tree-log.c

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/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/list_sort.h>
#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "locking.h"
#include "print-tree.h"
#include "backref.h"
#include "compat.h"
#include "tree-log.h"
#include "hash.h"

/* magic values for the inode_only field in btrfs_log_inode:
 *
 * LOG_INODE_ALL means to log everything
 * LOG_INODE_EXISTS means to log just enough to recreate the inode
 * during log replay
 */
#define LOG_INODE_ALL 0
#define LOG_INODE_EXISTS 1

/*
 * directory trouble cases
 *
 * 1) on rename or unlink, if the inode being unlinked isn't in the fsync
 * log, we must force a full commit before doing an fsync of the directory
 * where the unlink was done.
 * ---> record transid of last unlink/rename per directory
 *
 * mkdir foo/some_dir
 * normal commit
 * rename foo/some_dir foo2/some_dir
 * mkdir foo/some_dir
 * fsync foo/some_dir/some_file
 *
 * The fsync above will unlink the original some_dir without recording
 * it in its new location (foo2).  After a crash, some_dir will be gone
 * unless the fsync of some_file forces a full commit
 *
 * 2) we must log any new names for any file or dir that is in the fsync
 * log. ---> check inode while renaming/linking.
 *
 * 2a) we must log any new names for any file or dir during rename
 * when the directory they are being removed from was logged.
 * ---> check inode and old parent dir during rename
 *
 *  2a is actually the more important variant.  With the extra logging
 *  a crash might unlink the old name without recreating the new one
 *
 * 3) after a crash, we must go through any directories with a link count
 * of zero and redo the rm -rf
 *
 * mkdir f1/foo
 * normal commit
 * rm -rf f1/foo
 * fsync(f1)
 *
 * The directory f1 was fully removed from the FS, but fsync was never
 * called on f1, only its parent dir.  After a crash the rm -rf must
 * be replayed.  This must be able to recurse down the entire
 * directory tree.  The inode link count fixup code takes care of the
 * ugly details.
 */

/*
 * stages for the tree walking.  The first
 * stage (0) is to only pin down the blocks we find
 * the second stage (1) is to make sure that all the inodes
 * we find in the log are created in the subvolume.
 *
 * The last stage is to deal with directories and links and extents
 * and all the other fun semantics
 */
#define LOG_WALK_PIN_ONLY 0
#define LOG_WALK_REPLAY_INODES 1
#define LOG_WALK_REPLAY_ALL 2

static int btrfs_log_inode(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root, struct inode *inode,
                 int inode_only);
static int link_to_fixup_dir(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root,
                 struct btrfs_path *path, u64 objectid);
static noinline int replay_dir_deletes(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct btrfs_root *log,
                       struct btrfs_path *path,
                       u64 dirid, int del_all);

/*
 * tree logging is a special write ahead log used to make sure that
 * fsyncs and O_SYNCs can happen without doing full tree commits.
 *
 * Full tree commits are expensive because they require commonly
 * modified blocks to be recowed, creating many dirty pages in the
 * extent tree an 4x-6x higher write load than ext3.
 *
 * Instead of doing a tree commit on every fsync, we use the
 * key ranges and transaction ids to find items for a given file or directory
 * that have changed in this transaction.  Those items are copied into
 * a special tree (one per subvolume root), that tree is written to disk
 * and then the fsync is considered complete.
 *
 * After a crash, items are copied out of the log-tree back into the
 * subvolume tree.  Any file data extents found are recorded in the extent
 * allocation tree, and the log-tree freed.
 *
 * The log tree is read three times, once to pin down all the extents it is
 * using in ram and once, once to create all the inodes logged in the tree
 * and once to do all the other items.
 */

/*
 * start a sub transaction and setup the log tree
 * this increments the log tree writer count to make the people
 * syncing the tree wait for us to finish
 */
static int start_log_trans(struct btrfs_trans_handle *trans,
               struct btrfs_root *root)
{
    int ret;
    int err = 0;

    mutex_lock(&root->log_mutex);
    if (root->log_root) {
        if (!root->log_start_pid) {
            root->log_start_pid = current->pid;
            root->log_multiple_pids = false;
        } else if (root->log_start_pid != current->pid) {
            root->log_multiple_pids = true;
        }

        atomic_inc(&root->log_batch);
        atomic_inc(&root->log_writers);
        mutex_unlock(&root->log_mutex);
        return 0;
    }
    root->log_multiple_pids = false;
    root->log_start_pid = current->pid;
    mutex_lock(&root->fs_info->tree_log_mutex);
    if (!root->fs_info->log_root_tree) {
        ret = btrfs_init_log_root_tree(trans, root->fs_info);
        if (ret)
            err = ret;
    }
    if (err == 0 && !root->log_root) {
        ret = btrfs_add_log_tree(trans, root);
        if (ret)
            err = ret;
    }
    mutex_unlock(&root->fs_info->tree_log_mutex);
    atomic_inc(&root->log_batch);
    atomic_inc(&root->log_writers);
    mutex_unlock(&root->log_mutex);
    return err;
}

/*
 * returns 0 if there was a log transaction running and we were able
 * to join, or returns -ENOENT if there were not transactions
 * in progress
 */
static int join_running_log_trans(struct btrfs_root *root)
{
    int ret = -ENOENT;

    smp_mb();
    if (!root->log_root)
        return -ENOENT;

    mutex_lock(&root->log_mutex);
    if (root->log_root) {
        ret = 0;
        atomic_inc(&root->log_writers);
    }
    mutex_unlock(&root->log_mutex);
    return ret;
}

/*
 * This either makes the current running log transaction wait
 * until you call btrfs_end_log_trans() or it makes any future
 * log transactions wait until you call btrfs_end_log_trans()
 */
int btrfs_pin_log_trans(struct btrfs_root *root)
{
    int ret = -ENOENT;

    mutex_lock(&root->log_mutex);
    atomic_inc(&root->log_writers);
    mutex_unlock(&root->log_mutex);
    return ret;
}

/*
 * indicate we're done making changes to the log tree
 * and wake up anyone waiting to do a sync
 */
void btrfs_end_log_trans(struct btrfs_root *root)
{
    if (atomic_dec_and_test(&root->log_writers)) {
        smp_mb();
        if (waitqueue_active(&root->log_writer_wait))
            wake_up(&root->log_writer_wait);
    }
}


/*
 * the walk control struct is used to pass state down the chain when
 * processing the log tree.  The stage field tells us which part
 * of the log tree processing we are currently doing.  The others
 * are state fields used for that specific part
 */
struct walk_control {
    /* should we free the extent on disk when done?  This is used
     * at transaction commit time while freeing a log tree
     */
    int free;

    /* should we write out the extent buffer?  This is used
     * while flushing the log tree to disk during a sync
     */
    int write;

    /* should we wait for the extent buffer io to finish?  Also used
     * while flushing the log tree to disk for a sync
     */
    int wait;

    /* pin only walk, we record which extents on disk belong to the
     * log trees
     */
    int pin;

    /* what stage of the replay code we're currently in */
    int stage;

    /* the root we are currently replaying */
    struct btrfs_root *replay_dest;

    /* the trans handle for the current replay */
    struct btrfs_trans_handle *trans;

    /* the function that gets used to process blocks we find in the
     * tree.  Note the extent_buffer might not be up to date when it is
     * passed in, and it must be checked or read if you need the data
     * inside it
     */
    int (*process_func)(struct btrfs_root *log, struct extent_buffer *eb,
                struct walk_control *wc, u64 gen);
};

/*
 * process_func used to pin down extents, write them or wait on them
 */
static int process_one_buffer(struct btrfs_root *log,
                  struct extent_buffer *eb,
                  struct walk_control *wc, u64 gen)
{
    if (wc->pin)
        btrfs_pin_extent_for_log_replay(wc->trans,
                        log->fs_info->extent_root,
                        eb->start, eb->len);

    if (btrfs_buffer_uptodate(eb, gen, 0)) {
        if (wc->write)
            btrfs_write_tree_block(eb);
        if (wc->wait)
            btrfs_wait_tree_block_writeback(eb);
    }
    return 0;
}

/*
 * Item overwrite used by replay and tree logging.  eb, slot and key all refer
 * to the src data we are copying out.
 *
 * root is the tree we are copying into, and path is a scratch
 * path for use in this function (it should be released on entry and
 * will be released on exit).
 *
 * If the key is already in the destination tree the existing item is
 * overwritten.  If the existing item isn't big enough, it is extended.
 * If it is too large, it is truncated.
 *
 * If the key isn't in the destination yet, a new item is inserted.
 */
static noinline int overwrite_item(struct btrfs_trans_handle *trans,
                   struct btrfs_root *root,
                   struct btrfs_path *path,
                   struct extent_buffer *eb, int slot,
                   struct btrfs_key *key)
{
    int ret;
    u32 item_size;
    u64 saved_i_size = 0;
    int save_old_i_size = 0;
    unsigned long src_ptr;
    unsigned long dst_ptr;
    int overwrite_root = 0;

    if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
        overwrite_root = 1;

    item_size = btrfs_item_size_nr(eb, slot);
    src_ptr = btrfs_item_ptr_offset(eb, slot);

    /* look for the key in the destination tree */
    ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
    if (ret == 0) {
        char *src_copy;
        char *dst_copy;
        u32 dst_size = btrfs_item_size_nr(path->nodes[0],
                          path->slots[0]);
        if (dst_size != item_size)
            goto insert;

        if (item_size == 0) {
            btrfs_release_path(path);
            return 0;
        }
        dst_copy = kmalloc(item_size, GFP_NOFS);
        src_copy = kmalloc(item_size, GFP_NOFS);
        if (!dst_copy || !src_copy) {
            btrfs_release_path(path);
            kfree(dst_copy);
            kfree(src_copy);
            return -ENOMEM;
        }

        read_extent_buffer(eb, src_copy, src_ptr, item_size);

        dst_ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
        read_extent_buffer(path->nodes[0], dst_copy, dst_ptr,
                   item_size);
        ret = memcmp(dst_copy, src_copy, item_size);

        kfree(dst_copy);
        kfree(src_copy);
        /*
         * they have the same contents, just return, this saves
         * us from cowing blocks in the destination tree and doing
         * extra writes that may not have been done by a previous
         * sync
         */
        if (ret == 0) {
            btrfs_release_path(path);
            return 0;
        }

    }
insert:
    btrfs_release_path(path);
    /* try to insert the key into the destination tree */
    ret = btrfs_insert_empty_item(trans, root, path,
                      key, item_size);

    /* make sure any existing item is the correct size */
    if (ret == -EEXIST) {
        u32 found_size;
        found_size = btrfs_item_size_nr(path->nodes[0],
                        path->slots[0]);
        if (found_size > item_size)
            btrfs_truncate_item(trans, root, path, item_size, 1);
        else if (found_size < item_size)
            btrfs_extend_item(trans, root, path,
                      item_size - found_size);
    } else if (ret) {
        return ret;
    }
    dst_ptr = btrfs_item_ptr_offset(path->nodes[0],
                    path->slots[0]);

    /* don't overwrite an existing inode if the generation number
     * was logged as zero.  This is done when the tree logging code
     * is just logging an inode to make sure it exists after recovery.
     *
     * Also, don't overwrite i_size on directories during replay.
     * log replay inserts and removes directory items based on the
     * state of the tree found in the subvolume, and i_size is modified
     * as it goes
     */
    if (key->type == BTRFS_INODE_ITEM_KEY && ret == -EEXIST) {
        struct btrfs_inode_item *src_item;
        struct btrfs_inode_item *dst_item;

        src_item = (struct btrfs_inode_item *)src_ptr;
        dst_item = (struct btrfs_inode_item *)dst_ptr;

        if (btrfs_inode_generation(eb, src_item) == 0)
            goto no_copy;

        if (overwrite_root &&
            S_ISDIR(btrfs_inode_mode(eb, src_item)) &&
            S_ISDIR(btrfs_inode_mode(path->nodes[0], dst_item))) {
            save_old_i_size = 1;
            saved_i_size = btrfs_inode_size(path->nodes[0],
                            dst_item);
        }
    }

    copy_extent_buffer(path->nodes[0], eb, dst_ptr,
               src_ptr, item_size);

    if (save_old_i_size) {
        struct btrfs_inode_item *dst_item;
        dst_item = (struct btrfs_inode_item *)dst_ptr;
        btrfs_set_inode_size(path->nodes[0], dst_item, saved_i_size);
    }

    /* make sure the generation is filled in */
    if (key->type == BTRFS_INODE_ITEM_KEY) {
        struct btrfs_inode_item *dst_item;
        dst_item = (struct btrfs_inode_item *)dst_ptr;
        if (btrfs_inode_generation(path->nodes[0], dst_item) == 0) {
            btrfs_set_inode_generation(path->nodes[0], dst_item,
                           trans->transid);
        }
    }
no_copy:
    btrfs_mark_buffer_dirty(path->nodes[0]);
    btrfs_release_path(path);
    return 0;
}

/*
 * simple helper to read an inode off the disk from a given root
 * This can only be called for subvolume roots and not for the log
 */
static noinline struct inode *read_one_inode(struct btrfs_root *root,
                         u64 objectid)
{
    struct btrfs_key key;
    struct inode *inode;

    key.objectid = objectid;
    key.type = BTRFS_INODE_ITEM_KEY;
    key.offset = 0;
    inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
    if (IS_ERR(inode)) {
        inode = NULL;
    } else if (is_bad_inode(inode)) {
        iput(inode);
        inode = NULL;
    }
    return inode;
}

/* replays a single extent in 'eb' at 'slot' with 'key' into the
 * subvolume 'root'.  path is released on entry and should be released
 * on exit.
 *
 * extents in the log tree have not been allocated out of the extent
 * tree yet.  So, this completes the allocation, taking a reference
 * as required if the extent already exists or creating a new extent
 * if it isn't in the extent allocation tree yet.
 *
 * The extent is inserted into the file, dropping any existing extents
 * from the file that overlap the new one.
 */
static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      struct btrfs_path *path,
                      struct extent_buffer *eb, int slot,
                      struct btrfs_key *key)
{
    int found_type;
    u64 mask = root->sectorsize - 1;
    u64 extent_end;
    u64 start = key->offset;
    u64 saved_nbytes;
    struct btrfs_file_extent_item *item;
    struct inode *inode = NULL;
    unsigned long size;
    int ret = 0;

    item = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
    found_type = btrfs_file_extent_type(eb, item);

    if (found_type == BTRFS_FILE_EXTENT_REG ||
        found_type == BTRFS_FILE_EXTENT_PREALLOC)
        extent_end = start + btrfs_file_extent_num_bytes(eb, item);
    else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
        size = btrfs_file_extent_inline_len(eb, item);
        extent_end = (start + size + mask) & ~mask;
    } else {
        ret = 0;
        goto out;
    }

    inode = read_one_inode(root, key->objectid);
    if (!inode) {
        ret = -EIO;
        goto out;
    }

    /*
     * first check to see if we already have this extent in the
     * file.  This must be done before the btrfs_drop_extents run
     * so we don't try to drop this extent.
     */
    ret = btrfs_lookup_file_extent(trans, root, path, btrfs_ino(inode),
                       start, 0);

    if (ret == 0 &&
        (found_type == BTRFS_FILE_EXTENT_REG ||
         found_type == BTRFS_FILE_EXTENT_PREALLOC)) {
        struct btrfs_file_extent_item cmp1;
        struct btrfs_file_extent_item cmp2;
        struct btrfs_file_extent_item *existing;
        struct extent_buffer *leaf;

        leaf = path->nodes[0];
        existing = btrfs_item_ptr(leaf, path->slots[0],
                      struct btrfs_file_extent_item);

        read_extent_buffer(eb, &cmp1, (unsigned long)item,
                   sizeof(cmp1));
        read_extent_buffer(leaf, &cmp2, (unsigned long)existing,
                   sizeof(cmp2));

        /*
         * we already have a pointer to this exact extent,
         * we don't have to do anything
         */
        if (memcmp(&cmp1, &cmp2, sizeof(cmp1)) == 0) {
            btrfs_release_path(path);
            goto out;
        }
    }
    btrfs_release_path(path);

    saved_nbytes = inode_get_bytes(inode);
    /* drop any overlapping extents */
    ret = btrfs_drop_extents(trans, root, inode, start, extent_end, 1);
    BUG_ON(ret);

    if (found_type == BTRFS_FILE_EXTENT_REG ||
        found_type == BTRFS_FILE_EXTENT_PREALLOC) {
        u64 offset;
        unsigned long dest_offset;
        struct btrfs_key ins;

        ret = btrfs_insert_empty_item(trans, root, path, key,
                          sizeof(*item));
        BUG_ON(ret);
        dest_offset = btrfs_item_ptr_offset(path->nodes[0],
                            path->slots[0]);
        copy_extent_buffer(path->nodes[0], eb, dest_offset,
                (unsigned long)item,  sizeof(*item));

        ins.objectid = btrfs_file_extent_disk_bytenr(eb, item);
        ins.offset = btrfs_file_extent_disk_num_bytes(eb, item);
        ins.type = BTRFS_EXTENT_ITEM_KEY;
        offset = key->offset - btrfs_file_extent_offset(eb, item);

        if (ins.objectid > 0) {
            u64 csum_start;
            u64 csum_end;
            LIST_HEAD(ordered_sums);
            /*
             * is this extent already allocated in the extent
             * allocation tree?  If so, just add a reference
             */
            ret = btrfs_lookup_extent(root, ins.objectid,
                        ins.offset);
            if (ret == 0) {
                ret = btrfs_inc_extent_ref(trans, root,
                        ins.objectid, ins.offset,
                        0, root->root_key.objectid,
                        key->objectid, offset, 0);
                BUG_ON(ret);
            } else {
                /*
                 * insert the extent pointer in the extent
                 * allocation tree
                 */
                ret = btrfs_alloc_logged_file_extent(trans,
                        root, root->root_key.objectid,
                        key->objectid, offset, &ins);
                BUG_ON(ret);
            }
            btrfs_release_path(path);

            if (btrfs_file_extent_compression(eb, item)) {
                csum_start = ins.objectid;
                csum_end = csum_start + ins.offset;
            } else {
                csum_start = ins.objectid +
                    btrfs_file_extent_offset(eb, item);
                csum_end = csum_start +
                    btrfs_file_extent_num_bytes(eb, item);
            }

            ret = btrfs_lookup_csums_range(root->log_root,
                        csum_start, csum_end - 1,
                        &ordered_sums, 0);
            BUG_ON(ret);
            while (!list_empty(&ordered_sums)) {
                struct btrfs_ordered_sum *sums;
                sums = list_entry(ordered_sums.next,
                        struct btrfs_ordered_sum,
                        list);
                ret = btrfs_csum_file_blocks(trans,
                        root->fs_info->csum_root,
                        sums);
                BUG_ON(ret);
                list_del(&sums->list);
                kfree(sums);
            }
        } else {
            btrfs_release_path(path);
        }
    } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
        /* inline extents are easy, we just overwrite them */
        ret = overwrite_item(trans, root, path, eb, slot, key);
        BUG_ON(ret);
    }

    inode_set_bytes(inode, saved_nbytes);
    ret = btrfs_update_inode(trans, root, inode);
out:
    if (inode)
        iput(inode);
    return ret;
}

/*
 * when cleaning up conflicts between the directory names in the
 * subvolume, directory names in the log and directory names in the
 * inode back references, we may have to unlink inodes from directories.
 *
 * This is a helper function to do the unlink of a specific directory
 * item
 */
static noinline int drop_one_dir_item(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      struct btrfs_path *path,
                      struct inode *dir,
                      struct btrfs_dir_item *di)
{
    struct inode *inode;
    char *name;
    int name_len;
    struct extent_buffer *leaf;
    struct btrfs_key location;
    int ret;

    leaf = path->nodes[0];

    btrfs_dir_item_key_to_cpu(leaf, di, &location);
    name_len = btrfs_dir_name_len(leaf, di);
    name = kmalloc(name_len, GFP_NOFS);
    if (!name)
        return -ENOMEM;

    read_extent_buffer(leaf, name, (unsigned long)(di + 1), name_len);
    btrfs_release_path(path);

    inode = read_one_inode(root, location.objectid);
    if (!inode) {
        kfree(name);
        return -EIO;
    }

    ret = link_to_fixup_dir(trans, root, path, location.objectid);
    BUG_ON(ret);

    ret = btrfs_unlink_inode(trans, root, dir, inode, name, name_len);
    BUG_ON(ret);
    kfree(name);

    iput(inode);

    btrfs_run_delayed_items(trans, root);
    return ret;
}

/*
 * helper function to see if a given name and sequence number found
 * in an inode back reference are already in a directory and correctly
 * point to this inode
 */
static noinline int inode_in_dir(struct btrfs_root *root,
                 struct btrfs_path *path,
                 u64 dirid, u64 objectid, u64 index,
                 const char *name, int name_len)
{
    struct btrfs_dir_item *di;
    struct btrfs_key location;
    int match = 0;

    di = btrfs_lookup_dir_index_item(NULL, root, path, dirid,
                     index, name, name_len, 0);
    if (di && !IS_ERR(di)) {
        btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
        if (location.objectid != objectid)
            goto out;
    } else
        goto out;
    btrfs_release_path(path);

    di = btrfs_lookup_dir_item(NULL, root, path, dirid, name, name_len, 0);
    if (di && !IS_ERR(di)) {
        btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
        if (location.objectid != objectid)
            goto out;
    } else
        goto out;
    match = 1;
out:
    btrfs_release_path(path);
    return match;
}

/*
 * helper function to check a log tree for a named back reference in
 * an inode.  This is used to decide if a back reference that is
 * found in the subvolume conflicts with what we find in the log.
 *
 * inode backreferences may have multiple refs in a single item,
 * during replay we process one reference at a time, and we don't
 * want to delete valid links to a file from the subvolume if that
 * link is also in the log.
 */
static noinline int backref_in_log(struct btrfs_root *log,
                   struct btrfs_key *key,
                   u64 ref_objectid,
                   char *name, int namelen)
{
    struct btrfs_path *path;
    struct btrfs_inode_ref *ref;
    unsigned long ptr;
    unsigned long ptr_end;
    unsigned long name_ptr;
    int found_name_len;
    int item_size;
    int ret;
    int match = 0;

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

    ret = btrfs_search_slot(NULL, log, key, path, 0, 0);
    if (ret != 0)
        goto out;

    ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);

    if (key->type == BTRFS_INODE_EXTREF_KEY) {
        if (btrfs_find_name_in_ext_backref(path, ref_objectid,
                           name, namelen, NULL))
            match = 1;

        goto out;
    }

    item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
    ptr_end = ptr + item_size;
    while (ptr < ptr_end) {
        ref = (struct btrfs_inode_ref *)ptr;
        found_name_len = btrfs_inode_ref_name_len(path->nodes[0], ref);
        if (found_name_len == namelen) {
            name_ptr = (unsigned long)(ref + 1);
            ret = memcmp_extent_buffer(path->nodes[0], name,
                           name_ptr, namelen);
            if (ret == 0) {
                match = 1;
                goto out;
            }
        }
        ptr = (unsigned long)(ref + 1) + found_name_len;
    }
out:
    btrfs_free_path(path);
    return match;
}

static inline int __add_inode_ref(struct btrfs_trans_handle *trans,
                  struct btrfs_root *root,
                  struct btrfs_path *path,
                  struct btrfs_root *log_root,
                  struct inode *dir, struct inode *inode,
                  struct extent_buffer *eb,
                  u64 inode_objectid, u64 parent_objectid,
                  u64 ref_index, char *name, int namelen,
                  int *search_done)
{
    int ret;
    char *victim_name;
    int victim_name_len;
    struct extent_buffer *leaf;
    struct btrfs_dir_item *di;
    struct btrfs_key search_key;
    struct btrfs_inode_extref *extref;

again:
    /* Search old style refs */
    search_key.objectid = inode_objectid;
    search_key.type = BTRFS_INODE_REF_KEY;
    search_key.offset = parent_objectid;
    ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
    if (ret == 0) {
        struct btrfs_inode_ref *victim_ref;
        unsigned long ptr;
        unsigned long ptr_end;

        leaf = path->nodes[0];

        /* are we trying to overwrite a back ref for the root directory
         * if so, just jump out, we're done
         */
        if (search_key.objectid == search_key.offset)
            return 1;

        /* check all the names in this back reference to see
         * if they are in the log.  if so, we allow them to stay
         * otherwise they must be unlinked as a conflict
         */
        ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
        ptr_end = ptr + btrfs_item_size_nr(leaf, path->slots[0]);
        while (ptr < ptr_end) {
            victim_ref = (struct btrfs_inode_ref *)ptr;
            victim_name_len = btrfs_inode_ref_name_len(leaf,
                                   victim_ref);
            victim_name = kmalloc(victim_name_len, GFP_NOFS);
            BUG_ON(!victim_name);

            read_extent_buffer(leaf, victim_name,
                       (unsigned long)(victim_ref + 1),
                       victim_name_len);

            if (!backref_in_log(log_root, &search_key,
                        parent_objectid,
                        victim_name,
                        victim_name_len)) {
                btrfs_inc_nlink(inode);
                btrfs_release_path(path);

                ret = btrfs_unlink_inode(trans, root, dir,
                             inode, victim_name,
                             victim_name_len);
                BUG_ON(ret);
                btrfs_run_delayed_items(trans, root);
                kfree(victim_name);
                *search_done = 1;
                goto again;
            }
            kfree(victim_name);

            ptr = (unsigned long)(victim_ref + 1) + victim_name_len;
        }
        BUG_ON(ret);

        /*
         * NOTE: we have searched root tree and checked the
         * coresponding ref, it does not need to check again.
         */
        *search_done = 1;
    }
    btrfs_release_path(path);

    /* Same search but for extended refs */
    extref = btrfs_lookup_inode_extref(NULL, root, path, name, namelen,
                       inode_objectid, parent_objectid, 0,
                       0);
    if (!IS_ERR_OR_NULL(extref)) {
        u32 item_size;
        u32 cur_offset = 0;
        unsigned long base;
        struct inode *victim_parent;

        leaf = path->nodes[0];

        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
        base = btrfs_item_ptr_offset(leaf, path->slots[0]);

        while (cur_offset < item_size) {
            extref = (struct btrfs_inode_extref *)base + cur_offset;

            victim_name_len = btrfs_inode_extref_name_len(leaf, extref);

            if (btrfs_inode_extref_parent(leaf, extref) != parent_objectid)
                goto next;

            victim_name = kmalloc(victim_name_len, GFP_NOFS);
            read_extent_buffer(leaf, victim_name, (unsigned long)&extref->name,
                       victim_name_len);

            search_key.objectid = inode_objectid;
            search_key.type = BTRFS_INODE_EXTREF_KEY;
            search_key.offset = btrfs_extref_hash(parent_objectid,
                                  victim_name,
                                  victim_name_len);
            ret = 0;
            if (!backref_in_log(log_root, &search_key,
                        parent_objectid, victim_name,
                        victim_name_len)) {
                ret = -ENOENT;
                victim_parent = read_one_inode(root,
                                   parent_objectid);
                if (victim_parent) {
                    btrfs_inc_nlink(inode);
                    btrfs_release_path(path);

                    ret = btrfs_unlink_inode(trans, root,
                                 victim_parent,
                                 inode,
                                 victim_name,
                                 victim_name_len);
                    btrfs_run_delayed_items(trans, root);
                }
                BUG_ON(ret);
                iput(victim_parent);
                kfree(victim_name);
                *search_done = 1;
                goto again;
            }
            kfree(victim_name);
            BUG_ON(ret);
next:
            cur_offset += victim_name_len + sizeof(*extref);
        }
        *search_done = 1;
    }
    btrfs_release_path(path);

    /* look for a conflicting sequence number */
    di = btrfs_lookup_dir_index_item(trans, root, path, btrfs_ino(dir),
                     ref_index, name, namelen, 0);
    if (di && !IS_ERR(di)) {
        ret = drop_one_dir_item(trans, root, path, dir, di);
        BUG_ON(ret);
    }
    btrfs_release_path(path);

    /* look for a conflicing name */
    di = btrfs_lookup_dir_item(trans, root, path, btrfs_ino(dir),
                   name, namelen, 0);
    if (di && !IS_ERR(di)) {
        ret = drop_one_dir_item(trans, root, path, dir, di);
        BUG_ON(ret);
    }
    btrfs_release_path(path);

    return 0;
}

static int extref_get_fields(struct extent_buffer *eb, unsigned long ref_ptr,
                 u32 *namelen, char **name, u64 *index,
                 u64 *parent_objectid)
{
    struct btrfs_inode_extref *extref;

    extref = (struct btrfs_inode_extref *)ref_ptr;

    *namelen = btrfs_inode_extref_name_len(eb, extref);
    *name = kmalloc(*namelen, GFP_NOFS);
    if (*name == NULL)
        return -ENOMEM;

    read_extent_buffer(eb, *name, (unsigned long)&extref->name,
               *namelen);

    *index = btrfs_inode_extref_index(eb, extref);
    if (parent_objectid)
        *parent_objectid = btrfs_inode_extref_parent(eb, extref);

    return 0;
}

static int ref_get_fields(struct extent_buffer *eb, unsigned long ref_ptr,
              u32 *namelen, char **name, u64 *index)
{
    struct btrfs_inode_ref *ref;

    ref = (struct btrfs_inode_ref *)ref_ptr;

    *namelen = btrfs_inode_ref_name_len(eb, ref);
    *name = kmalloc(*namelen, GFP_NOFS);
    if (*name == NULL)
        return -ENOMEM;

    read_extent_buffer(eb, *name, (unsigned long)(ref + 1), *namelen);

    *index = btrfs_inode_ref_index(eb, ref);

    return 0;
}

/*
 * replay one inode back reference item found in the log tree.
 * eb, slot and key refer to the buffer and key found in the log tree.
 * root is the destination we are replaying into, and path is for temp
 * use by this function.  (it should be released on return).
 */
static noinline int add_inode_ref(struct btrfs_trans_handle *trans,
                  struct btrfs_root *root,
                  struct btrfs_root *log,
                  struct btrfs_path *path,
                  struct extent_buffer *eb, int slot,
                  struct btrfs_key *key)
{
    struct inode *dir;
    struct inode *inode;
    unsigned long ref_ptr;
    unsigned long ref_end;
    char *name;
    int namelen;
    int ret;
    int search_done = 0;
    int log_ref_ver = 0;
    u64 parent_objectid;
    u64 inode_objectid;
    u64 ref_index = 0;
    int ref_struct_size;

    ref_ptr = btrfs_item_ptr_offset(eb, slot);
    ref_end = ref_ptr + btrfs_item_size_nr(eb, slot);

    if (key->type == BTRFS_INODE_EXTREF_KEY) {
        struct btrfs_inode_extref *r;

        ref_struct_size = sizeof(struct btrfs_inode_extref);
        log_ref_ver = 1;
        r = (struct btrfs_inode_extref *)ref_ptr;
        parent_objectid = btrfs_inode_extref_parent(eb, r);
    } else {
        ref_struct_size = sizeof(struct btrfs_inode_ref);
        parent_objectid = key->offset;
    }
    inode_objectid = key->objectid;

    /*
     * it is possible that we didn't log all the parent directories
     * for a given inode.  If we don't find the dir, just don't
     * copy the back ref in.  The link count fixup code will take
     * care of the rest
     */
    dir = read_one_inode(root, parent_objectid);
    if (!dir)
        return -ENOENT;

    inode = read_one_inode(root, inode_objectid);
    if (!inode) {
        iput(dir);
        return -EIO;
    }

    while (ref_ptr < ref_end) {
        if (log_ref_ver) {
            ret = extref_get_fields(eb, ref_ptr, &namelen, &name,
                        &ref_index, &parent_objectid);
            /*
             * parent object can change from one array
             * item to another.
             */
            if (!dir)
                dir = read_one_inode(root, parent_objectid);
            if (!dir)
                return -ENOENT;
        } else {
            ret = ref_get_fields(eb, ref_ptr, &namelen, &name,
                         &ref_index);
        }
        if (ret)
            return ret;

        /* if we already have a perfect match, we're done */
        if (!inode_in_dir(root, path, btrfs_ino(dir), btrfs_ino(inode),
                  ref_index, name, namelen)) {
            /*
             * look for a conflicting back reference in the
             * metadata. if we find one we have to unlink that name
             * of the file before we add our new link.  Later on, we
             * overwrite any existing back reference, and we don't
             * want to create dangling pointers in the directory.
             */

            if (!search_done) {
                ret = __add_inode_ref(trans, root, path, log,
                              dir, inode, eb,
                              inode_objectid,
                              parent_objectid,
                              ref_index, name, namelen,
                              &search_done);
                if (ret == 1)
                    goto out;
                BUG_ON(ret);
            }

            /* insert our name */
            ret = btrfs_add_link(trans, dir, inode, name, namelen,
                         0, ref_index);
            BUG_ON(ret);

            btrfs_update_inode(trans, root, inode);
        }

        ref_ptr = (unsigned long)(ref_ptr + ref_struct_size) + namelen;
        kfree(name);
        if (log_ref_ver) {
            iput(dir);
            dir = NULL;
        }
    }

    /* finally write the back reference in the inode */
    ret = overwrite_item(trans, root, path, eb, slot, key);
    BUG_ON(ret);

out:
    btrfs_release_path(path);
    iput(dir);
    iput(inode);
    return 0;
}

static int insert_orphan_item(struct btrfs_trans_handle *trans,
                  struct btrfs_root *root, u64 offset)
{
    int ret;
    ret = btrfs_find_orphan_item(root, offset);
    if (ret > 0)
        ret = btrfs_insert_orphan_item(trans, root, offset);
    return ret;
}

static int count_inode_extrefs(struct btrfs_root *root,
                   struct inode *inode, struct btrfs_path *path)
{
    int ret = 0;
    int name_len;
    unsigned int nlink = 0;
    u32 item_size;
    u32 cur_offset = 0;
    u64 inode_objectid = btrfs_ino(inode);
    u64 offset = 0;
    unsigned long ptr;
    struct btrfs_inode_extref *extref;
    struct extent_buffer *leaf;

    while (1) {
        ret = btrfs_find_one_extref(root, inode_objectid, offset, path,
                        &extref, &offset);
        if (ret)
            break;

        leaf = path->nodes[0];
        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
        ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);

        while (cur_offset < item_size) {
            extref = (struct btrfs_inode_extref *) (ptr + cur_offset);
            name_len = btrfs_inode_extref_name_len(leaf, extref);

            nlink++;

            cur_offset += name_len + sizeof(*extref);
        }

        offset++;
        btrfs_release_path(path);
    }
    btrfs_release_path(path);

    if (ret < 0)
        return ret;
    return nlink;
}

static int count_inode_refs(struct btrfs_root *root,
                   struct inode *inode, struct btrfs_path *path)
{
    int ret;
    struct btrfs_key key;
    unsigned int nlink = 0;
    unsigned long ptr;
    unsigned long ptr_end;
    int name_len;
    u64 ino = btrfs_ino(inode);

    key.objectid = ino;
    key.type = BTRFS_INODE_REF_KEY;
    key.offset = (u64)-1;

    while (1) {
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
            break;
        if (ret > 0) {
            if (path->slots[0] == 0)
                break;
            path->slots[0]--;
        }
        btrfs_item_key_to_cpu(path->nodes[0], &key,
                      path->slots[0]);
        if (key.objectid != ino ||
            key.type != BTRFS_INODE_REF_KEY)
            break;
        ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
        ptr_end = ptr + btrfs_item_size_nr(path->nodes[0],
                           path->slots[0]);
        while (ptr < ptr_end) {
            struct btrfs_inode_ref *ref;

            ref = (struct btrfs_inode_ref *)ptr;
            name_len = btrfs_inode_ref_name_len(path->nodes[0],
                                ref);
            ptr = (unsigned long)(ref + 1) + name_len;
            nlink++;
        }

        if (key.offset == 0)
            break;
        key.offset--;
        btrfs_release_path(path);
    }
    btrfs_release_path(path);

    return nlink;
}

/*
 * There are a few corners where the link count of the file can't
 * be properly maintained during replay.  So, instead of adding
 * lots of complexity to the log code, we just scan the backrefs
 * for any file that has been through replay.
 *
 * The scan will update the link count on the inode to reflect the
 * number of back refs found.  If it goes down to zero, the iput
 * will free the inode.
 */
static noinline int fixup_inode_link_count(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct inode *inode)
{
    struct btrfs_path *path;
    int ret;
    u64 nlink = 0;
    u64 ino = btrfs_ino(inode);

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

    ret = count_inode_refs(root, inode, path);
    if (ret < 0)
        goto out;

    nlink = ret;

    ret = count_inode_extrefs(root, inode, path);
    if (ret == -ENOENT)
        ret = 0;

    if (ret < 0)
        goto out;

    nlink += ret;

    ret = 0;

    if (nlink != inode->i_nlink) {
        set_nlink(inode, nlink);
        btrfs_update_inode(trans, root, inode);
    }
    BTRFS_I(inode)->index_cnt = (u64)-1;

    if (inode->i_nlink == 0) {
        if (S_ISDIR(inode->i_mode)) {
            ret = replay_dir_deletes(trans, root, NULL, path,
                         ino, 1);
            BUG_ON(ret);
        }
        ret = insert_orphan_item(trans, root, ino);
        BUG_ON(ret);
    }

out:
    btrfs_free_path(path);
    return ret;
}

static noinline int fixup_inode_link_counts(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
                        struct btrfs_path *path)
{
    int ret;
    struct btrfs_key key;
    struct inode *inode;

    key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
    key.type = BTRFS_ORPHAN_ITEM_KEY;
    key.offset = (u64)-1;
    while (1) {
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0)
            break;

        if (ret == 1) {
            if (path->slots[0] == 0)
                break;
            path->slots[0]--;
        }

        btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
        if (key.objectid != BTRFS_TREE_LOG_FIXUP_OBJECTID ||
            key.type != BTRFS_ORPHAN_ITEM_KEY)
            break;

        ret = btrfs_del_item(trans, root, path);
        if (ret)
            goto out;

        btrfs_release_path(path);
        inode = read_one_inode(root, key.offset);
        if (!inode)
            return -EIO;

        ret = fixup_inode_link_count(trans, root, inode);
        BUG_ON(ret);

        iput(inode);

        /*
         * fixup on a directory may create new entries,
         * make sure we always look for the highset possible
         * offset
         */
        key.offset = (u64)-1;
    }
    ret = 0;
out:
    btrfs_release_path(path);
    return ret;
}


/*
 * record a given inode in the fixup dir so we can check its link
 * count when replay is done.  The link count is incremented here
 * so the inode won't go away until we check it
 */
static noinline int link_to_fixup_dir(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      struct btrfs_path *path,
                      u64 objectid)
{
    struct btrfs_key key;
    int ret = 0;
    struct inode *inode;

    inode = read_one_inode(root, objectid);
    if (!inode)
        return -EIO;

    key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
    btrfs_set_key_type(&key, BTRFS_ORPHAN_ITEM_KEY);
    key.offset = objectid;

    ret = btrfs_insert_empty_item(trans, root, path, &key, 0);

    btrfs_release_path(path);
    if (ret == 0) {
        btrfs_inc_nlink(inode);
        ret = btrfs_update_inode(trans, root, inode);
    } else if (ret == -EEXIST) {
        ret = 0;
    } else {
        BUG();
    }
    iput(inode);

    return ret;
}

/*
 * when replaying the log for a directory, we only insert names
 * for inodes that actually exist.  This means an fsync on a directory
 * does not implicitly fsync all the new files in it
 */
static noinline int insert_one_name(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root,
                    struct btrfs_path *path,
                    u64 dirid, u64 index,
                    char *name, int name_len, u8 type,
                    struct btrfs_key *location)
{
    struct inode *inode;
    struct inode *dir;
    int ret;

    inode = read_one_inode(root, location->objectid);
    if (!inode)
        return -ENOENT;

    dir = read_one_inode(root, dirid);
    if (!dir) {
        iput(inode);
        return -EIO;
    }
    ret = btrfs_add_link(trans, dir, inode, name, name_len, 1, index);

    /* FIXME, put inode into FIXUP list */

    iput(inode);
    iput(dir);
    return ret;
}

/*
 * take a single entry in a log directory item and replay it into
 * the subvolume.
 *
 * if a conflicting item exists in the subdirectory already,
 * the inode it points to is unlinked and put into the link count
 * fix up tree.
 *
 * If a name from the log points to a file or directory that does
 * not exist in the FS, it is skipped.  fsyncs on directories
 * do not force down inodes inside that directory, just changes to the
 * names or unlinks in a directory.
 */
static noinline int replay_one_name(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root,
                    struct btrfs_path *path,
                    struct extent_buffer *eb,
                    struct btrfs_dir_item *di,
                    struct btrfs_key *key)
{
    char *name;
    int name_len;
    struct btrfs_dir_item *dst_di;
    struct btrfs_key found_key;
    struct btrfs_key log_key;
    struct inode *dir;
    u8 log_type;
    int exists;
    int ret;

    dir = read_one_inode(root, key->objectid);
    if (!dir)
        return -EIO;

    name_len = btrfs_dir_name_len(eb, di);
    name = kmalloc(name_len, GFP_NOFS);
    if (!name)
        return -ENOMEM;

    log_type = btrfs_dir_type(eb, di);
    read_extent_buffer(eb, name, (unsigned long)(di + 1),
           name_len);

    btrfs_dir_item_key_to_cpu(eb, di, &log_key);
    exists = btrfs_lookup_inode(trans, root, path, &log_key, 0);
    if (exists == 0)
        exists = 1;
    else
        exists = 0;
    btrfs_release_path(path);

    if (key->type == BTRFS_DIR_ITEM_KEY) {
        dst_di = btrfs_lookup_dir_item(trans, root, path, key->objectid,
                       name, name_len, 1);
    } else if (key->type == BTRFS_DIR_INDEX_KEY) {
        dst_di = btrfs_lookup_dir_index_item(trans, root, path,
                             key->objectid,
                             key->offset, name,
                             name_len, 1);
    } else {
        BUG();
    }
    if (IS_ERR_OR_NULL(dst_di)) {
        /* we need a sequence number to insert, so we only
         * do inserts for the BTRFS_DIR_INDEX_KEY types
         */
        if (key->type != BTRFS_DIR_INDEX_KEY)
            goto out;
        goto insert;
    }

    btrfs_dir_item_key_to_cpu(path->nodes[0], dst_di, &found_key);
    /* the existing item matches the logged item */
    if (found_key.objectid == log_key.objectid &&
        found_key.type == log_key.type &&
        found_key.offset == log_key.offset &&
        btrfs_dir_type(path->nodes[0], dst_di) == log_type) {
        goto out;
    }

    /*
     * don't drop the conflicting directory entry if the inode
     * for the new entry doesn't exist
     */
    if (!exists)
        goto out;

    ret = drop_one_dir_item(trans, root, path, dir, dst_di);
    BUG_ON(ret);

    if (key->type == BTRFS_DIR_INDEX_KEY)
        goto insert;
out:
    btrfs_release_path(path);
    kfree(name);
    iput(dir);
    return 0;

insert:
    btrfs_release_path(path);
    ret = insert_one_name(trans, root, path, key->objectid, key->offset,
                  name, name_len, log_type, &log_key);

    BUG_ON(ret && ret != -ENOENT);
    goto out;
}

/*
 * find all the names in a directory item and reconcile them into
 * the subvolume.  Only BTRFS_DIR_ITEM_KEY types will have more than
 * one name in a directory item, but the same code gets used for
 * both directory index types
 */
static noinline int replay_one_dir_item(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root,
                    struct btrfs_path *path,
                    struct extent_buffer *eb, int slot,
                    struct btrfs_key *key)
{
    int ret;
    u32 item_size = btrfs_item_size_nr(eb, slot);
    struct btrfs_dir_item *di;
    int name_len;
    unsigned long ptr;
    unsigned long ptr_end;

    ptr = btrfs_item_ptr_offset(eb, slot);
    ptr_end = ptr + item_size;
    while (ptr < ptr_end) {
        di = (struct btrfs_dir_item *)ptr;
        if (verify_dir_item(root, eb, di))
            return -EIO;
        name_len = btrfs_dir_name_len(eb, di);
        ret = replay_one_name(trans, root, path, eb, di, key);
        BUG_ON(ret);
        ptr = (unsigned long)(di + 1);
        ptr += name_len;
    }
    return 0;
}

/*
 * directory replay has two parts.  There are the standard directory
 * items in the log copied from the subvolume, and range items
 * created in the log while the subvolume was logged.
 *
 * The range items tell us which parts of the key space the log
 * is authoritative for.  During replay, if a key in the subvolume
 * directory is in a logged range item, but not actually in the log
 * that means it was deleted from the directory before the fsync
 * and should be removed.
 */
static noinline int find_dir_range(struct btrfs_root *root,
                   struct btrfs_path *path,
                   u64 dirid, int key_type,
                   u64 *start_ret, u64 *end_ret)
{
    struct btrfs_key key;
    u64 found_end;
    struct btrfs_dir_log_item *item;
    int ret;
    int nritems;

    if (*start_ret == (u64)-1)
        return 1;

    key.objectid = dirid;
    key.type = key_type;
    key.offset = *start_ret;

    ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
    if (ret < 0)
        goto out;
    if (ret > 0) {
        if (path->slots[0] == 0)
            goto out;
        path->slots[0]--;
    }
    if (ret != 0)
        btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);

    if (key.type != key_type || key.objectid != dirid) {
        ret = 1;
        goto next;
    }
    item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                  struct btrfs_dir_log_item);
    found_end = btrfs_dir_log_end(path->nodes[0], item);

    if (*start_ret >= key.offset && *start_ret <= found_end) {
        ret = 0;
        *start_ret = key.offset;
        *end_ret = found_end;
        goto out;
    }
    ret = 1;
next:
    /* check the next slot in the tree to see if it is a valid item */
    nritems = btrfs_header_nritems(path->nodes[0]);
    if (path->slots[0] >= nritems) {
        ret = btrfs_next_leaf(root, path);
        if (ret)
            goto out;
    } else {
        path->slots[0]++;
    }

    btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);

    if (key.type != key_type || key.objectid != dirid) {
        ret = 1;
        goto out;
    }
    item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                  struct btrfs_dir_log_item);
    found_end = btrfs_dir_log_end(path->nodes[0], item);
    *start_ret = key.offset;
    *end_ret = found_end;
    ret = 0;
out:
    btrfs_release_path(path);
    return ret;
}

/*
 * this looks for a given directory item in the log.  If the directory
 * item is not in the log, the item is removed and the inode it points
 * to is unlinked
 */
static noinline int check_item_in_log(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      struct btrfs_root *log,
                      struct btrfs_path *path,
                      struct btrfs_path *log_path,
                      struct inode *dir,
                      struct btrfs_key *dir_key)
{
    int ret;
    struct extent_buffer *eb;
    int slot;
    u32 item_size;
    struct btrfs_dir_item *di;
    struct btrfs_dir_item *log_di;
    int name_len;
    unsigned long ptr;
    unsigned long ptr_end;
    char *name;
    struct inode *inode;
    struct btrfs_key location;

again:
    eb = path->nodes[0];
    slot = path->slots[0];
    item_size = btrfs_item_size_nr(eb, slot);
    ptr = btrfs_item_ptr_offset(eb, slot);
    ptr_end = ptr + item_size;
    while (ptr < ptr_end) {
        di = (struct btrfs_dir_item *)ptr;
        if (verify_dir_item(root, eb, di)) {
            ret = -EIO;
            goto out;
        }

        name_len = btrfs_dir_name_len(eb, di);
        name = kmalloc(name_len, GFP_NOFS);
        if (!name) {
            ret = -ENOMEM;
            goto out;
        }
        read_extent_buffer(eb, name, (unsigned long)(di + 1),
                  name_len);
        log_di = NULL;
        if (log && dir_key->type == BTRFS_DIR_ITEM_KEY) {
            log_di = btrfs_lookup_dir_item(trans, log, log_path,
                               dir_key->objectid,
                               name, name_len, 0);
        } else if (log && dir_key->type == BTRFS_DIR_INDEX_KEY) {
            log_di = btrfs_lookup_dir_index_item(trans, log,
                             log_path,
                             dir_key->objectid,
                             dir_key->offset,
                             name, name_len, 0);
        }
        if (IS_ERR_OR_NULL(log_di)) {
            btrfs_dir_item_key_to_cpu(eb, di, &location);
            btrfs_release_path(path);
            btrfs_release_path(log_path);
            inode = read_one_inode(root, location.objectid);
            if (!inode) {
                kfree(name);
                return -EIO;
            }

            ret = link_to_fixup_dir(trans, root,
                        path, location.objectid);
            BUG_ON(ret);
            btrfs_inc_nlink(inode);
            ret = btrfs_unlink_inode(trans, root, dir, inode,
                         name, name_len);
            BUG_ON(ret);

            btrfs_run_delayed_items(trans, root);

            kfree(name);
            iput(inode);

            /* there might still be more names under this key
             * check and repeat if required
             */
            ret = btrfs_search_slot(NULL, root, dir_key, path,
                        0, 0);
            if (ret == 0)
                goto again;
            ret = 0;
            goto out;
        }
        btrfs_release_path(log_path);
        kfree(name);

        ptr = (unsigned long)(di + 1);
        ptr += name_len;
    }
    ret = 0;
out:
    btrfs_release_path(path);
    btrfs_release_path(log_path);
    return ret;
}

/*
 * deletion replay happens before we copy any new directory items
 * out of the log or out of backreferences from inodes.  It
 * scans the log to find ranges of keys that log is authoritative for,
 * and then scans the directory to find items in those ranges that are
 * not present in the log.
 *
 * Anything we don't find in the log is unlinked and removed from the
 * directory.
 */
static noinline int replay_dir_deletes(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct btrfs_root *log,
                       struct btrfs_path *path,
                       u64 dirid, int del_all)
{
    u64 range_start;
    u64 range_end;
    int key_type = BTRFS_DIR_LOG_ITEM_KEY;
    int ret = 0;
    struct btrfs_key dir_key;
    struct btrfs_key found_key;
    struct btrfs_path *log_path;
    struct inode *dir;

    dir_key.objectid = dirid;
    dir_key.type = BTRFS_DIR_ITEM_KEY;
    log_path = btrfs_alloc_path();
    if (!log_path)
        return -ENOMEM;

    dir = read_one_inode(root, dirid);
    /* it isn't an error if the inode isn't there, that can happen
     * because we replay the deletes before we copy in the inode item
     * from the log
     */
    if (!dir) {
        btrfs_free_path(log_path);
        return 0;
    }
again:
    range_start = 0;
    range_end = 0;
    while (1) {
        if (del_all)
            range_end = (u64)-1;
        else {
            ret = find_dir_range(log, path, dirid, key_type,
                         &range_start, &range_end);
            if (ret != 0)
                break;
        }

        dir_key.offset = range_start;
        while (1) {
            int nritems;
            ret = btrfs_search_slot(NULL, root, &dir_key, path,
                        0, 0);
            if (ret < 0)
                goto out;

            nritems = btrfs_header_nritems(path->nodes[0]);
            if (path->slots[0] >= nritems) {
                ret = btrfs_next_leaf(root, path);
                if (ret)
                    break;
            }
            btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                          path->slots[0]);
            if (found_key.objectid != dirid ||
                found_key.type != dir_key.type)
                goto next_type;

            if (found_key.offset > range_end)
                break;

            ret = check_item_in_log(trans, root, log, path,
                        log_path, dir,
                        &found_key);
            BUG_ON(ret);
            if (found_key.offset == (u64)-1)
                break;
            dir_key.offset = found_key.offset + 1;
        }
        btrfs_release_path(path);
        if (range_end == (u64)-1)
            break;
        range_start = range_end + 1;
    }

next_type:
    ret = 0;
    if (key_type == BTRFS_DIR_LOG_ITEM_KEY) {
        key_type = BTRFS_DIR_LOG_INDEX_KEY;
        dir_key.type = BTRFS_DIR_INDEX_KEY;
        btrfs_release_path(path);
        goto again;
    }
out:
    btrfs_release_path(path);
    btrfs_free_path(log_path);
    iput(dir);
    return ret;
}

/*
 * the process_func used to replay items from the log tree.  This
 * gets called in two different stages.  The first stage just looks
 * for inodes and makes sure they are all copied into the subvolume.
 *
 * The second stage copies all the other item types from the log into
 * the subvolume.  The two stage approach is slower, but gets rid of
 * lots of complexity around inodes referencing other inodes that exist
 * only in the log (references come from either directory items or inode
 * back refs).
 */
static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
                 struct walk_control *wc, u64 gen)
{
    int nritems;
    struct btrfs_path *path;
    struct btrfs_root *root = wc->replay_dest;
    struct btrfs_key key;
    int level;
    int i;
    int ret;

    ret = btrfs_read_buffer(eb, gen);
    if (ret)
        return ret;

    level = btrfs_header_level(eb);

    if (level != 0)
        return 0;

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

    nritems = btrfs_header_nritems(eb);
    for (i = 0; i < nritems; i++) {
        btrfs_item_key_to_cpu(eb, &key, i);

        /* inode keys are done during the first stage */
        if (key.type == BTRFS_INODE_ITEM_KEY &&
            wc->stage == LOG_WALK_REPLAY_INODES) {
            struct btrfs_inode_item *inode_item;
            u32 mode;

            inode_item = btrfs_item_ptr(eb, i,
                        struct btrfs_inode_item);
            mode = btrfs_inode_mode(eb, inode_item);
            if (S_ISDIR(mode)) {
                ret = replay_dir_deletes(wc->trans,
                     root, log, path, key.objectid, 0);
                BUG_ON(ret);
            }
            ret = overwrite_item(wc->trans, root, path,
                         eb, i, &key);
            BUG_ON(ret);

            /* for regular files, make sure corresponding
             * orhpan item exist. extents past the new EOF
             * will be truncated later by orphan cleanup.
             */
            if (S_ISREG(mode)) {
                ret = insert_orphan_item(wc->trans, root,
                             key.objectid);
                BUG_ON(ret);
            }

            ret = link_to_fixup_dir(wc->trans, root,
                        path, key.objectid);
            BUG_ON(ret);
        }
        if (wc->stage < LOG_WALK_REPLAY_ALL)
            continue;

        /* these keys are simply copied */
        if (key.type == BTRFS_XATTR_ITEM_KEY) {
            ret = overwrite_item(wc->trans, root, path,
                         eb, i, &key);
            BUG_ON(ret);
        } else if (key.type == BTRFS_INODE_REF_KEY) {
            ret = add_inode_ref(wc->trans, root, log, path,
                        eb, i, &key);
            BUG_ON(ret && ret != -ENOENT);
        } else if (key.type == BTRFS_INODE_EXTREF_KEY) {
            ret = add_inode_ref(wc->trans, root, log, path,
                        eb, i, &key);
            BUG_ON(ret && ret != -ENOENT);
        } else if (key.type == BTRFS_EXTENT_DATA_KEY) {
            ret = replay_one_extent(wc->trans, root, path,
                        eb, i, &key);
            BUG_ON(ret);
        } else if (key.type == BTRFS_DIR_ITEM_KEY ||
               key.type == BTRFS_DIR_INDEX_KEY) {
            ret = replay_one_dir_item(wc->trans, root, path,
                          eb, i, &key);
            BUG_ON(ret);
        }
    }
    btrfs_free_path(path);
    return 0;
}

static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
                   struct btrfs_root *root,
                   struct btrfs_path *path, int *level,
                   struct walk_control *wc)
{
    u64 root_owner;
    u64 bytenr;
    u64 ptr_gen;
    struct extent_buffer *next;
    struct extent_buffer *cur;
    struct extent_buffer *parent;
    u32 blocksize;
    int ret = 0;

    WARN_ON(*level < 0);
    WARN_ON(*level >= BTRFS_MAX_LEVEL);

    while (*level > 0) {
        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);
        cur = path->nodes[*level];

        if (btrfs_header_level(cur) != *level)
            WARN_ON(1);

        if (path->slots[*level] >=
            btrfs_header_nritems(cur))
            break;

        bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
        ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
        blocksize = btrfs_level_size(root, *level - 1);

        parent = path->nodes[*level];
        root_owner = btrfs_header_owner(parent);

        next = btrfs_find_create_tree_block(root, bytenr, blocksize);
        if (!next)
            return -ENOMEM;

        if (*level == 1) {
            ret = wc->process_func(root, next, wc, ptr_gen);
            if (ret)
                return ret;

            path->slots[*level]++;
            if (wc->free) {
                ret = btrfs_read_buffer(next, ptr_gen);
                if (ret) {
                    free_extent_buffer(next);
                    return ret;
                }

                btrfs_tree_lock(next);
                btrfs_set_lock_blocking(next);
                clean_tree_block(trans, root, next);
                btrfs_wait_tree_block_writeback(next);
                btrfs_tree_unlock(next);

                WARN_ON(root_owner !=
                    BTRFS_TREE_LOG_OBJECTID);
                ret = btrfs_free_and_pin_reserved_extent(root,
                             bytenr, blocksize);
                BUG_ON(ret); /* -ENOMEM or logic errors */
            }
            free_extent_buffer(next);
            continue;
        }
        ret = btrfs_read_buffer(next, ptr_gen);
        if (ret) {
            free_extent_buffer(next);
            return ret;
        }

        WARN_ON(*level <= 0);
        if (path->nodes[*level-1])
            free_extent_buffer(path->nodes[*level-1]);
        path->nodes[*level-1] = next;
        *level = btrfs_header_level(next);
        path->slots[*level] = 0;
        cond_resched();
    }
    WARN_ON(*level < 0);
    WARN_ON(*level >= BTRFS_MAX_LEVEL);

    path->slots[*level] = btrfs_header_nritems(path->nodes[*level]);

    cond_resched();
    return 0;
}

static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root,
                 struct btrfs_path *path, int *level,
                 struct walk_control *wc)
{
    u64 root_owner;
    int i;
    int slot;
    int ret;

    for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
        slot = path->slots[i];
        if (slot + 1 < btrfs_header_nritems(path->nodes[i])) {
            path->slots[i]++;
            *level = i;
            WARN_ON(*level == 0);
            return 0;
        } else {
            struct extent_buffer *parent;
            if (path->nodes[*level] == root->node)
                parent = path->nodes[*level];
            else
                parent = path->nodes[*level + 1];

            root_owner = btrfs_header_owner(parent);
            ret = wc->process_func(root, path->nodes[*level], wc,
                 btrfs_header_generation(path->nodes[*level]));
            if (ret)
                return ret;

            if (wc->free) {
                struct extent_buffer *next;

                next = path->nodes[*level];

                btrfs_tree_lock(next);
                btrfs_set_lock_blocking(next);
                clean_tree_block(trans, root, next);
                btrfs_wait_tree_block_writeback(next);
                btrfs_tree_unlock(next);

                WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
                ret = btrfs_free_and_pin_reserved_extent(root,
                        path->nodes[*level]->start,
                        path->nodes[*level]->len);
                BUG_ON(ret);
            }
            free_extent_buffer(path->nodes[*level]);
            path->nodes[*level] = NULL;
            *level = i + 1;
        }
    }
    return 1;
}

/*
 * drop the reference count on the tree rooted at 'snap'.  This traverses
 * the tree freeing any blocks that have a ref count of zero after being
 * decremented.
 */
static int walk_log_tree(struct btrfs_trans_handle *trans,
             struct btrfs_root *log, struct walk_control *wc)
{
    int ret = 0;
    int wret;
    int level;
    struct btrfs_path *path;
    int i;
    int orig_level;

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

    level = btrfs_header_level(log->node);
    orig_level = level;
    path->nodes[level] = log->node;
    extent_buffer_get(log->node);
    path->slots[level] = 0;

    while (1) {
        wret = walk_down_log_tree(trans, log, path, &level, wc);
        if (wret > 0)
            break;
        if (wret < 0) {
            ret = wret;
            goto out;
        }

        wret = walk_up_log_tree(trans, log, path, &level, wc);
        if (wret > 0)
            break;
        if (wret < 0) {
            ret = wret;
            goto out;
        }
    }

    /* was the root node processed? if not, catch it here */
    if (path->nodes[orig_level]) {
        ret = wc->process_func(log, path->nodes[orig_level], wc,
             btrfs_header_generation(path->nodes[orig_level]));
        if (ret)
            goto out;
        if (wc->free) {
            struct extent_buffer *next;

            next = path->nodes[orig_level];

            btrfs_tree_lock(next);
            btrfs_set_lock_blocking(next);
            clean_tree_block(trans, log, next);
            btrfs_wait_tree_block_writeback(next);
            btrfs_tree_unlock(next);

            WARN_ON(log->root_key.objectid !=
                BTRFS_TREE_LOG_OBJECTID);
            ret = btrfs_free_and_pin_reserved_extent(log, next->start,
                             next->len);
            BUG_ON(ret); /* -ENOMEM or logic errors */
        }
    }

out:
    for (i = 0; i <= orig_level; i++) {
        if (path->nodes[i]) {
            free_extent_buffer(path->nodes[i]);
            path->nodes[i] = NULL;
        }
    }
    btrfs_free_path(path);
    return ret;
}

/*
 * helper function to update the item for a given subvolumes log root
 * in the tree of log roots
 */
static int update_log_root(struct btrfs_trans_handle *trans,
               struct btrfs_root *log)
{
    int ret;

    if (log->log_transid == 1) {
        /* insert root item on the first sync */
        ret = btrfs_insert_root(trans, log->fs_info->log_root_tree,
                &log->root_key, &log->root_item);
    } else {
        ret = btrfs_update_root(trans, log->fs_info->log_root_tree,
                &log->root_key, &log->root_item);
    }
    return ret;
}

static int wait_log_commit(struct btrfs_trans_handle *trans,
               struct btrfs_root *root, unsigned long transid)
{
    DEFINE_WAIT(wait);
    int index = transid % 2;

    /*
     * we only allow two pending log transactions at a time,
     * so we know that if ours is more than 2 older than the
     * current transaction, we're done
     */
    do {
        prepare_to_wait(&root->log_commit_wait[index],
                &wait, TASK_UNINTERRUPTIBLE);
        mutex_unlock(&root->log_mutex);

        if (root->fs_info->last_trans_log_full_commit !=
            trans->transid && root->log_transid < transid + 2 &&
            atomic_read(&root->log_commit[index]))
            schedule();

        finish_wait(&root->log_commit_wait[index], &wait);
        mutex_lock(&root->log_mutex);
    } while (root->fs_info->last_trans_log_full_commit !=
         trans->transid && root->log_transid < transid + 2 &&
         atomic_read(&root->log_commit[index]));
    return 0;
}

static void wait_for_writer(struct btrfs_trans_handle *trans,
                struct btrfs_root *root)
{
    DEFINE_WAIT(wait);
    while (root->fs_info->last_trans_log_full_commit !=
           trans->transid && atomic_read(&root->log_writers)) {
        prepare_to_wait(&root->log_writer_wait,
                &wait, TASK_UNINTERRUPTIBLE);
        mutex_unlock(&root->log_mutex);
        if (root->fs_info->last_trans_log_full_commit !=
            trans->transid && atomic_read(&root->log_writers))
            schedule();
        mutex_lock(&root->log_mutex);
        finish_wait(&root->log_writer_wait, &wait);
    }
}

/*
 * btrfs_sync_log does sends a given tree log down to the disk and
 * updates the super blocks to record it.  When this call is done,
 * you know that any inodes previously logged are safely on disk only
 * if it returns 0.
 *
 * Any other return value means you need to call btrfs_commit_transaction.
 * Some of the edge cases for fsyncing directories that have had unlinks
 * or renames done in the past mean that sometimes the only safe
 * fsync is to commit the whole FS.  When btrfs_sync_log returns -EAGAIN,
 * that has happened.
 */
int btrfs_sync_log(struct btrfs_trans_handle *trans,
           struct btrfs_root *root)
{
    int index1;
    int index2;
    int mark;
    int ret;
    struct btrfs_root *log = root->log_root;
    struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;
    unsigned long log_transid = 0;

    mutex_lock(&root->log_mutex);
    index1 = root->log_transid % 2;
    if (atomic_read(&root->log_commit[index1])) {
        wait_log_commit(trans, root, root->log_transid);
        mutex_unlock(&root->log_mutex);
        return 0;
    }
    atomic_set(&root->log_commit[index1], 1);

    /* wait for previous tree log sync to complete */
    if (atomic_read(&root->log_commit[(index1 + 1) % 2]))
        wait_log_commit(trans, root, root->log_transid - 1);
    while (1) {
        int batch = atomic_read(&root->log_batch);
        /* when we're on an ssd, just kick the log commit out */
        if (!btrfs_test_opt(root, SSD) && root->log_multiple_pids) {
            mutex_unlock(&root->log_mutex);
            schedule_timeout_uninterruptible(1);
            mutex_lock(&root->log_mutex);
        }
        wait_for_writer(trans, root);
        if (batch == atomic_read(&root->log_batch))
            break;
    }

    /* bail out if we need to do a full commit */
    if (root->fs_info->last_trans_log_full_commit == trans->transid) {
        ret = -EAGAIN;
        mutex_unlock(&root->log_mutex);
        goto out;
    }

    log_transid = root->log_transid;
    if (log_transid % 2 == 0)
        mark = EXTENT_DIRTY;
    else
        mark = EXTENT_NEW;

    /* we start IO on  all the marked extents here, but we don't actually
     * wait for them until later.
     */
    ret = btrfs_write_marked_extents(log, &log->dirty_log_pages, mark);
    if (ret) {
        btrfs_abort_transaction(trans, root, ret);
        mutex_unlock(&root->log_mutex);
        goto out;
    }

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

    root->log_transid++;
    log->log_transid = root->log_transid;
    root->log_start_pid = 0;
    smp_mb();
    /*
     * IO has been started, blocks of the log tree have WRITTEN flag set
     * in their headers. new modifications of the log will be written to
     * new positions. so it's safe to allow log writers to go in.
     */
    mutex_unlock(&root->log_mutex);

    mutex_lock(&log_root_tree->log_mutex);
    atomic_inc(&log_root_tree->log_batch);
    atomic_inc(&log_root_tree->log_writers);
    mutex_unlock(&log_root_tree->log_mutex);

    ret = update_log_root(trans, log);

    mutex_lock(&log_root_tree->log_mutex);
    if (atomic_dec_and_test(&log_root_tree->log_writers)) {
        smp_mb();
        if (waitqueue_active(&log_root_tree->log_writer_wait))
            wake_up(&log_root_tree->log_writer_wait);
    }

    if (ret) {
        if (ret != -ENOSPC) {
            btrfs_abort_transaction(trans, root, ret);
            mutex_unlock(&log_root_tree->log_mutex);
            goto out;
        }
        root->fs_info->last_trans_log_full_commit = trans->transid;
        btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
        mutex_unlock(&log_root_tree->log_mutex);
        ret = -EAGAIN;
        goto out;
    }

    index2 = log_root_tree->log_transid % 2;
    if (atomic_read(&log_root_tree->log_commit[index2])) {
        btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
        wait_log_commit(trans, log_root_tree,
                log_root_tree->log_transid);
        mutex_unlock(&log_root_tree->log_mutex);
        ret = 0;
        goto out;
    }
    atomic_set(&log_root_tree->log_commit[index2], 1);

    if (atomic_read(&log_root_tree->log_commit[(index2 + 1) % 2])) {
        wait_log_commit(trans, log_root_tree,
                log_root_tree->log_transid - 1);
    }

    wait_for_writer(trans, log_root_tree);

    /*
     * now that we've moved on to the tree of log tree roots,
     * check the full commit flag again
     */
    if (root->fs_info->last_trans_log_full_commit == trans->transid) {
        btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
        mutex_unlock(&log_root_tree->log_mutex);
        ret = -EAGAIN;
        goto out_wake_log_root;
    }

    ret = btrfs_write_and_wait_marked_extents(log_root_tree,
                &log_root_tree->dirty_log_pages,
                EXTENT_DIRTY | EXTENT_NEW);
    if (ret) {
        btrfs_abort_transaction(trans, root, ret);
        mutex_unlock(&log_root_tree->log_mutex);
        goto out_wake_log_root;
    }
    btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);

    btrfs_set_super_log_root(root->fs_info->super_for_commit,
                log_root_tree->node->start);
    btrfs_set_super_log_root_level(root->fs_info->super_for_commit,
                btrfs_header_level(log_root_tree->node));

    log_root_tree->log_transid++;
    smp_mb();

    mutex_unlock(&log_root_tree->log_mutex);

    /*
     * nobody else is going to jump in and write the the ctree
     * super here because the log_commit atomic below is protecting
     * us.  We must be called with a transaction handle pinning
     * the running transaction open, so a full commit can't hop
     * in and cause problems either.
     */
    btrfs_scrub_pause_super(root);
    ret = write_ctree_super(trans, root->fs_info->tree_root, 1);
    btrfs_scrub_continue_super(root);
    if (ret) {
        btrfs_abort_transaction(trans, root, ret);
        goto out_wake_log_root;
    }

    mutex_lock(&root->log_mutex);
    if (root->last_log_commit < log_transid)
        root->last_log_commit = log_transid;
    mutex_unlock(&root->log_mutex);

out_wake_log_root:
    atomic_set(&log_root_tree->log_commit[index2], 0);
    smp_mb();
    if (waitqueue_active(&log_root_tree->log_commit_wait[index2]))
        wake_up(&log_root_tree->log_commit_wait[index2]);
out:
    atomic_set(&root->log_commit[index1], 0);
    smp_mb();
    if (waitqueue_active(&root->log_commit_wait[index1]))
        wake_up(&root->log_commit_wait[index1]);
    return ret;
}

static void free_log_tree(struct btrfs_trans_handle *trans,
              struct btrfs_root *log)
{
    int ret;
    u64 start;
    u64 end;
    struct walk_control wc = {
        .free = 1,
        .process_func = process_one_buffer
    };

    ret = walk_log_tree(trans, log, &wc);
    BUG_ON(ret);

    while (1) {
        ret = find_first_extent_bit(&log->dirty_log_pages,
                0, &start, &end, EXTENT_DIRTY | EXTENT_NEW,
                NULL);
        if (ret)
            break;

        clear_extent_bits(&log->dirty_log_pages, start, end,
                  EXTENT_DIRTY | EXTENT_NEW, GFP_NOFS);
    }

    free_extent_buffer(log->node);
    kfree(log);
}

/*
 * free all the extents used by the tree log.  This should be called
 * at commit time of the full transaction
 */
int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root)
{
    if (root->log_root) {
        free_log_tree(trans, root->log_root);
        root->log_root = NULL;
    }
    return 0;
}

int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans,
                 struct btrfs_fs_info *fs_info)
{
    if (fs_info->log_root_tree) {
        free_log_tree(trans, fs_info->log_root_tree);
        fs_info->log_root_tree = NULL;
    }
    return 0;
}

/*
 * If both a file and directory are logged, and unlinks or renames are
 * mixed in, we have a few interesting corners:
 *
 * create file X in dir Y
 * link file X to X.link in dir Y
 * fsync file X
 * unlink file X but leave X.link
 * fsync dir Y
 *
 * After a crash we would expect only X.link to exist.  But file X
 * didn't get fsync'd again so the log has back refs for X and X.link.
 *
 * We solve this by removing directory entries and inode backrefs from the
 * log when a file that was logged in the current transaction is
 * unlinked.  Any later fsync will include the updated log entries, and
 * we'll be able to reconstruct the proper directory items from backrefs.
 *
 * This optimizations allows us to avoid relogging the entire inode
 * or the entire directory.
 */
int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root,
                 const char *name, int name_len,
                 struct inode *dir, u64 index)
{
    struct btrfs_root *log;
    struct btrfs_dir_item *di;
    struct btrfs_path *path;
    int ret;
    int err = 0;
    int bytes_del = 0;
    u64 dir_ino = btrfs_ino(dir);

    if (BTRFS_I(dir)->logged_trans < trans->transid)
        return 0;

    ret = join_running_log_trans(root);
    if (ret)
        return 0;

    mutex_lock(&BTRFS_I(dir)->log_mutex);

    log = root->log_root;
    path = btrfs_alloc_path();
    if (!path) {
        err = -ENOMEM;
        goto out_unlock;
    }

    di = btrfs_lookup_dir_item(trans, log, path, dir_ino,
                   name, name_len, -1);
    if (IS_ERR(di)) {
        err = PTR_ERR(di);
        goto fail;
    }
    if (di) {
        ret = btrfs_delete_one_dir_name(trans, log, path, di);
        bytes_del += name_len;
        BUG_ON(ret);
    }
    btrfs_release_path(path);
    di = btrfs_lookup_dir_index_item(trans, log, path, dir_ino,
                     index, name, name_len, -1);
    if (IS_ERR(di)) {
        err = PTR_ERR(di);
        goto fail;
    }
    if (di) {
        ret = btrfs_delete_one_dir_name(trans, log, path, di);
        bytes_del += name_len;
        BUG_ON(ret);
    }

    /* update the directory size in the log to reflect the names
     * we have removed
     */
    if (bytes_del) {
        struct btrfs_key key;

        key.objectid = dir_ino;
        key.offset = 0;
        key.type = BTRFS_INODE_ITEM_KEY;
        btrfs_release_path(path);

        ret = btrfs_search_slot(trans, log, &key, path, 0, 1);
        if (ret < 0) {
            err = ret;
            goto fail;
        }
        if (ret == 0) {
            struct btrfs_inode_item *item;
            u64 i_size;

            item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                          struct btrfs_inode_item);
            i_size = btrfs_inode_size(path->nodes[0], item);
            if (i_size > bytes_del)
                i_size -= bytes_del;
            else
                i_size = 0;
            btrfs_set_inode_size(path->nodes[0], item, i_size);
            btrfs_mark_buffer_dirty(path->nodes[0]);
        } else
            ret = 0;
        btrfs_release_path(path);
    }
fail:
    btrfs_free_path(path);
out_unlock:
    mutex_unlock(&BTRFS_I(dir)->log_mutex);
    if (ret == -ENOSPC) {
        root->fs_info->last_trans_log_full_commit = trans->transid;
        ret = 0;
    } else if (ret < 0)
        btrfs_abort_transaction(trans, root, ret);

    btrfs_end_log_trans(root);

    return err;
}

/* see comments for btrfs_del_dir_entries_in_log */
int btrfs_del_inode_ref_in_log(struct btrfs_trans_handle *trans,
                   struct btrfs_root *root,
                   const char *name, int name_len,
                   struct inode *inode, u64 dirid)
{
    struct btrfs_root *log;
    u64 index;
    int ret;

    if (BTRFS_I(inode)->logged_trans < trans->transid)
        return 0;

    ret = join_running_log_trans(root);
    if (ret)
        return 0;
    log = root->log_root;
    mutex_lock(&BTRFS_I(inode)->log_mutex);

    ret = btrfs_del_inode_ref(trans, log, name, name_len, btrfs_ino(inode),
                  dirid, &index);
    mutex_unlock(&BTRFS_I(inode)->log_mutex);
    if (ret == -ENOSPC) {
        root->fs_info->last_trans_log_full_commit = trans->transid;
        ret = 0;
    } else if (ret < 0 && ret != -ENOENT)
        btrfs_abort_transaction(trans, root, ret);
    btrfs_end_log_trans(root);

    return ret;
}

/*
 * creates a range item in the log for 'dirid'.  first_offset and
 * last_offset tell us which parts of the key space the log should
 * be considered authoritative for.
 */
static noinline int insert_dir_log_key(struct btrfs_trans_handle *trans,
                       struct btrfs_root *log,
                       struct btrfs_path *path,
                       int key_type, u64 dirid,
                       u64 first_offset, u64 last_offset)
{
    int ret;
    struct btrfs_key key;
    struct btrfs_dir_log_item *item;

    key.objectid = dirid;
    key.offset = first_offset;
    if (key_type == BTRFS_DIR_ITEM_KEY)
        key.type = BTRFS_DIR_LOG_ITEM_KEY;
    else
        key.type = BTRFS_DIR_LOG_INDEX_KEY;
    ret = btrfs_insert_empty_item(trans, log, path, &key, sizeof(*item));
    if (ret)
        return ret;

    item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                  struct btrfs_dir_log_item);
    btrfs_set_dir_log_end(path->nodes[0], item, last_offset);
    btrfs_mark_buffer_dirty(path->nodes[0]);
    btrfs_release_path(path);
    return 0;
}

/*
 * log all the items included in the current transaction for a given
 * directory.  This also creates the range items in the log tree required
 * to replay anything deleted before the fsync
 */
static noinline int log_dir_items(struct btrfs_trans_handle *trans,
              struct btrfs_root *root, struct inode *inode,
              struct btrfs_path *path,
              struct btrfs_path *dst_path, int key_type,
              u64 min_offset, u64 *last_offset_ret)
{
    struct btrfs_key min_key;
    struct btrfs_key max_key;
    struct btrfs_root *log = root->log_root;
    struct extent_buffer *src;
    int err = 0;
    int ret;
    int i;
    int nritems;
    u64 first_offset = min_offset;
    u64 last_offset = (u64)-1;
    u64 ino = btrfs_ino(inode);

    log = root->log_root;
    max_key.objectid = ino;
    max_key.offset = (u64)-1;
    max_key.type = key_type;

    min_key.objectid = ino;
    min_key.type = key_type;
    min_key.offset = min_offset;

    path->keep_locks = 1;

    ret = btrfs_search_forward(root, &min_key, &max_key,
                   path, 0, trans->transid);

    /*
     * we didn't find anything from this transaction, see if there
     * is anything at all
     */
    if (ret != 0 || min_key.objectid != ino || min_key.type != key_type) {
        min_key.objectid = ino;
        min_key.type = key_type;
        min_key.offset = (u64)-1;
        btrfs_release_path(path);
        ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
        if (ret < 0) {
            btrfs_release_path(path);
            return ret;
        }
        ret = btrfs_previous_item(root, path, ino, key_type);

        /* if ret == 0 there are items for this type,
         * create a range to tell us the last key of this type.
         * otherwise, there are no items in this directory after
         * *min_offset, and we create a range to indicate that.
         */
        if (ret == 0) {
            struct btrfs_key tmp;
            btrfs_item_key_to_cpu(path->nodes[0], &tmp,
                          path->slots[0]);
            if (key_type == tmp.type)
                first_offset = max(min_offset, tmp.offset) + 1;
        }
        goto done;
    }

    /* go backward to find any previous key */
    ret = btrfs_previous_item(root, path, ino, key_type);
    if (ret == 0) {
        struct btrfs_key tmp;
        btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);
        if (key_type == tmp.type) {
            first_offset = tmp.offset;
            ret = overwrite_item(trans, log, dst_path,
                         path->nodes[0], path->slots[0],
                         &tmp);
            if (ret) {
                err = ret;
                goto done;
            }
        }
    }
    btrfs_release_path(path);

    /* find the first key from this transaction again */
    ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
    if (ret != 0) {
        WARN_ON(1);
        goto done;
    }

    /*
     * we have a block from this transaction, log every item in it
     * from our directory
     */
    while (1) {
        struct btrfs_key tmp;
        src = path->nodes[0];
        nritems = btrfs_header_nritems(src);
        for (i = path->slots[0]; i < nritems; i++) {
            btrfs_item_key_to_cpu(src, &min_key, i);

            if (min_key.objectid != ino || min_key.type != key_type)
                goto done;
            ret = overwrite_item(trans, log, dst_path, src, i,
                         &min_key);
            if (ret) {
                err = ret;
                goto done;
            }
        }
        path->slots[0] = nritems;

        /*
         * look ahead to the next item and see if it is also
         * from this directory and from this transaction
         */
        ret = btrfs_next_leaf(root, path);
        if (ret == 1) {
            last_offset = (u64)-1;
            goto done;
        }
        btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);
        if (tmp.objectid != ino || tmp.type != key_type) {
            last_offset = (u64)-1;
            goto done;
        }
        if (btrfs_header_generation(path->nodes[0]) != trans->transid) {
            ret = overwrite_item(trans, log, dst_path,
                         path->nodes[0], path->slots[0],
                         &tmp);
            if (ret)
                err = ret;
            else
                last_offset = tmp.offset;
            goto done;
        }
    }
done:
    btrfs_release_path(path);
    btrfs_release_path(dst_path);

    if (err == 0) {
        *last_offset_ret = last_offset;
        /*
         * insert the log range keys to indicate where the log
         * is valid
         */
        ret = insert_dir_log_key(trans, log, path, key_type,
                     ino, first_offset, last_offset);
        if (ret)
            err = ret;
    }
    return err;
}

/*
 * logging directories is very similar to logging inodes, We find all the items
 * from the current transaction and write them to the log.
 *
 * The recovery code scans the directory in the subvolume, and if it finds a
 * key in the range logged that is not present in the log tree, then it means
 * that dir entry was unlinked during the transaction.
 *
 * In order for that scan to work, we must include one key smaller than
 * the smallest logged by this transaction and one key larger than the largest
 * key logged by this transaction.
 */
static noinline int log_directory_changes(struct btrfs_trans_handle *trans,
              struct btrfs_root *root, struct inode *inode,
              struct btrfs_path *path,
              struct btrfs_path *dst_path)
{
    u64 min_key;
    u64 max_key;
    int ret;
    int key_type = BTRFS_DIR_ITEM_KEY;

again:
    min_key = 0;
    max_key = 0;
    while (1) {
        ret = log_dir_items(trans, root, inode, path,
                    dst_path, key_type, min_key,
                    &max_key);
        if (ret)
            return ret;
        if (max_key == (u64)-1)
            break;
        min_key = max_key + 1;
    }

    if (key_type == BTRFS_DIR_ITEM_KEY) {
        key_type = BTRFS_DIR_INDEX_KEY;
        goto again;
    }
    return 0;
}

/*
 * a helper function to drop items from the log before we relog an
 * inode.  max_key_type indicates the highest item type to remove.
 * This cannot be run for file data extents because it does not
 * free the extents they point to.
 */
static int drop_objectid_items(struct btrfs_trans_handle *trans,
                  struct btrfs_root *log,
                  struct btrfs_path *path,
                  u64 objectid, int max_key_type)
{
    int ret;
    struct btrfs_key key;
    struct btrfs_key found_key;
    int start_slot;

    key.objectid = objectid;
    key.type = max_key_type;
    key.offset = (u64)-1;

    while (1) {
        ret = btrfs_search_slot(trans, log, &key, path, -1, 1);
        BUG_ON(ret == 0);
        if (ret < 0)
            break;

        if (path->slots[0] == 0)
            break;

        path->slots[0]--;
        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                      path->slots[0]);

        if (found_key.objectid != objectid)
            break;

        found_key.offset = 0;
        found_key.type = 0;
        ret = btrfs_bin_search(path->nodes[0], &found_key, 0,
                       &start_slot);

        ret = btrfs_del_items(trans, log, path, start_slot,
                      path->slots[0] - start_slot + 1);
        /*
         * If start slot isn't 0 then we don't need to re-search, we've
         * found the last guy with the objectid in this tree.
         */
        if (ret || start_slot != 0)
            break;
        btrfs_release_path(path);
    }
    btrfs_release_path(path);
    if (ret > 0)
        ret = 0;
    return ret;
}

static void fill_inode_item(struct btrfs_trans_handle *trans,
                struct extent_buffer *leaf,
                struct btrfs_inode_item *item,
                struct inode *inode, int log_inode_only)
{
    btrfs_set_inode_uid(leaf, item, i_uid_read(inode));
    btrfs_set_inode_gid(leaf, item, i_gid_read(inode));
    btrfs_set_inode_mode(leaf, item, inode->i_mode);
    btrfs_set_inode_nlink(leaf, item, inode->i_nlink);

    btrfs_set_timespec_sec(leaf, btrfs_inode_atime(item),
                   inode->i_atime.tv_sec);
    btrfs_set_timespec_nsec(leaf, btrfs_inode_atime(item),
                inode->i_atime.tv_nsec);

    btrfs_set_timespec_sec(leaf, btrfs_inode_mtime(item),
                   inode->i_mtime.tv_sec);
    btrfs_set_timespec_nsec(leaf, btrfs_inode_mtime(item),
                inode->i_mtime.tv_nsec);

    btrfs_set_timespec_sec(leaf, btrfs_inode_ctime(item),
                   inode->i_ctime.tv_sec);
    btrfs_set_timespec_nsec(leaf, btrfs_inode_ctime(item),
                inode->i_ctime.tv_nsec);

    btrfs_set_inode_nbytes(leaf, item, inode_get_bytes(inode));

    btrfs_set_inode_sequence(leaf, item, inode->i_version);
    btrfs_set_inode_transid(leaf, item, trans->transid);
    btrfs_set_inode_rdev(leaf, item, inode->i_rdev);
    btrfs_set_inode_flags(leaf, item, BTRFS_I(inode)->flags);
    btrfs_set_inode_block_group(leaf, item, 0);

    if (log_inode_only) {
        /* set the generation to zero so the recover code
         * can tell the difference between an logging
         * just to say 'this inode exists' and a logging
         * to say 'update this inode with these values'
         */
        btrfs_set_inode_generation(leaf, item, 0);
        btrfs_set_inode_size(leaf, item, 0);
    } else {
        btrfs_set_inode_generation(leaf, item,
                       BTRFS_I(inode)->generation);
        btrfs_set_inode_size(leaf, item, inode->i_size);
    }

}

static noinline int copy_items(struct btrfs_trans_handle *trans,
                   struct inode *inode,
                   struct btrfs_path *dst_path,
                   struct extent_buffer *src,
                   int start_slot, int nr, int inode_only)
{
    unsigned long src_offset;
    unsigned long dst_offset;
    struct btrfs_root *log = BTRFS_I(inode)->root->log_root;
    struct btrfs_file_extent_item *extent;
    struct btrfs_inode_item *inode_item;
    int ret;
    struct btrfs_key *ins_keys;
    u32 *ins_sizes;
    char *ins_data;
    int i;
    struct list_head ordered_sums;
    int skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

    INIT_LIST_HEAD(&ordered_sums);

    ins_data = kmalloc(nr * sizeof(struct btrfs_key) +
               nr * sizeof(u32), GFP_NOFS);
    if (!ins_data)
        return -ENOMEM;

    ins_sizes = (u32 *)ins_data;
    ins_keys = (struct btrfs_key *)(ins_data + nr * sizeof(u32));

    for (i = 0; i < nr; i++) {
        ins_sizes[i] = btrfs_item_size_nr(src, i + start_slot);
        btrfs_item_key_to_cpu(src, ins_keys + i, i + start_slot);
    }
    ret = btrfs_insert_empty_items(trans, log, dst_path,
                       ins_keys, ins_sizes, nr);
    if (ret) {
        kfree(ins_data);
        return ret;
    }

    for (i = 0; i < nr; i++, dst_path->slots[0]++) {
        dst_offset = btrfs_item_ptr_offset(dst_path->nodes[0],
                           dst_path->slots[0]);

        src_offset = btrfs_item_ptr_offset(src, start_slot + i);

        if (ins_keys[i].type == BTRFS_INODE_ITEM_KEY) {
            inode_item = btrfs_item_ptr(dst_path->nodes[0],
                            dst_path->slots[0],
                            struct btrfs_inode_item);
            fill_inode_item(trans, dst_path->nodes[0], inode_item,
                    inode, inode_only == LOG_INODE_EXISTS);
        } else {
            copy_extent_buffer(dst_path->nodes[0], src, dst_offset,
                       src_offset, ins_sizes[i]);
        }

        /* take a reference on file data extents so that truncates
         * or deletes of this inode don't have to relog the inode
         * again
         */
        if (btrfs_key_type(ins_keys + i) == BTRFS_EXTENT_DATA_KEY &&
            !skip_csum) {
            int found_type;
            extent = btrfs_item_ptr(src, start_slot + i,
                        struct btrfs_file_extent_item);

            if (btrfs_file_extent_generation(src, extent) < trans->transid)
                continue;

            found_type = btrfs_file_extent_type(src, extent);
            if (found_type == BTRFS_FILE_EXTENT_REG) {
                u64 ds, dl, cs, cl;
                ds = btrfs_file_extent_disk_bytenr(src,
                                extent);
                /* ds == 0 is a hole */
                if (ds == 0)
                    continue;

                dl = btrfs_file_extent_disk_num_bytes(src,
                                extent);
                cs = btrfs_file_extent_offset(src, extent);
                cl = btrfs_file_extent_num_bytes(src,
                                extent);
                if (btrfs_file_extent_compression(src,
                                  extent)) {
                    cs = 0;
                    cl = dl;
                }

                ret = btrfs_lookup_csums_range(
                        log->fs_info->csum_root,
                        ds + cs, ds + cs + cl - 1,
                        &ordered_sums, 0);
                BUG_ON(ret);
            }
        }
    }

    btrfs_mark_buffer_dirty(dst_path->nodes[0]);
    btrfs_release_path(dst_path);
    kfree(ins_data);

    /*
     * we have to do this after the loop above to avoid changing the
     * log tree while trying to change the log tree.
     */
    ret = 0;
    while (!list_empty(&ordered_sums)) {
        struct btrfs_ordered_sum *sums = list_entry(ordered_sums.next,
                           struct btrfs_ordered_sum,
                           list);
        if (!ret)
            ret = btrfs_csum_file_blocks(trans, log, sums);
        list_del(&sums->list);
        kfree(sums);
    }
    return ret;
}

static int extent_cmp(void *priv, struct list_head *a, struct list_head *b)
{
    struct extent_map *em1, *em2;

    em1 = list_entry(a, struct extent_map, list);
    em2 = list_entry(b, struct extent_map, list);

    if (em1->start < em2->start)
        return -1;
    else if (em1->start > em2->start)
        return 1;
    return 0;
}

struct log_args {
    struct extent_buffer *src;
    u64 next_offset;
    int start_slot;
    int nr;
};

static int log_one_extent(struct btrfs_trans_handle *trans,
              struct inode *inode, struct btrfs_root *root,
              struct extent_map *em, struct btrfs_path *path,
              struct btrfs_path *dst_path, struct log_args *args)
{
    struct btrfs_root *log = root->log_root;
    struct btrfs_file_extent_item *fi;
    struct btrfs_key key;
    u64 start = em->mod_start;
    u64 search_start = start;
    u64 len = em->mod_len;
    u64 num_bytes;
    int nritems;
    int ret;

    if (BTRFS_I(inode)->logged_trans == trans->transid) {
        ret = __btrfs_drop_extents(trans, log, inode, dst_path, start,
                       start + len, NULL, 0);
        if (ret)
            return ret;
    }

    while (len) {
        if (args->nr)
            goto next_slot;
again:
        key.objectid = btrfs_ino(inode);
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = search_start;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
            return ret;

        if (ret) {
            /*
             * A rare case were we can have an em for a section of a
             * larger extent so we need to make sure that this em
             * falls within the extent we've found.  If not we just
             * bail and go back to ye-olde way of doing things but
             * it happens often enough in testing that we need to do
             * this dance to make sure.
             */
            do {
                if (path->slots[0] == 0) {
                    btrfs_release_path(path);
                    if (search_start == 0)
                        return -ENOENT;
                    search_start--;
                    goto again;
                }

                path->slots[0]--;
                btrfs_item_key_to_cpu(path->nodes[0], &key,
                              path->slots[0]);
                if (key.objectid != btrfs_ino(inode) ||
                    key.type != BTRFS_EXTENT_DATA_KEY) {
                    btrfs_release_path(path);
                    return -ENOENT;
                }
            } while (key.offset > start);

            fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
                        struct btrfs_file_extent_item);
            num_bytes = btrfs_file_extent_num_bytes(path->nodes[0],
                                fi);
            if (key.offset + num_bytes <= start) {
                btrfs_release_path(path);
                return -ENOENT;
            }
        }
        args->src = path->nodes[0];
next_slot:
        btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
        fi = btrfs_item_ptr(args->src, path->slots[0],
                    struct btrfs_file_extent_item);
        if (args->nr &&
            args->start_slot + args->nr == path->slots[0]) {
            args->nr++;
        } else if (args->nr) {
            ret = copy_items(trans, inode, dst_path, args->src,
                     args->start_slot, args->nr,
                     LOG_INODE_ALL);
            if (ret)
                return ret;
            args->nr = 1;
            args->start_slot = path->slots[0];
        } else if (!args->nr) {
            args->nr = 1;
            args->start_slot = path->slots[0];
        }
        nritems = btrfs_header_nritems(path->nodes[0]);
        path->slots[0]++;
        num_bytes = btrfs_file_extent_num_bytes(args->src, fi);
        if (len < num_bytes) {
            /* I _think_ this is ok, envision we write to a
             * preallocated space that is adjacent to a previously
             * written preallocated space that gets merged when we
             * mark this preallocated space written.  If we do not
             * have the adjacent extent in cache then when we copy
             * this extent it could end up being larger than our EM
             * thinks it is, which is a-ok, so just set len to 0.
             */
            len = 0;
        } else {
            len -= num_bytes;
        }
        start = key.offset + num_bytes;
        args->next_offset = start;
        search_start = start;

        if (path->slots[0] < nritems) {
            if (len)
                goto next_slot;
            break;
        }

        if (args->nr) {
            ret = copy_items(trans, inode, dst_path, args->src,
                     args->start_slot, args->nr,
                     LOG_INODE_ALL);
            if (ret)
                return ret;
            args->nr = 0;
            btrfs_release_path(path);
        }
    }

    return 0;
}

static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root,
                     struct inode *inode,
                     struct btrfs_path *path,
                     struct btrfs_path *dst_path)
{
    struct log_args args;
    struct extent_map *em, *n;
    struct list_head extents;
    struct extent_map_tree *tree = &BTRFS_I(inode)->extent_tree;
    u64 test_gen;
    int ret = 0;

    INIT_LIST_HEAD(&extents);

    memset(&args, 0, sizeof(args));

    write_lock(&tree->lock);
    test_gen = root->fs_info->last_trans_committed;

    list_for_each_entry_safe(em, n, &tree->modified_extents, list) {
        list_del_init(&em->list);
        if (em->generation <= test_gen)
            continue;
        /* Need a ref to keep it from getting evicted from cache */
        atomic_inc(&em->refs);
        set_bit(EXTENT_FLAG_LOGGING, &em->flags);
        list_add_tail(&em->list, &extents);
    }

    list_sort(NULL, &extents, extent_cmp);

    while (!list_empty(&extents)) {
        em = list_entry(extents.next, struct extent_map, list);

        list_del_init(&em->list);
        clear_bit(EXTENT_FLAG_LOGGING, &em->flags);

        /*
         * If we had an error we just need to delete everybody from our
         * private list.
         */
        if (ret) {
            free_extent_map(em);
            continue;
        }

        write_unlock(&tree->lock);

        /*
         * If the previous EM and the last extent we left off on aren't
         * sequential then we need to copy the items we have and redo
         * our search
         */
        if (args.nr && em->mod_start != args.next_offset) {
            ret = copy_items(trans, inode, dst_path, args.src,
                     args.start_slot, args.nr,
                     LOG_INODE_ALL);
            if (ret) {
                free_extent_map(em);
                write_lock(&tree->lock);
                continue;
            }
            btrfs_release_path(path);
            args.nr = 0;
        }

        ret = log_one_extent(trans, inode, root, em, path, dst_path, &args);
        free_extent_map(em);
        write_lock(&tree->lock);
    }
    WARN_ON(!list_empty(&extents));
    write_unlock(&tree->lock);

    if (!ret && args.nr)
        ret = copy_items(trans, inode, dst_path, args.src,
                 args.start_slot, args.nr, LOG_INODE_ALL);
    btrfs_release_path(path);
    return ret;
}

/* log a single inode in the tree log.
 * At least one parent directory for this inode must exist in the tree
 * or be logged already.
 *
 * Any items from this inode changed by the current transaction are copied
 * to the log tree.  An extra reference is taken on any extents in this
 * file, allowing us to avoid a whole pile of corner cases around logging
 * blocks that have been removed from the tree.
 *
 * See LOG_INODE_ALL and related defines for a description of what inode_only
 * does.
 *
 * This handles both files and directories.
 */
static int btrfs_log_inode(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root, struct inode *inode,
                 int inode_only)
{
    struct btrfs_path *path;
    struct btrfs_path *dst_path;
    struct btrfs_key min_key;
    struct btrfs_key max_key;
    struct btrfs_root *log = root->log_root;
    struct extent_buffer *src = NULL;
    int err = 0;
    int ret;
    int nritems;
    int ins_start_slot = 0;
    int ins_nr;
    bool fast_search = false;
    u64 ino = btrfs_ino(inode);

    log = root->log_root;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;
    dst_path = btrfs_alloc_path();
    if (!dst_path) {
        btrfs_free_path(path);
        return -ENOMEM;
    }

    min_key.objectid = ino;
    min_key.type = BTRFS_INODE_ITEM_KEY;
    min_key.offset = 0;

    max_key.objectid = ino;


    /* today the code can only do partial logging of directories */
    if (inode_only == LOG_INODE_EXISTS || S_ISDIR(inode->i_mode))
        max_key.type = BTRFS_XATTR_ITEM_KEY;
    else
        max_key.type = (u8)-1;
    max_key.offset = (u64)-1;

    /* Only run delayed items if we are a dir or a new file */
    if (S_ISDIR(inode->i_mode) ||
        BTRFS_I(inode)->generation > root->fs_info->last_trans_committed) {
        ret = btrfs_commit_inode_delayed_items(trans, inode);
        if (ret) {
            btrfs_free_path(path);
            btrfs_free_path(dst_path);
            return ret;
        }
    }

    mutex_lock(&BTRFS_I(inode)->log_mutex);

    /*
     * a brute force approach to making sure we get the most uptodate
     * copies of everything.
     */
    if (S_ISDIR(inode->i_mode)) {
        int max_key_type = BTRFS_DIR_LOG_INDEX_KEY;

        if (inode_only == LOG_INODE_EXISTS)
            max_key_type = BTRFS_XATTR_ITEM_KEY;
        ret = drop_objectid_items(trans, log, path, ino, max_key_type);
    } else {
        if (test_and_clear_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                       &BTRFS_I(inode)->runtime_flags)) {
            ret = btrfs_truncate_inode_items(trans, log,
                             inode, 0, 0);
        } else {
            fast_search = true;
            max_key.type = BTRFS_XATTR_ITEM_KEY;
            ret = drop_objectid_items(trans, log, path, ino,
                          BTRFS_XATTR_ITEM_KEY);
        }
    }
    if (ret) {
        err = ret;
        goto out_unlock;
    }
    path->keep_locks = 1;

    while (1) {
        ins_nr = 0;
        ret = btrfs_search_forward(root, &min_key, &max_key,
                       path, 0, trans->transid);
        if (ret != 0)
            break;
again:
        /* note, ins_nr might be > 0 here, cleanup outside the loop */
        if (min_key.objectid != ino)
            break;
        if (min_key.type > max_key.type)
            break;

        src = path->nodes[0];
        if (ins_nr && ins_start_slot + ins_nr == path->slots[0]) {
            ins_nr++;
            goto next_slot;
        } else if (!ins_nr) {
            ins_start_slot = path->slots[0];
            ins_nr = 1;
            goto next_slot;
        }

        ret = copy_items(trans, inode, dst_path, src, ins_start_slot,
                 ins_nr, inode_only);
        if (ret) {
            err = ret;
            goto out_unlock;
        }
        ins_nr = 1;
        ins_start_slot = path->slots[0];
next_slot:

        nritems = btrfs_header_nritems(path->nodes[0]);
        path->slots[0]++;
        if (path->slots[0] < nritems) {
            btrfs_item_key_to_cpu(path->nodes[0], &min_key,
                          path->slots[0]);
            goto again;
        }
        if (ins_nr) {
            ret = copy_items(trans, inode, dst_path, src,
                     ins_start_slot,
                     ins_nr, inode_only);
            if (ret) {
                err = ret;
                goto out_unlock;
            }
            ins_nr = 0;
        }
        btrfs_release_path(path);

        if (min_key.offset < (u64)-1)
            min_key.offset++;
        else if (min_key.type < (u8)-1)
            min_key.type++;
        else if (min_key.objectid < (u64)-1)
            min_key.objectid++;
        else
            break;
    }
    if (ins_nr) {
        ret = copy_items(trans, inode, dst_path, src, ins_start_slot,
                 ins_nr, inode_only);
        if (ret) {
            err = ret;
            goto out_unlock;
        }
        ins_nr = 0;
    }

    if (fast_search) {
        btrfs_release_path(path);
        btrfs_release_path(dst_path);
        ret = btrfs_log_changed_extents(trans, root, inode, path,
                        dst_path);
        if (ret) {
            err = ret;
            goto out_unlock;
        }
    } else {
        struct extent_map_tree *tree = &BTRFS_I(inode)->extent_tree;
        struct extent_map *em, *n;

        list_for_each_entry_safe(em, n, &tree->modified_extents, list)
            list_del_init(&em->list);
    }

    if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {
        btrfs_release_path(path);
        btrfs_release_path(dst_path);
        ret = log_directory_changes(trans, root, inode, path, dst_path);
        if (ret) {
            err = ret;
            goto out_unlock;
        }
    }
    BTRFS_I(inode)->logged_trans = trans->transid;
    BTRFS_I(inode)->last_log_commit = BTRFS_I(inode)->last_sub_trans;
out_unlock:
    mutex_unlock(&BTRFS_I(inode)->log_mutex);

    btrfs_free_path(path);
    btrfs_free_path(dst_path);
    return err;
}

/*
 * follow the dentry parent pointers up the chain and see if any
 * of the directories in it require a full commit before they can
 * be logged.  Returns zero if nothing special needs to be done or 1 if
 * a full commit is required.
 */
static noinline int check_parent_dirs_for_sync(struct btrfs_trans_handle *trans,
                           struct inode *inode,
                           struct dentry *parent,
                           struct super_block *sb,
                           u64 last_committed)
{
    int ret = 0;
    struct btrfs_root *root;
    struct dentry *old_parent = NULL;

    /*
     * for regular files, if its inode is already on disk, we don't
     * have to worry about the parents at all.  This is because
     * we can use the last_unlink_trans field to record renames
     * and other fun in this file.
     */
    if (S_ISREG(inode->i_mode) &&
        BTRFS_I(inode)->generation <= last_committed &&
        BTRFS_I(inode)->last_unlink_trans <= last_committed)
            goto out;

    if (!S_ISDIR(inode->i_mode)) {
        if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
            goto out;
        inode = parent->d_inode;
    }

    while (1) {
        BTRFS_I(inode)->logged_trans = trans->transid;
        smp_mb();

        if (BTRFS_I(inode)->last_unlink_trans > last_committed) {
            root = BTRFS_I(inode)->root;

            /*
             * make sure any commits to the log are forced
             * to be full commits
             */
            root->fs_info->last_trans_log_full_commit =
                trans->transid;
            ret = 1;
            break;
        }

        if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
            break;

        if (IS_ROOT(parent))
            break;

        parent = dget_parent(parent);
        dput(old_parent);
        old_parent = parent;
        inode = parent->d_inode;

    }
    dput(old_parent);
out:
    return ret;
}

/*
 * helper function around btrfs_log_inode to make sure newly created
 * parent directories also end up in the log.  A minimal inode and backref
 * only logging is done of any parent directories that are older than
 * the last committed transaction
 */
int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
            struct btrfs_root *root, struct inode *inode,
            struct dentry *parent, int exists_only)
{
    int inode_only = exists_only ? LOG_INODE_EXISTS : LOG_INODE_ALL;
    struct super_block *sb;
    struct dentry *old_parent = NULL;
    int ret = 0;
    u64 last_committed = root->fs_info->last_trans_committed;

    sb = inode->i_sb;

    if (btrfs_test_opt(root, NOTREELOG)) {
        ret = 1;
        goto end_no_trans;
    }

    if (root->fs_info->last_trans_log_full_commit >
        root->fs_info->last_trans_committed) {
        ret = 1;
        goto end_no_trans;
    }

    if (root != BTRFS_I(inode)->root ||
        btrfs_root_refs(&root->root_item) == 0) {
        ret = 1;
        goto end_no_trans;
    }

    ret = check_parent_dirs_for_sync(trans, inode, parent,
                     sb, last_committed);
    if (ret)
        goto end_no_trans;

    if (btrfs_inode_in_log(inode, trans->transid)) {
        ret = BTRFS_NO_LOG_SYNC;
        goto end_no_trans;
    }

    ret = start_log_trans(trans, root);
    if (ret)
        goto end_trans;

    ret = btrfs_log_inode(trans, root, inode, inode_only);
    if (ret)
        goto end_trans;

    /*
     * for regular files, if its inode is already on disk, we don't
     * have to worry about the parents at all.  This is because
     * we can use the last_unlink_trans field to record renames
     * and other fun in this file.
     */
    if (S_ISREG(inode->i_mode) &&
        BTRFS_I(inode)->generation <= last_committed &&
        BTRFS_I(inode)->last_unlink_trans <= last_committed) {
        ret = 0;
        goto end_trans;
    }

    inode_only = LOG_INODE_EXISTS;
    while (1) {
        if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
            break;

        inode = parent->d_inode;
        if (root != BTRFS_I(inode)->root)
            break;

        if (BTRFS_I(inode)->generation >
            root->fs_info->last_trans_committed) {
            ret = btrfs_log_inode(trans, root, inode, inode_only);
            if (ret)
                goto end_trans;
        }
        if (IS_ROOT(parent))
            break;

        parent = dget_parent(parent);
        dput(old_parent);
        old_parent = parent;
    }
    ret = 0;
end_trans:
    dput(old_parent);
    if (ret < 0) {
        WARN_ON(ret != -ENOSPC);
        root->fs_info->last_trans_log_full_commit = trans->transid;
        ret = 1;
    }
    btrfs_end_log_trans(root);
end_no_trans:
    return ret;
}

/*
 * it is not safe to log dentry if the chunk root has added new
 * chunks.  This returns 0 if the dentry was logged, and 1 otherwise.
 * If this returns 1, you must commit the transaction to safely get your
 * data on disk.
 */
int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
              struct btrfs_root *root, struct dentry *dentry)
{
    struct dentry *parent = dget_parent(dentry);
    int ret;

    ret = btrfs_log_inode_parent(trans, root, dentry->d_inode, parent, 0);
    dput(parent);

    return ret;
}

/*
 * should be called during mount to recover any replay any log trees
 * from the FS
 */
int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
{
    int ret;
    struct btrfs_path *path;
    struct btrfs_trans_handle *trans;
    struct btrfs_key key;
    struct btrfs_key found_key;
    struct btrfs_key tmp_key;
    struct btrfs_root *log;
    struct btrfs_fs_info *fs_info = log_root_tree->fs_info;
    struct walk_control wc = {
        .process_func = process_one_buffer,
        .stage = 0,
    };

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

    fs_info->log_root_recovering = 1;

    trans = btrfs_start_transaction(fs_info->tree_root, 0);
    if (IS_ERR(trans)) {
        ret = PTR_ERR(trans);
        goto error;
    }

    wc.trans = trans;
    wc.pin = 1;

    ret = walk_log_tree(trans, log_root_tree, &wc);
    if (ret) {
        btrfs_error(fs_info, ret, "Failed to pin buffers while "
                "recovering log root tree.");
        goto error;
    }

again:
    key.objectid = BTRFS_TREE_LOG_OBJECTID;
    key.offset = (u64)-1;
    btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);

    while (1) {
        ret = btrfs_search_slot(NULL, log_root_tree, &key, path, 0, 0);

        if (ret < 0) {
            btrfs_error(fs_info, ret,
                    "Couldn't find tree log root.");
            goto error;
        }
        if (ret > 0) {
            if (path->slots[0] == 0)
                break;
            path->slots[0]--;
        }
        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                      path->slots[0]);
        btrfs_release_path(path);
        if (found_key.objectid != BTRFS_TREE_LOG_OBJECTID)
            break;

        log = btrfs_read_fs_root_no_radix(log_root_tree,
                          &found_key);
        if (IS_ERR(log)) {
            ret = PTR_ERR(log);
            btrfs_error(fs_info, ret,
                    "Couldn't read tree log root.");
            goto error;
        }

        tmp_key.objectid = found_key.offset;
        tmp_key.type = BTRFS_ROOT_ITEM_KEY;
        tmp_key.offset = (u64)-1;

        wc.replay_dest = btrfs_read_fs_root_no_name(fs_info, &tmp_key);
        if (IS_ERR(wc.replay_dest)) {
            ret = PTR_ERR(wc.replay_dest);
            btrfs_error(fs_info, ret, "Couldn't read target root "
                    "for tree log recovery.");
            goto error;
        }

        wc.replay_dest->log_root = log;
        btrfs_record_root_in_trans(trans, wc.replay_dest);
        ret = walk_log_tree(trans, log, &wc);
        BUG_ON(ret);

        if (wc.stage == LOG_WALK_REPLAY_ALL) {
            ret = fixup_inode_link_counts(trans, wc.replay_dest,
                              path);
            BUG_ON(ret);
        }

        key.offset = found_key.offset - 1;
        wc.replay_dest->log_root = NULL;
        free_extent_buffer(log->node);
        free_extent_buffer(log->commit_root);
        kfree(log);

        if (found_key.offset == 0)
            break;
    }
    btrfs_release_path(path);

    /* step one is to pin it all, step two is to replay just inodes */
    if (wc.pin) {
        wc.pin = 0;
        wc.process_func = replay_one_buffer;
        wc.stage = LOG_WALK_REPLAY_INODES;
        goto again;
    }
    /* step three is to replay everything */
    if (wc.stage < LOG_WALK_REPLAY_ALL) {
        wc.stage++;
        goto again;
    }

    btrfs_free_path(path);

    free_extent_buffer(log_root_tree->node);
    log_root_tree->log_root = NULL;
    fs_info->log_root_recovering = 0;

    /* step 4: commit the transaction, which also unpins the blocks */
    btrfs_commit_transaction(trans, fs_info->tree_root);

    kfree(log_root_tree);
    return 0;

error:
    btrfs_free_path(path);
    return ret;
}

/*
 * there are some corner cases where we want to force a full
 * commit instead of allowing a directory to be logged.
 *
 * They revolve around files there were unlinked from the directory, and
 * this function updates the parent directory so that a full commit is
 * properly done if it is fsync'd later after the unlinks are done.
 */
void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans,
                 struct inode *dir, struct inode *inode,
                 int for_rename)
{
    /*
     * when we're logging a file, if it hasn't been renamed
     * or unlinked, and its inode is fully committed on disk,
     * we don't have to worry about walking up the directory chain
     * to log its parents.
     *
     * So, we use the last_unlink_trans field to put this transid
     * into the file.  When the file is logged we check it and
     * don't log the parents if the file is fully on disk.
     */
    if (S_ISREG(inode->i_mode))
        BTRFS_I(inode)->last_unlink_trans = trans->transid;

    /*
     * if this directory was already logged any new
     * names for this file/dir will get recorded
     */
    smp_mb();
    if (BTRFS_I(dir)->logged_trans == trans->transid)
        return;

    /*
     * if the inode we're about to unlink was logged,
     * the log will be properly updated for any new names
     */
    if (BTRFS_I(inode)->logged_trans == trans->transid)
        return;

    /*
     * when renaming files across directories, if the directory
     * there we're unlinking from gets fsync'd later on, there's
     * no way to find the destination directory later and fsync it
     * properly.  So, we have to be conservative and force commits
     * so the new name gets discovered.
     */
    if (for_rename)
        goto record;

    /* we can safely do the unlink without any special recording */
    return;

record:
    BTRFS_I(dir)->last_unlink_trans = trans->transid;
}

/*
 * Call this after adding a new name for a file and it will properly
 * update the log to reflect the new name.
 *
 * It will return zero if all goes well, and it will return 1 if a
 * full transaction commit is required.
 */
int btrfs_log_new_name(struct btrfs_trans_handle *trans,
            struct inode *inode, struct inode *old_dir,
            struct dentry *parent)
{
    struct btrfs_root * root = BTRFS_I(inode)->root;

    /*
     * this will force the logging code to walk the dentry chain
     * up for the file
     */
    if (S_ISREG(inode->i_mode))
        BTRFS_I(inode)->last_unlink_trans = trans->transid;

    /*
     * if this inode hasn't been logged and directory we're renaming it
     * from hasn't been logged, we don't need to log it
     */
    if (BTRFS_I(inode)->logged_trans <=
        root->fs_info->last_trans_committed &&
        (!old_dir || BTRFS_I(old_dir)->logged_trans <=
            root->fs_info->last_trans_committed))
        return 0;

    return btrfs_log_inode_parent(trans, root, inode, parent, 1);
}