// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/list_sort.h>
#include <linux/iversion.h>
#include "misc.h"
#include "ctree.h"
#include "tree-log.h"
#include "disk-io.h"
#include "locking.h"
#include "print-tree.h"
#include "backref.h"
#include "compression.h"
#include "qgroup.h"
#include "block-group.h"
#include "space-info.h"
#include "zoned.h"
#include "inode-item.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
 */
enum {
        LOG_INODE_ALL,
        LOG_INODE_EXISTS,
        LOG_OTHER_INODE,
        LOG_OTHER_INODE_ALL,
};

/*
 * 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
 */
enum {
        LOG_WALK_PIN_ONLY,
        LOG_WALK_REPLAY_INODES,
        LOG_WALK_REPLAY_DIR_INDEX,
        LOG_WALK_REPLAY_ALL,
};

static int btrfs_log_inode(struct btrfs_trans_handle *trans,
                           struct btrfs_inode *inode,
                           int inode_only,
                           struct btrfs_log_ctx *ctx);
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);
static void wait_log_commit(struct btrfs_root *root, int transid);

/*
 * 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,
                           struct btrfs_log_ctx *ctx)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_root *tree_root = fs_info->tree_root;
        const bool zoned = btrfs_is_zoned(fs_info);
        int ret = 0;
        bool created = false;

        /*
         * First check if the log root tree was already created. If not, create
         * it before locking the root's log_mutex, just to keep lockdep happy.
         */
        if (!test_bit(BTRFS_ROOT_HAS_LOG_TREE, &tree_root->state)) {
                mutex_lock(&tree_root->log_mutex);
                if (!fs_info->log_root_tree) {
                        ret = btrfs_init_log_root_tree(trans, fs_info);
                        if (!ret) {
                                set_bit(BTRFS_ROOT_HAS_LOG_TREE, &tree_root->state);
                                created = true;
                        }
                }
                mutex_unlock(&tree_root->log_mutex);
                if (ret)
                        return ret;
        }

        mutex_lock(&root->log_mutex);

again:
        if (root->log_root) {
                int index = (root->log_transid + 1) % 2;

                if (btrfs_need_log_full_commit(trans)) {
                        ret = -EAGAIN;
                        goto out;
                }

                if (zoned && atomic_read(&root->log_commit[index])) {
                        wait_log_commit(root, root->log_transid - 1);
                        goto again;
                }

                if (!root->log_start_pid) {
                        clear_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state);
                        root->log_start_pid = current->pid;
                } else if (root->log_start_pid != current->pid) {
                        set_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state);
                }
        } else {
                /*
                 * This means fs_info->log_root_tree was already created
                 * for some other FS trees. Do the full commit not to mix
                 * nodes from multiple log transactions to do sequential
                 * writing.
                 */
                if (zoned && !created) {
                        ret = -EAGAIN;
                        goto out;
                }

                ret = btrfs_add_log_tree(trans, root);
                if (ret)
                        goto out;

                set_bit(BTRFS_ROOT_HAS_LOG_TREE, &root->state);
                clear_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state);
                root->log_start_pid = current->pid;
        }

        atomic_inc(&root->log_writers);
        if (!ctx->logging_new_name) {
                int index = root->log_transid % 2;
                list_add_tail(&ctx->list, &root->log_ctxs[index]);
                ctx->log_transid = root->log_transid;
        }

out:
        mutex_unlock(&root->log_mutex);
        return ret;
}

/*
 * 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)
{
        const bool zoned = btrfs_is_zoned(root->fs_info);
        int ret = -ENOENT;

        if (!test_bit(BTRFS_ROOT_HAS_LOG_TREE, &root->state))
                return ret;

        mutex_lock(&root->log_mutex);
again:
        if (root->log_root) {
                int index = (root->log_transid + 1) % 2;

                ret = 0;
                if (zoned && atomic_read(&root->log_commit[index])) {
                        wait_log_commit(root, root->log_transid - 1);
                        goto again;
                }
                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()
 */
void btrfs_pin_log_trans(struct btrfs_root *root)
{
        atomic_inc(&root->log_writers);
}

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

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

/*
 * 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;

        /* 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;

        /*
         * Ignore any items from the inode currently being processed. Needs
         * to be set every time we find a BTRFS_INODE_ITEM_KEY and we are in
         * the LOG_WALK_REPLAY_INODES stage.
         */
        bool ignore_cur_inode;

        /* 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, int level);
};

/*
 * 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, int level)
{
        struct btrfs_fs_info *fs_info = log->fs_info;
        int ret = 0;

        /*
         * If this fs is mixed then we need to be able to process the leaves to
         * pin down any logged extents, so we have to read the block.
         */
        if (btrfs_fs_incompat(fs_info, MIXED_GROUPS)) {
                ret = btrfs_read_extent_buffer(eb, gen, level, NULL);
                if (ret)
                        return ret;
        }

        if (wc->pin) {
                ret = btrfs_pin_extent_for_log_replay(wc->trans, eb->start,
                                                      eb->len);
                if (ret)
                        return ret;

                if (btrfs_buffer_uptodate(eb, gen, 0) &&
                    btrfs_header_level(eb) == 0)
                        ret = btrfs_exclude_logged_extents(eb);
        }
        return ret;
}

static int do_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;
        bool inode_item = key->type == BTRFS_INODE_ITEM_KEY;

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

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

        /* Our caller must have done a search for the key for us. */
        ASSERT(path->nodes[0] != NULL);

        /*
         * And the slot must point to the exact key or the slot where the key
         * should be at (the first item with a key greater than 'key')
         */
        if (path->slots[0] < btrfs_header_nritems(path->nodes[0])) {
                struct btrfs_key found_key;

                btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
                ret = btrfs_comp_cpu_keys(&found_key, key);
                ASSERT(ret >= 0);
        } else {
                ret = 1;
        }

        if (ret == 0) {
                char *src_copy;
                char *dst_copy;
                u32 dst_size = btrfs_item_size(path->nodes[0],
                                                  path->slots[0]);
                if (dst_size != item_size)
                        goto insert;

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

                read_extent_buffer(eb, src_copy, src_ptr, item_size);

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

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

                /*
                 * We need to load the old nbytes into the inode so when we
                 * replay the extents we've logged we get the right nbytes.
                 */
                if (inode_item) {
                        struct btrfs_inode_item *item;
                        u64 nbytes;
                        u32 mode;

                        item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                              struct btrfs_inode_item);
                        nbytes = btrfs_inode_nbytes(path->nodes[0], item);
                        item = btrfs_item_ptr(eb, slot,
                                              struct btrfs_inode_item);
                        btrfs_set_inode_nbytes(eb, item, nbytes);

                        /*
                         * If this is a directory we need to reset the i_size to
                         * 0 so that we can set it up properly when replaying
                         * the rest of the items in this log.
                         */
                        mode = btrfs_inode_mode(eb, item);
                        if (S_ISDIR(mode))
                                btrfs_set_inode_size(eb, item, 0);
                }
        } else if (inode_item) {
                struct btrfs_inode_item *item;
                u32 mode;

                /*
                 * New inode, set nbytes to 0 so that the nbytes comes out
                 * properly when we replay the extents.
                 */
                item = btrfs_item_ptr(eb, slot, struct btrfs_inode_item);
                btrfs_set_inode_nbytes(eb, item, 0);

                /*
                 * If this is a directory we need to reset the i_size to 0 so
                 * that we can set it up properly when replaying the rest of
                 * the items in this log.
                 */
                mode = btrfs_inode_mode(eb, item);
                if (S_ISDIR(mode))
                        btrfs_set_inode_size(eb, item, 0);
        }
insert:
        btrfs_release_path(path);
        /* try to insert the key into the destination tree */
        path->skip_release_on_error = 1;
        ret = btrfs_insert_empty_item(trans, root, path,
                                      key, item_size);
        path->skip_release_on_error = 0;

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

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

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

                if (btrfs_inode_generation(eb, src_item) == 0) {
                        struct extent_buffer *dst_eb = path->nodes[0];
                        const u64 ino_size = btrfs_inode_size(eb, src_item);

                        /*
                         * For regular files an ino_size == 0 is used only when
                         * logging that an inode exists, as part of a directory
                         * fsync, and the inode wasn't fsynced before. In this
                         * case don't set the size of the inode in the fs/subvol
                         * tree, otherwise we would be throwing valid data away.
                         */
                        if (S_ISREG(btrfs_inode_mode(eb, src_item)) &&
                            S_ISREG(btrfs_inode_mode(dst_eb, dst_item)) &&
                            ino_size != 0)
                                btrfs_set_inode_size(dst_eb, dst_item, ino_size);
                        goto no_copy;
                }

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

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

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

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

/*
 * 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 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;

        /* Look for the key in the destination tree. */
        ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
        if (ret < 0)
                return ret;

        return do_overwrite_item(trans, root, path, eb, slot, key);
}

/*
 * 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 inode *inode;

        inode = btrfs_iget(root->fs_info->sb, objectid, root);
        if (IS_ERR(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)
{
        struct btrfs_drop_extents_args drop_args = { 0 };
        struct btrfs_fs_info *fs_info = root->fs_info;
        int found_type;
        u64 extent_end;
        u64 start = key->offset;
        u64 nbytes = 0;
        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) {
                nbytes = btrfs_file_extent_num_bytes(eb, item);
                extent_end = start + nbytes;

                /*
                 * We don't add to the inodes nbytes if we are prealloc or a
                 * hole.
                 */
                if (btrfs_file_extent_disk_bytenr(eb, item) == 0)
                        nbytes = 0;
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                size = btrfs_file_extent_ram_bytes(eb, item);
                nbytes = btrfs_file_extent_ram_bytes(eb, item);
                extent_end = ALIGN(start + size,
                                   fs_info->sectorsize);
        } else {
                ret = 0;
                goto out;
        }

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

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

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

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

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

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

        /* drop any overlapping extents */
        drop_args.start = start;
        drop_args.end = extent_end;
        drop_args.drop_cache = true;
        ret = btrfs_drop_extents(trans, root, BTRFS_I(inode), &drop_args);
        if (ret)
                goto out;

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

                if (btrfs_file_extent_disk_bytenr(eb, item) == 0 &&
                    btrfs_fs_incompat(fs_info, NO_HOLES))
                        goto update_inode;

                ret = btrfs_insert_empty_item(trans, root, path, key,
                                              sizeof(*item));
                if (ret)
                        goto out;
                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);

                /*
                 * Manually record dirty extent, as here we did a shallow
                 * file extent item copy and skip normal backref update,
                 * but modifying extent tree all by ourselves.
                 * So need to manually record dirty extent for qgroup,
                 * as the owner of the file extent changed from log tree
                 * (doesn't affect qgroup) to fs/file tree(affects qgroup)
                 */
                ret = btrfs_qgroup_trace_extent(trans,
                                btrfs_file_extent_disk_bytenr(eb, item),
                                btrfs_file_extent_disk_num_bytes(eb, item),
                                GFP_NOFS);
                if (ret < 0)
                        goto out;

                if (ins.objectid > 0) {
                        struct btrfs_ref ref = { 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_data_extent(fs_info, ins.objectid,
                                                ins.offset);
                        if (ret < 0) {
                                goto out;
                        } else if (ret == 0) {
                                btrfs_init_generic_ref(&ref,
                                                BTRFS_ADD_DELAYED_REF,
                                                ins.objectid, ins.offset, 0);
                                btrfs_init_data_ref(&ref,
                                                root->root_key.objectid,
                                                key->objectid, offset, 0, false);
                                ret = btrfs_inc_extent_ref(trans, &ref);
                                if (ret)
                                        goto out;
                        } else {
                                /*
                                 * insert the extent pointer in the extent
                                 * allocation tree
                                 */
                                ret = btrfs_alloc_logged_file_extent(trans,
                                                root->root_key.objectid,
                                                key->objectid, offset, &ins);
                                if (ret)
                                        goto out;
                        }
                        btrfs_release_path(path);

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

                        ret = btrfs_lookup_csums_range(root->log_root,
                                                csum_start, csum_end - 1,
                                                &ordered_sums, 0);
                        if (ret)
                                goto out;
                        /*
                         * Now delete all existing cums in the csum root that
                         * cover our range. We do this because we can have an
                         * extent that is completely referenced by one file
                         * extent item and partially referenced by another
                         * file extent item (like after using the clone or
                         * extent_same ioctls). In this case if we end up doing
                         * the replay of the one that partially references the
                         * extent first, and we do not do the csum deletion
                         * below, we can get 2 csum items in the csum tree that
                         * overlap each other. For example, imagine our log has
                         * the two following file extent items:
                         *
                         * key (257 EXTENT_DATA 409600)
                         *     extent data disk byte 12845056 nr 102400
                         *     extent data offset 20480 nr 20480 ram 102400
                         *
                         * key (257 EXTENT_DATA 819200)
                         *     extent data disk byte 12845056 nr 102400
                         *     extent data offset 0 nr 102400 ram 102400
                         *
                         * Where the second one fully references the 100K extent
                         * that starts at disk byte 12845056, and the log tree
                         * has a single csum item that covers the entire range
                         * of the extent:
                         *
                         * key (EXTENT_CSUM EXTENT_CSUM 12845056) itemsize 100
                         *
                         * After the first file extent item is replayed, the
                         * csum tree gets the following csum item:
                         *
                         * key (EXTENT_CSUM EXTENT_CSUM 12865536) itemsize 20
                         *
                         * Which covers the 20K sub-range starting at offset 20K
                         * of our extent. Now when we replay the second file
                         * extent item, if we do not delete existing csum items
                         * that cover any of its blocks, we end up getting two
                         * csum items in our csum tree that overlap each other:
                         *
                         * key (EXTENT_CSUM EXTENT_CSUM 12845056) itemsize 100
                         * key (EXTENT_CSUM EXTENT_CSUM 12865536) itemsize 20
                         *
                         * Which is a problem, because after this anyone trying
                         * to lookup up for the checksum of any block of our
                         * extent starting at an offset of 40K or higher, will
                         * end up looking at the second csum item only, which
                         * does not contain the checksum for any block starting
                         * at offset 40K or higher of our extent.
                         */
                        while (!list_empty(&ordered_sums)) {
                                struct btrfs_ordered_sum *sums;
                                struct btrfs_root *csum_root;

                                sums = list_entry(ordered_sums.next,
                                                struct btrfs_ordered_sum,
                                                list);
                                csum_root = btrfs_csum_root(fs_info,
                                                            sums->bytenr);
                                if (!ret)
                                        ret = btrfs_del_csums(trans, csum_root,
                                                              sums->bytenr,
                                                              sums->len);
                                if (!ret)
                                        ret = btrfs_csum_file_blocks(trans,
                                                                     csum_root,
                                                                     sums);
                                list_del(&sums->list);
                                kfree(sums);
                        }
                        if (ret)
                                goto out;
                } else {
                        btrfs_release_path(path);
                }
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                /* inline extents are easy, we just overwrite them */
                ret = overwrite_item(trans, root, path, eb, slot, key);
                if (ret)
                        goto out;
        }

        ret = btrfs_inode_set_file_extent_range(BTRFS_I(inode), start,
                                                extent_end - start);
        if (ret)
                goto out;

update_inode:
        btrfs_update_inode_bytes(BTRFS_I(inode), nbytes, drop_args.bytes_found);
        ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
out:
        iput(inode);
        return ret;
}

static int unlink_inode_for_log_replay(struct btrfs_trans_handle *trans,
                                       struct btrfs_inode *dir,
                                       struct btrfs_inode *inode,
                                       const char *name,
                                       int name_len)
{
        int ret;

        ret = btrfs_unlink_inode(trans, dir, inode, name, name_len);
        if (ret)
                return ret;
        /*
         * Whenever we need to check if a name exists or not, we check the
         * fs/subvolume tree. So after an unlink we must run delayed items, so
         * that future checks for a name during log replay see that the name
         * does not exists anymore.
         */
        return btrfs_run_delayed_items(trans);
}

/*
 * 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_path *path,
                                      struct btrfs_inode *dir,
                                      struct btrfs_dir_item *di)
{
        struct btrfs_root *root = dir->root;
        struct inode *inode;
        char *name;
        int name_len;
        struct extent_buffer *leaf;
        struct btrfs_key location;
        int ret;

        leaf = path->nodes[0];

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

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

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

        ret = link_to_fixup_dir(trans, root, path, location.objectid);
        if (ret)
                goto out;

        ret = unlink_inode_for_log_replay(trans, dir, BTRFS_I(inode), name,
                        name_len);
out:
        kfree(name);
        iput(inode);
        return ret;
}

/*
 * 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.
 *
 * Returns: < 0 on error, 0 if the directory entry does not exists and 1 if it
 * exists.
 */
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 ret = 0;

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

        btrfs_release_path(path);

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

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

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

        ret = btrfs_search_slot(NULL, log, key, path, 0, 0);
        if (ret < 0) {
                goto out;
        } else if (ret == 1) {
                ret = 0;
                goto out;
        }

        if (key->type == BTRFS_INODE_EXTREF_KEY)
                ret = !!btrfs_find_name_in_ext_backref(path->nodes[0],
                                                       path->slots[0],
                                                       ref_objectid,
                                                       name, namelen);
        else
                ret = !!btrfs_find_name_in_backref(path->nodes[0],
                                                   path->slots[0],
                                                   name, namelen);
out:
        btrfs_free_path(path);
        return ret;
}

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

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

                leaf = path->nodes[0];

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

                /* check all the names in this back reference to see
                 * if they are in the log.  if so, we allow them to stay
                 * otherwise they must be unlinked as a conflict
                 */
                ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
                ptr_end = ptr + btrfs_item_size(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);
                        if (!victim_name)
                                return -ENOMEM;

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

                        ret = backref_in_log(log_root, &search_key,
                                             parent_objectid, victim_name,
                                             victim_name_len);
                        if (ret < 0) {
                                kfree(victim_name);
                                return ret;
                        } else if (!ret) {
                                inc_nlink(&inode->vfs_inode);
                                btrfs_release_path(path);

                                ret = unlink_inode_for_log_replay(trans, dir, inode,
                                                victim_name, victim_name_len);
                                kfree(victim_name);
                                if (ret)
                                        return ret;
                                *search_done = 1;
                                goto again;
                        }
                        kfree(victim_name);

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

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

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

                leaf = path->nodes[0];

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

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

                        victim_name_len = btrfs_inode_extref_name_len(leaf, extref);

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

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

                        search_key.objectid = inode_objectid;
                        search_key.type = BTRFS_INODE_EXTREF_KEY;
                        search_key.offset = btrfs_extref_hash(parent_objectid,
                                                              victim_name,
                                                              victim_name_len);
                        ret = backref_in_log(log_root, &search_key,
                                             parent_objectid, victim_name,
                                             victim_name_len);
                        if (ret < 0) {
                                kfree(victim_name);
                                return ret;
                        } else if (!ret) {
                                ret = -ENOENT;
                                victim_parent = read_one_inode(root,
                                                parent_objectid);
                                if (victim_parent) {
                                        inc_nlink(&inode->vfs_inode);
                                        btrfs_release_path(path);

                                        ret = unlink_inode_for_log_replay(trans,
                                                        BTRFS_I(victim_parent),
                                                        inode,
                                                        victim_name,
                                                        victim_name_len);
                                }
                                iput(victim_parent);
                                kfree(victim_name);
                                if (ret)
                                        return ret;
                                *search_done = 1;
                                goto again;
                        }
                        kfree(victim_name);
next:
                        cur_offset += victim_name_len + sizeof(*extref);
                }
                *search_done = 1;
        }
        btrfs_release_path(path);

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

        /* look for a conflicting name */
        di = btrfs_lookup_dir_item(trans, root, path, btrfs_ino(dir),
                                   name, namelen, 0);
        if (IS_ERR(di)) {
                return PTR_ERR(di);
        } else if (di) {
                ret = drop_one_dir_item(trans, path, dir, di);
                if (ret)
                        return ret;
        }
        btrfs_release_path(path);

        return 0;
}

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

        extref = (struct btrfs_inode_extref *)ref_ptr;

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

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

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

        return 0;
}

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

        ref = (struct btrfs_inode_ref *)ref_ptr;

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

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

        if (index)
                *index = btrfs_inode_ref_index(eb, ref);

        return 0;
}

/*
 * Take an inode reference item from the log tree and iterate all names from the
 * inode reference item in the subvolume tree with the same key (if it exists).
 * For any name that is not in the inode reference item from the log tree, do a
 * proper unlink of that name (that is, remove its entry from the inode
 * reference item and both dir index keys).
 */
static int unlink_old_inode_refs(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_inode *inode,
                                 struct extent_buffer *log_eb,
                                 int log_slot,
                                 struct btrfs_key *key)
{
        int ret;
        unsigned long ref_ptr;
        unsigned long ref_end;
        struct extent_buffer *eb;

again:
        btrfs_release_path(path);
        ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
        if (ret > 0) {
                ret = 0;
                goto out;
        }
        if (ret < 0)
                goto out;

        eb = path->nodes[0];
        ref_ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
        ref_end = ref_ptr + btrfs_item_size(eb, path->slots[0]);
        while (ref_ptr < ref_end) {
                char *name = NULL;
                int namelen;
                u64 parent_id;

                if (key->type == BTRFS_INODE_EXTREF_KEY) {
                        ret = extref_get_fields(eb, ref_ptr, &namelen, &name,
                                                NULL, &parent_id);
                } else {
                        parent_id = key->offset;
                        ret = ref_get_fields(eb, ref_ptr, &namelen, &name,
                                             NULL);
                }
                if (ret)
                        goto out;

                if (key->type == BTRFS_INODE_EXTREF_KEY)
                        ret = !!btrfs_find_name_in_ext_backref(log_eb, log_slot,
                                                               parent_id, name,
                                                               namelen);
                else
                        ret = !!btrfs_find_name_in_backref(log_eb, log_slot,
                                                           name, namelen);

                if (!ret) {
                        struct inode *dir;

                        btrfs_release_path(path);
                        dir = read_one_inode(root, parent_id);
                        if (!dir) {
                                ret = -ENOENT;
                                kfree(name);
                                goto out;
                        }
                        ret = unlink_inode_for_log_replay(trans, BTRFS_I(dir),
                                                 inode, name, namelen);
                        kfree(name);
                        iput(dir);
                        if (ret)
                                goto out;
                        goto again;
                }

                kfree(name);
                ref_ptr += namelen;
                if (key->type == BTRFS_INODE_EXTREF_KEY)
                        ref_ptr += sizeof(struct btrfs_inode_extref);
                else
                        ref_ptr += sizeof(struct btrfs_inode_ref);
        }
        ret = 0;
 out:
        btrfs_release_path(path);
        return ret;
}

static int btrfs_inode_ref_exists(struct inode *inode, struct inode *dir,
                                  const u8 ref_type, const char *name,
                                  const int namelen)
{
        struct btrfs_key key;
        struct btrfs_path *path;
        const u64 parent_id = btrfs_ino(BTRFS_I(dir));
        int ret;

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

        key.objectid = btrfs_ino(BTRFS_I(inode));
        key.type = ref_type;
        if (key.type == BTRFS_INODE_REF_KEY)
                key.offset = parent_id;
        else
                key.offset = btrfs_extref_hash(parent_id, name, namelen);

        ret = btrfs_search_slot(NULL, BTRFS_I(inode)->root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = 0;
                goto out;
        }
        if (key.type == BTRFS_INODE_EXTREF_KEY)
                ret = !!btrfs_find_name_in_ext_backref(path->nodes[0],
                                path->slots[0], parent_id, name, namelen);
        else
                ret = !!btrfs_find_name_in_backref(path->nodes[0], path->slots[0],
                                                   name, namelen);

out:
        btrfs_free_path(path);
        return ret;
}

static int add_link(struct btrfs_trans_handle *trans,
                    struct inode *dir, struct inode *inode, const char *name,
                    int namelen, u64 ref_index)
{
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_dir_item *dir_item;
        struct btrfs_key key;
        struct btrfs_path *path;
        struct inode *other_inode = NULL;
        int ret;

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

        dir_item = btrfs_lookup_dir_item(NULL, root, path,
                                         btrfs_ino(BTRFS_I(dir)),
                                         name, namelen, 0);
        if (!dir_item) {
                btrfs_release_path(path);
                goto add_link;
        } else if (IS_ERR(dir_item)) {
                ret = PTR_ERR(dir_item);
                goto out;
        }

        /*
         * Our inode's dentry collides with the dentry of another inode which is
         * in the log but not yet processed since it has a higher inode number.
         * So delete that other dentry.
         */
        btrfs_dir_item_key_to_cpu(path->nodes[0], dir_item, &key);
        btrfs_release_path(path);
        other_inode = read_one_inode(root, key.objectid);
        if (!other_inode) {
                ret = -ENOENT;
                goto out;
        }
        ret = unlink_inode_for_log_replay(trans, BTRFS_I(dir), BTRFS_I(other_inode),
                                          name, namelen);
        if (ret)
                goto out;
        /*
         * If we dropped the link count to 0, bump it so that later the iput()
         * on the inode will not free it. We will fixup the link count later.
         */
        if (other_inode->i_nlink == 0)
                inc_nlink(other_inode);
add_link:
        ret = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
                             name, namelen, 0, ref_index);
out:
        iput(other_inode);
        btrfs_free_path(path);

        return ret;
}

/*
 * 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 = NULL;
        struct inode *inode = NULL;
        unsigned long ref_ptr;
        unsigned long ref_end;
        char *name = NULL;
        int namelen;
        int ret;
        int search_done = 0;
        int log_ref_ver = 0;
        u64 parent_objectid;
        u64 inode_objectid;
        u64 ref_index = 0;
        int ref_struct_size;

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

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

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

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

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

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

                ret = inode_in_dir(root, path, btrfs_ino(BTRFS_I(dir)),
                                   btrfs_ino(BTRFS_I(inode)), ref_index,
                                   name, namelen);
                if (ret < 0) {
                        goto out;
                } else if (ret == 0) {
                        /*
                         * look for a conflicting back reference in the
                         * metadata. if we find one we have to unlink that name
                         * of the file before we add our new link.  Later on, we
                         * overwrite any existing back reference, and we don't
                         * want to create dangling pointers in the directory.
                         */

                        if (!search_done) {
                                ret = __add_inode_ref(trans, root, path, log,
                                                      BTRFS_I(dir),
                                                      BTRFS_I(inode),
                                                      inode_objectid,
                                                      parent_objectid,
                                                      ref_index, name, namelen,
                                                      &search_done);
                                if (ret) {
                                        if (ret == 1)
                                                ret = 0;
                                        goto out;
                                }
                        }

                        /*
                         * If a reference item already exists for this inode
                         * with the same parent and name, but different index,
                         * drop it and the corresponding directory index entries
                         * from the parent before adding the new reference item
                         * and dir index entries, otherwise we would fail with
                         * -EEXIST returned from btrfs_add_link() below.
                         */
                        ret = btrfs_inode_ref_exists(inode, dir, key->type,
                                                     name, namelen);
                        if (ret > 0) {
                                ret = unlink_inode_for_log_replay(trans,
                                                         BTRFS_I(dir),
                                                         BTRFS_I(inode),
                                                         name, namelen);
                                /*
                                 * If we dropped the link count to 0, bump it so
                                 * that later the iput() on the inode will not
                                 * free it. We will fixup the link count later.
                                 */
                                if (!ret && inode->i_nlink == 0)
                                        inc_nlink(inode);
                        }
                        if (ret < 0)
                                goto out;

                        /* insert our name */
                        ret = add_link(trans, dir, inode, name, namelen,
                                       ref_index);
                        if (ret)
                                goto out;

                        ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
                        if (ret)
                                goto out;
                }
                /* Else, ret == 1, we already have a perfect match, we're done. */

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

        /*
         * Before we overwrite the inode reference item in the subvolume tree
         * with the item from the log tree, we must unlink all names from the
         * parent directory that are in the subvolume's tree inode reference
         * item, otherwise we end up with an inconsistent subvolume tree where
         * dir index entries exist for a name but there is no inode reference
         * item with the same name.
         */
        ret = unlink_old_inode_refs(trans, root, path, BTRFS_I(inode), eb, slot,
                                    key);
        if (ret)
                goto out;

        /* finally write the back reference in the inode */
        ret = overwrite_item(trans, root, path, eb, slot, key);
out:
        btrfs_release_path(path);
        kfree(name);
        iput(dir);
        iput(inode);
        return ret;
}

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

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

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

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

                        nlink++;

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

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

        if (ret < 0 && ret != -ENOENT)
                return ret;
        return nlink;
}

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

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

        while (1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0)
                        break;
                if (ret > 0) {
                        if (path->slots[0] == 0)
                                break;
                        path->slots[0]--;
                }
process_slot:
                btrfs_item_key_to_cpu(path->nodes[0], &key,
                                      path->slots[0]);
                if (key.objectid != ino ||
                    key.type != BTRFS_INODE_REF_KEY)
                        break;
                ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
                ptr_end = ptr + btrfs_item_size(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;
                if (path->slots[0] > 0) {
                        path->slots[0]--;
                        goto process_slot;
                }
                key.offset--;
                btrfs_release_path(path);
        }
        btrfs_release_path(path);

        return nlink;
}

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

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

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

        nlink = ret;

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

        nlink += ret;

        ret = 0;

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

        if (inode->i_nlink == 0) {
                if (S_ISDIR(inode->i_mode)) {
                        ret = replay_dir_deletes(trans, root, NULL, path,
                                                 ino, 1);
                        if (ret)
                                goto out;
                }
                ret = btrfs_insert_orphan_item(trans, root, ino);
                if (ret == -EEXIST)
                        ret = 0;
        }

out:
        btrfs_free_path(path);
        return ret;
}

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

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

                if (ret == 1) {
                        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 != BTRFS_TREE_LOG_FIXUP_OBJECTID ||
                    key.type != BTRFS_ORPHAN_ITEM_KEY)
                        break;

                ret = btrfs_del_item(trans, root, path);
                if (ret)
                        break;

                btrfs_release_path(path);
                inode = read_one_inode(root, key.offset);
                if (!inode) {
                        ret = -EIO;
                        break;
                }

                ret = fixup_inode_link_count(trans, root, inode);
                iput(inode);
                if (ret)
                        break;

                /*
                 * 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(path);
        return ret;
}


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

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

        key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
        key.type = BTRFS_ORPHAN_ITEM_KEY;
        key.offset = objectid;

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

        btrfs_release_path(path);
        if (ret == 0) {
                if (!inode->i_nlink)
                        set_nlink(inode, 1);
                else
                        inc_nlink(inode);
                ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
        } else if (ret == -EEXIST) {
                ret = 0;
        }
        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,
                                    u64 dirid, u64 index,
                                    char *name, int name_len,
                                    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, BTRFS_I(dir), BTRFS_I(inode), name,
                        name_len, 1, index);

        /* FIXME, put inode into FIXUP list */

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

static int delete_conflicting_dir_entry(struct btrfs_trans_handle *trans,
                                        struct btrfs_inode *dir,
                                        struct btrfs_path *path,
                                        struct btrfs_dir_item *dst_di,
                                        const struct btrfs_key *log_key,
                                        u8 log_type,
                                        bool exists)
{
        struct btrfs_key found_key;

        btrfs_dir_item_key_to_cpu(path->nodes[0], dst_di, &found_key);
        /* The existing dentry points to the same inode, don't delete it. */
        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)
                return 1;

        /*
         * Don't drop the conflicting directory entry if the inode for the new
         * entry doesn't exist.
         */
        if (!exists)
                return 0;

        return drop_one_dir_item(trans, path, dir, dst_di);
}

/*
 * 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.
 *
 * Returns < 0 on error, 0 if the name wasn't replayed (dentry points to a
 * non-existing inode) and 1 if the name was replayed.
 */
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 *dir_dst_di;
        struct btrfs_dir_item *index_dst_di;
        bool dir_dst_matches = false;

        bool index_dst_matches = false;
        struct btrfs_key log_key;
        struct btrfs_key search_key;
        struct inode *dir;
        u8 log_type;
        bool exists;
        int ret;
        bool update_size = true;
        bool name_added = false;

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

        name_len = btrfs_dir_name_len(eb, di);
        name = kmalloc(name_len, GFP_NOFS);
        if (!name) {
                ret = -ENOMEM;
                goto out;
        }

        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);
        ret = btrfs_lookup_inode(trans, root, path, &log_key, 0);
        btrfs_release_path(path);
        if (ret < 0)
                goto out;
        exists = (ret == 0);
        ret = 0;

        dir_dst_di = btrfs_lookup_dir_item(trans, root, path, key->objectid,
                                           name, name_len, 1);
        if (IS_ERR(dir_dst_di)) {
                ret = PTR_ERR(dir_dst_di);
                goto out;
        } else if (dir_dst_di) {
                ret = delete_conflicting_dir_entry(trans, BTRFS_I(dir), path,
                                                   dir_dst_di, &log_key, log_type,
                                                   exists);
                if (ret < 0)
                        goto out;
                dir_dst_matches = (ret == 1);
        }

        btrfs_release_path(path);

        index_dst_di = btrfs_lookup_dir_index_item(trans, root, path,
                                                   key->objectid, key->offset,
                                                   name, name_len, 1);
        if (IS_ERR(index_dst_di)) {
                ret = PTR_ERR(index_dst_di);
                goto out;
        } else if (index_dst_di) {
                ret = delete_conflicting_dir_entry(trans, BTRFS_I(dir), path,
                                                   index_dst_di, &log_key,
                                                   log_type, exists);
                if (ret < 0)
                        goto out;
                index_dst_matches = (ret == 1);
        }

        btrfs_release_path(path);

        if (dir_dst_matches && index_dst_matches) {
                ret = 0;
                update_size = false;
                goto out;
        }

        /*
         * Check if the inode reference exists in the log for the given name,
         * inode and parent inode
         */
        search_key.objectid = log_key.objectid;
        search_key.type = BTRFS_INODE_REF_KEY;
        search_key.offset = key->objectid;
        ret = backref_in_log(root->log_root, &search_key, 0, name, name_len);
        if (ret < 0) {
                goto out;
        } else if (ret) {
                /* The dentry will be added later. */
                ret = 0;
                update_size = false;
                goto out;
        }

        search_key.objectid = log_key.objectid;
        search_key.type = BTRFS_INODE_EXTREF_KEY;
        search_key.offset = key->objectid;
        ret = backref_in_log(root->log_root, &search_key, key->objectid, name,
                             name_len);
        if (ret < 0) {
                goto out;
        } else if (ret) {
                /* The dentry will be added later. */
                ret = 0;
                update_size = false;
                goto out;
        }
        btrfs_release_path(path);
        ret = insert_one_name(trans, root, key->objectid, key->offset,
                              name, name_len, &log_key);
        if (ret && ret != -ENOENT && ret != -EEXIST)
                goto out;
        if (!ret)
                name_added = true;
        update_size = false;
        ret = 0;

out:
        if (!ret && update_size) {
                btrfs_i_size_write(BTRFS_I(dir), dir->i_size + name_len * 2);
                ret = btrfs_update_inode(trans, root, BTRFS_I(dir));
        }
        kfree(name);
        iput(dir);
        if (!ret && name_added)
                ret = 1;
        return ret;
}

/* Replay one dir item from a BTRFS_DIR_INDEX_KEY key. */
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;
        struct btrfs_dir_item *di;

        /* We only log dir index keys, which only contain a single dir item. */
        ASSERT(key->type == BTRFS_DIR_INDEX_KEY);

        di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
        ret = replay_one_name(trans, root, path, eb, di, key);
        if (ret < 0)
                return ret;

        /*
         * If this entry refers to a non-directory (directories can not have a
         * link count > 1) and it was added in the transaction that was not
         * committed, make sure we fixup the link count of the inode the entry
         * points to. Otherwise something like the following would result in a
         * directory pointing to an inode with a wrong link that does not account
         * for this dir entry:
         *
         * mkdir testdir
         * touch testdir/foo
         * touch testdir/bar
         * sync
         *
         * ln testdir/bar testdir/bar_link
         * ln testdir/foo testdir/foo_link
         * xfs_io -c "fsync" testdir/bar
         *
         * <power failure>
         *
         * mount fs, log replay happens
         *
         * File foo would remain with a link count of 1 when it has two entries
         * pointing to it in the directory testdir. This would make it impossible
         * to ever delete the parent directory has it would result in stale
         * dentries that can never be deleted.
         */
        if (ret == 1 && btrfs_dir_type(eb, di) != BTRFS_FT_DIR) {
                struct btrfs_path *fixup_path;
                struct btrfs_key di_key;

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

                btrfs_dir_item_key_to_cpu(eb, di, &di_key);
                ret = link_to_fixup_dir(trans, root, fixup_path, di_key.objectid);
                btrfs_free_path(fixup_path);
        }

        return ret;
}

/*
 * 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,
                                   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 = BTRFS_DIR_LOG_INDEX_KEY;
        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 != BTRFS_DIR_LOG_INDEX_KEY || 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]);
        path->slots[0]++;
        if (path->slots[0] >= nritems) {
                ret = btrfs_next_leaf(root, path);
                if (ret)
                        goto out;
        }

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

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

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

        /*
         * Currenly we only log dir index keys. Even if we replay a log created
         * by an older kernel that logged both dir index and dir item keys, all
         * we need to do is process the dir index keys, we (and our caller) can
         * safely ignore dir item keys (key type BTRFS_DIR_ITEM_KEY).
         */
        ASSERT(dir_key->type == BTRFS_DIR_INDEX_KEY);

        eb = path->nodes[0];
        slot = path->slots[0];
        di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
        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);

        if (log) {
                struct btrfs_dir_item *log_di;

                log_di = btrfs_lookup_dir_index_item(trans, log, log_path,
                                                     dir_key->objectid,
                                                     dir_key->offset,
                                                     name, name_len, 0);
                if (IS_ERR(log_di)) {
                        ret = PTR_ERR(log_di);
                        goto out;
                } else if (log_di) {
                        /* The dentry exists in the log, we have nothing to do. */
                        ret = 0;
                        goto out;
                }
        }

        btrfs_dir_item_key_to_cpu(eb, di, &location);
        btrfs_release_path(path);
        btrfs_release_path(log_path);
        inode = read_one_inode(root, location.objectid);
        if (!inode) {
                ret = -EIO;
                goto out;
        }

        ret = link_to_fixup_dir(trans, root, path, location.objectid);
        if (ret)
                goto out;

        inc_nlink(inode);
        ret = unlink_inode_for_log_replay(trans, BTRFS_I(dir), BTRFS_I(inode),
                                          name, name_len);
        /*
         * Unlike dir item keys, dir index keys can only have one name (entry) in
         * them, as there are no key collisions since each key has a unique offset
         * (an index number), so we're done.
         */
out:
        btrfs_release_path(path);
        btrfs_release_path(log_path);
        kfree(name);
        iput(inode);
        return ret;
}

static int replay_xattr_deletes(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_root *log,
                              struct btrfs_path *path,
                              const u64 ino)
{
        struct btrfs_key search_key;
        struct btrfs_path *log_path;
        int i;
        int nritems;
        int ret;

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

        search_key.objectid = ino;
        search_key.type = BTRFS_XATTR_ITEM_KEY;
        search_key.offset = 0;
again:
        ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
        if (ret < 0)
                goto out;
process_leaf:
        nritems = btrfs_header_nritems(path->nodes[0]);
        for (i = path->slots[0]; i < nritems; i++) {
                struct btrfs_key key;
                struct btrfs_dir_item *di;
                struct btrfs_dir_item *log_di;
                u32 total_size;
                u32 cur;

                btrfs_item_key_to_cpu(path->nodes[0], &key, i);
                if (key.objectid != ino || key.type != BTRFS_XATTR_ITEM_KEY) {
                        ret = 0;
                        goto out;
                }

                di = btrfs_item_ptr(path->nodes[0], i, struct btrfs_dir_item);
                total_size = btrfs_item_size(path->nodes[0], i);
                cur = 0;
                while (cur < total_size) {
                        u16 name_len = btrfs_dir_name_len(path->nodes[0], di);
                        u16 data_len = btrfs_dir_data_len(path->nodes[0], di);
                        u32 this_len = sizeof(*di) + name_len + data_len;
                        char *name;

                        name = kmalloc(name_len, GFP_NOFS);
                        if (!name) {
                                ret = -ENOMEM;
                                goto out;
                        }
                        read_extent_buffer(path->nodes[0], name,
                                           (unsigned long)(di + 1), name_len);

                        log_di = btrfs_lookup_xattr(NULL, log, log_path, ino,
                                                    name, name_len, 0);
                        btrfs_release_path(log_path);
                        if (!log_di) {
                                /* Doesn't exist in log tree, so delete it. */
                                btrfs_release_path(path);
                                di = btrfs_lookup_xattr(trans, root, path, ino,
                                                        name, name_len, -1);
                                kfree(name);
                                if (IS_ERR(di)) {
                                        ret = PTR_ERR(di);
                                        goto out;
                                }
                                ASSERT(di);
                                ret = btrfs_delete_one_dir_name(trans, root,
                                                                path, di);
                                if (ret)
                                        goto out;
                                btrfs_release_path(path);
                                search_key = key;
                                goto again;
                        }
                        kfree(name);
                        if (IS_ERR(log_di)) {
                                ret = PTR_ERR(log_di);
                                goto out;
                        }
                        cur += this_len;
                        di = (struct btrfs_dir_item *)((char *)di + this_len);
                }
        }
        ret = btrfs_next_leaf(root, path);
        if (ret > 0)
                ret = 0;
        else if (ret == 0)
                goto process_leaf;
out:
        btrfs_free_path(log_path);
        btrfs_release_path(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 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_INDEX_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;
        }

        range_start = 0;
        range_end = 0;
        while (1) {
                if (del_all)
                        range_end = (u64)-1;
                else {
                        ret = find_dir_range(log, path, dirid,
                                             &range_start, &range_end);
                        if (ret < 0)
                                goto out;
                        else 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 == 1)
                                        break;
                                else if (ret < 0)
                                        goto out;
                        }
                        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                                              path->slots[0]);
                        if (found_key.objectid != dirid ||
                            found_key.type != dir_key.type) {
                                ret = 0;
                                goto out;
                        }

                        if (found_key.offset > range_end)
                                break;

                        ret = check_item_in_log(trans, log, path,
                                                log_path, dir,
                                                &found_key);
                        if (ret)
                                goto out;
                        if (found_key.offset == (u64)-1)
                                break;
                        dir_key.offset = found_key.offset + 1;
                }
                btrfs_release_path(path);
                if (range_end == (u64)-1)
                        break;
                range_start = range_end + 1;
        }
        ret = 0;
out:
        btrfs_release_path(path);
        btrfs_free_path(log_path);
        iput(dir);
        return ret;
}

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

        ret = btrfs_read_extent_buffer(eb, gen, level, NULL);
        if (ret)
                return ret;

        level = btrfs_header_level(eb);

        if (level != 0)
                return 0;

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

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

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

                        inode_item = btrfs_item_ptr(eb, i,
                                            struct btrfs_inode_item);
                        /*
                         * If we have a tmpfile (O_TMPFILE) that got fsync'ed
                         * and never got linked before the fsync, skip it, as
                         * replaying it is pointless since it would be deleted
                         * later. We skip logging tmpfiles, but it's always
                         * possible we are replaying a log created with a kernel
                         * that used to log tmpfiles.
                         */
                        if (btrfs_inode_nlink(eb, inode_item) == 0) {
                                wc->ignore_cur_inode = true;
                                continue;
                        } else {
                                wc->ignore_cur_inode = false;
                        }
                        ret = replay_xattr_deletes(wc->trans, root, log,
                                                   path, key.objectid);
                        if (ret)
                                break;
                        mode = btrfs_inode_mode(eb, inode_item);
                        if (S_ISDIR(mode)) {
                                ret = replay_dir_deletes(wc->trans,
                                         root, log, path, key.objectid, 0);
                                if (ret)
                                        break;
                        }
                        ret = overwrite_item(wc->trans, root, path,
                                             eb, i, &key);
                        if (ret)
                                break;

                        /*
                         * Before replaying extents, truncate the inode to its
                         * size. We need to do it now and not after log replay
                         * because before an fsync we can have prealloc extents
                         * added beyond the inode's i_size. If we did it after,
                         * through orphan cleanup for example, we would drop
                         * those prealloc extents just after replaying them.
                         */
                        if (S_ISREG(mode)) {
                                struct btrfs_drop_extents_args drop_args = { 0 };
                                struct inode *inode;
                                u64 from;

                                inode = read_one_inode(root, key.objectid);
                                if (!inode) {
                                        ret = -EIO;
                                        break;
                                }
                                from = ALIGN(i_size_read(inode),
                                             root->fs_info->sectorsize);
                                drop_args.start = from;
                                drop_args.end = (u64)-1;
                                drop_args.drop_cache = true;
                                ret = btrfs_drop_extents(wc->trans, root,
                                                         BTRFS_I(inode),
                                                         &drop_args);
                                if (!ret) {
                                        inode_sub_bytes(inode,
                                                        drop_args.bytes_found);
                                        /* Update the inode's nbytes. */
                                        ret = btrfs_update_inode(wc->trans,
                                                        root, BTRFS_I(inode));
                                }
                                iput(inode);
                                if (ret)
                                        break;
                        }

                        ret = link_to_fixup_dir(wc->trans, root,
                                                path, key.objectid);
                        if (ret)
                                break;
                }

                if (wc->ignore_cur_inode)
                        continue;

                if (key.type == BTRFS_DIR_INDEX_KEY &&
                    wc->stage == LOG_WALK_REPLAY_DIR_INDEX) {
                        ret = replay_one_dir_item(wc->trans, root, path,
                                                  eb, i, &key);
                        if (ret)
                                break;
                }

                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);
                        if (ret)
                                break;
                } else if (key.type == BTRFS_INODE_REF_KEY ||
                           key.type == BTRFS_INODE_EXTREF_KEY) {
                        ret = add_inode_ref(wc->trans, root, log, path,
                                            eb, i, &key);
                        if (ret && ret != -ENOENT)
                                break;
                        ret = 0;
                } else if (key.type == BTRFS_EXTENT_DATA_KEY) {
                        ret = replay_one_extent(wc->trans, root, path,
                                                eb, i, &key);
                        if (ret)
                                break;
                }
                /*
                 * We don't log BTRFS_DIR_ITEM_KEY keys anymore, only the
                 * BTRFS_DIR_INDEX_KEY items which we use to derive the
                 * BTRFS_DIR_ITEM_KEY items. If we are replaying a log from an
                 * older kernel with such keys, ignore them.
                 */
        }
        btrfs_free_path(path);
        return ret;
}

/*
 * Correctly adjust the reserved bytes occupied by a log tree extent buffer
 */
static void unaccount_log_buffer(struct btrfs_fs_info *fs_info, u64 start)
{
        struct btrfs_block_group *cache;

        cache = btrfs_lookup_block_group(fs_info, start);
        if (!cache) {
                btrfs_err(fs_info, "unable to find block group for %llu", start);
                return;
        }

        spin_lock(&cache->space_info->lock);
        spin_lock(&cache->lock);
        cache->reserved -= fs_info->nodesize;
        cache->space_info->bytes_reserved -= fs_info->nodesize;
        spin_unlock(&cache->lock);
        spin_unlock(&cache->space_info->lock);

        btrfs_put_block_group(cache);
}

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)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        u64 bytenr;
        u64 ptr_gen;
        struct extent_buffer *next;
        struct extent_buffer *cur;
        u32 blocksize;
        int ret = 0;

        while (*level > 0) {
                struct btrfs_key first_key;

                cur = path->nodes[*level];

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

                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]);
                btrfs_node_key_to_cpu(cur, &first_key, path->slots[*level]);
                blocksize = fs_info->nodesize;

                next = btrfs_find_create_tree_block(fs_info, bytenr,
                                                    btrfs_header_owner(cur),
                                                    *level - 1);
                if (IS_ERR(next))
                        return PTR_ERR(next);

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

                        path->slots[*level]++;
                        if (wc->free) {
                                ret = btrfs_read_extent_buffer(next, ptr_gen,
                                                        *level - 1, &first_key);
                                if (ret) {
                                        free_extent_buffer(next);
                                        return ret;
                                }

                                if (trans) {
                                        btrfs_tree_lock(next);
                                        btrfs_clean_tree_block(next);
                                        btrfs_wait_tree_block_writeback(next);
                                        btrfs_tree_unlock(next);
                                        ret = btrfs_pin_reserved_extent(trans,
                                                        bytenr, blocksize);
                                        if (ret) {
                                                free_extent_buffer(next);
                                                return ret;
                                        }
                                        btrfs_redirty_list_add(
                                                trans->transaction, next);
                                } else {
                                        if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
                                                clear_extent_buffer_dirty(next);
                                        unaccount_log_buffer(fs_info, bytenr);
                                }
                        }
                        free_extent_buffer(next);
                        continue;
                }
                ret = btrfs_read_extent_buffer(next, ptr_gen, *level - 1, &first_key);
                if (ret) {
                        free_extent_buffer(next);
                        return ret;
                }

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

        cond_resched();
        return 0;
}

static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path, int *level,
                                 struct walk_control *wc)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        int i;
        int slot;
        int ret;

        for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
                slot = path->slots[i];
                if (slot + 1 < btrfs_header_nritems(path->nodes[i])) {
                        path->slots[i]++;
                        *level = i;
                        WARN_ON(*level == 0);
                        return 0;
                } else {
                        ret = wc->process_func(root, path->nodes[*level], wc,
                                 btrfs_header_generation(path->nodes[*level]),
                                 *level);
                        if (ret)
                                return ret;

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

                                next = path->nodes[*level];

                                if (trans) {
                                        btrfs_tree_lock(next);
                                        btrfs_clean_tree_block(next);
                                        btrfs_wait_tree_block_writeback(next);
                                        btrfs_tree_unlock(next);
                                        ret = btrfs_pin_reserved_extent(trans,
                                                     path->nodes[*level]->start,
                                                     path->nodes[*level]->len);
                                        if (ret)
                                                return ret;
                                        btrfs_redirty_list_add(trans->transaction,
                                                               next);
                                } else {
                                        if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
                                                clear_extent_buffer_dirty(next);

                                        unaccount_log_buffer(fs_info,
                                                path->nodes[*level]->start);
                                }
                        }
                        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)
{
        struct btrfs_fs_info *fs_info = log->fs_info;
        int ret = 0;
        int wret;
        int level;
        struct btrfs_path *path;
        int orig_level;

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

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

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

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

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

                        next = path->nodes[orig_level];

                        if (trans) {
                                btrfs_tree_lock(next);
                                btrfs_clean_tree_block(next);
                                btrfs_wait_tree_block_writeback(next);
                                btrfs_tree_unlock(next);
                                ret = btrfs_pin_reserved_extent(trans,
                                                next->start, next->len);
                                if (ret)
                                        goto out;
                                btrfs_redirty_list_add(trans->transaction, next);
                        } else {
                                if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
                                        clear_extent_buffer_dirty(next);
                                unaccount_log_buffer(fs_info, next->start);
                        }
                }
        }

out:
        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,
                           struct btrfs_root_item *root_item)
{
        struct btrfs_fs_info *fs_info = log->fs_info;
        int ret;

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

static void wait_log_commit(struct btrfs_root *root, int 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