/*
 * 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 "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "locking.h"
#include "print-tree.h"
#include "compat.h"
#include "tree-log.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;

        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;
                }

                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);
                BUG_ON(ret);
        }
        if (!root->log_root) {
                ret = btrfs_add_log_tree(trans, root);
                BUG_ON(ret);
        }
        mutex_unlock(&root->fs_info->tree_log_mutex);
        root->log_batch++;
        atomic_inc(&root->log_writers);
        mutex_unlock(&root->log_mutex);
        return 0;
}

/*
 * 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
 */
int 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);
        }
        return 0;
}


/*
 * 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(log->fs_info->extent_root,
                                 eb->start, eb->len, 0);

        if (btrfs_buffer_uptodate(eb, gen)) {
                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(root, path);
                        return 0;
                }
                dst_copy = kmalloc(item_size, GFP_NOFS);
                src_copy = kmalloc(item_size, GFP_NOFS);

                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(root, path);
                        return 0;
                }

        }
insert:
        btrfs_release_path(root, 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) {
                        ret = btrfs_extend_item(trans, root, path,
                                                item_size - found_size);
                        BUG_ON(ret);
                }
        } else if (ret) {
                BUG();
        }
        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(root, 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);
        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 alloc_hint;
        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, inode->i_ino,
                                       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(root, path);
                        goto out;
                }
        }
        btrfs_release_path(root, path);

        saved_nbytes = inode_get_bytes(inode);
        /* drop any overlapping extents */
        ret = btrfs_drop_extents(trans, root, inode,
                         start, extent_end, extent_end, start, &alloc_hint, 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);
                        } 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(root, 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);
                        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(root, 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);
        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);
        read_extent_buffer(leaf, name, (unsigned long)(di + 1), name_len);
        btrfs_release_path(root, path);

        inode = read_one_inode(root, location.objectid);
        BUG_ON(!inode);

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

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


/*
 * 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;
        int ret;
        struct btrfs_key location;
        struct btrfs_inode_ref *ref;
        struct btrfs_dir_item *di;
        struct inode *inode;
        char *name;
        int namelen;
        unsigned long ref_ptr;
        unsigned long ref_end;

        location.objectid = key->objectid;
        location.type = BTRFS_INODE_ITEM_KEY;
        location.offset = 0;

        /*
         * 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, key->offset);
        if (!dir)
                return -ENOENT;

        inode = read_one_inode(root, key->objectid);
        BUG_ON(!inode);

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

again:
        ref = (struct btrfs_inode_ref *)ref_ptr;

        namelen = btrfs_inode_ref_name_len(eb, ref);
        name = kmalloc(namelen, GFP_NOFS);
        BUG_ON(!name);

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

        /* if we already have a perfect match, we're done */
        if (inode_in_dir(root, path, dir->i_ino, inode->i_ino,
                         btrfs_inode_ref_index(eb, ref),
                         name, namelen)) {
                goto out;
        }

        /*
         * 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.
         */
conflict_again:
        ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
        if (ret == 0) {
                char *victim_name;
                int victim_name_len;
                struct btrfs_inode_ref *victim_ref;
                unsigned long ptr;
                unsigned long ptr_end;
                struct extent_buffer *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 (key->objectid == key->offset)
                        goto out_nowrite;

                /* 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, key, victim_name,
                                            victim_name_len)) {
                                btrfs_inc_nlink(inode);
                                btrfs_release_path(root, path);

                                ret = btrfs_unlink_inode(trans, root, dir,
                                                         inode, victim_name,
                                                         victim_name_len);
                                kfree(victim_name);
                                btrfs_release_path(root, path);
                                goto conflict_again;
                        }
                        kfree(victim_name);
                        ptr = (unsigned long)(victim_ref + 1) + victim_name_len;
                }
                BUG_ON(ret);
        }
        btrfs_release_path(root, path);

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


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

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

        btrfs_update_inode(trans, root, inode);

out:
        ref_ptr = (unsigned long)(ref + 1) + namelen;
        kfree(name);
        if (ref_ptr < ref_end)
                goto again;

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

out_nowrite:
        btrfs_release_path(root, path);
        iput(dir);
        iput(inode);
        return 0;
}

/*
 * 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;
        struct btrfs_key key;
        u64 nlink = 0;
        unsigned long ptr;
        unsigned long ptr_end;
        int name_len;

        key.objectid = inode->i_ino;
        key.type = BTRFS_INODE_REF_KEY;
        key.offset = (u64)-1;

        path = btrfs_alloc_path();

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

        if (inode->i_nlink == 0 && S_ISDIR(inode->i_mode)) {

                ret = replay_dir_deletes(trans, root, NULL, path,
                                         inode->i_ino, 1);
                BUG_ON(ret);
        }
        btrfs_free_path(path);

        return 0;
}

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);
                BUG_ON(ret);

                btrfs_release_path(root, path);
                inode = read_one_inode(root, key.offset);
                BUG_ON(!inode);

                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;
        }
        btrfs_release_path(root, path);
        return 0;
}


/*
 * 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);
        BUG_ON(!inode);

        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(root, path);
        if (ret == 0) {
                btrfs_inc_nlink(inode);
                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);
        BUG_ON(!dir);

        name_len = btrfs_dir_name_len(eb, di);
        name = kmalloc(name_len, GFP_NOFS);
        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(root, 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 (!dst_di || IS_ERR(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(root, path);
        kfree(name);
        iput(dir);
        return 0;

insert:
        btrfs_release_path(root, 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;
                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(root, 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;
                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 (!log_di || IS_ERR(log_di)) {
                        btrfs_dir_item_key_to_cpu(eb, di, &location);
                        btrfs_release_path(root, path);
                        btrfs_release_path(log, log_path);
                        inode = read_one_inode(root, location.objectid);
                        BUG_ON(!inode);

                        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);
                        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, log_path);
                kfree(name);

                ptr = (unsigned long)(di + 1);
                ptr += name_len;
        }
        ret = 0;
out:
        btrfs_release_path(root, path);
        btrfs_release_path(log, 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(root, 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(root, path);
                goto again;
        }
out:
        btrfs_release_path(root, 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;
        u32 item_size;
        int level;
        int i;
        int ret;

        btrfs_read_buffer(eb, gen);

        level = btrfs_header_level(eb);

        if (level != 0)
                return 0;

        path = btrfs_alloc_path();
        BUG_ON(!path);

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

                /* inode keys are done during the first stage */
                if (key.type == BTRFS_INODE_ITEM_KEY &&
                    wc->stage == LOG_WALK_REPLAY_INODES) {
                        struct inode *inode;
                        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, truncate away
                         * extents past the new EOF
                         */
                        if (S_ISREG(mode)) {
                                inode = read_one_inode(root,
                                                       key.objectid);
                                BUG_ON(!inode);

                                ret = btrfs_truncate_inode_items(wc->trans,
                                        root, inode, inode->i_size,
                                        BTRFS_EXTENT_DATA_KEY);
                                BUG_ON(ret);

                                /* if the nlink count is zero here, the iput
                                 * will free the inode.  We bump it to make
                                 * sure it doesn't get freed until the link
                                 * count fixup is done
                                 */
                                if (inode->i_nlink == 0) {
                                        btrfs_inc_nlink(inode);
                                        btrfs_update_inode(wc->trans,
                                                           root, inode);
                                }
                                iput(inode);
                        }
                        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_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 root_gen;
        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);
                root_gen = btrfs_header_generation(parent);

                next = btrfs_find_create_tree_block(root, bytenr, blocksize);

                wc->process_func(root, next, wc, ptr_gen);

                if (*level == 1) {
                        path->slots[*level]++;
                        if (wc->free) {
                                btrfs_read_buffer(next, ptr_gen);

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

                                WARN_ON(root_owner !=
                                        BTRFS_TREE_LOG_OBJECTID);
                                ret = btrfs_free_reserved_extent(root,
                                                         bytenr, blocksize);
                                BUG_ON(ret);
                        }
                        free_extent_buffer(next);
                        continue;
                }
                btrfs_read_buffer(next, ptr_gen);

                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);

        if (path->nodes[*level] == root->node)
                parent = path->nodes[*level];
        else
                parent = path->nodes[*level + 1];

        bytenr = path->nodes[*level]->start;

        blocksize = btrfs_level_size(root, *level);
        root_owner = btrfs_header_owner(parent);
        root_gen = btrfs_header_generation(parent);

        wc->process_func(root, path->nodes[*level], wc,
                         btrfs_header_generation(path->nodes[*level]));

        if (wc->free) {
                next = path->nodes[*level];
                btrfs_tree_lock(next);
                clean_tree_block(trans, root, next);
                btrfs_set_lock_blocking(next);
                btrfs_wait_tree_block_writeback(next);
                btrfs_tree_unlock(next);

                WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
                ret = btrfs_free_reserved_extent(root, bytenr, blocksize);
                BUG_ON(ret);
        }
        free_extent_buffer(path->nodes[*level]);
        path->nodes[*level] = NULL;
        *level += 1;

        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;
        u64 root_gen;
        int i;
        int slot;
        int ret;

        for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
                slot = path->slots[i];
                if (slot < btrfs_header_nritems(path->nodes[i]) - 1) {
                        struct extent_buffer *node;
                        node = 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);
                        root_gen = btrfs_header_generation(parent);
                        wc->process_func(root, path->nodes[*level], wc,
                                 btrfs_header_generation(path->nodes[*level]));
                        if (wc->free) {
                                struct extent_buffer *next;

                                next = path->nodes[*level];

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

                                WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
                                ret = btrfs_free_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();
        BUG_ON(!path);

        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;

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

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

                        next = path->nodes[orig_level];

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

                        WARN_ON(log->root_key.objectid !=
                                BTRFS_TREE_LOG_OBJECTID);
                        ret = btrfs_free_reserved_extent(log, next->start,
                                                         next->len);
                        BUG_ON(ret);
                }
        }

        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->log_transid < transid + 2 &&
                 atomic_read(&root->log_commit[index]));
        return 0;
}

static int wait_for_writer(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root)
{
        DEFINE_WAIT(wait);
        while (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);
        }
        return 0;
}

/*
 * 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 ret;
        struct btrfs_root *log = root->log_root;
        struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;
        u64 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) {
                unsigned long batch = root->log_batch;
                if (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 == 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;
        }

        /* 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);
        BUG_ON(ret);

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

        root->log_batch = 0;
        log_transid = root->log_transid;
        root->log_transid++;
        log->log_transid = root->log_transid;
        root->log_start_pid = 0;
        smp_mb();
        /*
         * log tree has been flushed to disk, 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);
        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);
        BUG_ON(ret);

        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);
        }

        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);
                wait_log_commit(trans, log_root_tree,
                                log_root_tree->log_transid);
                mutex_unlock(&log_root_tree->log_mutex);
                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);
                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);
        BUG_ON(ret);
        btrfs_wait_marked_extents(log, &log->dirty_log_pages);

        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_batch = 0;
        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.
         */
        write_ctree_super(trans, root->fs_info->tree_root, 1);
        ret = 0;

        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 0;
}

/*
 * 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)
{
        int ret;
        struct btrfs_root *log;
        struct key;
        u64 start;
        u64 end;
        struct walk_control wc = {
                .free = 1,
                .process_func = process_one_buffer
        };

        if (!root->log_root || root->fs_info->log_root_recovering)
                return 0;

        log = root->log_root;
        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);
                if (ret)
                        break;

                clear_extent_dirty(&log->dirty_log_pages,
                                   start, end, GFP_NOFS);
        }

        if (log->log_transid > 0) {
                ret = btrfs_del_root(trans, root->fs_info->log_root_tree,
                                     &log->root_key);
                BUG_ON(ret);
        }
        root->log_root = NULL;
        free_extent_buffer(log->node);
        kfree(log);
        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 bytes_del = 0;

        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();
        di = btrfs_lookup_dir_item(trans, log, path, dir->i_ino,
                                   name, name_len, -1);
        if (di && !IS_ERR(di)) {
                ret = btrfs_delete_one_dir_name(trans, log, path, di);
                bytes_del += name_len;
                BUG_ON(ret);
        }
        btrfs_release_path(log, path);
        di = btrfs_lookup_dir_index_item(trans, log, path, dir->i_ino,
                                         index, name, name_len, -1);
        if (di && !IS_ERR(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->i_ino;
                key.offset = 0;
                key.type = BTRFS_INODE_ITEM_KEY;
                btrfs_release_path(log, path);

                ret = btrfs_search_slot(trans, log, &key, path, 0, 1);
                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(log, path);
        }

        btrfs_free_path(path);
        mutex_unlock(&BTRFS_I(dir)->log_mutex);
        btrfs_end_log_trans(root);

        return 0;
}

/* 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, inode->i_ino,
                                  dirid, &index);
        mutex_unlock(&BTRFS_I(inode)->log_mutex);
        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));
        BUG_ON(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(log, 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 ret;
        int i;
        int nritems;
        u64 first_offset = min_offset;
        u64 last_offset = (u64)-1;

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

        min_key.objectid = inode->i_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 != inode->i_ino ||
            min_key.type != key_type) {
                min_key.objectid = inode->i_ino;
                min_key.type = key_type;
                min_key.offset = (u64)-1;
                btrfs_release_path(root, path);
                ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
                if (ret < 0) {
                        btrfs_release_path(root, path);
                        return ret;
                }
                ret = btrfs_previous_item(root, path, inode->i_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, inode->i_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);
                }
        }
        btrfs_release_path(root, 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 != inode->i_ino ||
                            min_key.type != key_type)
                                goto done;
                        ret = overwrite_item(trans, log, dst_path, src, i,
                                             &min_key);
                        BUG_ON(ret);
                }
                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 != inode->i_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);

                        BUG_ON(ret);
                        last_offset = tmp.offset;
                        goto done;
                }
        }
done:
        *last_offset_ret = last_offset;
        btrfs_release_path(root, path);
        btrfs_release_path(log, dst_path);

        /* insert the log range keys to indicate where the log is valid */
        ret = insert_dir_log_key(trans, log, path, key_type, inode->i_ino,
                                 first_offset, last_offset);
        BUG_ON(ret);
        return 0;
}

/*
 * 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);
                BUG_ON(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;

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

        while (1) {
                ret = btrfs_search_slot(trans, log, &key, path, -1, 1);

                if (ret != 1)
                        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;

                ret = btrfs_del_item(trans, log, path);
                BUG_ON(ret);
                btrfs_release_path(log, path);
        }
        btrfs_release_path(log, path);
        return 0;
}

static noinline int copy_items(struct btrfs_trans_handle *trans,
                               struct btrfs_root *log,
                               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_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;

        INIT_LIST_HEAD(&ordered_sums);

        ins_data = kmalloc(nr * sizeof(struct btrfs_key) +
                           nr * sizeof(u32), GFP_NOFS);
        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);
        BUG_ON(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);

                copy_extent_buffer(dst_path->nodes[0], src, dst_offset,
                                   src_offset, ins_sizes[i]);

                if (inode_only == LOG_INODE_EXISTS &&
                    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);
                        btrfs_set_inode_size(dst_path->nodes[0], inode_item, 0);

                        /* 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(dst_path->nodes[0],
                                                   inode_item, 0);
                }
                /* 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) {
                        int found_type;
                        extent = btrfs_item_ptr(src, start_slot + i,
                                                struct btrfs_file_extent_item);

                        found_type = btrfs_file_extent_type(src, extent);
                        if (found_type == BTRFS_FILE_EXTENT_REG ||
                            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                                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);
                                BUG_ON(ret);
                        }
                }
        }

        btrfs_mark_buffer_dirty(dst_path->nodes[0]);
        btrfs_release_path(log, 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.
         */
        while (!list_empty(&ordered_sums)) {
                struct btrfs_ordered_sum *sums = list_entry(ordered_sums.next,
                                                   struct btrfs_ordered_sum,
                                                   list);
                ret = btrfs_csum_file_blocks(trans, log, sums);
                BUG_ON(ret);
                list_del(&sums->list);
                kfree(sums);
        }
        return 0;
}

/* 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;
        u32 size;
        int ret;
        int nritems;
        int ins_start_slot = 0;
        int ins_nr;

        log = root->log_root;

        path = btrfs_alloc_path();
        dst_path = btrfs_alloc_path();

        min_key.objectid = inode->i_ino;
        min_key.type = BTRFS_INODE_ITEM_KEY;
        min_key.offset = 0;

        max_key.objectid = inode->i_ino;

        /* today the code can only do partial logging of directories */
        if (!S_ISDIR(inode->i_mode))
            inode_only = LOG_INODE_ALL;

        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;

        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,
                                          inode->i_ino, max_key_type);
        } else {
                ret = btrfs_truncate_inode_items(trans, log, inode, 0, 0);
        }
        BUG_ON(ret);
        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 != inode->i_ino)
                        break;
                if (min_key.type > max_key.type)
                        break;

                src = path->nodes[0];
                size = btrfs_item_size_nr(src, path->slots[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, log, dst_path, src, ins_start_slot,
                                 ins_nr, inode_only);
                BUG_ON(ret);
                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, log, dst_path, src,
                                         ins_start_slot,
                                         ins_nr, inode_only);
                        BUG_ON(ret);
                        ins_nr = 0;
                }
                btrfs_release_path(root, 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, log, dst_path, src,
                                 ins_start_slot,
                                 ins_nr, inode_only);
                BUG_ON(ret);
                ins_nr = 0;
        }
        WARN_ON(ins_nr);
        if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {
                btrfs_release_path(root, path);
                btrfs_release_path(log, dst_path);
                ret = log_directory_changes(trans, root, inode, path, dst_path);
                BUG_ON(ret);
        }
        BTRFS_I(inode)->logged_trans = trans->transid;
        mutex_unlock(&BTRFS_I(inode)->log_mutex);

        btrfs_free_path(path);
        btrfs_free_path(dst_path);
        return 0;
}

/*
 * 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;

        /*
         * 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 = parent->d_parent;
                inode = parent->d_inode;

        }
out:
        return ret;
}

static int inode_in_log(struct btrfs_trans_handle *trans,
                 struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        mutex_lock(&root->log_mutex);
        if (BTRFS_I(inode)->logged_trans == trans->transid &&
            BTRFS_I(inode)->last_sub_trans <= root->last_log_commit)
                ret = 1;
        mutex_unlock(&root->log_mutex);
        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;
        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 (inode_in_log(trans, inode)) {
                ret = BTRFS_NO_LOG_SYNC;
                goto end_no_trans;
        }

        start_log_trans(trans, root);

        ret = btrfs_log_inode(trans, root, inode, inode_only);
        BUG_ON(ret);

        /*
         * 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 no_parent;

        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);
                        BUG_ON(ret);
                }
                if (IS_ROOT(parent))
                        break;

                parent = parent->d_parent;
        }
no_parent:
        ret = 0;
        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)
{
        return btrfs_log_inode_parent(trans, root, dentry->d_inode,
                                      dentry->d_parent, 0);
}

/*
 * 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;