btrfs-progs: extent_io: Init eb->lru to avoid NULL pointer dereference

[btrfs-progs-unstable/devel.git] / extent_io.c

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

void extent_io_tree_init(struct extent_io_tree *tree)
{
        cache_tree_init(&tree->state);
        cache_tree_init(&tree->cache);
        INIT_LIST_HEAD(&tree->lru);
        tree->cache_size = 0;
        tree->max_cache_size = (u64)total_memory() / 4;
}

void extent_io_tree_init_cache_max(struct extent_io_tree *tree,
                                   u64 max_cache_size)
{
        extent_io_tree_init(tree);
        tree->max_cache_size = max_cache_size;
}

static struct extent_state *alloc_extent_state(void)
{
        struct extent_state *state;

        state = malloc(sizeof(*state));
        if (!state)
                return NULL;
        state->cache_node.objectid = 0;
        state->refs = 1;
        state->state = 0;
        state->xprivate = 0;
        return state;
}

static void btrfs_free_extent_state(struct extent_state *state)
{
        state->refs--;
        BUG_ON(state->refs < 0);
        if (state->refs == 0)
                free(state);
}

static void free_extent_state_func(struct cache_extent *cache)
{
        struct extent_state *es;

        es = container_of(cache, struct extent_state, cache_node);
        btrfs_free_extent_state(es);
}

static void free_extent_buffer_final(struct extent_buffer *eb);
void extent_io_tree_cleanup(struct extent_io_tree *tree)
{
        struct extent_buffer *eb;

        while(!list_empty(&tree->lru)) {
                eb = list_entry(tree->lru.next, struct extent_buffer, lru);
                if (eb->refs) {
                        fprintf(stderr,
                                "extent buffer leak: start %llu len %u\n",
                                (unsigned long long)eb->start, eb->len);
                        free_extent_buffer_nocache(eb);
                } else {
                        free_extent_buffer_final(eb);
                }
        }

        cache_tree_free_extents(&tree->state, free_extent_state_func);
}

static inline void update_extent_state(struct extent_state *state)
{
        state->cache_node.start = state->start;
        state->cache_node.size = state->end + 1 - state->start;
}

/*
 * 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
 */
static int merge_state(struct extent_io_tree *tree,
                       struct extent_state *state)
{
        struct extent_state *other;
        struct cache_extent *other_node;

        if (state->state & EXTENT_IOBITS)
                return 0;

        other_node = prev_cache_extent(&state->cache_node);
        if (other_node) {
                other = container_of(other_node, struct extent_state,
                                     cache_node);
                if (other->end == state->start - 1 &&
                    other->state == state->state) {
                        state->start = other->start;
                        update_extent_state(state);
                        remove_cache_extent(&tree->state, &other->cache_node);
                        btrfs_free_extent_state(other);
                }
        }
        other_node = next_cache_extent(&state->cache_node);
        if (other_node) {
                other = container_of(other_node, struct extent_state,
                                     cache_node);
                if (other->start == state->end + 1 &&
                    other->state == state->state) {
                        other->start = state->start;
                        update_extent_state(other);
                        remove_cache_extent(&tree->state, &state->cache_node);
                        btrfs_free_extent_state(state);
                }
        }
        return 0;
}

/*
 * insert an extent_state struct into the tree.  'bits' are set on the
 * struct before it is inserted.
 */
static int insert_state(struct extent_io_tree *tree,
                        struct extent_state *state, u64 start, u64 end,
                        int bits)
{
        int ret;

        BUG_ON(end < start);
        state->state |= bits;
        state->start = start;
        state->end = end;
        update_extent_state(state);
        ret = insert_cache_extent(&tree->state, &state->cache_node);
        BUG_ON(ret);
        merge_state(tree, state);
        return 0;
}

/*
 * 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.
 */
static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
                       struct extent_state *prealloc, u64 split)
{
        int ret;
        prealloc->start = orig->start;
        prealloc->end = split - 1;
        prealloc->state = orig->state;
        update_extent_state(prealloc);
        orig->start = split;
        update_extent_state(orig);
        ret = insert_cache_extent(&tree->state, &prealloc->cache_node);
        BUG_ON(ret);
        return 0;
}

/*
 * clear some bits on a range in the tree.
 */
static int clear_state_bit(struct extent_io_tree *tree,
                            struct extent_state *state, int bits)
{
        int ret = state->state & bits;

        state->state &= ~bits;
        if (state->state == 0) {
                remove_cache_extent(&tree->state, &state->cache_node);
                btrfs_free_extent_state(state);
        } else {
                merge_state(tree, state);
        }
        return ret;
}

/*
 * clear some bits on a range in the tree.
 */
int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end, int bits)
{
        struct extent_state *state;
        struct extent_state *prealloc = NULL;
        struct cache_extent *node;
        u64 last_end;
        int err;
        int set = 0;

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

        /*
         * this search will find the extents that end after
         * our range starts
         */
        node = search_cache_extent(&tree->state, start);
        if (!node)
                goto out;
        state = container_of(node, struct extent_state, cache_node);
        if (state->start > end)
                goto out;
        last_end = state->end;

        /*
         *     | ---- 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) {
                err = split_state(tree, state, prealloc, start);
                BUG_ON(err == -EEXIST);
                prealloc = NULL;
                if (err)
                        goto out;
                if (state->end <= end) {
                        set |= clear_state_bit(tree, state, bits);
                        if (last_end == (u64)-1)
                                goto out;
                        start = last_end + 1;
                } else {
                        start = state->start;
                }
                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) {
                err = split_state(tree, state, prealloc, end + 1);
                BUG_ON(err == -EEXIST);

                set |= clear_state_bit(tree, prealloc, bits);
                prealloc = NULL;
                goto out;
        }

        start = state->end + 1;
        set |= clear_state_bit(tree, state, bits);
        if (last_end == (u64)-1)
                goto out;
        start = last_end + 1;
        goto search_again;
out:
        if (prealloc)
                btrfs_free_extent_state(prealloc);
        return set;

search_again:
        if (start > end)
                goto out;
        goto again;
}

/*
 * set some bits on a range in the tree.
 */
int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end, int bits)
{
        struct extent_state *state;
        struct extent_state *prealloc = NULL;
        struct cache_extent *node;
        int err = 0;
        u64 last_start;
        u64 last_end;
again:
        if (!prealloc) {
                prealloc = alloc_extent_state();
                if (!prealloc)
                        return -ENOMEM;
        }

        /*
         * this search will find the extents that end after
         * our range starts
         */
        node = search_cache_extent(&tree->state, start);
        if (!node) {
                err = insert_state(tree, prealloc, start, end, bits);
                BUG_ON(err == -EEXIST);
                prealloc = NULL;
                goto out;
        }

        state = container_of(node, struct extent_state, cache_node);
        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) {
                state->state |= bits;
                merge_state(tree, state);
                if (last_end == (u64)-1)
                        goto out;
                start = last_end + 1;
                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) {
                err = split_state(tree, state, prealloc, start);
                BUG_ON(err == -EEXIST);
                prealloc = NULL;
                if (err)
                        goto out;
                if (state->end <= end) {
                        state->state |= bits;
                        start = state->end + 1;
                        merge_state(tree, state);
                        if (last_end == (u64)-1)
                                goto out;
                        start = last_end + 1;
                } else {
                        start = state->start;
                }
                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;
                err = insert_state(tree, prealloc, start, this_end,
                                bits);
                BUG_ON(err == -EEXIST);
                prealloc = NULL;
                if (err)
                        goto out;
                start = this_end + 1;
                goto search_again;
        }
        /*
         * | ---- desired range ---- |
         * | ---------- state ---------- |
         * We need to split the extent, and set the bit
         * on the first half
         */
        err = split_state(tree, state, prealloc, end + 1);
        BUG_ON(err == -EEXIST);

        state->state |= bits;
        merge_state(tree, prealloc);
        prealloc = NULL;
out:
        if (prealloc)
                btrfs_free_extent_state(prealloc);
        return err;
search_again:
        if (start > end)
                goto out;
        goto again;
}

int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end)
{
        return set_extent_bits(tree, start, end, EXTENT_DIRTY);
}

int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end)
{
        return clear_extent_bits(tree, start, end, EXTENT_DIRTY);
}

int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
                          u64 *start_ret, u64 *end_ret, int bits)
{
        struct cache_extent *node;
        struct extent_state *state;
        int ret = 1;

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

        while(1) {
                state = container_of(node, struct extent_state, cache_node);
                if (state->end >= start && (state->state & bits)) {
                        *start_ret = state->start;
                        *end_ret = state->end;
                        ret = 0;
                        break;
                }
                node = next_cache_extent(node);
                if (!node)
                        break;
        }
out:
        return ret;
}

int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
                   int bits, int filled)
{
        struct extent_state *state = NULL;
        struct cache_extent *node;
        int bitset = 0;

        node = search_cache_extent(&tree->state, start);
        while (node && start <= end) {
                state = container_of(node, struct extent_state, cache_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;
                }
                start = state->end + 1;
                if (start > end)
                        break;
                node = next_cache_extent(node);
                if (!node) {
                        if (filled)
                                bitset = 0;
                        break;
                }
        }
        return bitset;
}

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

        node = search_cache_extent(&tree->state, start);
        if (!node) {
                ret = -ENOENT;
                goto out;
        }
        state = container_of(node, struct extent_state, cache_node);
        if (state->start != start) {
                ret = -ENOENT;
                goto out;
        }
        state->xprivate = private;
out:
        return ret;
}

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

        node = search_cache_extent(&tree->state, start);
        if (!node) {
                ret = -ENOENT;
                goto out;
        }
        state = container_of(node, struct extent_state, cache_node);
        if (state->start != start) {
                ret = -ENOENT;
                goto out;
        }
        *private = state->xprivate;
out:
        return ret;
}

static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
                                                   u64 bytenr, u32 blocksize)
{
        struct extent_buffer *eb;

        eb = calloc(1, sizeof(struct extent_buffer) + blocksize);
        if (!eb)
                return NULL;

        eb->start = bytenr;
        eb->len = blocksize;
        eb->refs = 1;
        eb->flags = 0;
        eb->tree = tree;
        eb->fd = -1;
        eb->dev_bytenr = (u64)-1;
        eb->cache_node.start = bytenr;
        eb->cache_node.size = blocksize;
        INIT_LIST_HEAD(&eb->recow);
        INIT_LIST_HEAD(&eb->lru);

        return eb;
}

struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
{
        struct extent_buffer *new;

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

        copy_extent_buffer(new, src, 0, 0, src->len);
        new->flags |= EXTENT_BUFFER_DUMMY;

        return new;
}

static void free_extent_buffer_final(struct extent_buffer *eb)
{
        struct extent_io_tree *tree = eb->tree;

        BUG_ON(eb->refs);
        BUG_ON(tree && tree->cache_size < eb->len);
        list_del_init(&eb->lru);
        if (!(eb->flags & EXTENT_BUFFER_DUMMY)) {
                remove_cache_extent(&tree->cache, &eb->cache_node);
                tree->cache_size -= eb->len;
        }
        free(eb);
}

static void free_extent_buffer_internal(struct extent_buffer *eb, bool free_now)
{
        if (!eb || IS_ERR(eb))
                return;

        eb->refs--;
        BUG_ON(eb->refs < 0);
        if (eb->refs == 0) {
                BUG_ON(eb->flags & EXTENT_DIRTY);
                list_del_init(&eb->recow);
                if (eb->flags & EXTENT_BUFFER_DUMMY || free_now)
                        free_extent_buffer_final(eb);
        }
}

void free_extent_buffer(struct extent_buffer *eb)
{
        free_extent_buffer_internal(eb, 0);
}

void free_extent_buffer_nocache(struct extent_buffer *eb)
{
        free_extent_buffer_internal(eb, 1);
}

struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
                                         u64 bytenr, u32 blocksize)
{
        struct extent_buffer *eb = NULL;
        struct cache_extent *cache;

        cache = lookup_cache_extent(&tree->cache, bytenr, blocksize);
        if (cache && cache->start == bytenr &&
            cache->size == blocksize) {
                eb = container_of(cache, struct extent_buffer, cache_node);
                list_move_tail(&eb->lru, &tree->lru);
                eb->refs++;
        }
        return eb;
}

struct extent_buffer *find_first_extent_buffer(struct extent_io_tree *tree,
                                               u64 start)
{
        struct extent_buffer *eb = NULL;
        struct cache_extent *cache;

        cache = search_cache_extent(&tree->cache, start);
        if (cache) {
                eb = container_of(cache, struct extent_buffer, cache_node);
                list_move_tail(&eb->lru, &tree->lru);
                eb->refs++;
        }
        return eb;
}

static void trim_extent_buffer_cache(struct extent_io_tree *tree)
{
        struct extent_buffer *eb, *tmp;

        list_for_each_entry_safe(eb, tmp, &tree->lru, lru) {
                if (eb->refs == 0)
                        free_extent_buffer_final(eb);
                if (tree->cache_size <= ((tree->max_cache_size * 9) / 10))
                        break;
        }
}

struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
                                          u64 bytenr, u32 blocksize)
{
        struct extent_buffer *eb;
        struct cache_extent *cache;

        cache = lookup_cache_extent(&tree->cache, bytenr, blocksize);
        if (cache && cache->start == bytenr &&
            cache->size == blocksize) {
                eb = container_of(cache, struct extent_buffer, cache_node);
                list_move_tail(&eb->lru, &tree->lru);
                eb->refs++;
        } else {
                int ret;

                if (cache) {
                        eb = container_of(cache, struct extent_buffer,
                                          cache_node);
                        free_extent_buffer(eb);
                }
                eb = __alloc_extent_buffer(tree, bytenr, blocksize);
                if (!eb)
                        return NULL;
                ret = insert_cache_extent(&tree->cache, &eb->cache_node);
                if (ret) {
                        free(eb);
                        return NULL;
                }
                list_add_tail(&eb->lru, &tree->lru);
                tree->cache_size += blocksize;
                if (tree->cache_size >= tree->max_cache_size)
                        trim_extent_buffer_cache(tree);
        }
        return eb;
}

int read_extent_from_disk(struct extent_buffer *eb,
                          unsigned long offset, unsigned long len)
{
        int ret;
        ret = pread(eb->fd, eb->data + offset, len, eb->dev_bytenr);
        if (ret < 0) {
                ret = -errno;
                goto out;
        }
        if (ret != len) {
                ret = -EIO;
                goto out;
        }
        ret = 0;
out:
        return ret;
}

int write_extent_to_disk(struct extent_buffer *eb)
{
        int ret;
        ret = pwrite(eb->fd, eb->data, eb->len, eb->dev_bytenr);
        if (ret < 0)
                goto out;
        if (ret != eb->len) {
                ret = -EIO;
                goto out;
        }
        ret = 0;
out:
        return ret;
}

int read_data_from_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
                        u64 bytes, int mirror)
{
        struct btrfs_multi_bio *multi = NULL;
        struct btrfs_device *device;
        u64 bytes_left = bytes;
        u64 read_len;
        u64 total_read = 0;
        int ret;

        while (bytes_left) {
                read_len = bytes_left;
                ret = btrfs_map_block(info, READ, offset, &read_len, &multi,
                                      mirror, NULL);
                if (ret) {
                        fprintf(stderr, "Couldn't map the block %Lu\n",
                                offset);
                        return -EIO;
                }
                device = multi->stripes[0].dev;

                read_len = min(bytes_left, read_len);
                if (device->fd <= 0) {
                        kfree(multi);
                        return -EIO;
                }

                ret = pread(device->fd, buf + total_read, read_len,
                            multi->stripes[0].physical);
                kfree(multi);
                if (ret < 0) {
                        fprintf(stderr, "Error reading %Lu, %d\n", offset,
                                ret);
                        return ret;
                }
                if (ret != read_len) {
                        fprintf(stderr, "Short read for %Lu, read %d, "
                                "read_len %Lu\n", offset, ret, read_len);
                        return -EIO;
                }

                bytes_left -= read_len;
                offset += read_len;
                total_read += read_len;
        }

        return 0;
}

int write_data_to_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
                      u64 bytes, int mirror)
{
        struct btrfs_multi_bio *multi = NULL;
        struct btrfs_device *device;
        u64 bytes_left = bytes;
        u64 this_len;
        u64 total_write = 0;
        u64 *raid_map = NULL;
        u64 dev_bytenr;
        int dev_nr;
        int ret = 0;

        while (bytes_left > 0) {
                this_len = bytes_left;
                dev_nr = 0;

                ret = btrfs_map_block(info, WRITE, offset, &this_len, &multi,
                                      mirror, &raid_map);
                if (ret) {
                        fprintf(stderr, "Couldn't map the block %Lu\n",
                                offset);
                        return -EIO;
                }

                if (raid_map) {
                        struct extent_buffer *eb;
                        u64 stripe_len = this_len;

                        this_len = min(this_len, bytes_left);
                        this_len = min(this_len, (u64)info->nodesize);

                        eb = malloc(sizeof(struct extent_buffer) + this_len);
                        if (!eb) {
                                fprintf(stderr, "cannot allocate memory for eb\n");
                                ret = -ENOMEM;
                                goto out;
                        }

                        memset(eb, 0, sizeof(struct extent_buffer) + this_len);
                        eb->start = offset;
                        eb->len = this_len;

                        memcpy(eb->data, buf + total_write, this_len);
                        ret = write_raid56_with_parity(info, eb, multi,
                                                       stripe_len, raid_map);
                        BUG_ON(ret);

                        free(eb);
                        kfree(raid_map);
                        raid_map = NULL;
                } else while (dev_nr < multi->num_stripes) {
                        device = multi->stripes[dev_nr].dev;
                        if (device->fd <= 0) {
                                kfree(multi);
                                return -EIO;
                        }

                        dev_bytenr = multi->stripes[dev_nr].physical;
                        this_len = min(this_len, bytes_left);
                        dev_nr++;

                        ret = pwrite(device->fd, buf + total_write, this_len, dev_bytenr);
                        if (ret != this_len) {
                                if (ret < 0) {
                                        fprintf(stderr, "Error writing to "
                                                "device %d\n", errno);
                                        ret = errno;
                                        kfree(multi);
                                        return ret;
                                } else {
                                        fprintf(stderr, "Short write\n");
                                        kfree(multi);
                                        return -EIO;
                                }
                        }
                }

                BUG_ON(bytes_left < this_len);

                bytes_left -= this_len;
                offset += this_len;
                total_write += this_len;

                kfree(multi);
                multi = NULL;
        }
        return 0;

out:
        kfree(raid_map);
        return ret;
}

int set_extent_buffer_dirty(struct extent_buffer *eb)
{
        struct extent_io_tree *tree = eb->tree;
        if (!(eb->flags & EXTENT_DIRTY)) {
                eb->flags |= EXTENT_DIRTY;
                set_extent_dirty(tree, eb->start, eb->start + eb->len - 1);
                extent_buffer_get(eb);
        }
        return 0;
}

int clear_extent_buffer_dirty(struct extent_buffer *eb)
{
        struct extent_io_tree *tree = eb->tree;
        if (eb->flags & EXTENT_DIRTY) {
                eb->flags &= ~EXTENT_DIRTY;
                clear_extent_dirty(tree, eb->start, eb->start + eb->len - 1);
                free_extent_buffer(eb);
        }
        return 0;
}

int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
                         unsigned long start, unsigned long len)
{
        return memcmp(eb->data + start, ptrv, len);
}

void read_extent_buffer(struct extent_buffer *eb, void *dst,
                        unsigned long start, unsigned long len)
{
        memcpy(dst, eb->data + start, len);
}

void write_extent_buffer(struct extent_buffer *eb, const void *src,
                         unsigned long start, unsigned long len)
{
        memcpy(eb->data + start, src, len);
}

void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
                        unsigned long dst_offset, unsigned long src_offset,
                        unsigned long len)
{
        memcpy(dst->data + dst_offset, src->data + src_offset, len);
}

void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
                           unsigned long src_offset, unsigned long len)
{
        memmove(dst->data + dst_offset, dst->data + src_offset, len);
}

void memset_extent_buffer(struct extent_buffer *eb, char c,
                          unsigned long start, unsigned long len)
{
        memset(eb->data + start, c, len);
}

int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,
                           unsigned long nr)
{
        return le_test_bit(nr, (u8 *)eb->data + start);
}