "cannot mount because of unsupported optional features (%llx)",
                    features);
                err = -EINVAL;
                goto fail_alloc;
        }

        features = btrfs_super_incompat_flags(disk_super);
        features |= BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF;
        if (fs_info->compress_type == BTRFS_COMPRESS_LZO)
                features |= BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO;
        else if (fs_info->compress_type == BTRFS_COMPRESS_ZSTD)
                features |= BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD;

        if (features & BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA)
                btrfs_info(fs_info, "has skinny extents");

        /*
         * flag our filesystem as having big metadata blocks if
         * they are bigger than the page size
         */
        if (btrfs_super_nodesize(disk_super) > PAGE_SIZE) {
                if (!(features & BTRFS_FEATURE_INCOMPAT_BIG_METADATA))
                        btrfs_info(fs_info,
                                "flagging fs with big metadata feature");
                features |= BTRFS_FEATURE_INCOMPAT_BIG_METADATA;
        }

        nodesize = btrfs_super_nodesize(disk_super);
        sectorsize = btrfs_super_sectorsize(disk_super);
        stripesize = sectorsize;
        fs_info->dirty_metadata_batch = nodesize * (1 + ilog2(nr_cpu_ids));
        fs_info->delalloc_batch = sectorsize * 512 * (1 + ilog2(nr_cpu_ids));

        /* Cache block sizes */
        fs_info->nodesize = nodesize;
        fs_info->sectorsize = sectorsize;
        fs_info->stripesize = stripesize;

        /*
         * mixed block groups end up with duplicate but slightly offset
         * extent buffers for the same range.  It leads to corruptions
         */
        if ((features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
            (sectorsize != nodesize)) {
                btrfs_err(fs_info,
"unequal nodesize/sectorsize (%u != %u) are not allowed for mixed block groups",
                        nodesize, sectorsize);
                goto fail_alloc;
        }

        /*
         * Needn't use the lock because there is no other task which will
         * update the flag.
         */
        btrfs_set_super_incompat_flags(disk_super, features);

        features = btrfs_super_compat_ro_flags(disk_super) &
                ~BTRFS_FEATURE_COMPAT_RO_SUPP;
        if (!sb_rdonly(sb) && features) {
                btrfs_err(fs_info,
        "cannot mount read-write because of unsupported optional features (%llx)",
                       features);
                err = -EINVAL;
                goto fail_alloc;
        }

        ret = btrfs_init_workqueues(fs_info, fs_devices);
        if (ret) {
                err = ret;
                goto fail_sb_buffer;
        }

        sb->s_bdi->congested_fn = btrfs_congested_fn;
        sb->s_bdi->congested_data = fs_info;
        sb->s_bdi->capabilities |= BDI_CAP_CGROUP_WRITEBACK;
        sb->s_bdi->ra_pages = VM_READAHEAD_PAGES;
        sb->s_bdi->ra_pages *= btrfs_super_num_devices(disk_super);
        sb->s_bdi->ra_pages = max(sb->s_bdi->ra_pages, SZ_4M / PAGE_SIZE);

        sb->s_blocksize = sectorsize;
        sb->s_blocksize_bits = blksize_bits(sectorsize);
        memcpy(&sb->s_uuid, fs_info->fs_devices->fsid, BTRFS_FSID_SIZE);

        mutex_lock(&fs_info->chunk_mutex);
        ret = btrfs_read_sys_array(fs_info);
        mutex_unlock(&fs_info->chunk_mutex);
        if (ret) {
                btrfs_err(fs_info, "failed to read the system array: %d", ret);
                goto fail_sb_buffer;
        }

        generation = btrfs_super_chunk_root_generation(disk_super);
        level = btrfs_super_chunk_root_level(disk_super);

        __setup_root(chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);

        chunk_root->node = read_tree_block(fs_info,
                                           btrfs_super_chunk_root(disk_super),
                                           generation, level, NULL);
        if (IS_ERR(chunk_root->node) ||
            !extent_buffer_uptodate(chunk_root->node)) {
                btrfs_err(fs_info, "failed to read chunk root");
                if (!IS_ERR(chunk_root->node))
                        free_extent_buffer(chunk_root->node);
                chunk_root->node = NULL;
                goto fail_tree_roots;
        }
        btrfs_set_root_node(&chunk_root->root_item, chunk_root->node);
        chunk_root->commit_root = btrfs_root_node(chunk_root);

        read_extent_buffer(chunk_root->node, fs_info->chunk_tree_uuid,
           btrfs_header_chunk_tree_uuid(chunk_root->node), BTRFS_UUID_SIZE);

        ret = btrfs_read_chunk_tree(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to read chunk tree: %d", ret);
                goto fail_tree_roots;
        }

        /*
         * Keep the devid that is marked to be the target device for the
         * device replace procedure
         */
        btrfs_free_extra_devids(fs_devices, 0);

        if (!fs_devices->latest_bdev) {
                btrfs_err(fs_info, "failed to read devices");
                goto fail_tree_roots;
        }

retry_root_backup:
        generation = btrfs_super_generation(disk_super);
        level = btrfs_super_root_level(disk_super);

        tree_root->node = read_tree_block(fs_info,
                                          btrfs_super_root(disk_super),
                                          generation, level, NULL);
        if (IS_ERR(tree_root->node) ||
            !extent_buffer_uptodate(tree_root->node)) {
                btrfs_warn(fs_info, "failed to read tree root");
                if (!IS_ERR(tree_root->node))
                        free_extent_buffer(tree_root->node);
                tree_root->node = NULL;
                goto recovery_tree_root;
        }

        btrfs_set_root_node(&tree_root->root_item, tree_root->node);
        tree_root->commit_root = btrfs_root_node(tree_root);
        btrfs_set_root_refs(&tree_root->root_item, 1);

        mutex_lock(&tree_root->objectid_mutex);
        ret = btrfs_find_highest_objectid(tree_root,
                                        &tree_root->highest_objectid);
        if (ret) {
                mutex_unlock(&tree_root->objectid_mutex);
                goto recovery_tree_root;
        }

        ASSERT(tree_root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);

        mutex_unlock(&tree_root->objectid_mutex);

        ret = btrfs_read_roots(fs_info);
        if (ret)
                goto recovery_tree_root;

        fs_info->generation = generation;
        fs_info->last_trans_committed = generation;

        ret = btrfs_verify_dev_extents(fs_info);
        if (ret) {
                btrfs_err(fs_info,
                          "failed to verify dev extents against chunks: %d",
                          ret);
                goto fail_block_groups;
        }
        ret = btrfs_recover_balance(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to recover balance: %d", ret);
                goto fail_block_groups;
        }

        ret = btrfs_init_dev_stats(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to init dev_stats: %d", ret);
                goto fail_block_groups;
        }

        ret = btrfs_init_dev_replace(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to init dev_replace: %d", ret);
                goto fail_block_groups;
        }

        btrfs_free_extra_devids(fs_devices, 1);

        ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
        if (ret) {
                btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
                                ret);
                goto fail_block_groups;
        }

        ret = btrfs_sysfs_add_device(fs_devices);
        if (ret) {
                btrfs_err(fs_info, "failed to init sysfs device interface: %d",
                                ret);
                goto fail_fsdev_sysfs;
        }

        ret = btrfs_sysfs_add_mounted(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to init sysfs interface: %d", ret);
                goto fail_fsdev_sysfs;
        }

        ret = btrfs_init_space_info(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to initialize space info: %d", ret);
                goto fail_sysfs;
        }

        ret = btrfs_read_block_groups(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to read block groups: %d", ret);
                goto fail_sysfs;
        }

        if (!sb_rdonly(sb) && !btrfs_check_rw_degradable(fs_info, NULL)) {
                btrfs_warn(fs_info,
                "writable mount is not allowed due to too many missing devices");
                goto fail_sysfs;
        }

        fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
                                               "btrfs-cleaner");
        if (IS_ERR(fs_info->cleaner_kthread))
                goto fail_sysfs;

        fs_info->transaction_kthread = kthread_run(transaction_kthread,
                                                   tree_root,
                                                   "btrfs-transaction");
        if (IS_ERR(fs_info->transaction_kthread))
                goto fail_cleaner;

        if (!btrfs_test_opt(fs_info, NOSSD) &&
            !fs_info->fs_devices->rotating) {
                btrfs_set_and_info(fs_info, SSD, "enabling ssd optimizations");
        }

        /*
         * Mount does not set all options immediately, we can do it now and do
         * not have to wait for transaction commit
         */
        btrfs_apply_pending_changes(fs_info);

#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        if (btrfs_test_opt(fs_info, CHECK_INTEGRITY)) {
                ret = btrfsic_mount(fs_info, fs_devices,
                                    btrfs_test_opt(fs_info,
                                        CHECK_INTEGRITY_INCLUDING_EXTENT_DATA) ?
                                    1 : 0,
                                    fs_info->check_integrity_print_mask);
                if (ret)
                        btrfs_warn(fs_info,
                                "failed to initialize integrity check module: %d",
                                ret);
        }
#endif
        ret = btrfs_read_qgroup_config(fs_info);
        if (ret)
                goto fail_trans_kthread;

        if (btrfs_build_ref_tree(fs_info))
                btrfs_err(fs_info, "couldn't build ref tree");

        /* do not make disk changes in broken FS or nologreplay is given */
        if (btrfs_super_log_root(disk_super) != 0 &&
            !btrfs_test_opt(fs_info, NOLOGREPLAY)) {
                ret = btrfs_replay_log(fs_info, fs_devices);
                if (ret) {
                        err = ret;
                        goto fail_qgroup;
                }
        }

        ret = btrfs_find_orphan_roots(fs_info);
        if (ret)
                goto fail_qgroup;

        if (!sb_rdonly(sb)) {
                ret = btrfs_cleanup_fs_roots(fs_info);
                if (ret)
                        goto fail_qgroup;

                mutex_lock(&fs_info->cleaner_mutex);
                ret = btrfs_recover_relocation(tree_root);
                mutex_unlock(&fs_info->cleaner_mutex);
                if (ret < 0) {
                        btrfs_warn(fs_info, "failed to recover relocation: %d",
                                        ret);
                        err = -EINVAL;
                        goto fail_qgroup;
                }
        }

        location.objectid = BTRFS_FS_TREE_OBJECTID;
        location.type = BTRFS_ROOT_ITEM_KEY;
        location.offset = 0;

        fs_info->fs_root = btrfs_read_fs_root_no_name(fs_info, &location);
        if (IS_ERR(fs_info->fs_root)) {
                err = PTR_ERR(fs_info->fs_root);
                btrfs_warn(fs_info, "failed to read fs tree: %d", err);
                goto fail_qgroup;
        }

        if (sb_rdonly(sb))
                return 0;

        if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
            btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                clear_free_space_tree = 1;
        } else if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
                   !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID)) {
                btrfs_warn(fs_info, "free space tree is invalid");
                clear_free_space_tree = 1;
        }

        if (clear_free_space_tree) {
                btrfs_info(fs_info, "clearing free space tree");
                ret = btrfs_clear_free_space_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                   "failed to clear free space tree: %d", ret);
                        close_ctree(fs_info);
                        return ret;
                }
        }

        if (btrfs_test_opt(fs_info, FREE_SPACE_TREE) &&
            !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                btrfs_info(fs_info, "creating free space tree");
                ret = btrfs_create_free_space_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                "failed to create free space tree: %d", ret);
                        close_ctree(fs_info);
                        return ret;
                }
        }

        down_read(&fs_info->cleanup_work_sem);
        if ((ret = btrfs_orphan_cleanup(fs_info->fs_root)) ||
            (ret = btrfs_orphan_cleanup(fs_info->tree_root))) {
                up_read(&fs_info->cleanup_work_sem);
                close_ctree(fs_info);
                return ret;
        }
        up_read(&fs_info->cleanup_work_sem);

        ret = btrfs_resume_balance_async(fs_info);
        if (ret) {
                btrfs_warn(fs_info, "failed to resume balance: %d", ret);
                close_ctree(fs_info);
                return ret;
        }

        ret = btrfs_resume_dev_replace_async(fs_info);
        if (ret) {
                btrfs_warn(fs_info, "failed to resume device replace: %d", ret);
                close_ctree(fs_info);
                return ret;
        }

        btrfs_qgroup_rescan_resume(fs_info);

        if (!fs_info->uuid_root) {
                btrfs_info(fs_info, "creating UUID tree");
                ret = btrfs_create_uuid_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                "failed to create the UUID tree: %d", ret);
                        close_ctree(fs_info);
                        return ret;
                }
        } else if (btrfs_test_opt(fs_info, RESCAN_UUID_TREE) ||
                   fs_info->generation !=
                                btrfs_super_uuid_tree_generation(disk_super)) {
                btrfs_info(fs_info, "checking UUID tree");
                ret = btrfs_check_uuid_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                "failed to check the UUID tree: %d", ret);
                        close_ctree(fs_info);
                        return ret;
                }
        } else {
                set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
        }
        set_bit(BTRFS_FS_OPEN, &fs_info->flags);

        /*
         * backuproot only affect mount behavior, and if open_ctree succeeded,
         * no need to keep the flag
         */
        btrfs_clear_opt(fs_info->mount_opt, USEBACKUPROOT);

        return 0;

fail_qgroup:
        btrfs_free_qgroup_config(fs_info);
fail_trans_kthread:
        kthread_stop(fs_info->transaction_kthread);
        btrfs_cleanup_transaction(fs_info);
        btrfs_free_fs_roots(fs_info);
fail_cleaner:
        kthread_stop(fs_info->cleaner_kthread);

        /*
         * make sure we're done with the btree inode before we stop our
         * kthreads
         */
        filemap_write_and_wait(fs_info->btree_inode->i_mapping);

fail_sysfs:
        btrfs_sysfs_remove_mounted(fs_info);

fail_fsdev_sysfs:
        btrfs_sysfs_remove_fsid(fs_info->fs_devices);

fail_block_groups:
        btrfs_put_block_group_cache(fs_info);

fail_tree_roots:
        free_root_pointers(fs_info, 1);
        invalidate_inode_pages2(fs_info->btree_inode->i_mapping);

fail_sb_buffer:
        btrfs_stop_all_workers(fs_info);
        btrfs_free_block_groups(fs_info);
fail_alloc:
fail_iput:
        btrfs_mapping_tree_free(&fs_info->mapping_tree);

        iput(fs_info->btree_inode);
fail_bio_counter:
        percpu_counter_destroy(&fs_info->dev_replace.bio_counter);
fail_delalloc_bytes:
        percpu_counter_destroy(&fs_info->delalloc_bytes);
fail_dirty_metadata_bytes:
        percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
fail_dio_bytes:
        percpu_counter_destroy(&fs_info->dio_bytes);
fail_srcu:
        cleanup_srcu_struct(&fs_info->subvol_srcu);
fail:
        btrfs_free_stripe_hash_table(fs_info);
        btrfs_close_devices(fs_info->fs_devices);
        return err;

recovery_tree_root:
        if (!btrfs_test_opt(fs_info, USEBACKUPROOT))
                goto fail_tree_roots;

        free_root_pointers(fs_info, 0);

        /* don't use the log in recovery mode, it won't be valid */
        btrfs_set_super_log_root(disk_super, 0);

        /* we can't trust the free space cache either */
        btrfs_set_opt(fs_info->mount_opt, CLEAR_CACHE);

        ret = next_root_backup(fs_info, fs_info->super_copy,
                               &num_backups_tried, &backup_index);
        if (ret == -1)
                goto fail_block_groups;
        goto retry_root_backup;
}
ALLOW_ERROR_INJECTION(open_ctree, ERRNO);

static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
        if (uptodate) {
                set_buffer_uptodate(bh);
        } else {
                struct btrfs_device *device = (struct btrfs_device *)
                        bh->b_private;

                btrfs_warn_rl_in_rcu(device->fs_info,
                                "lost page write due to IO error on %s",
                                          rcu_str_deref(device->name));
                /* note, we don't set_buffer_write_io_error because we have
                 * our own ways of dealing with the IO errors
                 */
                clear_buffer_uptodate(bh);
                btrfs_dev_stat_inc_and_print(device, BTRFS_DEV_STAT_WRITE_ERRS);
        }
        unlock_buffer(bh);
        put_bh(bh);
}

int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
                        struct buffer_head **bh_ret)
{
        struct buffer_head *bh;
        struct btrfs_super_block *super;
        u64 bytenr;

        bytenr = btrfs_sb_offset(copy_num);
        if (bytenr + BTRFS_SUPER_INFO_SIZE >= i_size_read(bdev->bd_inode))
                return -EINVAL;

        bh = __bread(bdev, bytenr / BTRFS_BDEV_BLOCKSIZE, BTRFS_SUPER_INFO_SIZE);
        /*
         * If we fail to read from the underlying devices, as of now
         * the best option we have is to mark it EIO.
         */
        if (!bh)
                return -EIO;

        super = (struct btrfs_super_block *)bh->b_data;
        if (btrfs_super_bytenr(super) != bytenr ||
                    btrfs_super_magic(super) != BTRFS_MAGIC) {
                brelse(bh);
                return -EINVAL;
        }

        *bh_ret = bh;
        return 0;
}


struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
{
        struct buffer_head *bh;
        struct buffer_head *latest = NULL;
        struct btrfs_super_block *super;
        int i;
        u64 transid = 0;
        int ret = -EINVAL;

        /* we would like to check all the supers, but that would make
         * a btrfs mount succeed after a mkfs from a different FS.
         * So, we need to add a special mount option to scan for
         * later supers, using BTRFS_SUPER_MIRROR_MAX instead
         */
        for (i = 0; i < 1; i++) {
                ret = btrfs_read_dev_one_super(bdev, i, &bh);
                if (ret)
                        continue;

                super = (struct btrfs_super_block *)bh->b_data;

                if (!latest || btrfs_super_generation(super) > transid) {
                        brelse(latest);
                        latest = bh;
                        transid = btrfs_super_generation(super);
                } else {
                        brelse(bh);
                }
        }

        if (!latest)
                return ERR_PTR(ret);

        return latest;
}

/*
 * Write superblock @sb to the @device. Do not wait for completion, all the
 * buffer heads we write are pinned.
 *
 * Write @max_mirrors copies of the superblock, where 0 means default that fit
 * the expected device size at commit time. Note that max_mirrors must be
 * same for write and wait phases.
 *
 * Return number of errors when buffer head is not found or submission fails.
 */
static int write_dev_supers(struct btrfs_device *device,
                            struct btrfs_super_block *sb, int max_mirrors)
{
        struct buffer_head *bh;
        int i;
        int ret;
        int errors = 0;
        u32 crc;
        u64 bytenr;
        int op_flags;

        if (max_mirrors == 0)
                max_mirrors = BTRFS_SUPER_MIRROR_MAX;

        for (i = 0; i < max_mirrors; i++) {
                bytenr = btrfs_sb_offset(i);
                if (bytenr + BTRFS_SUPER_INFO_SIZE >=
                    device->commit_total_bytes)
                        break;

                btrfs_set_super_bytenr(sb, bytenr);

                crc = ~(u32)0;
                crc = btrfs_csum_data((const char *)sb + BTRFS_CSUM_SIZE, crc,
                                      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
                btrfs_csum_final(crc, sb->csum);

                /* One reference for us, and we leave it for the caller */
                bh = __getblk(device->bdev, bytenr / BTRFS_BDEV_BLOCKSIZE,
                              BTRFS_SUPER_INFO_SIZE);
                if (!bh) {
                        btrfs_err(device->fs_info,
                            "couldn't get super buffer head for bytenr %llu",
                            bytenr);
                        errors++;
                        continue;
                }

                memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);

                /* one reference for submit_bh */
                get_bh(bh);

                set_buffer_uptodate(bh);
                lock_buffer(bh);
                bh->b_end_io = btrfs_end_buffer_write_sync;
                bh->b_private = device;

                /*
                 * we fua the first super.  The others we allow
                 * to go down lazy.
                 */
                op_flags = REQ_SYNC | REQ_META | REQ_PRIO;
                if (i == 0 && !btrfs_test_opt(device->fs_info, NOBARRIER))
                        op_flags |= REQ_FUA;
                ret = btrfsic_submit_bh(REQ_OP_WRITE, op_flags, bh);
                if (ret)
                        errors++;
        }
        return errors < i ? 0 : -1;
}

/*
 * Wait for write completion of superblocks done by write_dev_supers,
 * @max_mirrors same for write and wait phases.
 *
 * Return number of errors when buffer head is not found or not marked up to
 * date.
 */
static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
{
        struct buffer_head *bh;
        int i;
        int errors = 0;
        bool primary_failed = false;
        u64 bytenr;

        if (max_mirrors == 0)
                max_mirrors = BTRFS_SUPER_MIRROR_MAX;

        for (i = 0; i < max_mirrors; i++) {
                bytenr = btrfs_sb_offset(i);
                if (bytenr + BTRFS_SUPER_INFO_SIZE >=
                    device->commit_total_bytes)
                        break;

                bh = __find_get_block(device->bdev,
                                      bytenr / BTRFS_BDEV_BLOCKSIZE,
                                      BTRFS_SUPER_INFO_SIZE);
                if (!bh) {
                        errors++;
                        if (i == 0)
                                primary_failed = true;
                        continue;
                }
                wait_on_buffer(bh);
                if (!buffer_uptodate(bh)) {
                        errors++;
                        if (i == 0)
                                primary_failed = true;
                }

                /* drop our reference */
                brelse(bh);

                /* drop the reference from the writing run */
                brelse(bh);
        }

        /* log error, force error return */
        if (primary_failed) {
                btrfs_err(device->fs_info, "error writing primary super block to device %llu",
                          device->devid);
                return -1;
        }

        return errors < i ? 0 : -1;
}

/*
 * endio for the write_dev_flush, this will wake anyone waiting
 * for the barrier when it is done
 */
static void btrfs_end_empty_barrier(struct bio *bio)
{
        complete(bio->bi_private);
}

/*
 * Submit a flush request to the device if it supports it. Error handling is
 * done in the waiting counterpart.
 */
static void write_dev_flush(struct btrfs_device *device)
{
        struct request_queue *q = bdev_get_queue(device->bdev);
        struct bio *bio = device->flush_bio;

        if (!test_bit(QUEUE_FLAG_WC, &q->queue_flags))
                return;

        bio_reset(bio);
        bio->bi_end_io = btrfs_end_empty_barrier;
        bio_set_dev(bio, device->bdev);
        bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH;
        init_completion(&device->flush_wait);
        bio->bi_private = &device->flush_wait;

        btrfsic_submit_bio(bio);
        set_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state);
}

/*
 * If the flush bio has been submitted by write_dev_flush, wait for it.
 */
static blk_status_t wait_dev_flush(struct btrfs_device *device)
{
        struct bio *bio = device->flush_bio;

        if (!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state))
                return BLK_STS_OK;

        clear_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state);
        wait_for_completion_io(&device->flush_wait);

        return bio->bi_status;
}

static int check_barrier_error(struct btrfs_fs_info *fs_info)
{
        if (!btrfs_check_rw_degradable(fs_info, NULL))
                return -EIO;
        return 0;
}

/*
 * send an empty flush down to each device in parallel,
 * then wait for them
 */
static int barrier_all_devices(struct btrfs_fs_info *info)
{
        struct list_head *head;
        struct btrfs_device *dev;
        int errors_wait = 0;
        blk_status_t ret;

        lockdep_assert_held(&info->fs_devices->device_list_mutex);
        /* send down all the barriers */
        head = &info->fs_devices->devices;
        list_for_each_entry(dev, head, dev_list) {
                if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
                        continue;
                if (!dev->bdev)
                        continue;
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

                write_dev_flush(dev);
                dev->last_flush_error = BLK_STS_OK;
        }

        /* wait for all the barriers */
        list_for_each_entry(dev, head, dev_list) {
                if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
                        continue;
                if (!dev->bdev) {
                        errors_wait++;
                        continue;
                }
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

                ret = wait_dev_flush(dev);
                if (ret) {
                        dev->last_flush_error = ret;
                        btrfs_dev_stat_inc_and_print(dev,
                                        BTRFS_DEV_STAT_FLUSH_ERRS);
                        errors_wait++;
                }
        }

        if (errors_wait) {
                /*
                 * At some point we need the status of all disks
                 * to arrive at the volume status. So error checking
                 * is being pushed to a separate loop.
                 */
                return check_barrier_error(info);
        }
        return 0;
}

int btrfs_get_num_tolerated_disk_barrier_failures(u64 flags)
{
        int raid_type;
        int min_tolerated = INT_MAX;

        if ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 ||
            (flags & BTRFS_AVAIL_ALLOC_BIT_SINGLE))
                min_tolerated = min_t(int, min_tolerated,
                                    btrfs_raid_array[BTRFS_RAID_SINGLE].
                                    tolerated_failures);

        for (raid_type = 0; raid_type < BTRFS_NR_RAID_TYPES; raid_type++) {
                if (raid_type == BTRFS_RAID_SINGLE)
                        continue;
                if (!(flags & btrfs_raid_array[raid_type].bg_flag))
                        continue;
                min_tolerated = min_t(int, min_tolerated,
                                    btrfs_raid_array[raid_type].
                                    tolerated_failures);
        }

        if (min_tolerated == INT_MAX) {
                pr_warn("BTRFS: unknown raid flag: %llu", flags);
                min_tolerated = 0;
        }

        return min_tolerated;
}

int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors)
{
        struct list_head *head;
        struct btrfs_device *dev;
        struct btrfs_super_block *sb;
        struct btrfs_dev_item *dev_item;
        int ret;
        int do_barriers;
        int max_errors;
        int total_errors = 0;
        u64 flags;

        do_barriers = !btrfs_test_opt(fs_info, NOBARRIER);

        /*
         * max_mirrors == 0 indicates we're from commit_transaction,
         * not from fsync where the tree roots in fs_info have not
         * been consistent on disk.
         */
        if (max_mirrors == 0)
                backup_super_roots(fs_info);

        sb = fs_info->super_for_commit;
        dev_item = &sb->dev_item;

        mutex_lock(&fs_info->fs_devices->device_list_mutex);
        head = &fs_info->fs_devices->devices;
        max_errors = btrfs_super_num_devices(fs_info->super_copy) - 1;

        if (do_barriers) {
                ret = barrier_all_devices(fs_info);
                if (ret) {
                        mutex_unlock(
                                &fs_info->fs_devices->device_list_mutex);
                        btrfs_handle_fs_error(fs_info, ret,
                                              "errors while submitting device barriers.");
                        return ret;
                }
        }

        list_for_each_entry(dev, head, dev_list) {
                if (!dev->bdev) {
                        total_errors++;
                        continue;
                }
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

              &nbs