disk-io.c

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/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>
#include <linux/swap.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/freezer.h>
#include <linux/crc32c.h>
#include <linux/slab.h>
#include <linux/migrate.h>
#include <linux/ratelimit.h>
#include <asm/unaligned.h>
#include "compat.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "volumes.h"
#include "print-tree.h"
#include "async-thread.h"
#include "locking.h"
#include "tree-log.h"
#include "free-space-cache.h"
#include "inode-map.h"
#include "check-integrity.h"
#include "rcu-string.h"

#ifdef CONFIG_X86
#include <asm/cpufeature.h>
#endif

static struct extent_io_ops btree_extent_io_ops;
static void end_workqueue_fn(struct btrfs_work *work);
static void free_fs_root(struct btrfs_root *root);
static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
                    int read_only);
static void btrfs_destroy_ordered_operations(struct btrfs_root *root);
static void btrfs_destroy_ordered_extents(struct btrfs_root *root);
static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
                      struct btrfs_root *root);
static void btrfs_destroy_pending_snapshots(struct btrfs_transaction *t);
static void btrfs_destroy_delalloc_inodes(struct btrfs_root *root);
static int btrfs_destroy_marked_extents(struct btrfs_root *root,
                    struct extent_io_tree *dirty_pages,
                    int mark);
static int btrfs_destroy_pinned_extent(struct btrfs_root *root,
                       struct extent_io_tree *pinned_extents);

/*
 * 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 end_io_wq {
    struct bio *bio;
    bio_end_io_t *end_io;
    void *private;
    struct btrfs_fs_info *info;
    int error;
    int metadata;
    struct list_head list;
    struct btrfs_work work;
};

/*
 * 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 {
    struct inode *inode;
    struct bio *bio;
    struct list_head list;
    extent_submit_bio_hook_t *submit_bio_start;
    extent_submit_bio_hook_t *submit_bio_done;
    int rw;
    int mirror_num;
    unsigned long bio_flags;
    /*
     * 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;
    int error;
};

/*
 * 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->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_ORPHAN_OBJECTID,      .name_stem = "orphan"   },
    { .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 = 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
 */
static struct extent_map *btree_get_extent(struct inode *inode,
        struct page *page, size_t pg_offset, u64 start, u64 len,
        int create)
{
    struct extent_map_tree *em_tree = &BTRFS_I(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 =
            BTRFS_I(inode)->root->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 = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;

    write_lock(&em_tree->lock);
    ret = add_extent_mapping(em_tree, em);
    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(struct btrfs_root *root, char *data, u32 seed, size_t len)
{
    return crc32c(seed, data, len);
}

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

/*
 * compute the csum for a btree block, and either verify it or write it
 * into the csum field of the block.
 */
static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
               int verify)
{
    u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
    char *result = NULL;
    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;
    unsigned long inline_result;

    len = buf->len - offset;
    while (len > 0) {
        err = map_private_extent_buffer(buf, offset, 32,
                    &kaddr, &map_start, &map_len);
        if (err)
            return 1;
        cur_len = min(len, map_len - (offset - map_start));
        crc = btrfs_csum_data(root, kaddr + offset - map_start,
                      crc, cur_len);
        len -= cur_len;
        offset += cur_len;
    }
    if (csum_size > sizeof(inline_result)) {
        result = kzalloc(csum_size * sizeof(char), GFP_NOFS);
        if (!result)
            return 1;
    } else {
        result = (char *)&inline_result;
    }

    btrfs_csum_final(crc, result);

    if (verify) {
        if (memcmp_extent_buffer(buf, result, 0, csum_size)) {
            u32 val;
            u32 found = 0;
            memcpy(&found, result, csum_size);

            read_extent_buffer(buf, &val, 0, csum_size);
            printk_ratelimited(KERN_INFO "btrfs: %s checksum verify "
                       "failed on %llu wanted %X found %X "
                       "level %d\n",
                       root->fs_info->sb->s_id,
                       (unsigned long long)buf->start, val, found,
                       btrfs_header_level(buf));
            if (result != (char *)&inline_result)
                kfree(result);
            return 1;
        }
    } else {
        write_extent_buffer(buf, result, 0, csum_size);
    }
    if (result != (char *)&inline_result)
        kfree(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;

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

    if (atomic)
        return -EAGAIN;

    lock_extent_bits(io_tree, eb->start, eb->start + eb->len - 1,
             0, &cached_state);
    if (extent_buffer_uptodate(eb) &&
        btrfs_header_generation(eb) == parent_transid) {
        ret = 0;
        goto out;
    }
    printk_ratelimited("parent transid verify failed on %llu wanted %llu "
               "found %llu\n",
               (unsigned long long)eb->start,
               (unsigned long long)parent_transid,
               (unsigned long long)btrfs_header_generation(eb));
    ret = 1;
    clear_extent_buffer_uptodate(eb);
out:
    unlock_extent_cached(io_tree, eb->start, eb->start + eb->len - 1,
                 &cached_state, GFP_NOFS);
    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.
 */
static int btree_read_extent_buffer_pages(struct btrfs_root *root,
                      struct extent_buffer *eb,
                      u64 start, u64 parent_transid)
{
    struct extent_io_tree *io_tree;
    int failed = 0;
    int ret;
    int num_copies = 0;
    int mirror_num = 0;
    int failed_mirror = 0;

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

        /*
         * This buffer's crc is fine, but its contents are corrupted, so
         * there is no reason to read the other copies, they won't be
         * any less wrong.
         */
        if (test_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags))
            break;

        num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
                          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)
        repair_eb_io_failure(root, 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_root *root, struct page *page)
{
    struct extent_io_tree *tree;
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 found_start;
    struct extent_buffer *eb;

    tree = &BTRFS_I(page->mapping->host)->io_tree;

    eb = (struct extent_buffer *)page->private;
    if (page != eb->pages[0])
        return 0;
    found_start = btrfs_header_bytenr(eb);
    if (found_start != start) {
        WARN_ON(1);
        return 0;
    }
    if (!PageUptodate(page)) {
        WARN_ON(1);
        return 0;
    }
    csum_tree_block(root, eb, 0);
    return 0;
}

static int check_tree_block_fsid(struct btrfs_root *root,
                 struct extent_buffer *eb)
{
    struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
    u8 fsid[BTRFS_UUID_SIZE];
    int ret = 1;

    read_extent_buffer(eb, fsid, (unsigned long)btrfs_header_fsid(eb),
               BTRFS_FSID_SIZE);
    while (fs_devices) {
        if (!memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE)) {
            ret = 0;
            break;
        }
        fs_devices = fs_devices->seed;
    }
    return ret;
}

#define CORRUPT(reason, eb, root, slot)             \
    printk(KERN_CRIT "btrfs: corrupt leaf, %s: block=%llu," \
           "root=%llu, slot=%d\n", reason,          \
           (unsigned long long)btrfs_header_bytenr(eb), \
           (unsigned long long)root->objectid, slot)

static noinline int check_leaf(struct btrfs_root *root,
                   struct extent_buffer *leaf)
{
    struct btrfs_key key;
    struct btrfs_key leaf_key;
    u32 nritems = btrfs_header_nritems(leaf);
    int slot;

    if (nritems == 0)
        return 0;

    /* Check the 0 item */
    if (btrfs_item_offset_nr(leaf, 0) + btrfs_item_size_nr(leaf, 0) !=
        BTRFS_LEAF_DATA_SIZE(root)) {
        CORRUPT("invalid item offset size pair", leaf, root, 0);
        return -EIO;
    }

    /*
     * Check to make sure each items keys are in the correct order and their
     * offsets make sense.  We only have to loop through nritems-1 because
     * we check the current slot against the next slot, which verifies the
     * next slot's offset+size makes sense and that the current's slot
     * offset is correct.
     */
    for (slot = 0; slot < nritems - 1; slot++) {
        btrfs_item_key_to_cpu(leaf, &leaf_key, slot);
        btrfs_item_key_to_cpu(leaf, &key, slot + 1);

        /* Make sure the keys are in the right order */
        if (btrfs_comp_cpu_keys(&leaf_key, &key) >= 0) {
            CORRUPT("bad key order", leaf, root, slot);
            return -EIO;
        }

        /*
         * Make sure the offset and ends are right, remember that the
         * item data starts at the end of the leaf and grows towards the
         * front.
         */
        if (btrfs_item_offset_nr(leaf, slot) !=
            btrfs_item_end_nr(leaf, slot + 1)) {
            CORRUPT("slot offset bad", leaf, root, slot);
            return -EIO;
        }

        /*
         * Check to make sure that we don't point outside of the leaf,
         * just incase all the items are consistent to eachother, but
         * all point outside of the leaf.
         */
        if (btrfs_item_end_nr(leaf, slot) >
            BTRFS_LEAF_DATA_SIZE(root)) {
            CORRUPT("slot end outside of leaf", leaf, root, slot);
            return -EIO;
        }
    }

    return 0;
}

struct extent_buffer *find_eb_for_page(struct extent_io_tree *tree,
                       struct page *page, int max_walk)
{
    struct extent_buffer *eb;
    u64 start = page_offset(page);
    u64 target = start;
    u64 min_start;

    if (start < max_walk)
        min_start = 0;
    else
        min_start = start - max_walk;

    while (start >= min_start) {
        eb = find_extent_buffer(tree, start, 0);
        if (eb) {
            /*
             * we found an extent buffer and it contains our page
             * horray!
             */
            if (eb->start <= target &&
                eb->start + eb->len > target)
                return eb;

            /* we found an extent buffer that wasn't for us */
            free_extent_buffer(eb);
            return NULL;
        }
        if (start == 0)
            break;
        start -= PAGE_CACHE_SIZE;
    }
    return NULL;
}

static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
                   struct extent_state *state, int mirror)
{
    struct extent_io_tree *tree;
    u64 found_start;
    int found_level;
    struct extent_buffer *eb;
    struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
    int ret = 0;
    int reads_done;

    if (!page->private)
        goto out;

    tree = &BTRFS_I(page->mapping->host)->io_tree;
    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_IOERR, &eb->bflags)) {
        ret = -EIO;
        goto err;
    }

    found_start = btrfs_header_bytenr(eb);
    if (found_start != eb->start) {
        printk_ratelimited(KERN_INFO "btrfs bad tree block start "
                   "%llu %llu\n",
                   (unsigned long long)found_start,
                   (unsigned long long)eb->start);
        ret = -EIO;
        goto err;
    }
    if (check_tree_block_fsid(root, eb)) {
        printk_ratelimited(KERN_INFO "btrfs bad fsid on block %llu\n",
                   (unsigned long long)eb->start);
        ret = -EIO;
        goto err;
    }
    found_level = btrfs_header_level(eb);

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

    ret = csum_tree_block(root, eb, 1);
    if (ret) {
        ret = -EIO;
        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 && check_leaf(root, eb)) {
        set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
        ret = -EIO;
    }

    if (!ret)
        set_extent_buffer_uptodate(eb);
err:
    if (test_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags)) {
        clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags);
        btree_readahead_hook(root, eb, eb->start, ret);
    }

    if (ret)
        clear_extent_buffer_uptodate(eb);
    free_extent_buffer(eb);
out:
    return ret;
}

static int btree_io_failed_hook(struct page *page, int failed_mirror)
{
    struct extent_buffer *eb;
    struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;

    eb = (struct extent_buffer *)page->private;
    set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
    eb->read_mirror = failed_mirror;
    if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
        btree_readahead_hook(root, eb, eb->start, -EIO);
    return -EIO;    /* we fixed nothing */
}

static void end_workqueue_bio(struct bio *bio, int err)
{
    struct end_io_wq *end_io_wq = bio->bi_private;
    struct btrfs_fs_info *fs_info;

    fs_info = end_io_wq->info;
    end_io_wq->error = err;
    end_io_wq->work.func = end_workqueue_fn;
    end_io_wq->work.flags = 0;

    if (bio->bi_rw & REQ_WRITE) {
        if (end_io_wq->metadata == 1)
            btrfs_queue_worker(&fs_info->endio_meta_write_workers,
                       &end_io_wq->work);
        else if (end_io_wq->metadata == 2)
            btrfs_queue_worker(&fs_info->endio_freespace_worker,
                       &end_io_wq->work);
        else
            btrfs_queue_worker(&fs_info->endio_write_workers,
                       &end_io_wq->work);
    } else {
        if (end_io_wq->metadata)
            btrfs_queue_worker(&fs_info->endio_meta_workers,
                       &end_io_wq->work);
        else
            btrfs_queue_worker(&fs_info->endio_workers,
                       &end_io_wq->work);
    }
}

/*
 * For the metadata arg you want
 *
 * 0 - if data
 * 1 - if normal metadta
 * 2 - if writing to the free space cache area
 */
int btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
            int metadata)
{
    struct end_io_wq *end_io_wq;
    end_io_wq = kmalloc(sizeof(*end_io_wq), GFP_NOFS);
    if (!end_io_wq)
        return -ENOMEM;

    end_io_wq->private = bio->bi_private;
    end_io_wq->end_io = bio->bi_end_io;
    end_io_wq->info = info;
    end_io_wq->error = 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;
}

unsigned long btrfs_async_submit_limit(struct btrfs_fs_info *info)
{
    unsigned long limit = min_t(unsigned long,
                    info->workers.max_workers,
                    info->fs_devices->open_devices);
    return 256 * limit;
}

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

    async = container_of(work, struct  async_submit_bio, work);
    ret = async->submit_bio_start(async->inode, async->rw, async->bio,
                      async->mirror_num, async->bio_flags,
                      async->bio_offset);
    if (ret)
        async->error = ret;
}

static void run_one_async_done(struct btrfs_work *work)
{
    struct btrfs_fs_info *fs_info;
    struct async_submit_bio *async;
    int limit;

    async = container_of(work, struct  async_submit_bio, work);
    fs_info = BTRFS_I(async->inode)->root->fs_info;

    limit = btrfs_async_submit_limit(fs_info);
    limit = limit * 2 / 3;

    if (atomic_dec_return(&fs_info->nr_async_submits) < limit &&
        waitqueue_active(&fs_info->async_submit_wait))
        wake_up(&fs_info->async_submit_wait);

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

    async->submit_bio_done(async->inode, async->rw, async->bio,
                   async->mirror_num, async->bio_flags,
                   async->bio_offset);
}

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);
}

int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
            int rw, struct bio *bio, int mirror_num,
            unsigned long bio_flags,
            u64 bio_offset,
            extent_submit_bio_hook_t *submit_bio_start,
            extent_submit_bio_hook_t *submit_bio_done)
{
    struct async_submit_bio *async;

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

    async->inode = inode;
    async->rw = rw;
    async->bio = bio;
    async->mirror_num = mirror_num;
    async->submit_bio_start = submit_bio_start;
    async->submit_bio_done = submit_bio_done;

    async->work.func = run_one_async_start;
    async->work.ordered_func = run_one_async_done;
    async->work.ordered_free = run_one_async_free;

    async->work.flags = 0;
    async->bio_flags = bio_flags;
    async->bio_offset = bio_offset;

    async->error = 0;

    atomic_inc(&fs_info->nr_async_submits);

    if (rw & REQ_SYNC)
        btrfs_set_work_high_prio(&async->work);

    btrfs_queue_worker(&fs_info->workers, &async->work);

    while (atomic_read(&fs_info->async_submit_draining) &&
          atomic_read(&fs_info->nr_async_submits)) {
        wait_event(fs_info->async_submit_wait,
               (atomic_read(&fs_info->nr_async_submits) == 0));
    }

    return 0;
}

static int btree_csum_one_bio(struct bio *bio)
{
    struct bio_vec *bvec = bio->bi_io_vec;
    int bio_index = 0;
    struct btrfs_root *root;
    int ret = 0;

    WARN_ON(bio->bi_vcnt <= 0);
    while (bio_index < bio->bi_vcnt) {
        root = BTRFS_I(bvec->bv_page->mapping->host)->root;
        ret = csum_dirty_buffer(root, bvec->bv_page);
        if (ret)
            break;
        bio_index++;
        bvec++;
    }
    return ret;
}

static int __btree_submit_bio_start(struct inode *inode, int rw,
                    struct bio *bio, int mirror_num,
                    unsigned long bio_flags,
                    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 __btree_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
                 int mirror_num, unsigned long bio_flags,
                 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 btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num, 1);
}

static int check_async_write(struct inode *inode, unsigned long bio_flags)
{
    if (bio_flags & EXTENT_BIO_TREE_LOG)
        return 0;
#ifdef CONFIG_X86
    if (cpu_has_xmm4_2)
        return 0;
#endif
    return 1;
}

static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
                 int mirror_num, unsigned long bio_flags,
                 u64 bio_offset)
{
    int async = check_async_write(inode, bio_flags);
    int ret;

    if (!(rw & REQ_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(BTRFS_I(inode)->root->fs_info,
                      bio, 1);
        if (ret)
            return ret;
        return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
                     mirror_num, 0);
    } else if (!async) {
        ret = btree_csum_one_bio(bio);
        if (ret)
            return ret;
        return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
                     mirror_num, 0);
    }

    /*
     * kthread helpers are used to submit writes so that checksumming
     * can happen in parallel across all CPUs
     */
    return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
                   inode, rw, bio, mirror_num, 0,
                   bio_offset,
                   __btree_submit_bio_start,
                   __btree_submit_bio_done);
}

#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 extent_io_tree *tree;
    tree = &BTRFS_I(mapping->host)->io_tree;
    if (wbc->sync_mode == WB_SYNC_NONE) {
        struct btrfs_root *root = BTRFS_I(mapping->host)->root;
        u64 num_dirty;
        unsigned long thresh = 32 * 1024 * 1024;

        if (wbc->for_kupdate)
            return 0;

        /* this is a bit racy, but that's ok */
        num_dirty = root->fs_info->dirty_metadata_bytes;
        if (num_dirty < thresh)
            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;
    /*
     * We need to mask out eg. __GFP_HIGHMEM and __GFP_DMA32 as we're doing
     * slab allocation from alloc_extent_state down the callchain where
     * it'd hit a BUG_ON as those flags are not allowed.
     */
    gfp_flags &= ~GFP_SLAB_BUG_MASK;

    return try_release_extent_buffer(page, gfp_flags);
}

static void btree_invalidatepage(struct page *page, unsigned long offset)
{
    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)) {
        printk(KERN_WARNING "btrfs warning page private not zero "
               "on page %llu\n", (unsigned long long)page_offset(page));
        ClearPagePrivate(page);
        set_page_private(page, 0);
        page_cache_release(page);
    }
}

static int btree_set_page_dirty(struct page *page)
{
    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);
    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,
};

int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
             u64 parent_transid)
{
    struct extent_buffer *buf = NULL;
    struct inode *btree_inode = root->fs_info->btree_inode;
    int ret = 0;

    buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
    if (!buf)
        return 0;
    read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
                 buf, 0, WAIT_NONE, btree_get_extent, 0);
    free_extent_buffer(buf);
    return ret;
}

int reada_tree_block_flagged(struct btrfs_root *root, u64 bytenr, u32 blocksize,
             int mirror_num, struct extent_buffer **eb)
{
    struct extent_buffer *buf = NULL;
    struct inode *btree_inode = root->fs_info->btree_inode;
    struct extent_io_tree *io_tree = &BTRFS_I(btree_inode)->io_tree;
    int ret;

    buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
    if (!buf)
        return 0;

    set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);

    ret = read_extent_buffer_pages(io_tree, buf, 0, WAIT_PAGE_LOCK,
                       btree_get_extent, mirror_num);
    if (ret) {
        free_extent_buffer(buf);
        return ret;
    }

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

struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
                        u64 bytenr, u32 blocksize)
{
    struct inode *btree_inode = root->fs_info->btree_inode;
    struct extent_buffer *eb;
    eb = find_extent_buffer(&BTRFS_I(btree_inode)->io_tree,
                bytenr, blocksize);
    return eb;
}

struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
                         u64 bytenr, u32 blocksize)
{
    struct inode *btree_inode = root->fs_info->btree_inode;
    struct extent_buffer *eb;

    eb = alloc_extent_buffer(&BTRFS_I(btree_inode)->io_tree,
                 bytenr, blocksize);
    return eb;
}


int btrfs_write_tree_block(struct extent_buffer *buf)
{
    return filemap_fdatawrite_range(buf->pages[0]->mapping, buf->start,
                    buf->start + buf->len - 1);
}

int btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
{
    return filemap_fdatawait_range(buf->pages[0]->mapping,
                       buf->start, buf->start + buf->len - 1);
}

struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
                      u32 blocksize, u64 parent_transid)
{
    struct extent_buffer *buf = NULL;
    int ret;

    buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
    if (!buf)
        return NULL;

    ret = btree_read_extent_buffer_pages(root, buf, 0, parent_transid);
    return buf;

}

void clean_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
              struct extent_buffer *buf)
{
    if (btrfs_header_generation(buf) ==
        root->fs_info->running_transaction->transid) {
        btrfs_assert_tree_locked(buf);

        if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &buf->bflags)) {
            spin_lock(&root->fs_info->delalloc_lock);
            if (root->fs_info->dirty_metadata_bytes >= buf->len)
                root->fs_info->dirty_metadata_bytes -= buf->len;
            else {
                spin_unlock(&root->fs_info->delalloc_lock);
                btrfs_panic(root->fs_info, -EOVERFLOW,
                      "Can't clear %lu bytes from "
                      " dirty_mdatadata_bytes (%llu)",
                      buf->len,
                      root->fs_info->dirty_metadata_bytes);
            }
            spin_unlock(&root->fs_info->delalloc_lock);
        }

        /* ugh, clear_extent_buffer_dirty needs to lock the page */
        btrfs_set_lock_blocking(buf);
        clear_extent_buffer_dirty(buf);
    }
}

static void __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
             u32 stripesize, struct btrfs_root *root,
             struct btrfs_fs_info *fs_info,
             u64 objectid)
{
    root->node = NULL;
    root->commit_root = NULL;
    root->sectorsize = sectorsize;
    root->nodesize = nodesize;
    root->leafsize = leafsize;
    root->stripesize = stripesize;
    root->ref_cows = 0;
    root->track_dirty = 0;
    root->in_radix = 0;
    root->orphan_item_inserted = 0;
    root->orphan_cleanup_state = 0;

    root->objectid = objectid;
    root->last_trans = 0;
    root->highest_objectid = 0;
    root->name = NULL;
    root->inode_tree = RB_ROOT;
    INIT_RADIX_TREE(&root->delayed_nodes_tree, GFP_ATOMIC);
    root->block_rsv = NULL;
    root->orphan_block_rsv = NULL;

    INIT_LIST_HEAD(&root->dirty_list);
    INIT_LIST_HEAD(&root->root_list);
    spin_lock_init(&root->orphan_lock);
    spin_lock_init(&root->inode_lock);
    spin_lock_init(&root->accounting_lock);
    mutex_init(&root->objectid_mutex);
    mutex_init(&root->log_mutex);
    init_waitqueue_head(&root->log_writer_wait);
    init_waitqueue_head(&root->log_commit_wait[0]);
    init_waitqueue_head(&root->log_commit_wait[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);
    atomic_set(&root->orphan_inodes, 0);
    root->log_transid = 0;
    root->last_log_commit = 0;
    extent_io_tree_init(&root->dirty_log_pages,
                 fs_info->btree_inode->i_mapping);

    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));
    memset(&root->root_kobj, 0, sizeof(root->root_kobj));
    root->defrag_trans_start = fs_info->generation;
    init_completion(&root->kobj_unregister);
    root->defrag_running = 0;
    root->root_key.objectid = objectid;
    root->anon_dev = 0;

    spin_lock_init(&root->root_times_lock);
}

static int __must_check find_and_setup_root(struct btrfs_root *tree_root,
                        struct btrfs_fs_info *fs_info,
                        u64 objectid,
                        struct btrfs_root *root)
{
    int ret;
    u32 blocksize;
    u64 generation;

    __setup_root(tree_root->nodesize, tree_root->leafsize,
             tree_root->sectorsize, tree_root->stripesize,
             root, fs_info, objectid);
    ret = btrfs_find_last_root(tree_root, objectid,
                   &root->root_item, &root->root_key);
    if (ret > 0)
        return -ENOENT;
    else if (ret < 0)
        return ret;

    generation = btrfs_root_generation(&root->root_item);
    blocksize = btrfs_level_size(root, btrfs_root_level(&root->root_item));
    root->commit_root = NULL;
    root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
                     blocksize, generation);
    if (!root->node || !btrfs_buffer_uptodate(root->node, generation, 0)) {
        free_extent_buffer(root->node);
        root->node = NULL;
        return -EIO;
    }
    root->commit_root = btrfs_root_node(root);
    return 0;
}

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

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

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

    __setup_root(tree_root->nodesize, tree_root->leafsize,
             tree_root->sectorsize, tree_root->stripesize,
             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_free_block(trans, root, root->leafsize,
                      0, objectid, NULL, 0, 0, 0);
    if (IS_ERR(leaf)) {
        ret = PTR_ERR(leaf);
        goto fail;
    }

    bytenr = leaf->start;
    memset_extent_buffer(leaf, 0, 0, sizeof(struct btrfs_header));
    btrfs_set_header_bytenr(leaf, leaf->start);
    btrfs_set_header_generation(leaf, trans->transid);
    btrfs_set_header_backref_rev(leaf, BTRFS_MIXED_BACKREF_REV);
    btrfs_set_header_owner(leaf, objectid);
    root->node = leaf;

    write_extent_buffer(leaf, fs_info->fsid,
                (unsigned long)btrfs_header_fsid(leaf),
                BTRFS_FSID_SIZE);
    write_extent_buffer(leaf, fs_info->chunk_tree_uuid,
                (unsigned long)btrfs_header_chunk_tree_uuid(leaf),
                BTRFS_UUID_SIZE);
    btrfs_mark_buffer_dirty(leaf);

    root->commit_root = btrfs_root_node(root);
    root->track_dirty = 1;


    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);
    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);

fail:
    if (ret)
        return ERR_PTR(ret);

    return root;
}

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

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

    __setup_root(tree_root->nodesize, tree_root->leafsize,
             tree_root->sectorsize, tree_root->stripesize,
             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;
    /*
     * 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).
     */
    root->ref_cows = 0;

    leaf = btrfs_alloc_free_block(trans, root, root->leafsize, 0,
                      BTRFS_TREE_LOG_OBJECTID, NULL,
                      0, 0, 0);
    if (IS_ERR(leaf)) {
        kfree(root);
        return ERR_CAST(leaf);
    }

    memset_extent_buffer(leaf, 0, 0, sizeof(struct btrfs_header));
    btrfs_set_header_bytenr(leaf, leaf->start);
    btrfs_set_header_generation(leaf, trans->transid);
    btrfs_set_header_backref_rev(leaf, BTRFS_MIXED_BACKREF_REV);
    btrfs_set_header_owner(leaf, BTRFS_TREE_LOG_OBJECTID);
    root->node = leaf;

    write_extent_buffer(root->node, root->fs_info->fsid,
                (unsigned long)btrfs_header_fsid(root->node),
                BTRFS_FSID_SIZE);
    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_root *log_root;
    struct btrfs_inode_item *inode_item;

    log_root = alloc_log_tree(trans, root->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;
    inode_item->generation = cpu_to_le64(1);
    inode_item->size = cpu_to_le64(3);
    inode_item->nlink = cpu_to_le32(1);
    inode_item->nbytes = cpu_to_le64(root->leafsize);
    inode_item->mode = cpu_to_le32(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->last_log_commit = 0;
    return 0;
}

struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
                           struct btrfs_key *location)
{
    struct btrfs_root *root;
    struct btrfs_fs_info *fs_info = tree_root->fs_info;
    struct btrfs_path *path;
    struct extent_buffer *l;
    u64 generation;
    u32 blocksize;
    int ret = 0;
    int slot;

    root = btrfs_alloc_root(fs_info);
    if (!root)
        return ERR_PTR(-ENOMEM);
    if (location->offset == (u64)-1) {
        ret = find_and_setup_root(tree_root, fs_info,
                      location->objectid, root);
        if (ret) {
            kfree(root);
            return ERR_PTR(ret);
        }
        goto out;
    }

    __setup_root(tree_root->nodesize, tree_root->leafsize,
             tree_root->sectorsize, tree_root->stripesize,
             root, fs_info, location->objectid);

    path = btrfs_alloc_path();
    if (!path) {
        kfree(root);
        return ERR_PTR(-ENOMEM);
    }
    ret = btrfs_search_slot(NULL, tree_root, location, path, 0, 0);
    if (ret == 0) {
        l = path->nodes[0];
        slot = path->slots[0];
        btrfs_read_root_item(tree_root, l, slot, &root->root_item);
        memcpy(&root->root_key, location, sizeof(*location));
    }
    btrfs_free_path(path);
    if (ret) {
        kfree(root);
        if (ret > 0)
            ret = -ENOENT;
        return ERR_PTR(ret);
    }

    generation = btrfs_root_generation(&root->root_item);
    blocksize = btrfs_level_size(root, btrfs_root_level(&root->root_item));
    root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
                     blocksize, generation);
    root->commit_root = btrfs_root_node(root);
    BUG_ON(!root->node); /* -ENOMEM */
out:
    if (location->objectid != BTRFS_TREE_LOG_OBJECTID) {
        root->ref_cows = 1;
        btrfs_check_and_init_root_item(&root->root_item);
    }

    return root;
}

struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
                          struct btrfs_key *location)
{
    struct btrfs_root *root;
    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);
again:
    spin_lock(&fs_info->fs_roots_radix_lock);
    root = radix_tree_lookup(&fs_info->fs_roots_radix,
                 (unsigned long)location->objectid);
    spin_unlock(&fs_info->fs_roots_radix_lock);
    if (root)
        return root;

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

    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;
    }

    btrfs_init_free_ino_ctl(root);
    mutex_init(&root->fs_commit_mutex);
    spin_lock_init(&root->cache_lock);
    init_waitqueue_head(&root->cache_wait);

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

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

    ret = btrfs_find_orphan_item(fs_info->tree_root, location->objectid);
    if (ret < 0)
        goto fail;
    if (ret == 0)
        root->orphan_item_inserted = 1;

    ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
    if (ret)
        goto fail;

    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)
        root->in_radix = 1;

    spin_unlock(&fs_info->fs_roots_radix_lock);
    radix_tree_preload_end();
    if (ret) {
        if (ret == -EEXIST) {
            free_fs_root(root);
            goto again;
        }
        goto fail;
    }

    ret = btrfs_find_dead_roots(fs_info->tree_root,
                    root->root_key.objectid);
    WARN_ON(ret);
    return root;
fail:
    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 = blk_get_backing_dev_info(device->bdev);
        if (bdi && bdi_congested(bdi, bdi_bits)) {
            ret = 1;
            break;
        }
    }
    rcu_read_unlock();
    return ret;
}

/*
 * If this fails, caller must call bdi_destroy() to get rid of the
 * bdi again.
 */
static int setup_bdi(struct btrfs_fs_info *info, struct backing_dev_info *bdi)
{
    int err;

    bdi->capabilities = BDI_CAP_MAP_COPY;
    err = bdi_setup_and_register(bdi, "btrfs", BDI_CAP_MAP_COPY);
    if (err)
        return err;

    bdi->ra_pages   = default_backing_dev_info.ra_pages;
    bdi->congested_fn   = btrfs_congested_fn;
    bdi->congested_data = info;
    return 0;
}

/*
 * 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 end_io_wq *end_io_wq;
    struct btrfs_fs_info *fs_info;
    int error;

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

    error = end_io_wq->error;
    bio->bi_private = end_io_wq->private;
    bio->bi_end_io = end_io_wq->end_io;
    kfree(end_io_wq);
    bio_endio(bio, error);
}

static int cleaner_kthread(void *arg)
{
    struct btrfs_root *root = arg;

    do {
        if (!(root->fs_info->sb->s_flags & MS_RDONLY) &&
            mutex_trylock(&root->fs_info->cleaner_mutex)) {
            btrfs_run_delayed_iputs(root);
            btrfs_clean_old_snapshots(root);
            mutex_unlock(&root->fs_info->cleaner_mutex);
            btrfs_run_defrag_inodes(root->fs_info);
        }

        if (!try_to_freeze()) {
            set_current_state(TASK_INTERRUPTIBLE);
            if (!kthread_should_stop())
                schedule();
            __set_current_state(TASK_RUNNING);
        }
    } while (!kthread_should_stop());
    return 0;
}

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

    do {
        cannot_commit = false;
        delay = HZ * 30;
        mutex_lock(&root->fs_info->transaction_kthread_mutex);

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

        now = get_seconds();
        if (!cur->blocked &&
            (now < cur->start_time || now - cur->start_time < 30)) {
            spin_unlock(&root->fs_info->trans_lock);
            delay = HZ * 5;
            goto sleep;
        }
        transid = cur->transid;
        spin_unlock(&root->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, root);
        } else {
            btrfs_end_transaction(trans, root);
        }
sleep:
        wake_up_process(root->fs_info->cleaner_kthread);
        mutex_unlock(&root->fs_info->transaction_kthread_mutex);

        if (!try_to_freeze()) {
            set_current_state(TASK_INTERRUPTIBLE);
            if (!kthread_should_stop() &&
                (!btrfs_transaction_blocked(root->fs_info) ||
                 cannot_commit))
                schedule_timeout(delay);
            __set_current_state(TASK_RUNNING);
        }
    } 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 tree roots */
static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
{
    free_extent_buffer(info->tree_root->node);
    free_extent_buffer(info->tree_root->commit_root);
    free_extent_buffer(info->dev_root->node);
    free_extent_buffer(info->dev_root->commit_root);
    free_extent_buffer(info->extent_root->node);
    free_extent_buffer(info->extent_root->commit_root);
    free_extent_buffer(info->csum_root->node);
    free_extent_buffer(info->csum_root->commit_root);
    if (info->quota_root) {
        free_extent_buffer(info->quota_root->node);
        free_extent_buffer(info->quota_root->commit_root);
    }

    info->tree_root->node = NULL;
    info->tree_root->commit_root = NULL;
    info->dev_root->node = NULL;
    info->dev_root->commit_root = NULL;
    info->extent_root->node = NULL;
    info->extent_root->commit_root = NULL;
    info->csum_root->node = NULL;
    info->csum_root->commit_root = NULL;
    if (info->quota_root) {
        info->quota_root->node = NULL;
        info->quota_root->commit_root = NULL;
    }

    if (chunk_root) {
        free_extent_buffer(info->chunk_root->node);
        free_extent_buffer(info->chunk_root->commit_root);
        info->chunk_root->node = NULL;
        info->chunk_root->commit_root = NULL;
    }
}


int open_ctree(struct super_block *sb,
           struct btrfs_fs_devices *fs_devices,
           char *options)
{
    u32 sectorsize;
    u32 nodesize;
    u32 leafsize;
    u32 blocksize;
    u32 stripesize;
    u64 generation;
    u64 features;
    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 *extent_root;
    struct btrfs_root *csum_root;
    struct btrfs_root *chunk_root;
    struct btrfs_root *dev_root;
    struct btrfs_root *quota_root;
    struct btrfs_root *log_tree_root;
    int ret;
    int err = -EINVAL;
    int num_backups_tried = 0;
    int backup_index = 0;

    tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info);
    extent_root = fs_info->extent_root = btrfs_alloc_root(fs_info);
    csum_root = fs_info->csum_root = btrfs_alloc_root(fs_info);
    chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info);
    dev_root = fs_info->dev_root = btrfs_alloc_root(fs_info);
    quota_root = fs_info->quota_root = btrfs_alloc_root(fs_info);

    if (!tree_root || !extent_root || !csum_root ||
        !chunk_root || !dev_root || !quota_root) {
        err = -ENOMEM;
        goto fail;
    }

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

    ret = setup_bdi(fs_info, &fs_info->bdi);
    if (ret) {
        err = ret;
        goto fail_srcu;
    }

    fs_info->btree_inode = new_inode(sb);
    if (!fs_info->btree_inode) {
        err = -ENOMEM;
        goto fail_bdi;
    }

    mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);

    INIT_RADIX_TREE(&fs_info->fs_roots_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_inodes);
    INIT_LIST_HEAD(&fs_info->ordered_operations);
    INIT_LIST_HEAD(&fs_info->caching_block_groups);
    spin_lock_init(&fs_info->delalloc_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->free_chunk_lock);
    spin_lock_init(&fs_info->tree_mod_seq_lock);
    rwlock_init(&fs_info->tree_mod_log_lock);
    mutex_init(&fs_info->reloc_mutex);

    init_completion(&fs_info->kobj_unregister);
    INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);
    INIT_LIST_HEAD(&fs_info->space_info);
    INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
    btrfs_mapping_init(&fs_info->mapping_tree);
    btrfs_init_block_rsv(&fs_info->global_block_rsv,
                 BTRFS_BLOCK_RSV_GLOBAL);
    btrfs_init_block_rsv(&fs_info->delalloc_block_rsv,
                 BTRFS_BLOCK_RSV_DELALLOC);
    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);
    atomic_set(&fs_info->nr_async_submits, 0);
    atomic_set(&fs_info->async_delalloc_pages, 0);
    atomic_set(&fs_info->async_submit_draining, 0);
    atomic_set(&fs_info->nr_async_bios, 0);
    atomic_set(&fs_info->defrag_running, 0);
    atomic_set(&fs_info->tree_mod_seq, 0);
    fs_info->sb = sb;
    fs_info->max_inline = 8192 * 1024;
    fs_info->metadata_ratio = 0;
    fs_info->defrag_inodes = RB_ROOT;
    fs_info->trans_no_join = 0;
    fs_info->free_chunk_space = 0;
    fs_info->tree_mod_log = RB_ROOT;

    /* readahead state */
    INIT_RADIX_TREE(&fs_info->reada_tree, GFP_NOFS & ~__GFP_WAIT);
    spin_lock_init(&fs_info->reada_lock);

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

    INIT_LIST_HEAD(&fs_info->ordered_extents);
    spin_lock_init(&fs_info->ordered_extent_lock);
    fs_info->delayed_root = kmalloc(sizeof(struct btrfs_delayed_root),
                    GFP_NOFS);
    if (!fs_info->delayed_root) {
        err = -ENOMEM;
        goto fail_iput;
    }
    btrfs_init_delayed_root(fs_info->delayed_root);

    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);
    init_rwsem(&fs_info->scrub_super_lock);
    fs_info->scrub_workers_refcnt = 0;
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
    fs_info->check_integrity_print_mask = 0;
#endif

    spin_lock_init(&fs_info->balance_lock);
    mutex_init(&fs_info->balance_mutex);
    atomic_set(&fs_info->balance_running, 0);
    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);

    sb->s_blocksize = 4096;
    sb->s_blocksize_bits = blksize_bits(4096);
    sb->s_bdi = &fs_info->bdi;

    fs_info->btree_inode->i_ino = BTRFS_BTREE_INODE_OBJECTID;
    set_nlink(fs_info->btree_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
     */
    fs_info->btree_inode->i_size = OFFSET_MAX;
    fs_info->btree_inode->i_mapping->a_ops = &btree_aops;
    fs_info->btree_inode->i_mapping->backing_dev_info = &fs_info->bdi;

    RB_CLEAR_NODE(&BTRFS_I(fs_info->btree_inode)->rb_node);
    extent_io_tree_init(&BTRFS_I(fs_info->btree_inode)->io_tree,
                 fs_info->btree_inode->i_mapping);
    BTRFS_I(fs_info->btree_inode)->io_tree.track_uptodate = 0;
    extent_map_tree_init(&BTRFS_I(fs_info->btree_inode)->extent_tree);

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

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

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

    extent_io_tree_init(&fs_info->freed_extents[0],
                 fs_info->btree_inode->i_mapping);
    extent_io_tree_init(&fs_info->freed_extents[1],
                 fs_info->btree_inode->i_mapping);
    fs_info->pinned_extents = &fs_info->freed_extents[0];
    fs_info->do_barriers = 1;


    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->volume_mutex);
    init_rwsem(&fs_info->extent_commit_sem);
    init_rwsem(&fs_info->cleanup_work_sem);
    init_rwsem(&fs_info->subvol_sem);

    spin_lock_init(&fs_info->qgroup_lock);
    fs_info->qgroup_tree = RB_ROOT;
    INIT_LIST_HEAD(&fs_info->dirty_qgroups);
    fs_info->qgroup_seq = 1;
    fs_info->quota_enabled = 0;
    fs_info->pending_quota_state = 0;

    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);

    __setup_root(4096, 4096, 4096, 4096, tree_root,
             fs_info, BTRFS_ROOT_TREE_OBJECTID);

    invalidate_bdev(fs_devices->latest_bdev);
    bh = btrfs_read_dev_super(fs_devices->latest_bdev);
    if (!bh) {
        err = -EINVAL;
        goto fail_alloc;
    }

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

    memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);

    disk_super = fs_info->super_copy;
    if (!btrfs_super_root(disk_super))
        goto fail_alloc;

    /* check FS state, whether FS is broken. */
    fs_info->fs_state |= btrfs_super_flags(disk_super);

    ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);
    if (ret) {
        printk(KERN_ERR "btrfs: superblock contains fatal errors\n");
        err = ret;
        goto fail_alloc;
    }

    /*
     * 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(tree_root, options);
    if (ret) {
        err = ret;
        goto fail_alloc;
    }

    features = btrfs_super_incompat_flags(disk_super) &
        ~BTRFS_FEATURE_INCOMPAT_SUPP;
    if (features) {
        printk(KERN_ERR "BTRFS: couldn't mount because of "
               "unsupported optional features (%Lx).\n",
               (unsigned long long)features);
        err = -EINVAL;
        goto fail_alloc;
    }

    if (btrfs_super_leafsize(disk_super) !=
        btrfs_super_nodesize(disk_super)) {
        printk(KERN_ERR "BTRFS: couldn't mount because metadata "
               "blocksizes don't match.  node %d leaf %d\n",
               btrfs_super_nodesize(disk_super),
               btrfs_super_leafsize(disk_super));
        err = -EINVAL;
        goto fail_alloc;
    }
    if (btrfs_super_leafsize(disk_super) > BTRFS_MAX_METADATA_BLOCKSIZE) {
        printk(KERN_ERR "BTRFS: couldn't mount because metadata "
               "blocksize (%d) was too large\n",
               btrfs_super_leafsize(disk_super));
        err = -EINVAL;
        goto fail_alloc;
    }

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

    /*
     * flag our filesystem as having big metadata blocks if
     * they are bigger than the page size
     */
    if (btrfs_super_leafsize(disk_super) > PAGE_CACHE_SIZE) {
        if (!(features & BTRFS_FEATURE_INCOMPAT_BIG_METADATA))
            printk(KERN_INFO "btrfs flagging fs with big metadata feature\n");
        features |= BTRFS_FEATURE_INCOMPAT_BIG_METADATA;
    }

    nodesize = btrfs_super_nodesize(disk_super);
    leafsize = btrfs_super_leafsize(disk_super);
    sectorsize = btrfs_super_sectorsize(disk_super);
    stripesize = btrfs_super_stripesize(disk_super);

    /*
     * 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 != leafsize)) {
        printk(KERN_WARNING "btrfs: unequal leaf/node/sector sizes "
                "are not allowed for mixed block groups on %s\n",
                sb->s_id);
        goto fail_alloc;
    }

    btrfs_set_super_incompat_flags(disk_super, features);

    features = btrfs_super_compat_ro_flags(disk_super) &
        ~BTRFS_FEATURE_COMPAT_RO_SUPP;
    if (!(sb->s_flags & MS_RDONLY) && features) {
        printk(KERN_ERR "BTRFS: couldn't mount RDWR because of "
               "unsupported option features (%Lx).\n",
               (unsigned long long)features);
        err = -EINVAL;
        goto fail_alloc;
    }

    btrfs_init_workers(&fs_info->generic_worker,
               "genwork", 1, NULL);

    btrfs_init_workers(&fs_info->workers, "worker",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);

    btrfs_init_workers(&fs_info->delalloc_workers, "delalloc",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);

    btrfs_init_workers(&fs_info->submit_workers, "submit",
               min_t(u64, fs_devices->num_devices,
               fs_info->thread_pool_size),
               &fs_info->generic_worker);

    btrfs_init_workers(&fs_info->caching_workers, "cache",
               2, &fs_info->generic_worker);

    /* 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.idle_thresh = 64;

    fs_info->workers.idle_thresh = 16;
    fs_info->workers.ordered = 1;

    fs_info->delalloc_workers.idle_thresh = 2;
    fs_info->delalloc_workers.ordered = 1;

    btrfs_init_workers(&fs_info->fixup_workers, "fixup", 1,
               &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->endio_workers, "endio",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->endio_meta_workers, "endio-meta",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->endio_meta_write_workers,
               "endio-meta-write", fs_info->thread_pool_size,
               &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->endio_write_workers, "endio-write",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->endio_freespace_worker, "freespace-write",
               1, &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->delayed_workers, "delayed-meta",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);
    btrfs_init_workers(&fs_info->readahead_workers, "readahead",
               fs_info->thread_pool_size,
               &fs_info->generic_worker);

    /*
     * endios are largely parallel and should have a very
     * low idle thresh
     */
    fs_info->endio_workers.idle_thresh = 4;
    fs_info->endio_meta_workers.idle_thresh = 4;

    fs_info->endio_write_workers.idle_thresh = 2;
    fs_info->endio_meta_write_workers.idle_thresh = 2;
    fs_info->readahead_workers.idle_thresh = 2;

    /*
     * btrfs_start_workers can really only fail because of ENOMEM so just
     * return -ENOMEM if any of these fail.
     */
    ret = btrfs_start_workers(&fs_info->workers);
    ret |= btrfs_start_workers(&fs_info->generic_worker);
    ret |= btrfs_start_workers(&fs_info->submit_workers);
    ret |= btrfs_start_workers(&fs_info->delalloc_workers);
    ret |= btrfs_start_workers(&fs_info->fixup_workers);
    ret |= btrfs_start_workers(&fs_info->endio_workers);
    ret |= btrfs_start_workers(&fs_info->endio_meta_workers);
    ret |= btrfs_start_workers(&fs_info->endio_meta_write_workers);
    ret |= btrfs_start_workers(&fs_info->endio_write_workers);
    ret |= btrfs_start_workers(&fs_info->endio_freespace_worker);
    ret |= btrfs_start_workers(&fs_info->delayed_workers);
    ret |= btrfs_start_workers(&fs_info->caching_workers);
    ret |= btrfs_start_workers(&fs_info->readahead_workers);
    if (ret) {
        err = -ENOMEM;
        goto fail_sb_buffer;
    }

    fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
    fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
                    4 * 1024 * 1024 / PAGE_CACHE_SIZE);

    tree_root->nodesize = nodesize;
    tree_root->leafsize = leafsize;
    tree_root->sectorsize = sectorsize;
    tree_root->stripesize = stripesize;

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

    if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
            sizeof(disk_super->magic))) {
        printk(KERN_INFO "btrfs: valid FS not found on %s\n", sb->s_id);
        goto fail_sb_buffer;
    }

    if (sectorsize != PAGE_SIZE) {
        printk(KERN_WARNING "btrfs: Incompatible sector size(%lu) "
               "found on %s\n", (unsigned long)sectorsize, sb->s_id);
        goto fail_sb_buffer;
    }

    mutex_lock(&fs_info->chunk_mutex);
    ret = btrfs_read_sys_array(tree_root);
    mutex_unlock(&fs_info->chunk_mutex);
    if (ret) {
        printk(KERN_WARNING "btrfs: failed to read the system "
               "array on %s\n", sb->s_id);
        goto fail_sb_buffer;
    }

    blocksize = btrfs_level_size(tree_root,
                     btrfs_super_chunk_root_level(disk_super));
    generation = btrfs_super_chunk_root_generation(disk_super);

    __setup_root(nodesize, leafsize, sectorsize, stripesize,
             chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);

    chunk_root->node = read_tree_block(chunk_root,
                       btrfs_super_chunk_root(disk_super),
                       blocksize, generation);
    BUG_ON(!chunk_root->node); /* -ENOMEM */
    if (!test_bit(EXTENT_BUFFER_UPTODATE, &chunk_root->node->bflags)) {
        printk(KERN_WARNING "btrfs: failed to read chunk root on %s\n",
               sb->s_id);
        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,
       (unsigned long)btrfs_header_chunk_tree_uuid(chunk_root->node),
       BTRFS_UUID_SIZE);

    ret = btrfs_read_chunk_tree(chunk_root);
    if (ret) {
        printk(KERN_WARNING "btrfs: failed to read chunk tree on %s\n",
               sb->s_id);
        goto fail_tree_roots;
    }

    btrfs_close_extra_devices(fs_devices);

    if (!fs_devices->latest_bdev) {
        printk(KERN_CRIT "btrfs: failed to read devices on %s\n",
               sb->s_id);
        goto fail_tree_roots;
    }

retry_root_backup:
    blocksize = btrfs_level_size(tree_root,
                     btrfs_super_root_level(disk_super));
    generation = btrfs_super_generation(disk_super);

    tree_root->node = read_tree_block(tree_root,
                      btrfs_super_root(disk_super),
                      blocksize, generation);
    if (!tree_root->node ||
        !test_bit(EXTENT_BUFFER_UPTODATE, &tree_root->node->bflags)) {
        printk(KERN_WARNING "btrfs: failed to read tree root on %s\n",
               sb->s_id);

        goto recovery_tree_root;
    }

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

    ret = find_and_setup_root(tree_root, fs_info,
                  BTRFS_EXTENT_TREE_OBJECTID, extent_root);
    if (ret)
        goto recovery_tree_root;
    extent_root->track_dirty = 1;

    ret = find_and_setup_root(tree_root, fs_info,
                  BTRFS_DEV_TREE_OBJECTID, dev_root);
    if (ret)
        goto recovery_tree_root;
    dev_root->track_dirty = 1;

    ret = find_and_setup_root(tree_root, fs_info,
                  BTRFS_CSUM_TREE_OBJECTID, csum_root);
    if (ret)
        goto recovery_tree_root;
    csum_root->track_dirty = 1;

    ret = find_and_setup_root(tree_root, fs_info,
                  BTRFS_QUOTA_TREE_OBJECTID, quota_root);
    if (ret) {
        kfree(quota_root);
        quota_root = fs_info->quota_root = NULL;
    } else {
        quota_root->track_dirty = 1;
        fs_info->quota_enabled = 1;
        fs_info->pending_quota_state = 1;
    }

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

    ret = btrfs_recover_balance(fs_info);
    if (ret) {
        printk(KERN_WARNING "btrfs: failed to recover balance\n");
        goto fail_block_groups;
    }

    ret = btrfs_init_dev_stats(fs_info);
    if (ret) {
        printk(KERN_ERR "btrfs: failed to init dev_stats: %d\n",
               ret);
        goto fail_block_groups;
    }

    ret = btrfs_init_space_info(fs_info);
    if (ret) {
        printk(KERN_ERR "Failed to initial space info: %d\n", ret);
        goto fail_block_groups;
    }

    ret = btrfs_read_block_groups(extent_root);
    if (ret) {
        printk(KERN_ERR "Failed to read block groups: %d\n", ret);
        goto fail_block_groups;
    }
    fs_info->num_tolerated_disk_barrier_failures =
        btrfs_calc_num_tolerated_disk_barrier_failures(fs_info);

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

    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(tree_root, SSD) &&
        !btrfs_test_opt(tree_root, NOSSD) &&
        !fs_info->fs_devices->rotating) {
        printk(KERN_INFO "Btrfs detected SSD devices, enabling SSD "
               "mode\n");
        btrfs_set_opt(fs_info->mount_opt, SSD);
    }

#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
    if (btrfs_test_opt(tree_root, CHECK_INTEGRITY)) {
        ret = btrfsic_mount(tree_root, fs_devices,
                    btrfs_test_opt(tree_root,
                    CHECK_INTEGRITY_INCLUDING_EXTENT_DATA) ?
                    1 : 0,
                    fs_info->check_integrity_print_mask);
        if (ret)
            printk(KERN_WARNING "btrfs: failed to initialize"
                   " integrity check module %s\n", sb->s_id);
    }
#endif
    ret = btrfs_read_qgroup_config(fs_info);
    if (ret)
        goto fail_trans_kthread;

    /* do not make disk changes in broken FS */
    if (btrfs_super_log_root(disk_super) != 0) {
        u64 bytenr = btrfs_super_log_root(disk_super);

        if (fs_devices->rw_devices == 0) {
            printk(KERN_WARNING "Btrfs log replay required "
                   "on RO media\n");
            err = -EIO;
            goto fail_qgroup;
        }
        blocksize =
             btrfs_level_size(tree_root,
                      btrfs_super_log_root_level(disk_super));

        log_tree_root = btrfs_alloc_root(fs_info);
        if (!log_tree_root) {
            err = -ENOMEM;
            goto fail_qgroup;
        }

        __setup_root(nodesize, leafsize, sectorsize, stripesize,
                 log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);

        log_tree_root->node = read_tree_block(tree_root, bytenr,
                              blocksize,
                              generation + 1);
        /* returns with log_tree_root freed on success */
        ret = btrfs_recover_log_trees(log_tree_root);
        if (ret) {
            btrfs_error(tree_root->fs_info, ret,
                    "Failed to recover log tree");
            free_extent_buffer(log_tree_root->node);
            kfree(log_tree_root);
            goto fail_trans_kthread;
        }

        if (sb->s_flags & MS_RDONLY) {
            ret = btrfs_commit_super(tree_root);
            if (ret)
                goto fail_trans_kthread;
        }
    }

    ret = btrfs_find_orphan_roots(tree_root);
    if (ret)
        goto fail_trans_kthread;

    if (!(sb->s_flags & MS_RDONLY)) {
        ret = btrfs_cleanup_fs_roots(fs_info);
        if (ret)
            goto fail_trans_kthread;

        ret = btrfs_recover_relocation(tree_root);
        if (ret < 0) {
            printk(KERN_WARNING
                   "btrfs: failed to recover relocation\n");
            err = -EINVAL;
            goto fail_qgroup;
        }
    }

    location.objectid = BTRFS_FS_TREE_OBJECTID;
    location.type = BTRFS_ROOT_ITEM_KEY;
    location.offset = (u64)-1;

    fs_info->fs_root = btrfs_read_fs_root_no_name(fs_info, &location);
    if (!fs_info->fs_root)
        goto fail_qgroup;
    if (IS_ERR(fs_info->fs_root)) {
        err = PTR_ERR(fs_info->fs_root);
        goto fail_qgroup;
    }

    if (sb->s_flags & MS_RDONLY)
        return 0;

    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(tree_root);
        return ret;
    }
    up_read(&fs_info->cleanup_work_sem);

    ret = btrfs_resume_balance_async(fs_info);
    if (ret) {
        printk(KERN_WARNING "btrfs: failed to resume balance\n");
        close_ctree(tree_root);
        return ret;
    }

    return 0;

fail_qgroup:
    btrfs_free_qgroup_config(fs_info);
fail_trans_kthread:
    kthread_stop(fs_info->transaction_kthread);
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);
    invalidate_inode_pages2(fs_info->btree_inode->i_mapping);

fail_block_groups:
    btrfs_free_block_groups(fs_info);

fail_tree_roots:
    free_root_pointers(fs_info, 1);

fail_sb_buffer:
    btrfs_stop_workers(&fs_info->generic_worker);
    btrfs_stop_workers(&fs_info->readahead_workers);
    btrfs_stop_workers(&fs_info->fixup_workers);
    btrfs_stop_workers(&fs_info->delalloc_workers);
    btrfs_stop_workers(&fs_info->workers);
    btrfs_stop_workers(&fs_info->endio_workers);
    btrfs_stop_workers(&fs_info->endio_meta_workers);
    btrfs_stop_workers(&fs_info->endio_meta_write_workers);
    btrfs_stop_workers(&fs_info->endio_write_workers);
    btrfs_stop_workers(&fs_info->endio_freespace_worker);
    btrfs_stop_workers(&fs_info->submit_workers);
    btrfs_stop_workers(&fs_info->delayed_workers);
    btrfs_stop_workers(&fs_info->caching_workers);
fail_alloc:
fail_iput:
    btrfs_mapping_tree_free(&fs_info->mapping_tree);

    invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
    iput(fs_info->btree_inode);
fail_bdi:
    bdi_destroy(&fs_info->bdi);
fail_srcu:
    cleanup_srcu_struct(&fs_info->subvol_srcu);
fail:
    btrfs_close_devices(fs_info->fs_devices);
    return err;

recovery_tree_root:
    if (!btrfs_test_opt(tree_root, RECOVERY))
        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;
}

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;

        printk_ratelimited_in_rcu(KERN_WARNING "lost page write due to "
                      "I/O error on %s\n",
                      rcu_str_deref(device->name));
        /* note, we dont' 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);
}

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;
    u64 bytenr;

    /* 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++) {
        bytenr = btrfs_sb_offset(i);
        if (bytenr + 4096 >= i_size_read(bdev->bd_inode))
            break;
        bh = __bread(bdev, bytenr / 4096, 4096);
        if (!bh)
            continue;

        super = (struct btrfs_super_block *)bh->b_data;
        if (btrfs_super_bytenr(super) != bytenr ||
            strncmp((char *)(&super->magic), BTRFS_MAGIC,
                sizeof(super->magic))) {
            brelse(bh);
            continue;
        }

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

/*
 * this should be called twice, once with wait == 0 and
 * once with wait == 1.  When wait == 0 is done, all the buffer heads
 * we write are pinned.
 *
 * They are released when wait == 1 is done.
 * max_mirrors must be the same for both runs, and it indicates how
 * many supers on this one device should be written.
 *
 * max_mirrors == 0 means to write them all.
 */
static int write_dev_supers(struct btrfs_device *device,
                struct btrfs_super_block *sb,
                int do_barriers, int wait, int max_mirrors)
{
    struct buffer_head *bh;
    int i;
    int ret;
    int errors = 0;
    u32 crc;
    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->total_bytes)
            break;

        if (wait) {
            bh = __find_get_block(device->bdev, bytenr / 4096,
                          BTRFS_SUPER_INFO_SIZE);
            BUG_ON(!bh);
            wait_on_buffer(bh);
            if (!buffer_uptodate(bh))
                errors++;

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

            /* drop the reference from the wait == 0 run */
            brelse(bh);
            continue;
        } else {
            btrfs_set_super_bytenr(sb, bytenr);

            crc = ~(u32)0;
            crc = btrfs_csum_data(NULL, (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 / 4096,
                      BTRFS_SUPER_INFO_SIZE);
            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.
         */
        ret = btrfsic_submit_bh(WRITE_FUA, bh);
        if (ret)
            errors++;
    }
    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, int err)
{
    if (err) {
        if (err == -EOPNOTSUPP)
            set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
        clear_bit(BIO_UPTODATE, &bio->bi_flags);
    }
    if (bio->bi_private)
        complete(bio->bi_private);
    bio_put(bio);
}

/*
 * trigger flushes for one the devices.  If you pass wait == 0, the flushes are
 * sent down.  With wait == 1, it waits for the previous flush.
 *
 * any device where the flush fails with eopnotsupp are flagged as not-barrier
 * capable
 */
static int write_dev_flush(struct btrfs_device *device, int wait)
{
    struct bio *bio;
    int ret = 0;

    if (device->nobarriers)
        return 0;

    if (wait) {
        bio = device->flush_bio;
        if (!bio)
            return 0;

        wait_for_completion(&device->flush_wait);

        if (bio_flagged(bio, BIO_EOPNOTSUPP)) {
            printk_in_rcu("btrfs: disabling barriers on dev %s\n",
                      rcu_str_deref(device->name));
            device->nobarriers = 1;
        } else if (!bio_flagged(bio, BIO_UPTODATE)) {
            ret = -EIO;
            btrfs_dev_stat_inc_and_print(device,
                BTRFS_DEV_STAT_FLUSH_ERRS);
        }

        /* drop the reference from the wait == 0 run */
        bio_put(bio);
        device->flush_bio = NULL;

        return ret;
    }

    /*
     * one reference for us, and we leave it for the
     * caller
     */
    device->flush_bio = NULL;
    bio = bio_alloc(GFP_NOFS, 0);
    if (!bio)
        return -ENOMEM;

    bio->bi_end_io = btrfs_end_empty_barrier;
    bio->bi_bdev = device->bdev;
    init_completion(&device->flush_wait);
    bio->bi_private = &device->flush_wait;
    device->flush_bio = bio;

    bio_get(bio);
    btrfsic_submit_bio(WRITE_FLUSH, bio);

    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_send = 0;
    int errors_wait = 0;
    int ret;

    /* send down all the barriers */
    head = &info->fs_devices->devices;
    list_for_each_entry_rcu(dev, head, dev_list) {
        if (!dev->bdev) {
            errors_send++;
            continue;
        }
        if (!dev->in_fs_metadata || !dev->writeable)
            continue;

        ret = write_dev_flush(dev, 0);
        if (ret)
            errors_send++;
    }

    /* wait for all the barriers */
    list_for_each_entry_rcu(dev, head, dev_list) {
        if (!dev->bdev) {
            errors_wait++;
            continue;
        }
        if (!dev->in_fs_metadata || !dev->writeable)
            continue;

        ret = write_dev_flush(dev, 1);
        if (ret)
            errors_wait++;
    }
    if (errors_send > info->num_tolerated_disk_barrier_failures ||
        errors_wait > info->num_tolerated_disk_barrier_failures)
        return -EIO;
    return 0;
}

int btrfs_calc_num_tolerated_disk_barrier_failures(
    struct btrfs_fs_info *fs_info)
{
    struct btrfs_ioctl_space_info space;
    struct btrfs_space_info *sinfo;
    u64 types[] = {BTRFS_BLOCK_GROUP_DATA,
               BTRFS_BLOCK_GROUP_SYSTEM,
               BTRFS_BLOCK_GROUP_METADATA,
               BTRFS_BLOCK_GROUP_DATA | BTRFS_BLOCK_GROUP_METADATA};
    int num_types = 4;
    int i;
    int c;
    int num_tolerated_disk_barrier_failures =
        (int)fs_info->fs_devices->num_devices;

    for (i = 0; i < num_types; i++) {
        struct btrfs_space_info *tmp;

        sinfo = NULL;
        rcu_read_lock();
        list_for_each_entry_rcu(tmp, &fs_info->space_info, list) {
            if (tmp->flags == types[i]) {
                sinfo = tmp;
                break;
            }
        }
        rcu_read_unlock();

        if (!sinfo)
            continue;

        down_read(&sinfo->groups_sem);
        for (c = 0; c < BTRFS_NR_RAID_TYPES; c++) {
            if (!list_empty(&sinfo->block_groups[c])) {
                u64 flags;

                btrfs_get_block_group_info(
                    &sinfo->block_groups[c], &space);
                if (space.total_bytes == 0 ||
                    space.used_bytes == 0)
                    continue;
                flags = space.flags;
                /*
                 * return
                 * 0: if dup, single or RAID0 is configured for
                 *    any of metadata, system or data, else
                 * 1: if RAID5 is configured, or if RAID1 or
                 *    RAID10 is configured and only two mirrors
                 *    are used, else
                 * 2: if RAID6 is configured, else
                 * num_mirrors - 1: if RAID1 or RAID10 is
                 *                  configured and more than
                 *                  2 mirrors are used.
                 */
                if (num_tolerated_disk_barrier_failures > 0 &&
                    ((flags & (BTRFS_BLOCK_GROUP_DUP |
                           BTRFS_BLOCK_GROUP_RAID0)) ||
                     ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK)
                      == 0)))
                    num_tolerated_disk_barrier_failures = 0;
                else if (num_tolerated_disk_barrier_failures > 1
                     &&
                     (flags & (BTRFS_BLOCK_GROUP_RAID1 |
                           BTRFS_BLOCK_GROUP_RAID10)))
                    num_tolerated_disk_barrier_failures = 1;
            }
        }
        up_read(&sinfo->groups_sem);
    }

    return num_tolerated_disk_barrier_failures;
}

int write_all_supers(struct btrfs_root *root, 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;

    max_errors = btrfs_super_num_devices(root->fs_info->super_copy) - 1;
    do_barriers = !btrfs_test_opt(root, NOBARRIER);
    backup_super_roots(root->fs_info);

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

    mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
    head = &root->fs_info->fs_devices->devices;

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

    list_for_each_entry_rcu(dev, head, dev_list) {
        if (!dev->bdev) {
            total_errors++;
            continue;
        }
        if (!dev->in_fs_metadata || !dev->writeable)
            continue;

        btrfs_set_stack_device_generation(dev_item, 0);
        btrfs_set_stack_device_type(dev_item, dev->type);
        btrfs_set_stack_device_id(dev_item, dev->devid);
        btrfs_set_stack_device_total_bytes(dev_item, dev->total_bytes);
        btrfs_set_stack_device_bytes_used(dev_item, dev->bytes_used);
        btrfs_set_stack_device_io_align(dev_item, dev->io_align);
        btrfs_set_stack_device_io_width(dev_item, dev->io_width);
        btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
        memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
        memcpy(dev_item->fsid, dev->fs_devices->fsid, BTRFS_UUID_SIZE);

        flags = btrfs_super_flags(sb);
        btrfs_set_super_flags(sb, flags | BTRFS_HEADER_FLAG_WRITTEN);

        ret = write_dev_supers(dev, sb, do_barriers, 0, max_mirrors);
        if (ret)
            total_errors++;
    }
    if (total_errors > max_errors) {
        printk(KERN_ERR "btrfs: %d errors while writing supers\n",
               total_errors);

        /* This shouldn't happen. FUA is masked off if unsupported */
        BUG();
    }

    total_errors = 0;
    list_for_each_entry_rcu(dev, head, dev_list) {
        if (!dev->bdev)
            continue;
        if (!dev->in_fs_metadata || !dev->writeable)
            continue;

        ret = write_dev_supers(dev, sb, do_barriers, 1, max_mirrors);
        if (ret)
            total_errors++;
    }
    mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
    if (total_errors > max_errors) {
        btrfs_error(root->fs_info, -EIO,
                "%d errors while writing supers", total_errors);
        return -EIO;
    }
    return 0;
}

int write_ctree_super(struct btrfs_trans_handle *trans,
              struct btrfs_root *root, int max_mirrors)
{
    int ret;

    ret = write_all_supers(root, max_mirrors);
    return ret;
}

void btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
{
    spin_lock(&fs_info->fs_roots_radix_lock);
    radix_tree_delete(&fs_info->fs_roots_radix,
              (unsigned long)root->root_key.objectid);
    spin_unlock(&fs_info->fs_roots_radix_lock);

    if (btrfs_root_refs(&root->root_item) == 0)
        synchronize_srcu(&fs_info->subvol_srcu);

    __btrfs_remove_free_space_cache(root->free_ino_pinned);
    __btrfs_remove_free_space_cache(root->free_ino_ctl);
    free_fs_root(root);
}

static void free_fs_root(struct btrfs_root *root)
{
    iput(root->cache_inode);
    WARN_ON(!RB_EMPTY_ROOT(&root->inode_tree));
    if (root->anon_dev)
        free_anon_bdev(root->anon_dev);
    free_extent_buffer(root->node);
    free_extent_buffer(root->commit_root);
    kfree(root->free_ino_ctl);
    kfree(root->free_ino_pinned);
    kfree(root->name);
    kfree(root);
}

static void del_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 (gang[0]->in_radix) {
            btrfs_free_fs_root(fs_info, gang[0]);
        } else {
            free_extent_buffer(gang[0]->node);
            free_extent_buffer(gang[0]->commit_root);
            kfree(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_free_fs_root(fs_info, gang[i]);
    }
}

int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info)
{
    u64 root_objectid = 0;
    struct btrfs_root *gang[8];
    int i;
    int ret;

    while (1) {
        ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
                         (void **)gang, root_objectid,
                         ARRAY_SIZE(gang));
        if (!ret)
            break;

        root_objectid = gang[ret - 1]->root_key.objectid + 1;
        for (i = 0; i < ret; i++) {
            int err;

            root_objectid = gang[i]->root_key.objectid;
            err = btrfs_orphan_cleanup(gang[i]);
            if (err)
                return err;
        }
        root_objectid++;
    }
    return 0;
}

int btrfs_commit_super(struct btrfs_root *root)
{
    struct btrfs_trans_handle *trans;
    int ret;

    mutex_lock(&root->fs_info->cleaner_mutex);
    btrfs_run_delayed_iputs(root);
    btrfs_clean_old_snapshots(root);
    mutex_unlock(&root->fs_info->cleaner_mutex);

    /* wait until ongoing cleanup work done */
    down_write(&root->fs_info->cleanup_work_sem);
    up_write(&root->fs_info->cleanup_work_sem);

    trans = btrfs_join_transaction(root);
    if (IS_ERR(trans))
        return PTR_ERR(trans);
    ret = btrfs_commit_transaction(trans, root);
    if (ret)
        return ret;
    /* run commit again to drop the original snapshot */
    trans = btrfs_join_transaction(root);
    if (IS_ERR(trans))
        return PTR_ERR(trans);
    ret = btrfs_commit_transaction(trans, root);
    if (ret)
        return ret;
    ret = btrfs_write_and_wait_transaction(NULL, root);
    if (ret) {
        btrfs_error(root->fs_info, ret,
                "Failed to sync btree inode to disk.");
        return ret;
    }

    ret = write_ctree_super(NULL, root, 0);
    return ret;
}

int close_ctree(struct btrfs_root *root)
{
    struct btrfs_fs_info *fs_info = root->fs_info;
    int ret;

    fs_info->closing = 1;
    smp_mb();

    /* pause restriper - we want to resume on mount */
    btrfs_pause_balance(root->fs_info);

    btrfs_scrub_cancel(root);

    /* wait for any defraggers to finish */
    wait_event(fs_info->transaction_wait,
           (atomic_read(&fs_info->defrag_running) == 0));

    /* clear out the rbtree of defraggable inodes */
    btrfs_run_defrag_inodes(fs_info);

    if (!(fs_info->sb->s_flags & MS_RDONLY)) {
        ret = btrfs_commit_super(root);
        if (ret)
            printk(KERN_ERR "btrfs: commit super ret %d\n", ret);
    }

    if (fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
        btrfs_error_commit_super(root);

    btrfs_put_block_group_cache(fs_info);

    kthread_stop(fs_info->transaction_kthread);
    kthread_stop(fs_info->cleaner_kthread);

    fs_info->closing = 2;
    smp_mb();

    btrfs_free_qgroup_config(root->fs_info);

    if (fs_info->delalloc_bytes) {
        printk(KERN_INFO "btrfs: at unmount delalloc count %llu\n",
               (unsigned long long)fs_info->delalloc_bytes);
    }

    free_extent_buffer(fs_info->extent_root->node);
    free_extent_buffer(fs_info->extent_root->commit_root);
    free_extent_buffer(fs_info->tree_root->node);
    free_extent_buffer(fs_info->tree_root->commit_root);
    free_extent_buffer(fs_info->chunk_root->node);
    free_extent_buffer(fs_info->chunk_root->commit_root);
    free_extent_buffer(fs_info->dev_root->node);
    free_extent_buffer(fs_info->dev_root->commit_root);
    free_extent_buffer(fs_info->csum_root->node);
    free_extent_buffer(fs_info->csum_root->commit_root);
    if (fs_info->quota_root) {
        free_extent_buffer(fs_info->quota_root->node);
        free_extent_buffer(fs_info->quota_root->commit_root);
    }

    btrfs_free_block_groups(fs_info);

    del_fs_roots(fs_info);

    iput(fs_info->btree_inode);

    btrfs_stop_workers(&fs_info->generic_worker);
    btrfs_stop_workers(&fs_info->fixup_workers);
    btrfs_stop_workers(&fs_info->delalloc_workers);
    btrfs_stop_workers(&fs_info->workers);
    btrfs_stop_workers(&fs_info->endio_workers);
    btrfs_stop_workers(&fs_info->endio_meta_workers);
    btrfs_stop_workers(&fs_info->endio_meta_write_workers);
    btrfs_stop_workers(&fs_info->endio_write_workers);
    btrfs_stop_workers(&fs_info->endio_freespace_worker);
    btrfs_stop_workers(&fs_info->submit_workers);
    btrfs_stop_workers(&fs_info->delayed_workers);
    btrfs_stop_workers(&fs_info->caching_workers);
    btrfs_stop_workers(&fs_info->readahead_workers);

#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
    if (btrfs_test_opt(root, CHECK_INTEGRITY))
        btrfsic_unmount(root, fs_info->fs_devices);
#endif

    btrfs_close_devices(fs_info->fs_devices);
    btrfs_mapping_tree_free(&fs_info->mapping_tree);

    bdi_destroy(&fs_info->bdi);
    cleanup_srcu_struct(&fs_info->subvol_srcu);

    return 0;
}

int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,
              int atomic)
{
    int ret;
    struct inode *btree_inode = buf->pages[0]->mapping->host;

    ret = extent_buffer_uptodate(buf);
    if (!ret)
        return ret;

    ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf,
                    parent_transid, atomic);
    if (ret == -EAGAIN)
        return ret;
    return !ret;
}

int btrfs_set_buffer_uptodate(struct extent_buffer *buf)
{
    return set_extent_buffer_uptodate(buf);
}

void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
{
    struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
    u64 transid = btrfs_header_generation(buf);
    int was_dirty;

    btrfs_assert_tree_locked(buf);
    if (transid != root->fs_info->generation) {
        printk(KERN_CRIT "btrfs transid mismatch buffer %llu, "
               "found %llu running %llu\n",
            (unsigned long long)buf->start,
            (unsigned long long)transid,
            (unsigned long long)root->fs_info->generation);
        WARN_ON(1);
    }
    was_dirty = set_extent_buffer_dirty(buf);
    if (!was_dirty) {
        spin_lock(&root->fs_info->delalloc_lock);
        root->fs_info->dirty_metadata_bytes += buf->len;
        spin_unlock(&root->fs_info->delalloc_lock);
    }
}

void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
{
    /*
     * looks as though older kernels can get into trouble with
     * this code, they end up stuck in balance_dirty_pages forever
     */
    u64 num_dirty;
    unsigned long thresh = 32 * 1024 * 1024;

    if (current->flags & PF_MEMALLOC)
        return;

    btrfs_balance_delayed_items(root);

    num_dirty = root->fs_info->dirty_metadata_bytes;

    if (num_dirty > thresh) {
        balance_dirty_pages_ratelimited_nr(
                   root->fs_info->btree_inode->i_mapping, 1);
    }
    return;
}

void __btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
{
    /*
     * looks as though older kernels can get into trouble with
     * this code, they end up stuck in balance_dirty_pages forever
     */
    u64 num_dirty;
    unsigned long thresh = 32 * 1024 * 1024;

    if (current->flags & PF_MEMALLOC)
        return;

    num_dirty = root->fs_info->dirty_metadata_bytes;

    if (num_dirty > thresh) {
        balance_dirty_pages_ratelimited_nr(
                   root->fs_info->btree_inode->i_mapping, 1);
    }
    return;
}

int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)
{
    struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
    return btree_read_extent_buffer_pages(root, buf, 0, parent_transid);
}

static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
                  int read_only)
{
    if (btrfs_super_csum_type(fs_info->super_copy) >= ARRAY_SIZE(btrfs_csum_sizes)) {
        printk(KERN_ERR "btrfs: unsupported checksum algorithm\n");
        return -EINVAL;
    }

    if (read_only)
        return 0;

    return 0;
}

void btrfs_error_commit_super(struct btrfs_root *root)
{
    mutex_lock(&root->fs_info->cleaner_mutex);
    btrfs_run_delayed_iputs(root);
    mutex_unlock(&root->fs_info->cleaner_mutex);

    down_write(&root->fs_info->cleanup_work_sem);
    up_write(&root->fs_info->cleanup_work_sem);

    /* cleanup FS via transaction */
    btrfs_cleanup_transaction(root);
}

static void btrfs_destroy_ordered_operations(struct btrfs_root *root)
{
    struct btrfs_inode *btrfs_inode;
    struct list_head splice;

    INIT_LIST_HEAD(&splice);

    mutex_lock(&root->fs_info->ordered_operations_mutex);
    spin_lock(&root->fs_info->ordered_extent_lock);

    list_splice_init(&root->fs_info->ordered_operations, &splice);
    while (!list_empty(&splice)) {
        btrfs_inode = list_entry(splice.next, struct btrfs_inode,
                     ordered_operations);

        list_del_init(&btrfs_inode->ordered_operations);

        btrfs_invalidate_inodes(btrfs_inode->root);
    }

    spin_unlock(&root->fs_info->ordered_extent_lock);
    mutex_unlock(&root->fs_info->ordered_operations_mutex);
}

static void btrfs_destroy_ordered_extents(struct btrfs_root *root)
{
    struct list_head splice;
    struct btrfs_ordered_extent *ordered;
    struct inode *inode;

    INIT_LIST_HEAD(&splice);

    spin_lock(&root->fs_info->ordered_extent_lock);

    list_splice_init(&root->fs_info->ordered_extents, &splice);
    while (!list_empty(&splice)) {
        ordered = list_entry(splice.next, struct btrfs_ordered_extent,
                     root_extent_list);

        list_del_init(&ordered->root_extent_list);
        atomic_inc(&ordered->refs);

        /* the inode may be getting freed (in sys_unlink path). */
        inode = igrab(ordered->inode);

        spin_unlock(&root->fs_info->ordered_extent_lock);
        if (inode)
            iput(inode);

        atomic_set(&ordered->refs, 1);
        btrfs_put_ordered_extent(ordered);

        spin_lock(&root->fs_info->ordered_extent_lock);
    }

    spin_unlock(&root->fs_info->ordered_extent_lock);
}

int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
                   struct btrfs_root *root)
{
    struct rb_node *node;
    struct btrfs_delayed_ref_root *delayed_refs;
    struct btrfs_delayed_ref_node *ref;
    int ret = 0;

    delayed_refs = &trans->delayed_refs;

    spin_lock(&delayed_refs->lock);
    if (delayed_refs->num_entries == 0) {
        spin_unlock(&delayed_refs->lock);
        printk(KERN_INFO "delayed_refs has NO entry\n");
        return ret;
    }

    while ((node = rb_first(&delayed_refs->root)) != NULL) {
        ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);

        atomic_set(&ref->refs, 1);
        if (btrfs_delayed_ref_is_head(ref)) {
            struct btrfs_delayed_ref_head *head;

            head = btrfs_delayed_node_to_head(ref);
            if (!mutex_trylock(&head->mutex)) {
                atomic_inc(&ref->refs);
                spin_unlock(&delayed_refs->lock);

                /* Need to wait for the delayed ref to run */
                mutex_lock(&head->mutex);
                mutex_unlock(&head->mutex);
                btrfs_put_delayed_ref(ref);

                spin_lock(&delayed_refs->lock);
                continue;
            }

            kfree(head->extent_op);
            delayed_refs->num_heads--;
            if (list_empty(&head->cluster))
                delayed_refs->num_heads_ready--;
            list_del_init(&head->cluster);
        }
        ref->in_tree = 0;
        rb_erase(&ref->rb_node, &delayed_refs->root);
        delayed_refs->num_entries--;

        spin_unlock(&delayed_refs->lock);
        btrfs_put_delayed_ref(ref);

        cond_resched();
        spin_lock(&delayed_refs->lock);
    }

    spin_unlock(&delayed_refs->lock);

    return ret;
}

static void btrfs_destroy_pending_snapshots(struct btrfs_transaction *t)
{
    struct btrfs_pending_snapshot *snapshot;
    struct list_head splice;

    INIT_LIST_HEAD(&splice);

    list_splice_init(&t->pending_snapshots, &splice);

    while (!list_empty(&splice)) {
        snapshot = list_entry(splice.next,
                      struct btrfs_pending_snapshot,
                      list);

        list_del_init(&snapshot->list);

        kfree(snapshot);
    }
}

static void btrfs_destroy_delalloc_inodes(struct btrfs_root *root)
{
    struct btrfs_inode *btrfs_inode;
    struct list_head splice;

    INIT_LIST_HEAD(&splice);

    spin_lock(&root->fs_info->delalloc_lock);
    list_splice_init(&root->fs_info->delalloc_inodes, &splice);

    while (!list_empty(&splice)) {
        btrfs_inode = list_entry(splice.next, struct btrfs_inode,
                    delalloc_inodes);

        list_del_init(&btrfs_inode->delalloc_inodes);

        btrfs_invalidate_inodes(btrfs_inode->root);
    }

    spin_unlock(&root->fs_info->delalloc_lock);
}

static int btrfs_destroy_marked_extents(struct btrfs_root *root,
                    struct extent_io_tree *dirty_pages,
                    int mark)
{
    int ret;
    struct page *page;
    struct inode *btree_inode = root->fs_info->btree_inode;
    struct extent_buffer *eb;
    u64 start = 0;
    u64 end;
    u64 offset;
    unsigned long index;

    while (1) {
        ret = find_first_extent_bit(dirty_pages, start, &start, &end,
                        mark, NULL);
        if (ret)
            break;

        clear_extent_bits(dirty_pages, start, end, mark, GFP_NOFS);
        while (start <= end) {
            index = start >> PAGE_CACHE_SHIFT;
            start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
            page = find_get_page(btree_inode->i_mapping, index);
            if (!page)
                continue;
            offset = page_offset(page);

            spin_lock(&dirty_pages->buffer_lock);
            eb = radix_tree_lookup(
                 &(&BTRFS_I(page->mapping->host)->io_tree)->buffer,
                           offset >> PAGE_CACHE_SHIFT);
            spin_unlock(&dirty_pages->buffer_lock);
            if (eb)
                ret = test_and_clear_bit(EXTENT_BUFFER_DIRTY,
                             &eb->bflags);
            if (PageWriteback(page))
                end_page_writeback(page);

            lock_page(page);
            if (PageDirty(page)) {
                clear_page_dirty_for_io(page);
                spin_lock_irq(&page->mapping->tree_lock);
                radix_tree_tag_clear(&page->mapping->page_tree,
                            page_index(page),
                            PAGECACHE_TAG_DIRTY);
                spin_unlock_irq(&page->mapping->tree_lock);
            }

            unlock_page(page);
            page_cache_release(page);
        }
    }

    return ret;
}

static int btrfs_destroy_pinned_extent(struct btrfs_root *root,
                       struct extent_io_tree *pinned_extents)
{
    struct extent_io_tree *unpin;
    u64 start;
    u64 end;
    int ret;
    bool loop = true;

    unpin = pinned_extents;
again:
    while (1) {
        ret = find_first_extent_bit(unpin, 0, &start, &end,
                        EXTENT_DIRTY, NULL);
        if (ret)
            break;

        /* opt_discard */
        if (btrfs_test_opt(root, DISCARD))
            ret = btrfs_error_discard_extent(root, start,
                             end + 1 - start,
                             NULL);

        clear_extent_dirty(unpin, start, end, GFP_NOFS);
        btrfs_error_unpin_extent_range(root, start, end);
        cond_resched();
    }

    if (loop) {
        if (unpin == &root->fs_info->freed_extents[0])
            unpin = &root->fs_info->freed_extents[1];
        else
            unpin = &root->fs_info->freed_extents[0];
        loop = false;
        goto again;
    }

    return 0;
}

void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
                   struct btrfs_root *root)
{
    btrfs_destroy_delayed_refs(cur_trans, root);
    btrfs_block_rsv_release(root, &root->fs_info->trans_block_rsv,
                cur_trans->dirty_pages.dirty_bytes);

    /* FIXME: cleanup wait for commit */
    cur_trans->in_commit = 1;
    cur_trans->blocked = 1;
    wake_up(&root->fs_info->transaction_blocked_wait);

    cur_trans->blocked = 0;
    wake_up(&root->fs_info->transaction_wait);

    cur_trans->commit_done = 1;
    wake_up(&cur_trans->commit_wait);

    btrfs_destroy_delayed_inodes(root);
    btrfs_assert_delayed_root_empty(root);

    btrfs_destroy_pending_snapshots(cur_trans);

    btrfs_destroy_marked_extents(root, &cur_trans->dirty_pages,
                     EXTENT_DIRTY);
    btrfs_destroy_pinned_extent(root,
                    root->fs_info->pinned_extents);

    /*
    memset(cur_trans, 0, sizeof(*cur_trans));
    kmem_cache_free(btrfs_transaction_cachep, cur_trans);
    */
}

int btrfs_cleanup_transaction(struct btrfs_root *root)
{
    struct btrfs_transaction *t;
    LIST_HEAD(list);

    mutex_lock(&root->fs_info->transaction_kthread_mutex);

    spin_lock(&root->fs_info->trans_lock);
    list_splice_init(&root->fs_info->trans_list, &list);
    root->fs_info->trans_no_join = 1;
    spin_unlock(&root->fs_info->trans_lock);

    while (!list_empty(&list)) {
        t = list_entry(list.next, struct btrfs_transaction, list);
        if (!t)
            break;

        btrfs_destroy_ordered_operations(root);

        btrfs_destroy_ordered_extents(root);

        btrfs_destroy_delayed_refs(t, root);

        btrfs_block_rsv_release(root,
                    &root->fs_info->trans_block_rsv,
                    t->dirty_pages.dirty_bytes);

        /* FIXME: cleanup wait for commit */
        t->in_commit = 1;
        t->blocked = 1;
        smp_mb();
        if (waitqueue_active(&root->fs_info->transaction_blocked_wait))
            wake_up(&root->fs_info->transaction_blocked_wait);

        t->blocked = 0;
        smp_mb();
        if (waitqueue_active(&root->fs_info->transaction_wait))
            wake_up(&root->fs_info->transaction_wait);

        t->commit_done = 1;
        smp_mb();
        if (waitqueue_active(&t->commit_wait))
            wake_up(&t->commit_wait);

        btrfs_destroy_delayed_inodes(root);
        btrfs_assert_delayed_root_empty(root);

        btrfs_destroy_pending_snapshots(t);

        btrfs_destroy_delalloc_inodes(root);

        spin_lock(&root->fs_info->trans_lock);
        root->fs_info->running_transaction = NULL;
        spin_unlock(&root->fs_info->trans_lock);

        btrfs_destroy_marked_extents(root, &t->dirty_pages,
                         EXTENT_DIRTY);

        btrfs_destroy_pinned_extent(root,
                        root->fs_info->pinned_extents);

        atomic_set(&t->use_count, 0);
        list_del_init(&t->list);
        memset(t, 0, sizeof(*t));
        kmem_cache_free(btrfs_transaction_cachep, t);
    }

    spin_lock(&root->fs_info->trans_lock);
    root->fs_info->trans_no_join = 0;
    spin_unlock(&root->fs_info->trans_lock);
    mutex_unlock(&root->fs_info->transaction_kthread_mutex);

    return 0;
}

static struct extent_io_ops btree_extent_io_ops = {
    .readpage_end_io_hook = btree_readpage_end_io_hook,
    .readpage_io_failed_hook = btree_io_failed_hook,
    .submit_bio_hook = btree_submit_bio_hook,
    /* note we're sharing with inode.c for the merge bio hook */
    .merge_bio_hook = btrfs_merge_bio_hook,
};