extent_io.c

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#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/bio.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/page-flags.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/blkdev.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/prefetch.h>
#include <linux/cleancache.h>
#include "extent_io.h"
#include "extent_map.h"
#include "compat.h"
#include "ctree.h"
#include "btrfs_inode.h"
#include "volumes.h"
#include "check-integrity.h"
#include "locking.h"
#include "rcu-string.h"

static struct kmem_cache *extent_state_cache;
static struct kmem_cache *extent_buffer_cache;

static LIST_HEAD(buffers);
static LIST_HEAD(states);

#define LEAK_DEBUG 0
#if LEAK_DEBUG
static DEFINE_SPINLOCK(leak_lock);
#endif

#define BUFFER_LRU_MAX 64

struct tree_entry {
    u64 start;
    u64 end;
    struct rb_node rb_node;
};

struct extent_page_data {
    struct bio *bio;
    struct extent_io_tree *tree;
    get_extent_t *get_extent;
    unsigned long bio_flags;

    /* tells writepage not to lock the state bits for this range
     * it still does the unlocking
     */
    unsigned int extent_locked:1;

    /* tells the submit_bio code to use a WRITE_SYNC */
    unsigned int sync_io:1;
};

static noinline void flush_write_bio(void *data);
static inline struct btrfs_fs_info *
tree_fs_info(struct extent_io_tree *tree)
{
    return btrfs_sb(tree->mapping->host->i_sb);
}

int __init extent_io_init(void)
{
    extent_state_cache = kmem_cache_create("btrfs_extent_state",
            sizeof(struct extent_state), 0,
            SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
    if (!extent_state_cache)
        return -ENOMEM;

    extent_buffer_cache = kmem_cache_create("btrfs_extent_buffer",
            sizeof(struct extent_buffer), 0,
            SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
    if (!extent_buffer_cache)
        goto free_state_cache;
    return 0;

free_state_cache:
    kmem_cache_destroy(extent_state_cache);
    return -ENOMEM;
}

void extent_io_exit(void)
{
    struct extent_state *state;
    struct extent_buffer *eb;

    while (!list_empty(&states)) {
        state = list_entry(states.next, struct extent_state, leak_list);
        printk(KERN_ERR "btrfs state leak: start %llu end %llu "
               "state %lu in tree %p refs %d\n",
               (unsigned long long)state->start,
               (unsigned long long)state->end,
               state->state, state->tree, atomic_read(&state->refs));
        list_del(&state->leak_list);
        kmem_cache_free(extent_state_cache, state);

    }

    while (!list_empty(&buffers)) {
        eb = list_entry(buffers.next, struct extent_buffer, leak_list);
        printk(KERN_ERR "btrfs buffer leak start %llu len %lu "
               "refs %d\n", (unsigned long long)eb->start,
               eb->len, atomic_read(&eb->refs));
        list_del(&eb->leak_list);
        kmem_cache_free(extent_buffer_cache, eb);
    }

    /*
     * Make sure all delayed rcu free are flushed before we
     * destroy caches.
     */
    rcu_barrier();
    if (extent_state_cache)
        kmem_cache_destroy(extent_state_cache);
    if (extent_buffer_cache)
        kmem_cache_destroy(extent_buffer_cache);
}

void extent_io_tree_init(struct extent_io_tree *tree,
             struct address_space *mapping)
{
    tree->state = RB_ROOT;
    INIT_RADIX_TREE(&tree->buffer, GFP_ATOMIC);
    tree->ops = NULL;
    tree->dirty_bytes = 0;
    spin_lock_init(&tree->lock);
    spin_lock_init(&tree->buffer_lock);
    tree->mapping = mapping;
}

static struct extent_state *alloc_extent_state(gfp_t mask)
{
    struct extent_state *state;
#if LEAK_DEBUG
    unsigned long flags;
#endif

    state = kmem_cache_alloc(extent_state_cache, mask);
    if (!state)
        return state;
    state->state = 0;
    state->private = 0;
    state->tree = NULL;
#if LEAK_DEBUG
    spin_lock_irqsave(&leak_lock, flags);
    list_add(&state->leak_list, &states);
    spin_unlock_irqrestore(&leak_lock, flags);
#endif
    atomic_set(&state->refs, 1);
    init_waitqueue_head(&state->wq);
    trace_alloc_extent_state(state, mask, _RET_IP_);
    return state;
}

void free_extent_state(struct extent_state *state)
{
    if (!state)
        return;
    if (atomic_dec_and_test(&state->refs)) {
#if LEAK_DEBUG
        unsigned long flags;
#endif
        WARN_ON(state->tree);
#if LEAK_DEBUG
        spin_lock_irqsave(&leak_lock, flags);
        list_del(&state->leak_list);
        spin_unlock_irqrestore(&leak_lock, flags);
#endif
        trace_free_extent_state(state, _RET_IP_);
        kmem_cache_free(extent_state_cache, state);
    }
}

static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
                   struct rb_node *node)
{
    struct rb_node **p = &root->rb_node;
    struct rb_node *parent = NULL;
    struct tree_entry *entry;

    while (*p) {
        parent = *p;
        entry = rb_entry(parent, struct tree_entry, rb_node);

        if (offset < entry->start)
            p = &(*p)->rb_left;
        else if (offset > entry->end)
            p = &(*p)->rb_right;
        else
            return parent;
    }

    rb_link_node(node, parent, p);
    rb_insert_color(node, root);
    return NULL;
}

static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset,
                     struct rb_node **prev_ret,
                     struct rb_node **next_ret)
{
    struct rb_root *root = &tree->state;
    struct rb_node *n = root->rb_node;
    struct rb_node *prev = NULL;
    struct rb_node *orig_prev = NULL;
    struct tree_entry *entry;
    struct tree_entry *prev_entry = NULL;

    while (n) {
        entry = rb_entry(n, struct tree_entry, rb_node);
        prev = n;
        prev_entry = entry;

        if (offset < entry->start)
            n = n->rb_left;
        else if (offset > entry->end)
            n = n->rb_right;
        else
            return n;
    }

    if (prev_ret) {
        orig_prev = prev;
        while (prev && offset > prev_entry->end) {
            prev = rb_next(prev);
            prev_entry = rb_entry(prev, struct tree_entry, rb_node);
        }
        *prev_ret = prev;
        prev = orig_prev;
    }

    if (next_ret) {
        prev_entry = rb_entry(prev, struct tree_entry, rb_node);
        while (prev && offset < prev_entry->start) {
            prev = rb_prev(prev);
            prev_entry = rb_entry(prev, struct tree_entry, rb_node);
        }
        *next_ret = prev;
    }
    return NULL;
}

static inline struct rb_node *tree_search(struct extent_io_tree *tree,
                      u64 offset)
{
    struct rb_node *prev = NULL;
    struct rb_node *ret;

    ret = __etree_search(tree, offset, &prev, NULL);
    if (!ret)
        return prev;
    return ret;
}

static void merge_cb(struct extent_io_tree *tree, struct extent_state *new,
             struct extent_state *other)
{
    if (tree->ops && tree->ops->merge_extent_hook)
        tree->ops->merge_extent_hook(tree->mapping->host, new,
                         other);
}

/*
 * utility function to look for merge candidates inside a given range.
 * Any extents with matching state are merged together into a single
 * extent in the tree.  Extents with EXTENT_IO in their state field
 * are not merged because the end_io handlers need to be able to do
 * operations on them without sleeping (or doing allocations/splits).
 *
 * This should be called with the tree lock held.
 */
static void merge_state(struct extent_io_tree *tree,
                struct extent_state *state)
{
    struct extent_state *other;
    struct rb_node *other_node;

    if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY))
        return;

    other_node = rb_prev(&state->rb_node);
    if (other_node) {
        other = rb_entry(other_node, struct extent_state, rb_node);
        if (other->end == state->start - 1 &&
            other->state == state->state) {
            merge_cb(tree, state, other);
            state->start = other->start;
            other->tree = NULL;
            rb_erase(&other->rb_node, &tree->state);
            free_extent_state(other);
        }
    }
    other_node = rb_next(&state->rb_node);
    if (other_node) {
        other = rb_entry(other_node, struct extent_state, rb_node);
        if (other->start == state->end + 1 &&
            other->state == state->state) {
            merge_cb(tree, state, other);
            state->end = other->end;
            other->tree = NULL;
            rb_erase(&other->rb_node, &tree->state);
            free_extent_state(other);
        }
    }
}

static void set_state_cb(struct extent_io_tree *tree,
             struct extent_state *state, int *bits)
{
    if (tree->ops && tree->ops->set_bit_hook)
        tree->ops->set_bit_hook(tree->mapping->host, state, bits);
}

static void clear_state_cb(struct extent_io_tree *tree,
               struct extent_state *state, int *bits)
{
    if (tree->ops && tree->ops->clear_bit_hook)
        tree->ops->clear_bit_hook(tree->mapping->host, state, bits);
}

static void set_state_bits(struct extent_io_tree *tree,
               struct extent_state *state, int *bits);

/*
 * insert an extent_state struct into the tree.  'bits' are set on the
 * struct before it is inserted.
 *
 * This may return -EEXIST if the extent is already there, in which case the
 * state struct is freed.
 *
 * The tree lock is not taken internally.  This is a utility function and
 * probably isn't what you want to call (see set/clear_extent_bit).
 */
static int insert_state(struct extent_io_tree *tree,
            struct extent_state *state, u64 start, u64 end,
            int *bits)
{
    struct rb_node *node;

    if (end < start) {
        printk(KERN_ERR "btrfs end < start %llu %llu\n",
               (unsigned long long)end,
               (unsigned long long)start);
        WARN_ON(1);
    }
    state->start = start;
    state->end = end;

    set_state_bits(tree, state, bits);

    node = tree_insert(&tree->state, end, &state->rb_node);
    if (node) {
        struct extent_state *found;
        found = rb_entry(node, struct extent_state, rb_node);
        printk(KERN_ERR "btrfs found node %llu %llu on insert of "
               "%llu %llu\n", (unsigned long long)found->start,
               (unsigned long long)found->end,
               (unsigned long long)start, (unsigned long long)end);
        return -EEXIST;
    }
    state->tree = tree;
    merge_state(tree, state);
    return 0;
}

static void split_cb(struct extent_io_tree *tree, struct extent_state *orig,
             u64 split)
{
    if (tree->ops && tree->ops->split_extent_hook)
        tree->ops->split_extent_hook(tree->mapping->host, orig, split);
}

/*
 * split a given extent state struct in two, inserting the preallocated
 * struct 'prealloc' as the newly created second half.  'split' indicates an
 * offset inside 'orig' where it should be split.
 *
 * Before calling,
 * the tree has 'orig' at [orig->start, orig->end].  After calling, there
 * are two extent state structs in the tree:
 * prealloc: [orig->start, split - 1]
 * orig: [ split, orig->end ]
 *
 * The tree locks are not taken by this function. They need to be held
 * by the caller.
 */
static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
               struct extent_state *prealloc, u64 split)
{
    struct rb_node *node;

    split_cb(tree, orig, split);

    prealloc->start = orig->start;
    prealloc->end = split - 1;
    prealloc->state = orig->state;
    orig->start = split;

    node = tree_insert(&tree->state, prealloc->end, &prealloc->rb_node);
    if (node) {
        free_extent_state(prealloc);
        return -EEXIST;
    }
    prealloc->tree = tree;
    return 0;
}

static struct extent_state *next_state(struct extent_state *state)
{
    struct rb_node *next = rb_next(&state->rb_node);
    if (next)
        return rb_entry(next, struct extent_state, rb_node);
    else
        return NULL;
}

/*
 * utility function to clear some bits in an extent state struct.
 * it will optionally wake up any one waiting on this state (wake == 1).
 *
 * If no bits are set on the state struct after clearing things, the
 * struct is freed and removed from the tree
 */
static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
                        struct extent_state *state,
                        int *bits, int wake)
{
    struct extent_state *next;
    int bits_to_clear = *bits & ~EXTENT_CTLBITS;

    if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {
        u64 range = state->end - state->start + 1;
        WARN_ON(range > tree->dirty_bytes);
        tree->dirty_bytes -= range;
    }
    clear_state_cb(tree, state, bits);
    state->state &= ~bits_to_clear;
    if (wake)
        wake_up(&state->wq);
    if (state->state == 0) {
        next = next_state(state);
        if (state->tree) {
            rb_erase(&state->rb_node, &tree->state);
            state->tree = NULL;
            free_extent_state(state);
        } else {
            WARN_ON(1);
        }
    } else {
        merge_state(tree, state);
        next = next_state(state);
    }
    return next;
}

static struct extent_state *
alloc_extent_state_atomic(struct extent_state *prealloc)
{
    if (!prealloc)
        prealloc = alloc_extent_state(GFP_ATOMIC);

    return prealloc;
}

void extent_io_tree_panic(struct extent_io_tree *tree, int err)
{
    btrfs_panic(tree_fs_info(tree), err, "Locking error: "
            "Extent tree was modified by another "
            "thread while locked.");
}

/*
 * clear some bits on a range in the tree.  This may require splitting
 * or inserting elements in the tree, so the gfp mask is used to
 * indicate which allocations or sleeping are allowed.
 *
 * pass 'wake' == 1 to kick any sleepers, and 'delete' == 1 to remove
 * the given range from the tree regardless of state (ie for truncate).
 *
 * the range [start, end] is inclusive.
 *
 * This takes the tree lock, and returns 0 on success and < 0 on error.
 */
int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
             int bits, int wake, int delete,
             struct extent_state **cached_state,
             gfp_t mask)
{
    struct extent_state *state;
    struct extent_state *cached;
    struct extent_state *prealloc = NULL;
    struct rb_node *node;
    u64 last_end;
    int err;
    int clear = 0;

    if (delete)
        bits |= ~EXTENT_CTLBITS;
    bits |= EXTENT_FIRST_DELALLOC;

    if (bits & (EXTENT_IOBITS | EXTENT_BOUNDARY))
        clear = 1;
again:
    if (!prealloc && (mask & __GFP_WAIT)) {
        prealloc = alloc_extent_state(mask);
        if (!prealloc)
            return -ENOMEM;
    }

    spin_lock(&tree->lock);
    if (cached_state) {
        cached = *cached_state;

        if (clear) {
            *cached_state = NULL;
            cached_state = NULL;
        }

        if (cached && cached->tree && cached->start <= start &&
            cached->end > start) {
            if (clear)
                atomic_dec(&cached->refs);
            state = cached;
            goto hit_next;
        }
        if (clear)
            free_extent_state(cached);
    }
    /*
     * this search will find the extents that end after
     * our range starts
     */
    node = tree_search(tree, start);
    if (!node)
        goto out;
    state = rb_entry(node, struct extent_state, rb_node);
hit_next:
    if (state->start > end)
        goto out;
    WARN_ON(state->end < start);
    last_end = state->end;

    /* the state doesn't have the wanted bits, go ahead */
    if (!(state->state & bits)) {
        state = next_state(state);
        goto next;
    }

    /*
     *     | ---- desired range ---- |
     *  | state | or
     *  | ------------- state -------------- |
     *
     * We need to split the extent we found, and may flip
     * bits on second half.
     *
     * If the extent we found extends past our range, we
     * just split and search again.  It'll get split again
     * the next time though.
     *
     * If the extent we found is inside our range, we clear
     * the desired bit on it.
     */

    if (state->start < start) {
        prealloc = alloc_extent_state_atomic(prealloc);
        BUG_ON(!prealloc);
        err = split_state(tree, state, prealloc, start);
        if (err)
            extent_io_tree_panic(tree, err);

        prealloc = NULL;
        if (err)
            goto out;
        if (state->end <= end) {
            state = clear_state_bit(tree, state, &bits, wake);
            goto next;
        }
        goto search_again;
    }
    /*
     * | ---- desired range ---- |
     *                        | state |
     * We need to split the extent, and clear the bit
     * on the first half
     */
    if (state->start <= end && state->end > end) {
        prealloc = alloc_extent_state_atomic(prealloc);
        BUG_ON(!prealloc);
        err = split_state(tree, state, prealloc, end + 1);
        if (err)
            extent_io_tree_panic(tree, err);

        if (wake)
            wake_up(&state->wq);

        clear_state_bit(tree, prealloc, &bits, wake);

        prealloc = NULL;
        goto out;
    }

    state = clear_state_bit(tree, state, &bits, wake);
next:
    if (last_end == (u64)-1)
        goto out;
    start = last_end + 1;
    if (start <= end && state && !need_resched())
        goto hit_next;
    goto search_again;

out:
    spin_unlock(&tree->lock);
    if (prealloc)
        free_extent_state(prealloc);

    return 0;

search_again:
    if (start > end)
        goto out;
    spin_unlock(&tree->lock);
    if (mask & __GFP_WAIT)
        cond_resched();
    goto again;
}

static void wait_on_state(struct extent_io_tree *tree,
              struct extent_state *state)
        __releases(tree->lock)
        __acquires(tree->lock)
{
    DEFINE_WAIT(wait);
    prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
    spin_unlock(&tree->lock);
    schedule();
    spin_lock(&tree->lock);
    finish_wait(&state->wq, &wait);
}

/*
 * waits for one or more bits to clear on a range in the state tree.
 * The range [start, end] is inclusive.
 * The tree lock is taken by this function
 */
void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, int bits)
{
    struct extent_state *state;
    struct rb_node *node;

    spin_lock(&tree->lock);
again:
    while (1) {
        /*
         * this search will find all the extents that end after
         * our range starts
         */
        node = tree_search(tree, start);
        if (!node)
            break;

        state = rb_entry(node, struct extent_state, rb_node);

        if (state->start > end)
            goto out;

        if (state->state & bits) {
            start = state->start;
            atomic_inc(&state->refs);
            wait_on_state(tree, state);
            free_extent_state(state);
            goto again;
        }
        start = state->end + 1;

        if (start > end)
            break;

        cond_resched_lock(&tree->lock);
    }
out:
    spin_unlock(&tree->lock);
}

static void set_state_bits(struct extent_io_tree *tree,
               struct extent_state *state,
               int *bits)
{
    int bits_to_set = *bits & ~EXTENT_CTLBITS;

    set_state_cb(tree, state, bits);
    if ((bits_to_set & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {
        u64 range = state->end - state->start + 1;
        tree->dirty_bytes += range;
    }
    state->state |= bits_to_set;
}

static void cache_state(struct extent_state *state,
            struct extent_state **cached_ptr)
{
    if (cached_ptr && !(*cached_ptr)) {
        if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY)) {
            *cached_ptr = state;
            atomic_inc(&state->refs);
        }
    }
}

static void uncache_state(struct extent_state **cached_ptr)
{
    if (cached_ptr && (*cached_ptr)) {
        struct extent_state *state = *cached_ptr;
        *cached_ptr = NULL;
        free_extent_state(state);
    }
}

/*
 * set some bits on a range in the tree.  This may require allocations or
 * sleeping, so the gfp mask is used to indicate what is allowed.
 *
 * If any of the exclusive bits are set, this will fail with -EEXIST if some
 * part of the range already has the desired bits set.  The start of the
 * existing range is returned in failed_start in this case.
 *
 * [start, end] is inclusive This takes the tree lock.
 */

static int __must_check
__set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
         int bits, int exclusive_bits, u64 *failed_start,
         struct extent_state **cached_state, gfp_t mask)
{
    struct extent_state *state;
    struct extent_state *prealloc = NULL;
    struct rb_node *node;
    int err = 0;
    u64 last_start;
    u64 last_end;

    bits |= EXTENT_FIRST_DELALLOC;
again:
    if (!prealloc && (mask & __GFP_WAIT)) {
        prealloc = alloc_extent_state(mask);
        BUG_ON(!prealloc);
    }

    spin_lock(&tree->lock);
    if (cached_state && *cached_state) {
        state = *cached_state;
        if (state->start <= start && state->end > start &&
            state->tree) {
            node = &state->rb_node;
            goto hit_next;
        }
    }
    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, start);
    if (!node) {
        prealloc = alloc_extent_state_atomic(prealloc);
        BUG_ON(!prealloc);
        err = insert_state(tree, prealloc, start, end, &bits);
        if (err)
            extent_io_tree_panic(tree, err);

        prealloc = NULL;
        goto out;
    }
    state = rb_entry(node, struct extent_state, rb_node);
hit_next:
    last_start = state->start;
    last_end = state->end;

    /*
     * | ---- desired range ---- |
     * | state |
     *
     * Just lock what we found and keep going
     */
    if (state->start == start && state->end <= end) {
        if (state->state & exclusive_bits) {
            *failed_start = state->start;
            err = -EEXIST;
            goto out;
        }

        set_state_bits(tree, state, &bits);
        cache_state(state, cached_state);
        merge_state(tree, state);
        if (last_end == (u64)-1)
            goto out;
        start = last_end + 1;
        state = next_state(state);
        if (start < end && state && state->start == start &&
            !need_resched())
            goto hit_next;
        goto search_again;
    }

    /*
     *     | ---- desired range ---- |
     * | state |
     *   or
     * | ------------- state -------------- |
     *
     * We need to split the extent we found, and may flip bits on
     * second half.
     *
     * If the extent we found extends past our
     * range, we just split and search again.  It'll get split
     * again the next time though.
     *
     * If the extent we found is inside our range, we set the
     * desired bit on it.
     */
    if (state->start < start) {
        if (state->state & exclusive_bits) {
            *failed_start = start;
            err = -EEXIST;
            goto out;
        }

        prealloc = alloc_extent_state_atomic(prealloc);
        BUG_ON(!prealloc);
        err = split_state(tree, state, prealloc, start);
        if (err)
            extent_io_tree_panic(tree, err);

        prealloc = NULL;
        if (err)
            goto out;
        if (state->end <= end) {
            set_state_bits(tree, state, &bits);
            cache_state(state, cached_state);
            merge_state(tree, state);
            if (last_end == (u64)-1)
                goto out;
            start = last_end + 1;
            state = next_state(state);
            if (start < end && state && state->start == start &&
                !need_resched())
                goto hit_next;
        }
        goto search_again;
    }
    /*
     * | ---- desired range ---- |
     *     | state | or               | state |
     *
     * There's a hole, we need to insert something in it and
     * ignore the extent we found.
     */
    if (state->start > start) {
        u64 this_end;
        if (end < last_start)
            this_end = end;
        else
            this_end = last_start - 1;

        prealloc = alloc_extent_state_atomic(prealloc);
        BUG_ON(!prealloc);

        /*
         * Avoid to free 'prealloc' if it can be merged with
         * the later extent.
         */
        err = insert_state(tree, prealloc, start, this_end,
                   &bits);
        if (err)
            extent_io_tree_panic(tree, err);

        cache_state(prealloc, cached_state);
        prealloc = NULL;
        start = this_end + 1;
        goto search_again;
    }
    /*
     * | ---- desired range ---- |
     *                        | state |
     * We need to split the extent, and set the bit
     * on the first half
     */
    if (state->start <= end && state->end > end) {
        if (state->state & exclusive_bits) {
            *failed_start = start;
            err = -EEXIST;
            goto out;
        }

        prealloc = alloc_extent_state_atomic(prealloc);
        BUG_ON(!prealloc);
        err = split_state(tree, state, prealloc, end + 1);
        if (err)
            extent_io_tree_panic(tree, err);

        set_state_bits(tree, prealloc, &bits);
        cache_state(prealloc, cached_state);
        merge_state(tree, prealloc);
        prealloc = NULL;
        goto out;
    }

    goto search_again;

out:
    spin_unlock(&tree->lock);
    if (prealloc)
        free_extent_state(prealloc);

    return err;

search_again:
    if (start > end)
        goto out;
    spin_unlock(&tree->lock);
    if (mask & __GFP_WAIT)
        cond_resched();
    goto again;
}

int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, int bits,
           u64 *failed_start, struct extent_state **cached_state,
           gfp_t mask)
{
    return __set_extent_bit(tree, start, end, bits, 0, failed_start,
                cached_state, mask);
}


int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
               int bits, int clear_bits,
               struct extent_state **cached_state, gfp_t mask)
{
    struct extent_state *state;
    struct extent_state *prealloc = NULL;
    struct rb_node *node;
    int err = 0;
    u64 last_start;
    u64 last_end;

again:
    if (!prealloc && (mask & __GFP_WAIT)) {
        prealloc = alloc_extent_state(mask);
        if (!prealloc)
            return -ENOMEM;
    }

    spin_lock(&tree->lock);
    if (cached_state && *cached_state) {
        state = *cached_state;
        if (state->start <= start && state->end > start &&
            state->tree) {
            node = &state->rb_node;
            goto hit_next;
        }
    }

    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, start);
    if (!node) {
        prealloc = alloc_extent_state_atomic(prealloc);
        if (!prealloc) {
            err = -ENOMEM;
            goto out;
        }
        err = insert_state(tree, prealloc, start, end, &bits);
        prealloc = NULL;
        if (err)
            extent_io_tree_panic(tree, err);
        goto out;
    }
    state = rb_entry(node, struct extent_state, rb_node);
hit_next:
    last_start = state->start;
    last_end = state->end;

    /*
     * | ---- desired range ---- |
     * | state |
     *
     * Just lock what we found and keep going
     */
    if (state->start == start && state->end <= end) {
        set_state_bits(tree, state, &bits);
        cache_state(state, cached_state);
        state = clear_state_bit(tree, state, &clear_bits, 0);
        if (last_end == (u64)-1)
            goto out;
        start = last_end + 1;
        if (start < end && state && state->start == start &&
            !need_resched())
            goto hit_next;
        goto search_again;
    }

    /*
     *     | ---- desired range ---- |
     * | state |
     *   or
     * | ------------- state -------------- |
     *
     * We need to split the extent we found, and may flip bits on
     * second half.
     *
     * If the extent we found extends past our
     * range, we just split and search again.  It'll get split
     * again the next time though.
     *
     * If the extent we found is inside our range, we set the
     * desired bit on it.
     */
    if (state->start < start) {
        prealloc = alloc_extent_state_atomic(prealloc);
        if (!prealloc) {
            err = -ENOMEM;
            goto out;
        }
        err = split_state(tree, state, prealloc, start);
        if (err)
            extent_io_tree_panic(tree, err);
        prealloc = NULL;
        if (err)
            goto out;
        if (state->end <= end) {
            set_state_bits(tree, state, &bits);
            cache_state(state, cached_state);
            state = clear_state_bit(tree, state, &clear_bits, 0);
            if (last_end == (u64)-1)
                goto out;
            start = last_end + 1;
            if (start < end && state && state->start == start &&
                !need_resched())
                goto hit_next;
        }
        goto search_again;
    }
    /*
     * | ---- desired range ---- |
     *     | state | or               | state |
     *
     * There's a hole, we need to insert something in it and
     * ignore the extent we found.
     */
    if (state->start > start) {
        u64 this_end;
        if (end < last_start)
            this_end = end;
        else
            this_end = last_start - 1;

        prealloc = alloc_extent_state_atomic(prealloc);
        if (!prealloc) {
            err = -ENOMEM;
            goto out;
        }

        /*
         * Avoid to free 'prealloc' if it can be merged with
         * the later extent.
         */
        err = insert_state(tree, prealloc, start, this_end,
                   &bits);
        if (err)
            extent_io_tree_panic(tree, err);
        cache_state(prealloc, cached_state);
        prealloc = NULL;
        start = this_end + 1;
        goto search_again;
    }
    /*
     * | ---- desired range ---- |
     *                        | state |
     * We need to split the extent, and set the bit
     * on the first half
     */
    if (state->start <= end && state->end > end) {
        prealloc = alloc_extent_state_atomic(prealloc);
        if (!prealloc) {
            err = -ENOMEM;
            goto out;
        }

        err = split_state(tree, state, prealloc, end + 1);
        if (err)
            extent_io_tree_panic(tree, err);

        set_state_bits(tree, prealloc, &bits);
        cache_state(prealloc, cached_state);
        clear_state_bit(tree, prealloc, &clear_bits, 0);
        prealloc = NULL;
        goto out;
    }

    goto search_again;

out:
    spin_unlock(&tree->lock);
    if (prealloc)
        free_extent_state(prealloc);

    return err;

search_again:
    if (start > end)
        goto out;
    spin_unlock(&tree->lock);
    if (mask & __GFP_WAIT)
        cond_resched();
    goto again;
}

/* wrappers around set/clear extent bit */
int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
             gfp_t mask)
{
    return set_extent_bit(tree, start, end, EXTENT_DIRTY, NULL,
                  NULL, mask);
}

int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
            int bits, gfp_t mask)
{
    return set_extent_bit(tree, start, end, bits, NULL,
                  NULL, mask);
}

int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
              int bits, gfp_t mask)
{
    return clear_extent_bit(tree, start, end, bits, 0, 0, NULL, mask);
}

int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
            struct extent_state **cached_state, gfp_t mask)
{
    return set_extent_bit(tree, start, end,
                  EXTENT_DELALLOC | EXTENT_UPTODATE,
                  NULL, cached_state, mask);
}

int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end,
              struct extent_state **cached_state, gfp_t mask)
{
    return set_extent_bit(tree, start, end,
                  EXTENT_DELALLOC | EXTENT_UPTODATE | EXTENT_DEFRAG,
                  NULL, cached_state, mask);
}

int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
               gfp_t mask)
{
    return clear_extent_bit(tree, start, end,
                EXTENT_DIRTY | EXTENT_DELALLOC |
                EXTENT_DO_ACCOUNTING, 0, 0, NULL, mask);
}

int set_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
             gfp_t mask)
{
    return set_extent_bit(tree, start, end, EXTENT_NEW, NULL,
                  NULL, mask);
}

int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
            struct extent_state **cached_state, gfp_t mask)
{
    return set_extent_bit(tree, start, end, EXTENT_UPTODATE, 0,
                  cached_state, mask);
}

int clear_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
              struct extent_state **cached_state, gfp_t mask)
{
    return clear_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, 0,
                cached_state, mask);
}

/*
 * either insert or lock state struct between start and end use mask to tell
 * us if waiting is desired.
 */
int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
             int bits, struct extent_state **cached_state)
{
    int err;
    u64 failed_start;
    while (1) {
        err = __set_extent_bit(tree, start, end, EXTENT_LOCKED | bits,
                       EXTENT_LOCKED, &failed_start,
                       cached_state, GFP_NOFS);
        if (err == -EEXIST) {
            wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
            start = failed_start;
        } else
            break;
        WARN_ON(start > end);
    }
    return err;
}

int lock_extent(struct extent_io_tree *tree, u64 start, u64 end)
{
    return lock_extent_bits(tree, start, end, 0, NULL);
}

int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end)
{
    int err;
    u64 failed_start;

    err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
                   &failed_start, NULL, GFP_NOFS);
    if (err == -EEXIST) {
        if (failed_start > start)
            clear_extent_bit(tree, start, failed_start - 1,
                     EXTENT_LOCKED, 1, 0, NULL, GFP_NOFS);
        return 0;
    }
    return 1;
}

int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
             struct extent_state **cached, gfp_t mask)
{
    return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, cached,
                mask);
}

int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end)
{
    return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,
                GFP_NOFS);
}

/*
 * helper function to set both pages and extents in the tree writeback
 */
static int set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
{
    unsigned long index = start >> PAGE_CACHE_SHIFT;
    unsigned long end_index = end >> PAGE_CACHE_SHIFT;
    struct page *page;

    while (index <= end_index) {
        page = find_get_page(tree->mapping, index);
        BUG_ON(!page); /* Pages should be in the extent_io_tree */
        set_page_writeback(page);
        page_cache_release(page);
        index++;
    }
    return 0;
}

/* find the first state struct with 'bits' set after 'start', and
 * return it.  tree->lock must be held.  NULL will returned if
 * nothing was found after 'start'
 */
struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
                         u64 start, int bits)
{
    struct rb_node *node;
    struct extent_state *state;

    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, start);
    if (!node)
        goto out;

    while (1) {
        state = rb_entry(node, struct extent_state, rb_node);
        if (state->end >= start && (state->state & bits))
            return state;

        node = rb_next(node);
        if (!node)
            break;
    }
out:
    return NULL;
}

/*
 * find the first offset in the io tree with 'bits' set. zero is
 * returned if we find something, and *start_ret and *end_ret are
 * set to reflect the state struct that was found.
 *
 * If nothing was found, 1 is returned. If found something, return 0.
 */
int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
              u64 *start_ret, u64 *end_ret, int bits,
              struct extent_state **cached_state)
{
    struct extent_state *state;
    struct rb_node *n;
    int ret = 1;

    spin_lock(&tree->lock);
    if (cached_state && *cached_state) {
        state = *cached_state;
        if (state->end == start - 1 && state->tree) {
            n = rb_next(&state->rb_node);
            while (n) {
                state = rb_entry(n, struct extent_state,
                         rb_node);
                if (state->state & bits)
                    goto got_it;
                n = rb_next(n);
            }
            free_extent_state(*cached_state);
            *cached_state = NULL;
            goto out;
        }
        free_extent_state(*cached_state);
        *cached_state = NULL;
    }

    state = find_first_extent_bit_state(tree, start, bits);
got_it:
    if (state) {
        cache_state(state, cached_state);
        *start_ret = state->start;
        *end_ret = state->end;
        ret = 0;
    }
out:
    spin_unlock(&tree->lock);
    return ret;
}

/*
 * find a contiguous range of bytes in the file marked as delalloc, not
 * more than 'max_bytes'.  start and end are used to return the range,
 *
 * 1 is returned if we find something, 0 if nothing was in the tree
 */
static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
                    u64 *start, u64 *end, u64 max_bytes,
                    struct extent_state **cached_state)
{
    struct rb_node *node;
    struct extent_state *state;
    u64 cur_start = *start;
    u64 found = 0;
    u64 total_bytes = 0;

    spin_lock(&tree->lock);

    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, cur_start);
    if (!node) {
        if (!found)
            *end = (u64)-1;
        goto out;
    }

    while (1) {
        state = rb_entry(node, struct extent_state, rb_node);
        if (found && (state->start != cur_start ||
                  (state->state & EXTENT_BOUNDARY))) {
            goto out;
        }
        if (!(state->state & EXTENT_DELALLOC)) {
            if (!found)
                *end = state->end;
            goto out;
        }
        if (!found) {
            *start = state->start;
            *cached_state = state;
            atomic_inc(&state->refs);
        }
        found++;
        *end = state->end;
        cur_start = state->end + 1;
        node = rb_next(node);
        if (!node)
            break;
        total_bytes += state->end - state->start + 1;
        if (total_bytes >= max_bytes)
            break;
    }
out:
    spin_unlock(&tree->lock);
    return found;
}

static noinline void __unlock_for_delalloc(struct inode *inode,
                       struct page *locked_page,
                       u64 start, u64 end)
{
    int ret;
    struct page *pages[16];
    unsigned long index = start >> PAGE_CACHE_SHIFT;
    unsigned long end_index = end >> PAGE_CACHE_SHIFT;
    unsigned long nr_pages = end_index - index + 1;
    int i;

    if (index == locked_page->index && end_index == index)
        return;

    while (nr_pages > 0) {
        ret = find_get_pages_contig(inode->i_mapping, index,
                     min_t(unsigned long, nr_pages,
                     ARRAY_SIZE(pages)), pages);
        for (i = 0; i < ret; i++) {
            if (pages[i] != locked_page)
                unlock_page(pages[i]);
            page_cache_release(pages[i]);
        }
        nr_pages -= ret;
        index += ret;
        cond_resched();
    }
}

static noinline int lock_delalloc_pages(struct inode *inode,
                    struct page *locked_page,
                    u64 delalloc_start,
                    u64 delalloc_end)
{
    unsigned long index = delalloc_start >> PAGE_CACHE_SHIFT;
    unsigned long start_index = index;
    unsigned long end_index = delalloc_end >> PAGE_CACHE_SHIFT;
    unsigned long pages_locked = 0;
    struct page *pages[16];
    unsigned long nrpages;
    int ret;
    int i;

    /* the caller is responsible for locking the start index */
    if (index == locked_page->index && index == end_index)
        return 0;

    /* skip the page at the start index */
    nrpages = end_index - index + 1;
    while (nrpages > 0) {
        ret = find_get_pages_contig(inode->i_mapping, index,
                     min_t(unsigned long,
                     nrpages, ARRAY_SIZE(pages)), pages);
        if (ret == 0) {
            ret = -EAGAIN;
            goto done;
        }
        /* now we have an array of pages, lock them all */
        for (i = 0; i < ret; i++) {
            /*
             * the caller is taking responsibility for
             * locked_page
             */
            if (pages[i] != locked_page) {
                lock_page(pages[i]);
                if (!PageDirty(pages[i]) ||
                    pages[i]->mapping != inode->i_mapping) {
                    ret = -EAGAIN;
                    unlock_page(pages[i]);
                    page_cache_release(pages[i]);
                    goto done;
                }
            }
            page_cache_release(pages[i]);
            pages_locked++;
        }
        nrpages -= ret;
        index += ret;
        cond_resched();
    }
    ret = 0;
done:
    if (ret && pages_locked) {
        __unlock_for_delalloc(inode, locked_page,
                  delalloc_start,
                  ((u64)(start_index + pages_locked - 1)) <<
                  PAGE_CACHE_SHIFT);
    }
    return ret;
}

/*
 * find a contiguous range of bytes in the file marked as delalloc, not
 * more than 'max_bytes'.  start and end are used to return the range,
 *
 * 1 is returned if we find something, 0 if nothing was in the tree
 */
static noinline u64 find_lock_delalloc_range(struct inode *inode,
                         struct extent_io_tree *tree,
                         struct page *locked_page,
                         u64 *start, u64 *end,
                         u64 max_bytes)
{
    u64 delalloc_start;
    u64 delalloc_end;
    u64 found;
    struct extent_state *cached_state = NULL;
    int ret;
    int loops = 0;

again:
    /* step one, find a bunch of delalloc bytes starting at start */
    delalloc_start = *start;
    delalloc_end = 0;
    found = find_delalloc_range(tree, &delalloc_start, &delalloc_end,
                    max_bytes, &cached_state);
    if (!found || delalloc_end <= *start) {
        *start = delalloc_start;
        *end = delalloc_end;
        free_extent_state(cached_state);
        return found;
    }

    /*
     * start comes from the offset of locked_page.  We have to lock
     * pages in order, so we can't process delalloc bytes before
     * locked_page
     */
    if (delalloc_start < *start)
        delalloc_start = *start;

    /*
     * make sure to limit the number of pages we try to lock down
     * if we're looping.
     */
    if (delalloc_end + 1 - delalloc_start > max_bytes && loops)
        delalloc_end = delalloc_start + PAGE_CACHE_SIZE - 1;

    /* step two, lock all the pages after the page that has start */
    ret = lock_delalloc_pages(inode, locked_page,
                  delalloc_start, delalloc_end);
    if (ret == -EAGAIN) {
        /* some of the pages are gone, lets avoid looping by
         * shortening the size of the delalloc range we're searching
         */
        free_extent_state(cached_state);
        if (!loops) {
            unsigned long offset = (*start) & (PAGE_CACHE_SIZE - 1);
            max_bytes = PAGE_CACHE_SIZE - offset;
            loops = 1;
            goto again;
        } else {
            found = 0;
            goto out_failed;
        }
    }
    BUG_ON(ret); /* Only valid values are 0 and -EAGAIN */

    /* step three, lock the state bits for the whole range */
    lock_extent_bits(tree, delalloc_start, delalloc_end, 0, &cached_state);

    /* then test to make sure it is all still delalloc */
    ret = test_range_bit(tree, delalloc_start, delalloc_end,
                 EXTENT_DELALLOC, 1, cached_state);
    if (!ret) {
        unlock_extent_cached(tree, delalloc_start, delalloc_end,
                     &cached_state, GFP_NOFS);
        __unlock_for_delalloc(inode, locked_page,
                  delalloc_start, delalloc_end);
        cond_resched();
        goto again;
    }
    free_extent_state(cached_state);
    *start = delalloc_start;
    *end = delalloc_end;
out_failed:
    return found;
}

int extent_clear_unlock_delalloc(struct inode *inode,
                struct extent_io_tree *tree,
                u64 start, u64 end, struct page *locked_page,
                unsigned long op)
{
    int ret;
    struct page *pages[16];
    unsigned long index = start >> PAGE_CACHE_SHIFT;
    unsigned long end_index = end >> PAGE_CACHE_SHIFT;
    unsigned long nr_pages = end_index - index + 1;
    int i;
    int clear_bits = 0;

    if (op & EXTENT_CLEAR_UNLOCK)
        clear_bits |= EXTENT_LOCKED;
    if (op & EXTENT_CLEAR_DIRTY)
        clear_bits |= EXTENT_DIRTY;

    if (op & EXTENT_CLEAR_DELALLOC)
        clear_bits |= EXTENT_DELALLOC;

    clear_extent_bit(tree, start, end, clear_bits, 1, 0, NULL, GFP_NOFS);
    if (!(op & (EXTENT_CLEAR_UNLOCK_PAGE | EXTENT_CLEAR_DIRTY |
            EXTENT_SET_WRITEBACK | EXTENT_END_WRITEBACK |
            EXTENT_SET_PRIVATE2)))
        return 0;

    while (nr_pages > 0) {
        ret = find_get_pages_contig(inode->i_mapping, index,
                     min_t(unsigned long,
                     nr_pages, ARRAY_SIZE(pages)), pages);
        for (i = 0; i < ret; i++) {

            if (op & EXTENT_SET_PRIVATE2)
                SetPagePrivate2(pages[i]);

            if (pages[i] == locked_page) {
                page_cache_release(pages[i]);
                continue;
            }
            if (op & EXTENT_CLEAR_DIRTY)
                clear_page_dirty_for_io(pages[i]);
            if (op & EXTENT_SET_WRITEBACK)
                set_page_writeback(pages[i]);
            if (op & EXTENT_END_WRITEBACK)
                end_page_writeback(pages[i]);
            if (op & EXTENT_CLEAR_UNLOCK_PAGE)
                unlock_page(pages[i]);
            page_cache_release(pages[i]);
        }
        nr_pages -= ret;
        index += ret;
        cond_resched();
    }
    return 0;
}

/*
 * count the number of bytes in the tree that have a given bit(s)
 * set.  This can be fairly slow, except for EXTENT_DIRTY which is
 * cached.  The total number found is returned.
 */
u64 count_range_bits(struct extent_io_tree *tree,
             u64 *start, u64 search_end, u64 max_bytes,
             unsigned long bits, int contig)
{
    struct rb_node *node;
    struct extent_state *state;
    u64 cur_start = *start;
    u64 total_bytes = 0;
    u64 last = 0;
    int found = 0;

    if (search_end <= cur_start) {
        WARN_ON(1);
        return 0;
    }

    spin_lock(&tree->lock);
    if (cur_start == 0 && bits == EXTENT_DIRTY) {
        total_bytes = tree->dirty_bytes;
        goto out;
    }
    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, cur_start);
    if (!node)
        goto out;

    while (1) {
        state = rb_entry(node, struct extent_state, rb_node);
        if (state->start > search_end)
            break;
        if (contig && found && state->start > last + 1)
            break;
        if (state->end >= cur_start && (state->state & bits) == bits) {
            total_bytes += min(search_end, state->end) + 1 -
                       max(cur_start, state->start);
            if (total_bytes >= max_bytes)
                break;
            if (!found) {
                *start = max(cur_start, state->start);
                found = 1;
            }
            last = state->end;
        } else if (contig && found) {
            break;
        }
        node = rb_next(node);
        if (!node)
            break;
    }
out:
    spin_unlock(&tree->lock);
    return total_bytes;
}

/*
 * set the private field for a given byte offset in the tree.  If there isn't
 * an extent_state there already, this does nothing.
 */
int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
{
    struct rb_node *node;
    struct extent_state *state;
    int ret = 0;

    spin_lock(&tree->lock);
    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, start);
    if (!node) {
        ret = -ENOENT;
        goto out;
    }
    state = rb_entry(node, struct extent_state, rb_node);
    if (state->start != start) {
        ret = -ENOENT;
        goto out;
    }
    state->private = private;
out:
    spin_unlock(&tree->lock);
    return ret;
}

int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private)
{
    struct rb_node *node;
    struct extent_state *state;
    int ret = 0;

    spin_lock(&tree->lock);
    /*
     * this search will find all the extents that end after
     * our range starts.
     */
    node = tree_search(tree, start);
    if (!node) {
        ret = -ENOENT;
        goto out;
    }
    state = rb_entry(node, struct extent_state, rb_node);
    if (state->start != start) {
        ret = -ENOENT;
        goto out;
    }
    *private = state->private;
out:
    spin_unlock(&tree->lock);
    return ret;
}

/*
 * searches a range in the state tree for a given mask.
 * If 'filled' == 1, this returns 1 only if every extent in the tree
 * has the bits set.  Otherwise, 1 is returned if any bit in the
 * range is found set.
 */
int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
           int bits, int filled, struct extent_state *cached)
{
    struct extent_state *state = NULL;
    struct rb_node *node;
    int bitset = 0;

    spin_lock(&tree->lock);
    if (cached && cached->tree && cached->start <= start &&
        cached->end > start)
        node = &cached->rb_node;
    else
        node = tree_search(tree, start);
    while (node && start <= end) {
        state = rb_entry(node, struct extent_state, rb_node);

        if (filled && state->start > start) {
            bitset = 0;
            break;
        }

        if (state->start > end)
            break;

        if (state->state & bits) {
            bitset = 1;
            if (!filled)
                break;
        } else if (filled) {
            bitset = 0;
            break;
        }

        if (state->end == (u64)-1)
            break;

        start = state->end + 1;
        if (start > end)
            break;
        node = rb_next(node);
        if (!node) {
            if (filled)
                bitset = 0;
            break;
        }
    }
    spin_unlock(&tree->lock);
    return bitset;
}

/*
 * helper function to set a given page up to date if all the
 * extents in the tree for that page are up to date
 */
static void check_page_uptodate(struct extent_io_tree *tree, struct page *page)
{
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 end = start + PAGE_CACHE_SIZE - 1;
    if (test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL))
        SetPageUptodate(page);
}

/*
 * helper function to unlock a page if all the extents in the tree
 * for that page are unlocked
 */
static void check_page_locked(struct extent_io_tree *tree, struct page *page)
{
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 end = start + PAGE_CACHE_SIZE - 1;
    if (!test_range_bit(tree, start, end, EXTENT_LOCKED, 0, NULL))
        unlock_page(page);
}

/*
 * helper function to end page writeback if all the extents
 * in the tree for that page are done with writeback
 */
static void check_page_writeback(struct extent_io_tree *tree,
                 struct page *page)
{
    end_page_writeback(page);
}

/*
 * When IO fails, either with EIO or csum verification fails, we
 * try other mirrors that might have a good copy of the data.  This
 * io_failure_record is used to record state as we go through all the
 * mirrors.  If another mirror has good data, the page is set up to date
 * and things continue.  If a good mirror can't be found, the original
 * bio end_io callback is called to indicate things have failed.
 */
struct io_failure_record {
    struct page *page;
    u64 start;
    u64 len;
    u64 logical;
    unsigned long bio_flags;
    int this_mirror;
    int failed_mirror;
    int in_validation;
};

static int free_io_failure(struct inode *inode, struct io_failure_record *rec,
                int did_repair)
{
    int ret;
    int err = 0;
    struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;

    set_state_private(failure_tree, rec->start, 0);
    ret = clear_extent_bits(failure_tree, rec->start,
                rec->start + rec->len - 1,
                EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
    if (ret)
        err = ret;

    if (did_repair) {
        ret = clear_extent_bits(&BTRFS_I(inode)->io_tree, rec->start,
                    rec->start + rec->len - 1,
                    EXTENT_DAMAGED, GFP_NOFS);
        if (ret && !err)
            err = ret;
    }

    kfree(rec);
    return err;
}

static void repair_io_failure_callback(struct bio *bio, int err)
{
    complete(bio->bi_private);
}

/*
 * this bypasses the standard btrfs submit functions deliberately, as
 * the standard behavior is to write all copies in a raid setup. here we only
 * want to write the one bad copy. so we do the mapping for ourselves and issue
 * submit_bio directly.
 * to avoid any synchonization issues, wait for the data after writing, which
 * actually prevents the read that triggered the error from finishing.
 * currently, there can be no more than two copies of every data bit. thus,
 * exactly one rewrite is required.
 */
int repair_io_failure(struct btrfs_mapping_tree *map_tree, u64 start,
            u64 length, u64 logical, struct page *page,
            int mirror_num)
{
    struct bio *bio;
    struct btrfs_device *dev;
    DECLARE_COMPLETION_ONSTACK(compl);
    u64 map_length = 0;
    u64 sector;
    struct btrfs_bio *bbio = NULL;
    int ret;

    BUG_ON(!mirror_num);

    bio = bio_alloc(GFP_NOFS, 1);
    if (!bio)
        return -EIO;
    bio->bi_private = &compl;
    bio->bi_end_io = repair_io_failure_callback;
    bio->bi_size = 0;
    map_length = length;

    ret = btrfs_map_block(map_tree, WRITE, logical,
                  &map_length, &bbio, mirror_num);
    if (ret) {
        bio_put(bio);
        return -EIO;
    }
    BUG_ON(mirror_num != bbio->mirror_num);
    sector = bbio->stripes[mirror_num-1].physical >> 9;
    bio->bi_sector = sector;
    dev = bbio->stripes[mirror_num-1].dev;
    kfree(bbio);
    if (!dev || !dev->bdev || !dev->writeable) {
        bio_put(bio);
        return -EIO;
    }
    bio->bi_bdev = dev->bdev;
    bio_add_page(bio, page, length, start-page_offset(page));
    btrfsic_submit_bio(WRITE_SYNC, bio);
    wait_for_completion(&compl);

    if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
        /* try to remap that extent elsewhere? */
        bio_put(bio);
        btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
        return -EIO;
    }

    printk_ratelimited_in_rcu(KERN_INFO "btrfs read error corrected: ino %lu off %llu "
              "(dev %s sector %llu)\n", page->mapping->host->i_ino,
              start, rcu_str_deref(dev->name), sector);

    bio_put(bio);
    return 0;
}

int repair_eb_io_failure(struct btrfs_root *root, struct extent_buffer *eb,
             int mirror_num)
{
    struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
    u64 start = eb->start;
    unsigned long i, num_pages = num_extent_pages(eb->start, eb->len);
    int ret = 0;

    for (i = 0; i < num_pages; i++) {
        struct page *p = extent_buffer_page(eb, i);
        ret = repair_io_failure(map_tree, start, PAGE_CACHE_SIZE,
                    start, p, mirror_num);
        if (ret)
            break;
        start += PAGE_CACHE_SIZE;
    }

    return ret;
}

/*
 * each time an IO finishes, we do a fast check in the IO failure tree
 * to see if we need to process or clean up an io_failure_record
 */
static int clean_io_failure(u64 start, struct page *page)
{
    u64 private;
    u64 private_failure;
    struct io_failure_record *failrec;
    struct btrfs_mapping_tree *map_tree;
    struct extent_state *state;
    int num_copies;
    int did_repair = 0;
    int ret;
    struct inode *inode = page->mapping->host;

    private = 0;
    ret = count_range_bits(&BTRFS_I(inode)->io_failure_tree, &private,
                (u64)-1, 1, EXTENT_DIRTY, 0);
    if (!ret)
        return 0;

    ret = get_state_private(&BTRFS_I(inode)->io_failure_tree, start,
                &private_failure);
    if (ret)
        return 0;

    failrec = (struct io_failure_record *)(unsigned long) private_failure;
    BUG_ON(!failrec->this_mirror);

    if (failrec->in_validation) {
        /* there was no real error, just free the record */
        pr_debug("clean_io_failure: freeing dummy error at %llu\n",
             failrec->start);
        did_repair = 1;
        goto out;
    }

    spin_lock(&BTRFS_I(inode)->io_tree.lock);
    state = find_first_extent_bit_state(&BTRFS_I(inode)->io_tree,
                        failrec->start,
                        EXTENT_LOCKED);
    spin_unlock(&BTRFS_I(inode)->io_tree.lock);

    if (state && state->start == failrec->start) {
        map_tree = &BTRFS_I(inode)->root->fs_info->mapping_tree;
        num_copies = btrfs_num_copies(map_tree, failrec->logical,
                        failrec->len);
        if (num_copies > 1)  {
            ret = repair_io_failure(map_tree, start, failrec->len,
                        failrec->logical, page,
                        failrec->failed_mirror);
            did_repair = !ret;
        }
    }

out:
    if (!ret)
        ret = free_io_failure(inode, failrec, did_repair);

    return ret;
}

/*
 * this is a generic handler for readpage errors (default
 * readpage_io_failed_hook). if other copies exist, read those and write back
 * good data to the failed position. does not investigate in remapping the
 * failed extent elsewhere, hoping the device will be smart enough to do this as
 * needed
 */

static int bio_readpage_error(struct bio *failed_bio, struct page *page,
                u64 start, u64 end, int failed_mirror,
                struct extent_state *state)
{
    struct io_failure_record *failrec = NULL;
    u64 private;
    struct extent_map *em;
    struct inode *inode = page->mapping->host;
    struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
    struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
    struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
    struct bio *bio;
    int num_copies;
    int ret;
    int read_mode;
    u64 logical;

    BUG_ON(failed_bio->bi_rw & REQ_WRITE);

    ret = get_state_private(failure_tree, start, &private);
    if (ret) {
        failrec = kzalloc(sizeof(*failrec), GFP_NOFS);
        if (!failrec)
            return -ENOMEM;
        failrec->start = start;
        failrec->len = end - start + 1;
        failrec->this_mirror = 0;
        failrec->bio_flags = 0;
        failrec->in_validation = 0;

        read_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, failrec->len);
        if (!em) {
            read_unlock(&em_tree->lock);
            kfree(failrec);
            return -EIO;
        }

        if (em->start > start || em->start + em->len < start) {
            free_extent_map(em);
            em = NULL;
        }
        read_unlock(&em_tree->lock);

        if (!em) {
            kfree(failrec);
            return -EIO;
        }
        logical = start - em->start;
        logical = em->block_start + logical;
        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
            logical = em->block_start;
            failrec->bio_flags = EXTENT_BIO_COMPRESSED;
            extent_set_compress_type(&failrec->bio_flags,
                         em->compress_type);
        }
        pr_debug("bio_readpage_error: (new) logical=%llu, start=%llu, "
             "len=%llu\n", logical, start, failrec->len);
        failrec->logical = logical;
        free_extent_map(em);

        /* set the bits in the private failure tree */
        ret = set_extent_bits(failure_tree, start, end,
                    EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
        if (ret >= 0)
            ret = set_state_private(failure_tree, start,
                        (u64)(unsigned long)failrec);
        /* set the bits in the inode's tree */
        if (ret >= 0)
            ret = set_extent_bits(tree, start, end, EXTENT_DAMAGED,
                        GFP_NOFS);
        if (ret < 0) {
            kfree(failrec);
            return ret;
        }
    } else {
        failrec = (struct io_failure_record *)(unsigned long)private;
        pr_debug("bio_readpage_error: (found) logical=%llu, "
             "start=%llu, len=%llu, validation=%d\n",
             failrec->logical, failrec->start, failrec->len,
             failrec->in_validation);
        /*
         * when data can be on disk more than twice, add to failrec here
         * (e.g. with a list for failed_mirror) to make
         * clean_io_failure() clean all those errors at once.
         */
    }
    num_copies = btrfs_num_copies(
                  &BTRFS_I(inode)->root->fs_info->mapping_tree,
                  failrec->logical, failrec->len);
    if (num_copies == 1) {
        /*
         * we only have a single copy of the data, so don't bother with
         * all the retry and error correction code that follows. no
         * matter what the error is, it is very likely to persist.
         */
        pr_debug("bio_readpage_error: cannot repair, num_copies == 1. "
             "state=%p, num_copies=%d, next_mirror %d, "
             "failed_mirror %d\n", state, num_copies,
             failrec->this_mirror, failed_mirror);
        free_io_failure(inode, failrec, 0);
        return -EIO;
    }

    if (!state) {
        spin_lock(&tree->lock);
        state = find_first_extent_bit_state(tree, failrec->start,
                            EXTENT_LOCKED);
        if (state && state->start != failrec->start)
            state = NULL;
        spin_unlock(&tree->lock);
    }

    /*
     * there are two premises:
     *  a) deliver good data to the caller
     *  b) correct the bad sectors on disk
     */
    if (failed_bio->bi_vcnt > 1) {
        /*
         * to fulfill b), we need to know the exact failing sectors, as
         * we don't want to rewrite any more than the failed ones. thus,
         * we need separate read requests for the failed bio
         *
         * if the following BUG_ON triggers, our validation request got
         * merged. we need separate requests for our algorithm to work.
         */
        BUG_ON(failrec->in_validation);
        failrec->in_validation = 1;
        failrec->this_mirror = failed_mirror;
        read_mode = READ_SYNC | REQ_FAILFAST_DEV;
    } else {
        /*
         * we're ready to fulfill a) and b) alongside. get a good copy
         * of the failed sector and if we succeed, we have setup
         * everything for repair_io_failure to do the rest for us.
         */
        if (failrec->in_validation) {
            BUG_ON(failrec->this_mirror != failed_mirror);
            failrec->in_validation = 0;
            failrec->this_mirror = 0;
        }
        failrec->failed_mirror = failed_mirror;
        failrec->this_mirror++;
        if (failrec->this_mirror == failed_mirror)
            failrec->this_mirror++;
        read_mode = READ_SYNC;
    }

    if (!state || failrec->this_mirror > num_copies) {
        pr_debug("bio_readpage_error: (fail) state=%p, num_copies=%d, "
             "next_mirror %d, failed_mirror %d\n", state,
             num_copies, failrec->this_mirror, failed_mirror);
        free_io_failure(inode, failrec, 0);
        return -EIO;
    }

    bio = bio_alloc(GFP_NOFS, 1);
    if (!bio) {
        free_io_failure(inode, failrec, 0);
        return -EIO;
    }
    bio->bi_private = state;
    bio->bi_end_io = failed_bio->bi_end_io;
    bio->bi_sector = failrec->logical >> 9;
    bio->bi_bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
    bio->bi_size = 0;

    bio_add_page(bio, page, failrec->len, start - page_offset(page));

    pr_debug("bio_readpage_error: submitting new read[%#x] to "
         "this_mirror=%d, num_copies=%d, in_validation=%d\n", read_mode,
         failrec->this_mirror, num_copies, failrec->in_validation);

    ret = tree->ops->submit_bio_hook(inode, read_mode, bio,
                     failrec->this_mirror,
                     failrec->bio_flags, 0);
    return ret;
}

/* lots and lots of room for performance fixes in the end_bio funcs */

int end_extent_writepage(struct page *page, int err, u64 start, u64 end)
{
    int uptodate = (err == 0);
    struct extent_io_tree *tree;
    int ret;

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

    if (tree->ops && tree->ops->writepage_end_io_hook) {
        ret = tree->ops->writepage_end_io_hook(page, start,
                           end, NULL, uptodate);
        if (ret)
            uptodate = 0;
    }

    if (!uptodate) {
        ClearPageUptodate(page);
        SetPageError(page);
    }
    return 0;
}

/*
 * after a writepage IO is done, we need to:
 * clear the uptodate bits on error
 * clear the writeback bits in the extent tree for this IO
 * end_page_writeback if the page has no more pending IO
 *
 * Scheduling is not allowed, so the extent state tree is expected
 * to have one and only one object corresponding to this IO.
 */
static void end_bio_extent_writepage(struct bio *bio, int err)
{
    struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
    struct extent_io_tree *tree;
    u64 start;
    u64 end;
    int whole_page;

    do {
        struct page *page = bvec->bv_page;
        tree = &BTRFS_I(page->mapping->host)->io_tree;

        start = ((u64)page->index << PAGE_CACHE_SHIFT) +
             bvec->bv_offset;
        end = start + bvec->bv_len - 1;

        if (bvec->bv_offset == 0 && bvec->bv_len == PAGE_CACHE_SIZE)
            whole_page = 1;
        else
            whole_page = 0;

        if (--bvec >= bio->bi_io_vec)
            prefetchw(&bvec->bv_page->flags);

        if (end_extent_writepage(page, err, start, end))
            continue;

        if (whole_page)
            end_page_writeback(page);
        else
            check_page_writeback(tree, page);
    } while (bvec >= bio->bi_io_vec);

    bio_put(bio);
}

/*
 * after a readpage IO is done, we need to:
 * clear the uptodate bits on error
 * set the uptodate bits if things worked
 * set the page up to date if all extents in the tree are uptodate
 * clear the lock bit in the extent tree
 * unlock the page if there are no other extents locked for it
 *
 * Scheduling is not allowed, so the extent state tree is expected
 * to have one and only one object corresponding to this IO.
 */
static void end_bio_extent_readpage(struct bio *bio, int err)
{
    int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
    struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
    struct bio_vec *bvec = bio->bi_io_vec;
    struct extent_io_tree *tree;
    u64 start;
    u64 end;
    int whole_page;
    int mirror;
    int ret;

    if (err)
        uptodate = 0;

    do {
        struct page *page = bvec->bv_page;
        struct extent_state *cached = NULL;
        struct extent_state *state;

        pr_debug("end_bio_extent_readpage: bi_sector=%llu, err=%d, "
             "mirror=%ld\n", (u64)bio->bi_sector, err,
             (long int)bio->bi_bdev);
        tree = &BTRFS_I(page->mapping->host)->io_tree;

        start = ((u64)page->index << PAGE_CACHE_SHIFT) +
            bvec->bv_offset;
        end = start + bvec->bv_len - 1;

        if (bvec->bv_offset == 0 && bvec->bv_len == PAGE_CACHE_SIZE)
            whole_page = 1;
        else
            whole_page = 0;

        if (++bvec <= bvec_end)
            prefetchw(&bvec->bv_page->flags);

        spin_lock(&tree->lock);
        state = find_first_extent_bit_state(tree, start, EXTENT_LOCKED);
        if (state && state->start == start) {
            /*
             * take a reference on the state, unlock will drop
             * the ref
             */
            cache_state(state, &cached);
        }
        spin_unlock(&tree->lock);

        mirror = (int)(unsigned long)bio->bi_bdev;
        if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {
            ret = tree->ops->readpage_end_io_hook(page, start, end,
                                  state, mirror);
            if (ret)
                uptodate = 0;
            else
                clean_io_failure(start, page);
        }

        if (!uptodate && tree->ops && tree->ops->readpage_io_failed_hook) {
            ret = tree->ops->readpage_io_failed_hook(page, mirror);
            if (!ret && !err &&
                test_bit(BIO_UPTODATE, &bio->bi_flags))
                uptodate = 1;
        } else if (!uptodate) {
            /*
             * The generic bio_readpage_error handles errors the
             * following way: If possible, new read requests are
             * created and submitted and will end up in
             * end_bio_extent_readpage as well (if we're lucky, not
             * in the !uptodate case). In that case it returns 0 and
             * we just go on with the next page in our bio. If it
             * can't handle the error it will return -EIO and we
             * remain responsible for that page.
             */
            ret = bio_readpage_error(bio, page, start, end, mirror, NULL);
            if (ret == 0) {
                uptodate =
                    test_bit(BIO_UPTODATE, &bio->bi_flags);
                if (err)
                    uptodate = 0;
                uncache_state(&cached);
                continue;
            }
        }

        if (uptodate && tree->track_uptodate) {
            set_extent_uptodate(tree, start, end, &cached,
                        GFP_ATOMIC);
        }
        unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);

        if (whole_page) {
            if (uptodate) {
                SetPageUptodate(page);
            } else {
                ClearPageUptodate(page);
                SetPageError(page);
            }
            unlock_page(page);
        } else {
            if (uptodate) {
                check_page_uptodate(tree, page);
            } else {
                ClearPageUptodate(page);
                SetPageError(page);
            }
            check_page_locked(tree, page);
        }
    } while (bvec <= bvec_end);

    bio_put(bio);
}

struct bio *
btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
        gfp_t gfp_flags)
{
    struct bio *bio;

    bio = bio_alloc(gfp_flags, nr_vecs);

    if (bio == NULL && (current->flags & PF_MEMALLOC)) {
        while (!bio && (nr_vecs /= 2))
            bio = bio_alloc(gfp_flags, nr_vecs);
    }

    if (bio) {
        bio->bi_size = 0;
        bio->bi_bdev = bdev;
        bio->bi_sector = first_sector;
    }
    return bio;
}

/*
 * Since writes are async, they will only return -ENOMEM.
 * Reads can return the full range of I/O error conditions.
 */
static int __must_check submit_one_bio(int rw, struct bio *bio,
                       int mirror_num, unsigned long bio_flags)
{
    int ret = 0;
    struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
    struct page *page = bvec->bv_page;
    struct extent_io_tree *tree = bio->bi_private;
    u64 start;

    start = ((u64)page->index << PAGE_CACHE_SHIFT) + bvec->bv_offset;

    bio->bi_private = NULL;

    bio_get(bio);

    if (tree->ops && tree->ops->submit_bio_hook)
        ret = tree->ops->submit_bio_hook(page->mapping->host, rw, bio,
                       mirror_num, bio_flags, start);
    else
        btrfsic_submit_bio(rw, bio);

    if (bio_flagged(bio, BIO_EOPNOTSUPP))
        ret = -EOPNOTSUPP;
    bio_put(bio);
    return ret;
}

static int merge_bio(struct extent_io_tree *tree, struct page *page,
             unsigned long offset, size_t size, struct bio *bio,
             unsigned long bio_flags)
{
    int ret = 0;
    if (tree->ops && tree->ops->merge_bio_hook)
        ret = tree->ops->merge_bio_hook(page, offset, size, bio,
                        bio_flags);
    BUG_ON(ret < 0);
    return ret;

}

static int submit_extent_page(int rw, struct extent_io_tree *tree,
                  struct page *page, sector_t sector,
                  size_t size, unsigned long offset,
                  struct block_device *bdev,
                  struct bio **bio_ret,
                  unsigned long max_pages,
                  bio_end_io_t end_io_func,
                  int mirror_num,
                  unsigned long prev_bio_flags,
                  unsigned long bio_flags)
{
    int ret = 0;
    struct bio *bio;
    int nr;
    int contig = 0;
    int this_compressed = bio_flags & EXTENT_BIO_COMPRESSED;
    int old_compressed = prev_bio_flags & EXTENT_BIO_COMPRESSED;
    size_t page_size = min_t(size_t, size, PAGE_CACHE_SIZE);

    if (bio_ret && *bio_ret) {
        bio = *bio_ret;
        if (old_compressed)
            contig = bio->bi_sector == sector;
        else
            contig = bio->bi_sector + (bio->bi_size >> 9) ==
                sector;

        if (prev_bio_flags != bio_flags || !contig ||
            merge_bio(tree, page, offset, page_size, bio, bio_flags) ||
            bio_add_page(bio, page, page_size, offset) < page_size) {
            ret = submit_one_bio(rw, bio, mirror_num,
                         prev_bio_flags);
            if (ret < 0)
                return ret;
            bio = NULL;
        } else {
            return 0;
        }
    }
    if (this_compressed)
        nr = BIO_MAX_PAGES;
    else
        nr = bio_get_nr_vecs(bdev);

    bio = btrfs_bio_alloc(bdev, sector, nr, GFP_NOFS | __GFP_HIGH);
    if (!bio)
        return -ENOMEM;

    bio_add_page(bio, page, page_size, offset);
    bio->bi_end_io = end_io_func;
    bio->bi_private = tree;

    if (bio_ret)
        *bio_ret = bio;
    else
        ret = submit_one_bio(rw, bio, mirror_num, bio_flags);

    return ret;
}

void attach_extent_buffer_page(struct extent_buffer *eb, struct page *page)
{
    if (!PagePrivate(page)) {
        SetPagePrivate(page);
        page_cache_get(page);
        set_page_private(page, (unsigned long)eb);
    } else {
        WARN_ON(page->private != (unsigned long)eb);
    }
}

void set_page_extent_mapped(struct page *page)
{
    if (!PagePrivate(page)) {
        SetPagePrivate(page);
        page_cache_get(page);
        set_page_private(page, EXTENT_PAGE_PRIVATE);
    }
}

/*
 * basic readpage implementation.  Locked extent state structs are inserted
 * into the tree that are removed when the IO is done (by the end_io
 * handlers)
 * XXX JDM: This needs looking at to ensure proper page locking
 */
static int __extent_read_full_page(struct extent_io_tree *tree,
                   struct page *page,
                   get_extent_t *get_extent,
                   struct bio **bio, int mirror_num,
                   unsigned long *bio_flags)
{
    struct inode *inode = page->mapping->host;
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 page_end = start + PAGE_CACHE_SIZE - 1;
    u64 end;
    u64 cur = start;
    u64 extent_offset;
    u64 last_byte = i_size_read(inode);
    u64 block_start;
    u64 cur_end;
    sector_t sector;
    struct extent_map *em;
    struct block_device *bdev;
    struct btrfs_ordered_extent *ordered;
    int ret;
    int nr = 0;
    size_t pg_offset = 0;
    size_t iosize;
    size_t disk_io_size;
    size_t blocksize = inode->i_sb->s_blocksize;
    unsigned long this_bio_flag = 0;

    set_page_extent_mapped(page);

    if (!PageUptodate(page)) {
        if (cleancache_get_page(page) == 0) {
            BUG_ON(blocksize != PAGE_SIZE);
            goto out;
        }
    }

    end = page_end;
    while (1) {
        lock_extent(tree, start, end);
        ordered = btrfs_lookup_ordered_extent(inode, start);
        if (!ordered)
            break;
        unlock_extent(tree, start, end);
        btrfs_start_ordered_extent(inode, ordered, 1);
        btrfs_put_ordered_extent(ordered);
    }

    if (page->index == last_byte >> PAGE_CACHE_SHIFT) {
        char *userpage;
        size_t zero_offset = last_byte & (PAGE_CACHE_SIZE - 1);

        if (zero_offset) {
            iosize = PAGE_CACHE_SIZE - zero_offset;
            userpage = kmap_atomic(page);
            memset(userpage + zero_offset, 0, iosize);
            flush_dcache_page(page);
            kunmap_atomic(userpage);
        }
    }
    while (cur <= end) {
        if (cur >= last_byte) {
            char *userpage;
            struct extent_state *cached = NULL;

            iosize = PAGE_CACHE_SIZE - pg_offset;
            userpage = kmap_atomic(page);
            memset(userpage + pg_offset, 0, iosize);
            flush_dcache_page(page);
            kunmap_atomic(userpage);
            set_extent_uptodate(tree, cur, cur + iosize - 1,
                        &cached, GFP_NOFS);
            unlock_extent_cached(tree, cur, cur + iosize - 1,
                         &cached, GFP_NOFS);
            break;
        }
        em = get_extent(inode, page, pg_offset, cur,
                end - cur + 1, 0);
        if (IS_ERR_OR_NULL(em)) {
            SetPageError(page);
            unlock_extent(tree, cur, end);
            break;
        }
        extent_offset = cur - em->start;
        BUG_ON(extent_map_end(em) <= cur);
        BUG_ON(end < cur);

        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
            this_bio_flag = EXTENT_BIO_COMPRESSED;
            extent_set_compress_type(&this_bio_flag,
                         em->compress_type);
        }

        iosize = min(extent_map_end(em) - cur, end - cur + 1);
        cur_end = min(extent_map_end(em) - 1, end);
        iosize = (iosize + blocksize - 1) & ~((u64)blocksize - 1);
        if (this_bio_flag & EXTENT_BIO_COMPRESSED) {
            disk_io_size = em->block_len;
            sector = em->block_start >> 9;
        } else {
            sector = (em->block_start + extent_offset) >> 9;
            disk_io_size = iosize;
        }
        bdev = em->bdev;
        block_start = em->block_start;
        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
            block_start = EXTENT_MAP_HOLE;
        free_extent_map(em);
        em = NULL;

        /* we've found a hole, just zero and go on */
        if (block_start == EXTENT_MAP_HOLE) {
            char *userpage;
            struct extent_state *cached = NULL;

            userpage = kmap_atomic(page);
            memset(userpage + pg_offset, 0, iosize);
            flush_dcache_page(page);
            kunmap_atomic(userpage);

            set_extent_uptodate(tree, cur, cur + iosize - 1,
                        &cached, GFP_NOFS);
            unlock_extent_cached(tree, cur, cur + iosize - 1,
                                 &cached, GFP_NOFS);
            cur = cur + iosize;
            pg_offset += iosize;
            continue;
        }
        /* the get_extent function already copied into the page */
        if (test_range_bit(tree, cur, cur_end,
                   EXTENT_UPTODATE, 1, NULL)) {
            check_page_uptodate(tree, page);
            unlock_extent(tree, cur, cur + iosize - 1);
            cur = cur + iosize;
            pg_offset += iosize;
            continue;
        }
        /* we have an inline extent but it didn't get marked up
         * to date.  Error out
         */
        if (block_start == EXTENT_MAP_INLINE) {
            SetPageError(page);
            unlock_extent(tree, cur, cur + iosize - 1);
            cur = cur + iosize;
            pg_offset += iosize;
            continue;
        }

        ret = 0;
        if (tree->ops && tree->ops->readpage_io_hook) {
            ret = tree->ops->readpage_io_hook(page, cur,
                              cur + iosize - 1);
        }
        if (!ret) {
            unsigned long pnr = (last_byte >> PAGE_CACHE_SHIFT) + 1;
            pnr -= page->index;
            ret = submit_extent_page(READ, tree, page,
                     sector, disk_io_size, pg_offset,
                     bdev, bio, pnr,
                     end_bio_extent_readpage, mirror_num,
                     *bio_flags,
                     this_bio_flag);
            if (!ret) {
                nr++;
                *bio_flags = this_bio_flag;
            }
        }
        if (ret) {
            SetPageError(page);
            unlock_extent(tree, cur, cur + iosize - 1);
        }
        cur = cur + iosize;
        pg_offset += iosize;
    }
out:
    if (!nr) {
        if (!PageError(page))
            SetPageUptodate(page);
        unlock_page(page);
    }
    return 0;
}

int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
                get_extent_t *get_extent, int mirror_num)
{
    struct bio *bio = NULL;
    unsigned long bio_flags = 0;
    int ret;

    ret = __extent_read_full_page(tree, page, get_extent, &bio, mirror_num,
                      &bio_flags);
    if (bio)
        ret = submit_one_bio(READ, bio, mirror_num, bio_flags);
    return ret;
}

static noinline void update_nr_written(struct page *page,
                      struct writeback_control *wbc,
                      unsigned long nr_written)
{
    wbc->nr_to_write -= nr_written;
    if (wbc->range_cyclic || (wbc->nr_to_write > 0 &&
        wbc->range_start == 0 && wbc->range_end == LLONG_MAX))
        page->mapping->writeback_index = page->index + nr_written;
}

/*
 * the writepage semantics are similar to regular writepage.  extent
 * records are inserted to lock ranges in the tree, and as dirty areas
 * are found, they are marked writeback.  Then the lock bits are removed
 * and the end_io handler clears the writeback ranges
 */
static int __extent_writepage(struct page *page, struct writeback_control *wbc,
                  void *data)
{
    struct inode *inode = page->mapping->host;
    struct extent_page_data *epd = data;
    struct extent_io_tree *tree = epd->tree;
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 delalloc_start;
    u64 page_end = start + PAGE_CACHE_SIZE - 1;
    u64 end;
    u64 cur = start;
    u64 extent_offset;
    u64 last_byte = i_size_read(inode);
    u64 block_start;
    u64 iosize;
    sector_t sector;
    struct extent_state *cached_state = NULL;
    struct extent_map *em;
    struct block_device *bdev;
    int ret;
    int nr = 0;
    size_t pg_offset = 0;
    size_t blocksize;
    loff_t i_size = i_size_read(inode);
    unsigned long end_index = i_size >> PAGE_CACHE_SHIFT;
    u64 nr_delalloc;
    u64 delalloc_end;
    int page_started;
    int compressed;
    int write_flags;
    unsigned long nr_written = 0;
    bool fill_delalloc = true;

    if (wbc->sync_mode == WB_SYNC_ALL)
        write_flags = WRITE_SYNC;
    else
        write_flags = WRITE;

    trace___extent_writepage(page, inode, wbc);

    WARN_ON(!PageLocked(page));

    ClearPageError(page);

    pg_offset = i_size & (PAGE_CACHE_SIZE - 1);
    if (page->index > end_index ||
       (page->index == end_index && !pg_offset)) {
        page->mapping->a_ops->invalidatepage(page, 0);
        unlock_page(page);
        return 0;
    }

    if (page->index == end_index) {
        char *userpage;

        userpage = kmap_atomic(page);
        memset(userpage + pg_offset, 0,
               PAGE_CACHE_SIZE - pg_offset);
        kunmap_atomic(userpage);
        flush_dcache_page(page);
    }
    pg_offset = 0;

    set_page_extent_mapped(page);

    if (!tree->ops || !tree->ops->fill_delalloc)
        fill_delalloc = false;

    delalloc_start = start;
    delalloc_end = 0;
    page_started = 0;
    if (!epd->extent_locked && fill_delalloc) {
        u64 delalloc_to_write = 0;
        /*
         * make sure the wbc mapping index is at least updated
         * to this page.
         */
        update_nr_written(page, wbc, 0);

        while (delalloc_end < page_end) {
            nr_delalloc = find_lock_delalloc_range(inode, tree,
                               page,
                               &delalloc_start,
                               &delalloc_end,
                               128 * 1024 * 1024);
            if (nr_delalloc == 0) {
                delalloc_start = delalloc_end + 1;
                continue;
            }
            ret = tree->ops->fill_delalloc(inode, page,
                               delalloc_start,
                               delalloc_end,
                               &page_started,
                               &nr_written);
            /* File system has been set read-only */
            if (ret) {
                SetPageError(page);
                goto done;
            }
            /*
             * delalloc_end is already one less than the total
             * length, so we don't subtract one from
             * PAGE_CACHE_SIZE
             */
            delalloc_to_write += (delalloc_end - delalloc_start +
                          PAGE_CACHE_SIZE) >>
                          PAGE_CACHE_SHIFT;
            delalloc_start = delalloc_end + 1;
        }
        if (wbc->nr_to_write < delalloc_to_write) {
            int thresh = 8192;

            if (delalloc_to_write < thresh * 2)
                thresh = delalloc_to_write;
            wbc->nr_to_write = min_t(u64, delalloc_to_write,
                         thresh);
        }

        /* did the fill delalloc function already unlock and start
         * the IO?
         */
        if (page_started) {
            ret = 0;
            /*
             * we've unlocked the page, so we can't update
             * the mapping's writeback index, just update
             * nr_to_write.
             */
            wbc->nr_to_write -= nr_written;
            goto done_unlocked;
        }
    }
    if (tree->ops && tree->ops->writepage_start_hook) {
        ret = tree->ops->writepage_start_hook(page, start,
                              page_end);
        if (ret) {
            /* Fixup worker will requeue */
            if (ret == -EBUSY)
                wbc->pages_skipped++;
            else
                redirty_page_for_writepage(wbc, page);
            update_nr_written(page, wbc, nr_written);
            unlock_page(page);
            ret = 0;
            goto done_unlocked;
        }
    }

    /*
     * we don't want to touch the inode after unlocking the page,
     * so we update the mapping writeback index now
     */
    update_nr_written(page, wbc, nr_written + 1);

    end = page_end;
    if (last_byte <= start) {
        if (tree->ops && tree->ops->writepage_end_io_hook)
            tree->ops->writepage_end_io_hook(page, start,
                             page_end, NULL, 1);
        goto done;
    }

    blocksize = inode->i_sb->s_blocksize;

    while (cur <= end) {
        if (cur >= last_byte) {
            if (tree->ops && tree->ops->writepage_end_io_hook)
                tree->ops->writepage_end_io_hook(page, cur,
                             page_end, NULL, 1);
            break;
        }
        em = epd->get_extent(inode, page, pg_offset, cur,
                     end - cur + 1, 1);
        if (IS_ERR_OR_NULL(em)) {
            SetPageError(page);
            break;
        }

        extent_offset = cur - em->start;
        BUG_ON(extent_map_end(em) <= cur);
        BUG_ON(end < cur);
        iosize = min(extent_map_end(em) - cur, end - cur + 1);
        iosize = (iosize + blocksize - 1) & ~((u64)blocksize - 1);
        sector = (em->block_start + extent_offset) >> 9;
        bdev = em->bdev;
        block_start = em->block_start;
        compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
        free_extent_map(em);
        em = NULL;

        /*
         * compressed and inline extents are written through other
         * paths in the FS
         */
        if (compressed || block_start == EXTENT_MAP_HOLE ||
            block_start == EXTENT_MAP_INLINE) {
            /*
             * end_io notification does not happen here for
             * compressed extents
             */
            if (!compressed && tree->ops &&
                tree->ops->writepage_end_io_hook)
                tree->ops->writepage_end_io_hook(page, cur,
                             cur + iosize - 1,
                             NULL, 1);
            else if (compressed) {
                /* we don't want to end_page_writeback on
                 * a compressed extent.  this happens
                 * elsewhere
                 */
                nr++;
            }

            cur += iosize;
            pg_offset += iosize;
            continue;
        }
        /* leave this out until we have a page_mkwrite call */
        if (0 && !test_range_bit(tree, cur, cur + iosize - 1,
                   EXTENT_DIRTY, 0, NULL)) {
            cur = cur + iosize;
            pg_offset += iosize;
            continue;
        }

        if (tree->ops && tree->ops->writepage_io_hook) {
            ret = tree->ops->writepage_io_hook(page, cur,
                        cur + iosize - 1);
        } else {
            ret = 0;
        }
        if (ret) {
            SetPageError(page);
        } else {
            unsigned long max_nr = end_index + 1;

            set_range_writeback(tree, cur, cur + iosize - 1);
            if (!PageWriteback(page)) {
                printk(KERN_ERR "btrfs warning page %lu not "
                       "writeback, cur %llu end %llu\n",
                       page->index, (unsigned long long)cur,
                       (unsigned long long)end);
            }

            ret = submit_extent_page(write_flags, tree, page,
                         sector, iosize, pg_offset,
                         bdev, &epd->bio, max_nr,
                         end_bio_extent_writepage,
                         0, 0, 0);
            if (ret)
                SetPageError(page);
        }
        cur = cur + iosize;
        pg_offset += iosize;
        nr++;
    }
done:
    if (nr == 0) {
        /* make sure the mapping tag for page dirty gets cleared */
        set_page_writeback(page);
        end_page_writeback(page);
    }
    unlock_page(page);

done_unlocked:

    /* drop our reference on any cached states */
    free_extent_state(cached_state);
    return 0;
}

static int eb_wait(void *word)
{
    io_schedule();
    return 0;
}

static void wait_on_extent_buffer_writeback(struct extent_buffer *eb)
{
    wait_on_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK, eb_wait,
            TASK_UNINTERRUPTIBLE);
}

static int lock_extent_buffer_for_io(struct extent_buffer *eb,
                     struct btrfs_fs_info *fs_info,
                     struct extent_page_data *epd)
{
    unsigned long i, num_pages;
    int flush = 0;
    int ret = 0;

    if (!btrfs_try_tree_write_lock(eb)) {
        flush = 1;
        flush_write_bio(epd);
        btrfs_tree_lock(eb);
    }

    if (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags)) {
        btrfs_tree_unlock(eb);
        if (!epd->sync_io)
            return 0;
        if (!flush) {
            flush_write_bio(epd);
            flush = 1;
        }
        while (1) {
            wait_on_extent_buffer_writeback(eb);
            btrfs_tree_lock(eb);
            if (!test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags))
                break;
            btrfs_tree_unlock(eb);
        }
    }

    /*
     * We need to do this to prevent races in people who check if the eb is
     * under IO since we can end up having no IO bits set for a short period
     * of time.
     */
    spin_lock(&eb->refs_lock);
    if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
        set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
        spin_unlock(&eb->refs_lock);
        btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
        spin_lock(&fs_info->delalloc_lock);
        if (fs_info->dirty_metadata_bytes >= eb->len)
            fs_info->dirty_metadata_bytes -= eb->len;
        else
            WARN_ON(1);
        spin_unlock(&fs_info->delalloc_lock);
        ret = 1;
    } else {
        spin_unlock(&eb->refs_lock);
    }

    btrfs_tree_unlock(eb);

    if (!ret)
        return ret;

    num_pages = num_extent_pages(eb->start, eb->len);
    for (i = 0; i < num_pages; i++) {
        struct page *p = extent_buffer_page(eb, i);

        if (!trylock_page(p)) {
            if (!flush) {
                flush_write_bio(epd);
                flush = 1;
            }
            lock_page(p);
        }
    }

    return ret;
}

static void end_extent_buffer_writeback(struct extent_buffer *eb)
{
    clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
    smp_mb__after_clear_bit();
    wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK);
}

static void end_bio_extent_buffer_writepage(struct bio *bio, int err)
{
    int uptodate = err == 0;
    struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
    struct extent_buffer *eb;
    int done;

    do {
        struct page *page = bvec->bv_page;

        bvec--;
        eb = (struct extent_buffer *)page->private;
        BUG_ON(!eb);
        done = atomic_dec_and_test(&eb->io_pages);

        if (!uptodate || test_bit(EXTENT_BUFFER_IOERR, &eb->bflags)) {
            set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
            ClearPageUptodate(page);
            SetPageError(page);
        }

        end_page_writeback(page);

        if (!done)
            continue;

        end_extent_buffer_writeback(eb);
    } while (bvec >= bio->bi_io_vec);

    bio_put(bio);

}

static int write_one_eb(struct extent_buffer *eb,
            struct btrfs_fs_info *fs_info,
            struct writeback_control *wbc,
            struct extent_page_data *epd)
{
    struct block_device *bdev = fs_info->fs_devices->latest_bdev;
    u64 offset = eb->start;
    unsigned long i, num_pages;
    unsigned long bio_flags = 0;
    int rw = (epd->sync_io ? WRITE_SYNC : WRITE);
    int ret = 0;

    clear_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
    num_pages = num_extent_pages(eb->start, eb->len);
    atomic_set(&eb->io_pages, num_pages);
    if (btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID)
        bio_flags = EXTENT_BIO_TREE_LOG;

    for (i = 0; i < num_pages; i++) {
        struct page *p = extent_buffer_page(eb, i);

        clear_page_dirty_for_io(p);
        set_page_writeback(p);
        ret = submit_extent_page(rw, eb->tree, p, offset >> 9,
                     PAGE_CACHE_SIZE, 0, bdev, &epd->bio,
                     -1, end_bio_extent_buffer_writepage,
                     0, epd->bio_flags, bio_flags);
        epd->bio_flags = bio_flags;
        if (ret) {
            set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
            SetPageError(p);
            if (atomic_sub_and_test(num_pages - i, &eb->io_pages))
                end_extent_buffer_writeback(eb);
            ret = -EIO;
            break;
        }
        offset += PAGE_CACHE_SIZE;
        update_nr_written(p, wbc, 1);
        unlock_page(p);
    }

    if (unlikely(ret)) {
        for (; i < num_pages; i++) {
            struct page *p = extent_buffer_page(eb, i);
            unlock_page(p);
        }
    }

    return ret;
}

int btree_write_cache_pages(struct address_space *mapping,
                   struct writeback_control *wbc)
{
    struct extent_io_tree *tree = &BTRFS_I(mapping->host)->io_tree;
    struct btrfs_fs_info *fs_info = BTRFS_I(mapping->host)->root->fs_info;
    struct extent_buffer *eb, *prev_eb = NULL;
    struct extent_page_data epd = {
        .bio = NULL,
        .tree = tree,
        .extent_locked = 0,
        .sync_io = wbc->sync_mode == WB_SYNC_ALL,
        .bio_flags = 0,
    };
    int ret = 0;
    int done = 0;
    int nr_to_write_done = 0;
    struct pagevec pvec;
    int nr_pages;
    pgoff_t index;
    pgoff_t end;        /* Inclusive */
    int scanned = 0;
    int tag;

    pagevec_init(&pvec, 0);
    if (wbc->range_cyclic) {
        index = mapping->writeback_index; /* Start from prev offset */
        end = -1;
    } else {
        index = wbc->range_start >> PAGE_CACHE_SHIFT;
        end = wbc->range_end >> PAGE_CACHE_SHIFT;
        scanned = 1;
    }
    if (wbc->sync_mode == WB_SYNC_ALL)
        tag = PAGECACHE_TAG_TOWRITE;
    else
        tag = PAGECACHE_TAG_DIRTY;
retry:
    if (wbc->sync_mode == WB_SYNC_ALL)
        tag_pages_for_writeback(mapping, index, end);
    while (!done && !nr_to_write_done && (index <= end) &&
           (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
            min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
        unsigned i;

        scanned = 1;
        for (i = 0; i < nr_pages; i++) {
            struct page *page = pvec.pages[i];

            if (!PagePrivate(page))
                continue;

            if (!wbc->range_cyclic && page->index > end) {
                done = 1;
                break;
            }

            spin_lock(&mapping->private_lock);
            if (!PagePrivate(page)) {
                spin_unlock(&mapping->private_lock);
                continue;
            }

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

            /*
             * Shouldn't happen and normally this would be a BUG_ON
             * but no sense in crashing the users box for something
             * we can survive anyway.
             */
            if (!eb) {
                spin_unlock(&mapping->private_lock);
                WARN_ON(1);
                continue;
            }

            if (eb == prev_eb) {
                spin_unlock(&mapping->private_lock);
                continue;
            }

            ret = atomic_inc_not_zero(&eb->refs);
            spin_unlock(&mapping->private_lock);
            if (!ret)
                continue;

            prev_eb = eb;
            ret = lock_extent_buffer_for_io(eb, fs_info, &epd);
            if (!ret) {
                free_extent_buffer(eb);
                continue;
            }

            ret = write_one_eb(eb, fs_info, wbc, &epd);
            if (ret) {
                done = 1;
                free_extent_buffer(eb);
                break;
            }
            free_extent_buffer(eb);

            /*
             * the filesystem may choose to bump up nr_to_write.
             * We have to make sure to honor the new nr_to_write
             * at any time
             */
            nr_to_write_done = wbc->nr_to_write <= 0;
        }
        pagevec_release(&pvec);
        cond_resched();
    }
    if (!scanned && !done) {
        /*
         * We hit the last page and there is more work to be done: wrap
         * back to the start of the file
         */
        scanned = 1;
        index = 0;
        goto retry;
    }
    flush_write_bio(&epd);
    return ret;
}

static int extent_write_cache_pages(struct extent_io_tree *tree,
                 struct address_space *mapping,
                 struct writeback_control *wbc,
                 writepage_t writepage, void *data,
                 void (*flush_fn)(void *))
{
    struct inode *inode = mapping->host;
    int ret = 0;
    int done = 0;
    int nr_to_write_done = 0;
    struct pagevec pvec;
    int nr_pages;
    pgoff_t index;
    pgoff_t end;        /* Inclusive */
    int scanned = 0;
    int tag;

    /*
     * We have to hold onto the inode so that ordered extents can do their
     * work when the IO finishes.  The alternative to this is failing to add
     * an ordered extent if the igrab() fails there and that is a huge pain
     * to deal with, so instead just hold onto the inode throughout the
     * writepages operation.  If it fails here we are freeing up the inode
     * anyway and we'd rather not waste our time writing out stuff that is
     * going to be truncated anyway.
     */
    if (!igrab(inode))
        return 0;

    pagevec_init(&pvec, 0);
    if (wbc->range_cyclic) {
        index = mapping->writeback_index; /* Start from prev offset */
        end = -1;
    } else {
        index = wbc->range_start >> PAGE_CACHE_SHIFT;
        end = wbc->range_end >> PAGE_CACHE_SHIFT;
        scanned = 1;
    }
    if (wbc->sync_mode == WB_SYNC_ALL)
        tag = PAGECACHE_TAG_TOWRITE;
    else
        tag = PAGECACHE_TAG_DIRTY;
retry:
    if (wbc->sync_mode == WB_SYNC_ALL)
        tag_pages_for_writeback(mapping, index, end);
    while (!done && !nr_to_write_done && (index <= end) &&
           (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
            min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
        unsigned i;

        scanned = 1;
        for (i = 0; i < nr_pages; i++) {
            struct page *page = pvec.pages[i];

            /*
             * At this point we hold neither mapping->tree_lock nor
             * lock on the page itself: the page may be truncated or
             * invalidated (changing page->mapping to NULL), or even
             * swizzled back from swapper_space to tmpfs file
             * mapping
             */
            if (tree->ops &&
                tree->ops->write_cache_pages_lock_hook) {
                tree->ops->write_cache_pages_lock_hook(page,
                                   data, flush_fn);
            } else {
                if (!trylock_page(page)) {
                    flush_fn(data);
                    lock_page(page);
                }
            }

            if (unlikely(page->mapping != mapping)) {
                unlock_page(page);
                continue;
            }

            if (!wbc->range_cyclic && page->index > end) {
                done = 1;
                unlock_page(page);
                continue;
            }

            if (wbc->sync_mode != WB_SYNC_NONE) {
                if (PageWriteback(page))
                    flush_fn(data);
                wait_on_page_writeback(page);
            }

            if (PageWriteback(page) ||
                !clear_page_dirty_for_io(page)) {
                unlock_page(page);
                continue;
            }

            ret = (*writepage)(page, wbc, data);

            if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
                unlock_page(page);
                ret = 0;
            }
            if (ret)
                done = 1;

            /*
             * the filesystem may choose to bump up nr_to_write.
             * We have to make sure to honor the new nr_to_write
             * at any time
             */
            nr_to_write_done = wbc->nr_to_write <= 0;
        }
        pagevec_release(&pvec);
        cond_resched();
    }
    if (!scanned && !done) {
        /*
         * We hit the last page and there is more work to be done: wrap
         * back to the start of the file
         */
        scanned = 1;
        index = 0;
        goto retry;
    }
    btrfs_add_delayed_iput(inode);
    return ret;
}

static void flush_epd_write_bio(struct extent_page_data *epd)
{
    if (epd->bio) {
        int rw = WRITE;
        int ret;

        if (epd->sync_io)
            rw = WRITE_SYNC;

        ret = submit_one_bio(rw, epd->bio, 0, epd->bio_flags);
        BUG_ON(ret < 0); /* -ENOMEM */
        epd->bio = NULL;
    }
}

static noinline void flush_write_bio(void *data)
{
    struct extent_page_data *epd = data;
    flush_epd_write_bio(epd);
}

int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
              get_extent_t *get_extent,
              struct writeback_control *wbc)
{
    int ret;
    struct extent_page_data epd = {
        .bio = NULL,
        .tree = tree,
        .get_extent = get_extent,
        .extent_locked = 0,
        .sync_io = wbc->sync_mode == WB_SYNC_ALL,
        .bio_flags = 0,
    };

    ret = __extent_writepage(page, wbc, &epd);

    flush_epd_write_bio(&epd);
    return ret;
}

int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode,
                  u64 start, u64 end, get_extent_t *get_extent,
                  int mode)
{
    int ret = 0;
    struct address_space *mapping = inode->i_mapping;
    struct page *page;
    unsigned long nr_pages = (end - start + PAGE_CACHE_SIZE) >>
        PAGE_CACHE_SHIFT;

    struct extent_page_data epd = {
        .bio = NULL,
        .tree = tree,
        .get_extent = get_extent,
        .extent_locked = 1,
        .sync_io = mode == WB_SYNC_ALL,
        .bio_flags = 0,
    };
    struct writeback_control wbc_writepages = {
        .sync_mode  = mode,
        .nr_to_write    = nr_pages * 2,
        .range_start    = start,
        .range_end  = end + 1,
    };

    while (start <= end) {
        page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
        if (clear_page_dirty_for_io(page))
            ret = __extent_writepage(page, &wbc_writepages, &epd);
        else {
            if (tree->ops && tree->ops->writepage_end_io_hook)
                tree->ops->writepage_end_io_hook(page, start,
                         start + PAGE_CACHE_SIZE - 1,
                         NULL, 1);
            unlock_page(page);
        }
        page_cache_release(page);
        start += PAGE_CACHE_SIZE;
    }

    flush_epd_write_bio(&epd);
    return ret;
}

int extent_writepages(struct extent_io_tree *tree,
              struct address_space *mapping,
              get_extent_t *get_extent,
              struct writeback_control *wbc)
{
    int ret = 0;
    struct extent_page_data epd = {
        .bio = NULL,
        .tree = tree,
        .get_extent = get_extent,
        .extent_locked = 0,
        .sync_io = wbc->sync_mode == WB_SYNC_ALL,
        .bio_flags = 0,
    };

    ret = extent_write_cache_pages(tree, mapping, wbc,
                       __extent_writepage, &epd,
                       flush_write_bio);
    flush_epd_write_bio(&epd);
    return ret;
}

int extent_readpages(struct extent_io_tree *tree,
             struct address_space *mapping,
             struct list_head *pages, unsigned nr_pages,
             get_extent_t get_extent)
{
    struct bio *bio = NULL;
    unsigned page_idx;
    unsigned long bio_flags = 0;
    struct page *pagepool[16];
    struct page *page;
    int i = 0;
    int nr = 0;

    for (page_idx = 0; page_idx < nr_pages; page_idx++) {
        page = list_entry(pages->prev, struct page, lru);

        prefetchw(&page->flags);
        list_del(&page->lru);
        if (add_to_page_cache_lru(page, mapping,
                    page->index, GFP_NOFS)) {
            page_cache_release(page);
            continue;
        }

        pagepool[nr++] = page;
        if (nr < ARRAY_SIZE(pagepool))
            continue;
        for (i = 0; i < nr; i++) {
            __extent_read_full_page(tree, pagepool[i], get_extent,
                    &bio, 0, &bio_flags);
            page_cache_release(pagepool[i]);
        }
        nr = 0;
    }
    for (i = 0; i < nr; i++) {
        __extent_read_full_page(tree, pagepool[i], get_extent,
                    &bio, 0, &bio_flags);
        page_cache_release(pagepool[i]);
    }

    BUG_ON(!list_empty(pages));
    if (bio)
        return submit_one_bio(READ, bio, 0, bio_flags);
    return 0;
}

/*
 * basic invalidatepage code, this waits on any locked or writeback
 * ranges corresponding to the page, and then deletes any extent state
 * records from the tree
 */
int extent_invalidatepage(struct extent_io_tree *tree,
              struct page *page, unsigned long offset)
{
    struct extent_state *cached_state = NULL;
    u64 start = ((u64)page->index << PAGE_CACHE_SHIFT);
    u64 end = start + PAGE_CACHE_SIZE - 1;
    size_t blocksize = page->mapping->host->i_sb->s_blocksize;

    start += (offset + blocksize - 1) & ~(blocksize - 1);
    if (start > end)
        return 0;

    lock_extent_bits(tree, start, end, 0, &cached_state);
    wait_on_page_writeback(page);
    clear_extent_bit(tree, start, end,
             EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
             EXTENT_DO_ACCOUNTING,
             1, 1, &cached_state, GFP_NOFS);
    return 0;
}

/*
 * a helper for releasepage, this tests for areas of the page that
 * are locked or under IO and drops the related state bits if it is safe
 * to drop the page.
 */
int try_release_extent_state(struct extent_map_tree *map,
                 struct extent_io_tree *tree, struct page *page,
                 gfp_t mask)
{
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 end = start + PAGE_CACHE_SIZE - 1;
    int ret = 1;

    if (test_range_bit(tree, start, end,
               EXTENT_IOBITS, 0, NULL))
        ret = 0;
    else {
        if ((mask & GFP_NOFS) == GFP_NOFS)
            mask = GFP_NOFS;
        /*
         * at this point we can safely clear everything except the
         * locked bit and the nodatasum bit
         */
        ret = clear_extent_bit(tree, start, end,
                 ~(EXTENT_LOCKED | EXTENT_NODATASUM),
                 0, 0, NULL, mask);

        /* if clear_extent_bit failed for enomem reasons,
         * we can't allow the release to continue.
         */
        if (ret < 0)
            ret = 0;
        else
            ret = 1;
    }
    return ret;
}

/*
 * a helper for releasepage.  As long as there are no locked extents
 * in the range corresponding to the page, both state records and extent
 * map records are removed
 */
int try_release_extent_mapping(struct extent_map_tree *map,
                   struct extent_io_tree *tree, struct page *page,
                   gfp_t mask)
{
    struct extent_map *em;
    u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
    u64 end = start + PAGE_CACHE_SIZE - 1;

    if ((mask & __GFP_WAIT) &&
        page->mapping->host->i_size > 16 * 1024 * 1024) {
        u64 len;
        while (start <= end) {
            len = end - start + 1;
            write_lock(&map->lock);
            em = lookup_extent_mapping(map, start, len);
            if (!em) {
                write_unlock(&map->lock);
                break;
            }
            if (test_bit(EXTENT_FLAG_PINNED, &em->flags) ||
                em->start != start) {
                write_unlock(&map->lock);
                free_extent_map(em);
                break;
            }
            if (!test_range_bit(tree, em->start,
                        extent_map_end(em) - 1,
                        EXTENT_LOCKED | EXTENT_WRITEBACK,
                        0, NULL)) {
                remove_extent_mapping(map, em);
                /* once for the rb tree */
                free_extent_map(em);
            }
            start = extent_map_end(em);
            write_unlock(&map->lock);

            /* once for us */
            free_extent_map(em);
        }
    }
    return try_release_extent_state(map, tree, page, mask);
}

/*
 * helper function for fiemap, which doesn't want to see any holes.
 * This maps until we find something past 'last'
 */
static struct extent_map *get_extent_skip_holes(struct inode *inode,
                        u64 offset,
                        u64 last,
                        get_extent_t *get_extent)
{
    u64 sectorsize = BTRFS_I(inode)->root->sectorsize;
    struct extent_map *em;
    u64 len;

    if (offset >= last)
        return NULL;

    while(1) {
        len = last - offset;
        if (len == 0)
            break;
        len = (len + sectorsize - 1) & ~(sectorsize - 1);
        em = get_extent(inode, NULL, 0, offset, len, 0);
        if (IS_ERR_OR_NULL(em))
            return em;

        /* if this isn't a hole return it */
        if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags) &&
            em->block_start != EXTENT_MAP_HOLE) {
            return em;
        }

        /* this is a hole, advance to the next extent */
        offset = extent_map_end(em);
        free_extent_map(em);
        if (offset >= last)
            break;
    }
    return NULL;
}

int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
        __u64 start, __u64 len, get_extent_t *get_extent)
{
    int ret = 0;
    u64 off = start;
    u64 max = start + len;
    u32 flags = 0;
    u32 found_type;
    u64 last;
    u64 last_for_get_extent = 0;
    u64 disko = 0;
    u64 isize = i_size_read(inode);
    struct btrfs_key found_key;
    struct extent_map *em = NULL;
    struct extent_state *cached_state = NULL;
    struct btrfs_path *path;
    struct btrfs_file_extent_item *item;
    int end = 0;
    u64 em_start = 0;
    u64 em_len = 0;
    u64 em_end = 0;
    unsigned long emflags;

    if (len == 0)
        return -EINVAL;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;
    path->leave_spinning = 1;

    start = ALIGN(start, BTRFS_I(inode)->root->sectorsize);
    len = ALIGN(len, BTRFS_I(inode)->root->sectorsize);

    /*
     * lookup the last file extent.  We're not using i_size here
     * because there might be preallocation past i_size
     */
    ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root,
                       path, btrfs_ino(inode), -1, 0);
    if (ret < 0) {
        btrfs_free_path(path);
        return ret;
    }
    WARN_ON(!ret);
    path->slots[0]--;
    item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                  struct btrfs_file_extent_item);
    btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
    found_type = btrfs_key_type(&found_key);

    /* No extents, but there might be delalloc bits */
    if (found_key.objectid != btrfs_ino(inode) ||
        found_type != BTRFS_EXTENT_DATA_KEY) {
        /* have to trust i_size as the end */
        last = (u64)-1;
        last_for_get_extent = isize;
    } else {
        /*
         * remember the start of the last extent.  There are a
         * bunch of different factors that go into the length of the
         * extent, so its much less complex to remember where it started
         */
        last = found_key.offset;
        last_for_get_extent = last + 1;
    }
    btrfs_free_path(path);

    /*
     * we might have some extents allocated but more delalloc past those
     * extents.  so, we trust isize unless the start of the last extent is
     * beyond isize
     */
    if (last < isize) {
        last = (u64)-1;
        last_for_get_extent = isize;
    }

    lock_extent_bits(&BTRFS_I(inode)->io_tree, start, start + len, 0,
             &cached_state);

    em = get_extent_skip_holes(inode, start, last_for_get_extent,
                   get_extent);
    if (!em)
        goto out;
    if (IS_ERR(em)) {
        ret = PTR_ERR(em);
        goto out;
    }

    while (!end) {
        u64 offset_in_extent;

        /* break if the extent we found is outside the range */
        if (em->start >= max || extent_map_end(em) < off)
            break;

        /*
         * get_extent may return an extent that starts before our
         * requested range.  We have to make sure the ranges
         * we return to fiemap always move forward and don't
         * overlap, so adjust the offsets here
         */
        em_start = max(em->start, off);

        /*
         * record the offset from the start of the extent
         * for adjusting the disk offset below
         */
        offset_in_extent = em_start - em->start;
        em_end = extent_map_end(em);
        em_len = em_end - em_start;
        emflags = em->flags;
        disko = 0;
        flags = 0;

        /*
         * bump off for our next call to get_extent
         */
        off = extent_map_end(em);
        if (off >= max)
            end = 1;

        if (em->block_start == EXTENT_MAP_LAST_BYTE) {
            end = 1;
            flags |= FIEMAP_EXTENT_LAST;
        } else if (em->block_start == EXTENT_MAP_INLINE) {
            flags |= (FIEMAP_EXTENT_DATA_INLINE |
                  FIEMAP_EXTENT_NOT_ALIGNED);
        } else if (em->block_start == EXTENT_MAP_DELALLOC) {
            flags |= (FIEMAP_EXTENT_DELALLOC |
                  FIEMAP_EXTENT_UNKNOWN);
        } else {
            disko = em->block_start + offset_in_extent;
        }
        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
            flags |= FIEMAP_EXTENT_ENCODED;

        free_extent_map(em);
        em = NULL;
        if ((em_start >= last) || em_len == (u64)-1 ||
           (last == (u64)-1 && isize <= em_end)) {
            flags |= FIEMAP_EXTENT_LAST;
            end = 1;
        }

        /* now scan forward to see if this is really the last extent. */
        em = get_extent_skip_holes(inode, off, last_for_get_extent,
                       get_extent);
        if (IS_ERR(em)) {
            ret = PTR_ERR(em);
            goto out;
        }
        if (!em) {
            flags |= FIEMAP_EXTENT_LAST;
            end = 1;
        }
        ret = fiemap_fill_next_extent(fieinfo, em_start, disko,
                          em_len, flags);
        if (ret)
            goto out_free;
    }
out_free:
    free_extent_map(em);
out:
    unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len,
                 &cached_state, GFP_NOFS);
    return ret;
}

static void __free_extent_buffer(struct extent_buffer *eb)
{
#if LEAK_DEBUG
    unsigned long flags;
    spin_lock_irqsave(&leak_lock, flags);
    list_del(&eb->leak_list);
    spin_unlock_irqrestore(&leak_lock, flags);
#endif
    if (eb->pages && eb->pages != eb->inline_pages)
        kfree(eb->pages);
    kmem_cache_free(extent_buffer_cache, eb);
}

static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
                           u64 start,
                           unsigned long len,
                           gfp_t mask)
{
    struct extent_buffer *eb = NULL;
#if LEAK_DEBUG
    unsigned long flags;
#endif

    eb = kmem_cache_zalloc(extent_buffer_cache, mask);
    if (eb == NULL)
        return NULL;
    eb->start = start;
    eb->len = len;
    eb->tree = tree;
    eb->bflags = 0;
    rwlock_init(&eb->lock);
    atomic_set(&eb->write_locks, 0);
    atomic_set(&eb->read_locks, 0);
    atomic_set(&eb->blocking_readers, 0);
    atomic_set(&eb->blocking_writers, 0);
    atomic_set(&eb->spinning_readers, 0);
    atomic_set(&eb->spinning_writers, 0);
    eb->lock_nested = 0;
    init_waitqueue_head(&eb->write_lock_wq);
    init_waitqueue_head(&eb->read_lock_wq);

#if LEAK_DEBUG
    spin_lock_irqsave(&leak_lock, flags);
    list_add(&eb->leak_list, &buffers);
    spin_unlock_irqrestore(&leak_lock, flags);
#endif
    spin_lock_init(&eb->refs_lock);
    atomic_set(&eb->refs, 1);
    atomic_set(&eb->io_pages, 0);

    if (len > MAX_INLINE_EXTENT_BUFFER_SIZE) {
        struct page **pages;
        int num_pages = (len + PAGE_CACHE_SIZE - 1) >>
            PAGE_CACHE_SHIFT;
        pages = kzalloc(num_pages, mask);
        if (!pages) {
            __free_extent_buffer(eb);
            return NULL;
        }
        eb->pages = pages;
    } else {
        eb->pages = eb->inline_pages;
    }

    return eb;
}

struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
{
    unsigned long i;
    struct page *p;
    struct extent_buffer *new;
    unsigned long num_pages = num_extent_pages(src->start, src->len);

    new = __alloc_extent_buffer(NULL, src->start, src->len, GFP_ATOMIC);
    if (new == NULL)
        return NULL;

    for (i = 0; i < num_pages; i++) {
        p = alloc_page(GFP_ATOMIC);
        BUG_ON(!p);
        attach_extent_buffer_page(new, p);
        WARN_ON(PageDirty(p));
        SetPageUptodate(p);
        new->pages[i] = p;
    }

    copy_extent_buffer(new, src, 0, 0, src->len);
    set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags);
    set_bit(EXTENT_BUFFER_DUMMY, &new->bflags);

    return new;
}

struct extent_buffer *alloc_dummy_extent_buffer(u64 start, unsigned long len)
{
    struct extent_buffer *eb;
    unsigned long num_pages = num_extent_pages(0, len);
    unsigned long i;

    eb = __alloc_extent_buffer(NULL, start, len, GFP_ATOMIC);
    if (!eb)
        return NULL;

    for (i = 0; i < num_pages; i++) {
        eb->pages[i] = alloc_page(GFP_ATOMIC);
        if (!eb->pages[i])
            goto err;
    }
    set_extent_buffer_uptodate(eb);
    btrfs_set_header_nritems(eb, 0);
    set_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);

    return eb;
err:
    for (; i > 0; i--)
        __free_page(eb->pages[i - 1]);
    __free_extent_buffer(eb);
    return NULL;
}

static int extent_buffer_under_io(struct extent_buffer *eb)
{
    return (atomic_read(&eb->io_pages) ||
        test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
        test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
}

/*
 * Helper for releasing extent buffer page.
 */
static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
                        unsigned long start_idx)
{
    unsigned long index;
    unsigned long num_pages;
    struct page *page;
    int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);

    BUG_ON(extent_buffer_under_io(eb));

    num_pages = num_extent_pages(eb->start, eb->len);
    index = start_idx + num_pages;
    if (start_idx >= index)
        return;

    do {
        index--;
        page = extent_buffer_page(eb, index);
        if (page && mapped) {
            spin_lock(&page->mapping->private_lock);
            /*
             * We do this since we'll remove the pages after we've
             * removed the eb from the radix tree, so we could race
             * and have this page now attached to the new eb.  So
             * only clear page_private if it's still connected to
             * this eb.
             */
            if (PagePrivate(page) &&
                page->private == (unsigned long)eb) {
                BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
                BUG_ON(PageDirty(page));
                BUG_ON(PageWriteback(page));
                /*
                 * We need to make sure we haven't be attached
                 * to a new eb.
                 */
                ClearPagePrivate(page);
                set_page_private(page, 0);
                /* One for the page private */
                page_cache_release(page);
            }
            spin_unlock(&page->mapping->private_lock);

        }
        if (page) {
            /* One for when we alloced the page */
            page_cache_release(page);
        }
    } while (index != start_idx);
}

/*
 * Helper for releasing the extent buffer.
 */
static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
{
    btrfs_release_extent_buffer_page(eb, 0);
    __free_extent_buffer(eb);
}

static void check_buffer_tree_ref(struct extent_buffer *eb)
{
    /* the ref bit is tricky.  We have to make sure it is set
     * if we have the buffer dirty.   Otherwise the
     * code to free a buffer can end up dropping a dirty
     * page
     *
     * Once the ref bit is set, it won't go away while the
     * buffer is dirty or in writeback, and it also won't
     * go away while we have the reference count on the
     * eb bumped.
     *
     * We can't just set the ref bit without bumping the
     * ref on the eb because free_extent_buffer might
     * see the ref bit and try to clear it.  If this happens
     * free_extent_buffer might end up dropping our original
     * ref by mistake and freeing the page before we are able
     * to add one more ref.
     *
     * So bump the ref count first, then set the bit.  If someone
     * beat us to it, drop the ref we added.
     */
    spin_lock(&eb->refs_lock);
    if (!test_and_set_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
        atomic_inc(&eb->refs);
    spin_unlock(&eb->refs_lock);
}

static void mark_extent_buffer_accessed(struct extent_buffer *eb)
{
    unsigned long num_pages, i;

    check_buffer_tree_ref(eb);

    num_pages = num_extent_pages(eb->start, eb->len);
    for (i = 0; i < num_pages; i++) {
        struct page *p = extent_buffer_page(eb, i);
        mark_page_accessed(p);
    }
}

struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
                      u64 start, unsigned long len)
{
    unsigned long num_pages = num_extent_pages(start, len);
    unsigned long i;
    unsigned long index = start >> PAGE_CACHE_SHIFT;
    struct extent_buffer *eb;
    struct extent_buffer *exists = NULL;
    struct page *p;
    struct address_space *mapping = tree->mapping;
    int uptodate = 1;
    int ret;

    rcu_read_lock();
    eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
    if (eb && atomic_inc_not_zero(&eb->refs)) {
        rcu_read_unlock();
        mark_extent_buffer_accessed(eb);
        return eb;
    }
    rcu_read_unlock();

    eb = __alloc_extent_buffer(tree, start, len, GFP_NOFS);
    if (!eb)
        return NULL;

    for (i = 0; i < num_pages; i++, index++) {
        p = find_or_create_page(mapping, index, GFP_NOFS);
        if (!p)
            goto free_eb;

        spin_lock(&mapping->private_lock);
        if (PagePrivate(p)) {
            /*
             * We could have already allocated an eb for this page
             * and attached one so lets see if we can get a ref on
             * the existing eb, and if we can we know it's good and
             * we can just return that one, else we know we can just
             * overwrite page->private.
             */
            exists = (struct extent_buffer *)p->private;
            if (atomic_inc_not_zero(&exists->refs)) {
                spin_unlock(&mapping->private_lock);
                unlock_page(p);
                page_cache_release(p);
                mark_extent_buffer_accessed(exists);
                goto free_eb;
            }

            /*
             * Do this so attach doesn't complain and we need to
             * drop the ref the old guy had.
             */
            ClearPagePrivate(p);
            WARN_ON(PageDirty(p));
            page_cache_release(p);
        }
        attach_extent_buffer_page(eb, p);
        spin_unlock(&mapping->private_lock);
        WARN_ON(PageDirty(p));
        mark_page_accessed(p);
        eb->pages[i] = p;
        if (!PageUptodate(p))
            uptodate = 0;

        /*
         * see below about how we avoid a nasty race with release page
         * and why we unlock later
         */
    }
    if (uptodate)
        set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
again:
    ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
    if (ret)
        goto free_eb;

    spin_lock(&tree->buffer_lock);
    ret = radix_tree_insert(&tree->buffer, start >> PAGE_CACHE_SHIFT, eb);
    if (ret == -EEXIST) {
        exists = radix_tree_lookup(&tree->buffer,
                        start >> PAGE_CACHE_SHIFT);
        if (!atomic_inc_not_zero(&exists->refs)) {
            spin_unlock(&tree->buffer_lock);
            radix_tree_preload_end();
            exists = NULL;
            goto again;
        }
        spin_unlock(&tree->buffer_lock);
        radix_tree_preload_end();
        mark_extent_buffer_accessed(exists);
        goto free_eb;
    }
    /* add one reference for the tree */
    check_buffer_tree_ref(eb);
    spin_unlock(&tree->buffer_lock);
    radix_tree_preload_end();

    /*
     * there is a race where release page may have
     * tried to find this extent buffer in the radix
     * but failed.  It will tell the VM it is safe to
     * reclaim the, and it will clear the page private bit.
     * We must make sure to set the page private bit properly
     * after the extent buffer is in the radix tree so
     * it doesn't get lost
     */
    SetPageChecked(eb->pages[0]);
    for (i = 1; i < num_pages; i++) {
        p = extent_buffer_page(eb, i);
        ClearPageChecked(p);
        unlock_page(p);
    }
    unlock_page(eb->pages[0]);
    return eb;

free_eb:
    for (i = 0; i < num_pages; i++) {
        if (eb->pages[i])
            unlock_page(eb->pages[i]);
    }

    WARN_ON(!atomic_dec_and_test(&eb->refs));
    btrfs_release_extent_buffer(eb);
    return exists;
}

struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
                     u64 start, unsigned long len)
{
    struct extent_buffer *eb;

    rcu_read_lock();
    eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
    if (eb && atomic_inc_not_zero(&eb->refs)) {
        rcu_read_unlock();
        mark_extent_buffer_accessed(eb);
        return eb;
    }
    rcu_read_unlock();

    return NULL;
}

static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
{
    struct extent_buffer *eb =
            container_of(head, struct extent_buffer, rcu_head);

    __free_extent_buffer(eb);
}

/* Expects to have eb->eb_lock already held */
static int release_extent_buffer(struct extent_buffer *eb, gfp_t mask)
{
    WARN_ON(atomic_read(&eb->refs) == 0);
    if (atomic_dec_and_test(&eb->refs)) {
        if (test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags)) {
            spin_unlock(&eb->refs_lock);
        } else {
            struct extent_io_tree *tree = eb->tree;

            spin_unlock(&eb->refs_lock);

            spin_lock(&tree->buffer_lock);
            radix_tree_delete(&tree->buffer,
                      eb->start >> PAGE_CACHE_SHIFT);
            spin_unlock(&tree->buffer_lock);
        }

        /* Should be safe to release our pages at this point */
        btrfs_release_extent_buffer_page(eb, 0);
        call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
        return 1;
    }
    spin_unlock(&eb->refs_lock);

    return 0;
}

void free_extent_buffer(struct extent_buffer *eb)
{
    if (!eb)
        return;

    spin_lock(&eb->refs_lock);
    if (atomic_read(&eb->refs) == 2 &&
        test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags))
        atomic_dec(&eb->refs);

    if (atomic_read(&eb->refs) == 2 &&
        test_bit(EXTENT_BUFFER_STALE, &eb->bflags) &&
        !extent_buffer_under_io(eb) &&
        test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
        atomic_dec(&eb->refs);

    /*
     * I know this is terrible, but it's temporary until we stop tracking
     * the uptodate bits and such for the extent buffers.
     */
    release_extent_buffer(eb, GFP_ATOMIC);
}

void free_extent_buffer_stale(struct extent_buffer *eb)
{
    if (!eb)
        return;

    spin_lock(&eb->refs_lock);
    set_bit(EXTENT_BUFFER_STALE, &eb->bflags);

    if (atomic_read(&eb->refs) == 2 && !extent_buffer_under_io(eb) &&
        test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
        atomic_dec(&eb->refs);
    release_extent_buffer(eb, GFP_NOFS);
}

void clear_extent_buffer_dirty(struct extent_buffer *eb)
{
    unsigned long i;
    unsigned long num_pages;
    struct page *page;

    num_pages = num_extent_pages(eb->start, eb->len);

    for (i = 0; i < num_pages; i++) {
        page = extent_buffer_page(eb, i);
        if (!PageDirty(page))
            continue;

        lock_page(page);
        WARN_ON(!PagePrivate(page));

        clear_page_dirty_for_io(page);
        spin_lock_irq(&page->mapping->tree_lock);
        if (!PageDirty(page)) {
            radix_tree_tag_clear(&page->mapping->page_tree,
                        page_index(page),
                        PAGECACHE_TAG_DIRTY);
        }
        spin_unlock_irq(&page->mapping->tree_lock);
        ClearPageError(page);
        unlock_page(page);
    }
    WARN_ON(atomic_read(&eb->refs) == 0);
}

int set_extent_buffer_dirty(struct extent_buffer *eb)
{
    unsigned long i;
    unsigned long num_pages;
    int was_dirty = 0;

    check_buffer_tree_ref(eb);

    was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);

    num_pages = num_extent_pages(eb->start, eb->len);
    WARN_ON(atomic_read(&eb->refs) == 0);
    WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));

    for (i = 0; i < num_pages; i++)
        set_page_dirty(extent_buffer_page(eb, i));
    return was_dirty;
}

static int range_straddles_pages(u64 start, u64 len)
{
    if (len < PAGE_CACHE_SIZE)
        return 1;
    if (start & (PAGE_CACHE_SIZE - 1))
        return 1;
    if ((start + len) & (PAGE_CACHE_SIZE - 1))
        return 1;
    return 0;
}

int clear_extent_buffer_uptodate(struct extent_buffer *eb)
{
    unsigned long i;
    struct page *page;
    unsigned long num_pages;

    clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
    num_pages = num_extent_pages(eb->start, eb->len);
    for (i = 0; i < num_pages; i++) {
        page = extent_buffer_page(eb, i);
        if (page)
            ClearPageUptodate(page);
    }
    return 0;
}

int set_extent_buffer_uptodate(struct extent_buffer *eb)
{
    unsigned long i;
    struct page *page;
    unsigned long num_pages;

    set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
    num_pages = num_extent_pages(eb->start, eb->len);
    for (i = 0; i < num_pages; i++) {
        page = extent_buffer_page(eb, i);
        SetPageUptodate(page);
    }
    return 0;
}

int extent_range_uptodate(struct extent_io_tree *tree,
              u64 start, u64 end)
{
    struct page *page;
    int ret;
    int pg_uptodate = 1;
    int uptodate;
    unsigned long index;

    if (range_straddles_pages(start, end - start + 1)) {
        ret = test_range_bit(tree, start, end,
                     EXTENT_UPTODATE, 1, NULL);
        if (ret)
            return 1;
    }
    while (start <= end) {
        index = start >> PAGE_CACHE_SHIFT;
        page = find_get_page(tree->mapping, index);
        if (!page)
            return 1;
        uptodate = PageUptodate(page);
        page_cache_release(page);
        if (!uptodate) {
            pg_uptodate = 0;
            break;
        }
        start += PAGE_CACHE_SIZE;
    }
    return pg_uptodate;
}

int extent_buffer_uptodate(struct extent_buffer *eb)
{
    return test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
}

int read_extent_buffer_pages(struct extent_io_tree *tree,
                 struct extent_buffer *eb, u64 start, int wait,
                 get_extent_t *get_extent, int mirror_num)
{
    unsigned long i;
    unsigned long start_i;
    struct page *page;
    int err;
    int ret = 0;
    int locked_pages = 0;
    int all_uptodate = 1;
    unsigned long num_pages;
    unsigned long num_reads = 0;
    struct bio *bio = NULL;
    unsigned long bio_flags = 0;

    if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
        return 0;

    if (start) {
        WARN_ON(start < eb->start);
        start_i = (start >> PAGE_CACHE_SHIFT) -
            (eb->start >> PAGE_CACHE_SHIFT);
    } else {
        start_i = 0;
    }

    num_pages = num_extent_pages(eb->start, eb->len);
    for (i = start_i; i < num_pages; i++) {
        page = extent_buffer_page(eb, i);
        if (wait == WAIT_NONE) {
            if (!trylock_page(page))
                goto unlock_exit;
        } else {
            lock_page(page);
        }
        locked_pages++;
        if (!PageUptodate(page)) {
            num_reads++;
            all_uptodate = 0;
        }
    }
    if (all_uptodate) {
        if (start_i == 0)
            set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
        goto unlock_exit;
    }

    clear_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
    eb->read_mirror = 0;
    atomic_set(&eb->io_pages, num_reads);
    for (i = start_i; i < num_pages; i++) {
        page = extent_buffer_page(eb, i);
        if (!PageUptodate(page)) {
            ClearPageError(page);
            err = __extent_read_full_page(tree, page,
                              get_extent, &bio,
                              mirror_num, &bio_flags);
            if (err)
                ret = err;
        } else {
            unlock_page(page);
        }
    }

    if (bio) {
        err = submit_one_bio(READ, bio, mirror_num, bio_flags);
        if (err)
            return err;
    }

    if (ret || wait != WAIT_COMPLETE)
        return ret;

    for (i = start_i; i < num_pages; i++) {
        page = extent_buffer_page(eb, i);
        wait_on_page_locked(page);
        if (!PageUptodate(page))
            ret = -EIO;
    }

    return ret;

unlock_exit:
    i = start_i;
    while (locked_pages > 0) {
        page = extent_buffer_page(eb, i);
        i++;
        unlock_page(page);
        locked_pages--;
    }
    return ret;
}

void read_extent_buffer(struct extent_buffer *eb, void *dstv,
            unsigned long start,
            unsigned long len)
{
    size_t cur;
    size_t offset;
    struct page *page;
    char *kaddr;
    char *dst = (char *)dstv;
    size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;

    WARN_ON(start > eb->len);
    WARN_ON(start + len > eb->start + eb->len);

    offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);

    while (len > 0) {
        page = extent_buffer_page(eb, i);

        cur = min(len, (PAGE_CACHE_SIZE - offset));
        kaddr = page_address(page);
        memcpy(dst, kaddr + offset, cur);

        dst += cur;
        len -= cur;
        offset = 0;
        i++;
    }
}

int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
                   unsigned long min_len, char **map,
                   unsigned long *map_start,
                   unsigned long *map_len)
{
    size_t offset = start & (PAGE_CACHE_SIZE - 1);
    char *kaddr;
    struct page *p;
    size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
    unsigned long end_i = (start_offset + start + min_len - 1) >>
        PAGE_CACHE_SHIFT;

    if (i != end_i)
        return -EINVAL;

    if (i == 0) {
        offset = start_offset;
        *map_start = 0;
    } else {
        offset = 0;
        *map_start = ((u64)i << PAGE_CACHE_SHIFT) - start_offset;
    }

    if (start + min_len > eb->len) {
        printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
               "wanted %lu %lu\n", (unsigned long long)eb->start,
               eb->len, start, min_len);
        WARN_ON(1);
        return -EINVAL;
    }

    p = extent_buffer_page(eb, i);
    kaddr = page_address(p);
    *map = kaddr + offset;
    *map_len = PAGE_CACHE_SIZE - offset;
    return 0;
}

int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
              unsigned long start,
              unsigned long len)
{
    size_t cur;
    size_t offset;
    struct page *page;
    char *kaddr;
    char *ptr = (char *)ptrv;
    size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
    int ret = 0;

    WARN_ON(start > eb->len);
    WARN_ON(start + len > eb->start + eb->len);

    offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);

    while (len > 0) {
        page = extent_buffer_page(eb, i);

        cur = min(len, (PAGE_CACHE_SIZE - offset));

        kaddr = page_address(page);
        ret = memcmp(ptr, kaddr + offset, cur);
        if (ret)
            break;

        ptr += cur;
        len -= cur;
        offset = 0;
        i++;
    }
    return ret;
}

void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
             unsigned long start, unsigned long len)
{
    size_t cur;
    size_t offset;
    struct page *page;
    char *kaddr;
    char *src = (char *)srcv;
    size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;

    WARN_ON(start > eb->len);
    WARN_ON(start + len > eb->start + eb->len);

    offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);

    while (len > 0) {
        page = extent_buffer_page(eb, i);
        WARN_ON(!PageUptodate(page));

        cur = min(len, PAGE_CACHE_SIZE - offset);
        kaddr = page_address(page);
        memcpy(kaddr + offset, src, cur);

        src += cur;
        len -= cur;
        offset = 0;
        i++;
    }
}

void memset_extent_buffer(struct extent_buffer *eb, char c,
              unsigned long start, unsigned long len)
{
    size_t cur;
    size_t offset;
    struct page *page;
    char *kaddr;
    size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;

    WARN_ON(start > eb->len);
    WARN_ON(start + len > eb->start + eb->len);

    offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);

    while (len > 0) {
        page = extent_buffer_page(eb, i);
        WARN_ON(!PageUptodate(page));

        cur = min(len, PAGE_CACHE_SIZE - offset);
        kaddr = page_address(page);
        memset(kaddr + offset, c, cur);

        len -= cur;
        offset = 0;
        i++;
    }
}

void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
            unsigned long dst_offset, unsigned long src_offset,
            unsigned long len)
{
    u64 dst_len = dst->len;
    size_t cur;
    size_t offset;
    struct page *page;
    char *kaddr;
    size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long i = (start_offset + dst_offset) >> PAGE_CACHE_SHIFT;

    WARN_ON(src->len != dst_len);

    offset = (start_offset + dst_offset) &
        ((unsigned long)PAGE_CACHE_SIZE - 1);

    while (len > 0) {
        page = extent_buffer_page(dst, i);
        WARN_ON(!PageUptodate(page));

        cur = min(len, (unsigned long)(PAGE_CACHE_SIZE - offset));

        kaddr = page_address(page);
        read_extent_buffer(src, kaddr + offset, src_offset, cur);

        src_offset += cur;
        len -= cur;
        offset = 0;
        i++;
    }
}

static void move_pages(struct page *dst_page, struct page *src_page,
               unsigned long dst_off, unsigned long src_off,
               unsigned long len)
{
    char *dst_kaddr = page_address(dst_page);
    if (dst_page == src_page) {
        memmove(dst_kaddr + dst_off, dst_kaddr + src_off, len);
    } else {
        char *src_kaddr = page_address(src_page);
        char *p = dst_kaddr + dst_off + len;
        char *s = src_kaddr + src_off + len;

        while (len--)
            *--p = *--s;
    }
}

static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)
{
    unsigned long distance = (src > dst) ? src - dst : dst - src;
    return distance < len;
}

static void copy_pages(struct page *dst_page, struct page *src_page,
               unsigned long dst_off, unsigned long src_off,
               unsigned long len)
{
    char *dst_kaddr = page_address(dst_page);
    char *src_kaddr;
    int must_memmove = 0;

    if (dst_page != src_page) {
        src_kaddr = page_address(src_page);
    } else {
        src_kaddr = dst_kaddr;
        if (areas_overlap(src_off, dst_off, len))
            must_memmove = 1;
    }

    if (must_memmove)
        memmove(dst_kaddr + dst_off, src_kaddr + src_off, len);
    else
        memcpy(dst_kaddr + dst_off, src_kaddr + src_off, len);
}

void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
               unsigned long src_offset, unsigned long len)
{
    size_t cur;
    size_t dst_off_in_page;
    size_t src_off_in_page;
    size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long dst_i;
    unsigned long src_i;

    if (src_offset + len > dst->len) {
        printk(KERN_ERR "btrfs memmove bogus src_offset %lu move "
               "len %lu dst len %lu\n", src_offset, len, dst->len);
        BUG_ON(1);
    }
    if (dst_offset + len > dst->len) {
        printk(KERN_ERR "btrfs memmove bogus dst_offset %lu move "
               "len %lu dst len %lu\n", dst_offset, len, dst->len);
        BUG_ON(1);
    }

    while (len > 0) {
        dst_off_in_page = (start_offset + dst_offset) &
            ((unsigned long)PAGE_CACHE_SIZE - 1);
        src_off_in_page = (start_offset + src_offset) &
            ((unsigned long)PAGE_CACHE_SIZE - 1);

        dst_i = (start_offset + dst_offset) >> PAGE_CACHE_SHIFT;
        src_i = (start_offset + src_offset) >> PAGE_CACHE_SHIFT;

        cur = min(len, (unsigned long)(PAGE_CACHE_SIZE -
                           src_off_in_page));
        cur = min_t(unsigned long, cur,
            (unsigned long)(PAGE_CACHE_SIZE - dst_off_in_page));

        copy_pages(extent_buffer_page(dst, dst_i),
               extent_buffer_page(dst, src_i),
               dst_off_in_page, src_off_in_page, cur);

        src_offset += cur;
        dst_offset += cur;
        len -= cur;
    }
}

void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
               unsigned long src_offset, unsigned long len)
{
    size_t cur;
    size_t dst_off_in_page;
    size_t src_off_in_page;
    unsigned long dst_end = dst_offset + len - 1;
    unsigned long src_end = src_offset + len - 1;
    size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
    unsigned long dst_i;
    unsigned long src_i;

    if (src_offset + len > dst->len) {
        printk(KERN_ERR "btrfs memmove bogus src_offset %lu move "
               "len %lu len %lu\n", src_offset, len, dst->len);
        BUG_ON(1);
    }
    if (dst_offset + len > dst->len) {
        printk(KERN_ERR "btrfs memmove bogus dst_offset %lu move "
               "len %lu len %lu\n", dst_offset, len, dst->len);
        BUG_ON(1);
    }
    if (dst_offset < src_offset) {
        memcpy_extent_buffer(dst, dst_offset, src_offset, len);
        return;
    }
    while (len > 0) {
        dst_i = (start_offset + dst_end) >> PAGE_CACHE_SHIFT;
        src_i = (start_offset + src_end) >> PAGE_CACHE_SHIFT;

        dst_off_in_page = (start_offset + dst_end) &
            ((unsigned long)PAGE_CACHE_SIZE - 1);
        src_off_in_page = (start_offset + src_end) &
            ((unsigned long)PAGE_CACHE_SIZE - 1);

        cur = min_t(unsigned long, len, src_off_in_page + 1);
        cur = min(cur, dst_off_in_page + 1);
        move_pages(extent_buffer_page(dst, dst_i),
               extent_buffer_page(dst, src_i),
               dst_off_in_page - cur + 1,
               src_off_in_page - cur + 1, cur);

        dst_end -= cur;
        src_end -= cur;
        len -= cur;
    }
}

int try_release_extent_buffer(struct page *page, gfp_t mask)
{
    struct extent_buffer *eb;

    /*
     * We need to make sure noboody is attaching this page to an eb right
     * now.
     */
    spin_lock(&page->mapping->private_lock);
    if (!PagePrivate(page)) {
        spin_unlock(&page->mapping->private_lock);
        return 1;
    }

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

    /*
     * This is a little awful but should be ok, we need to make sure that
     * the eb doesn't disappear out from under us while we're looking at
     * this page.
     */
    spin_lock(&eb->refs_lock);
    if (atomic_read(&eb->refs) != 1 || extent_buffer_under_io(eb)) {
        spin_unlock(&eb->refs_lock);
        spin_unlock(&page->mapping->private_lock);
        return 0;
    }
    spin_unlock(&page->mapping->private_lock);

    if ((mask & GFP_NOFS) == GFP_NOFS)
        mask = GFP_NOFS;

    /*
     * If tree ref isn't set then we know the ref on this eb is a real ref,
     * so just return, this page will likely be freed soon anyway.
     */
    if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
        spin_unlock(&eb->refs_lock);
        return 0;
    }

    return release_extent_buffer(eb, mask);
}