Btrfs: Create orphan inode records to prevent lost files after a crash

[deliverable/linux.git] / fs / btrfs / inode.c

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

#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/smp_lock.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/bit_spinlock.h>
#include <linux/version.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "ioctl.h"
#include "print-tree.h"
#include "volumes.h"
#include "ordered-data.h"

struct btrfs_iget_args {
        u64 ino;
        struct btrfs_root *root;
};

static struct inode_operations btrfs_dir_inode_operations;
static struct inode_operations btrfs_symlink_inode_operations;
static struct inode_operations btrfs_dir_ro_inode_operations;
static struct inode_operations btrfs_special_inode_operations;
static struct inode_operations btrfs_file_inode_operations;
static struct address_space_operations btrfs_aops;
static struct address_space_operations btrfs_symlink_aops;
static struct file_operations btrfs_dir_file_operations;
static struct extent_io_ops btrfs_extent_io_ops;

static struct kmem_cache *btrfs_inode_cachep;
struct kmem_cache *btrfs_trans_handle_cachep;
struct kmem_cache *btrfs_transaction_cachep;
struct kmem_cache *btrfs_bit_radix_cachep;
struct kmem_cache *btrfs_path_cachep;

#define S_SHIFT 12
static unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
        [S_IFREG >> S_SHIFT]    = BTRFS_FT_REG_FILE,
        [S_IFDIR >> S_SHIFT]    = BTRFS_FT_DIR,
        [S_IFCHR >> S_SHIFT]    = BTRFS_FT_CHRDEV,
        [S_IFBLK >> S_SHIFT]    = BTRFS_FT_BLKDEV,
        [S_IFIFO >> S_SHIFT]    = BTRFS_FT_FIFO,
        [S_IFSOCK >> S_SHIFT]   = BTRFS_FT_SOCK,
        [S_IFLNK >> S_SHIFT]    = BTRFS_FT_SYMLINK,
};

static void btrfs_truncate(struct inode *inode);

int btrfs_check_free_space(struct btrfs_root *root, u64 num_required,
                           int for_del)
{
        u64 total;
        u64 used;
        u64 thresh;
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&root->fs_info->delalloc_lock, flags);
        total = btrfs_super_total_bytes(&root->fs_info->super_copy);
        used = btrfs_super_bytes_used(&root->fs_info->super_copy);
        if (for_del)
                thresh = total * 90;
        else
                thresh = total * 85;

        do_div(thresh, 100);

        if (used + root->fs_info->delalloc_bytes + num_required > thresh)
                ret = -ENOSPC;
        spin_unlock_irqrestore(&root->fs_info->delalloc_lock, flags);
        return ret;
}

static int cow_file_range(struct inode *inode, u64 start, u64 end)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        u64 alloc_hint = 0;
        u64 num_bytes;
        u64 cur_alloc_size;
        u64 blocksize = root->sectorsize;
        u64 orig_num_bytes;
        struct btrfs_key ins;
        struct extent_map *em;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        int ret = 0;

        trans = btrfs_join_transaction(root, 1);
        BUG_ON(!trans);
        btrfs_set_trans_block_group(trans, inode);

        num_bytes = (end - start + blocksize) & ~(blocksize - 1);
        num_bytes = max(blocksize,  num_bytes);
        orig_num_bytes = num_bytes;

        if (alloc_hint == EXTENT_MAP_INLINE)
                goto out;

        BUG_ON(num_bytes > btrfs_super_total_bytes(&root->fs_info->super_copy));
        mutex_lock(&BTRFS_I(inode)->extent_mutex);
        btrfs_drop_extent_cache(inode, start, start + num_bytes - 1);
        mutex_unlock(&BTRFS_I(inode)->extent_mutex);

        while(num_bytes > 0) {
                cur_alloc_size = min(num_bytes, root->fs_info->max_extent);
                ret = btrfs_reserve_extent(trans, root, cur_alloc_size,
                                           root->sectorsize, 0, 0,
                                           (u64)-1, &ins, 1);
                if (ret) {
                        WARN_ON(1);
                        goto out;
                }
                em = alloc_extent_map(GFP_NOFS);
                em->start = start;
                em->len = ins.offset;
                em->block_start = ins.objectid;
                em->bdev = root->fs_info->fs_devices->latest_bdev;
                mutex_lock(&BTRFS_I(inode)->extent_mutex);
                set_bit(EXTENT_FLAG_PINNED, &em->flags);
                while(1) {
                        spin_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em);
                        spin_unlock(&em_tree->lock);
                        if (ret != -EEXIST) {
                                free_extent_map(em);
                                break;
                        }
                        btrfs_drop_extent_cache(inode, start,
                                                start + ins.offset - 1);
                }
                mutex_unlock(&BTRFS_I(inode)->extent_mutex);

                cur_alloc_size = ins.offset;
                ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
                                               ins.offset);
                BUG_ON(ret);
                if (num_bytes < cur_alloc_size) {
                        printk("num_bytes %Lu cur_alloc %Lu\n", num_bytes,
                               cur_alloc_size);
                        break;
                }
                num_bytes -= cur_alloc_size;
                alloc_hint = ins.objectid + ins.offset;
                start += cur_alloc_size;
        }
out:
        btrfs_end_transaction(trans, root);
        return ret;
}

static int run_delalloc_nocow(struct inode *inode, u64 start, u64 end)
{
        u64 extent_start;
        u64 extent_end;
        u64 bytenr;
        u64 cow_end;
        u64 loops = 0;
        u64 total_fs_bytes;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_group_cache *block_group;
        struct extent_buffer *leaf;
        int found_type;
        struct btrfs_path *path;
        struct btrfs_file_extent_item *item;
        int ret;
        int err;
        struct btrfs_key found_key;

        total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
        path = btrfs_alloc_path();
        BUG_ON(!path);
again:
        ret = btrfs_lookup_file_extent(NULL, root, path,
                                       inode->i_ino, start, 0);
        if (ret < 0) {
                btrfs_free_path(path);
                return ret;
        }

        cow_end = end;
        if (ret != 0) {
                if (path->slots[0] == 0)
                        goto not_found;
                path->slots[0]--;
        }

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

        /* are we inside the extent that was found? */
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
        found_type = btrfs_key_type(&found_key);
        if (found_key.objectid != inode->i_ino ||
            found_type != BTRFS_EXTENT_DATA_KEY)
                goto not_found;

        found_type = btrfs_file_extent_type(leaf, item);
        extent_start = found_key.offset;
        if (found_type == BTRFS_FILE_EXTENT_REG) {
                u64 extent_num_bytes;

                extent_num_bytes = btrfs_file_extent_num_bytes(leaf, item);
                extent_end = extent_start + extent_num_bytes;
                err = 0;

                if (loops && start != extent_start)
                        goto not_found;

                if (start < extent_start || start >= extent_end)
                        goto not_found;

                cow_end = min(end, extent_end - 1);
                bytenr = btrfs_file_extent_disk_bytenr(leaf, item);
                if (bytenr == 0)
                        goto not_found;

                if (btrfs_count_snapshots_in_path(root, path, inode->i_ino,
                                                  bytenr) != 1) {
                        goto not_found;
                }

                /*
                 * we may be called by the resizer, make sure we're inside
                 * the limits of the FS
                 */
                block_group = btrfs_lookup_block_group(root->fs_info,
                                                       bytenr);
                if (!block_group || block_group->ro)
                        goto not_found;

                start = extent_end;
        } else {
                goto not_found;
        }
loop:
        if (start > end) {
                btrfs_free_path(path);
                return 0;
        }
        btrfs_release_path(root, path);
        loops++;
        goto again;

not_found:
        cow_file_range(inode, start, end);
        start = end + 1;
        goto loop;
}

static int run_delalloc_range(struct inode *inode, u64 start, u64 end)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        if (btrfs_test_opt(root, NODATACOW) ||
            btrfs_test_flag(inode, NODATACOW))
                ret = run_delalloc_nocow(inode, start, end);
        else
                ret = cow_file_range(inode, start, end);

        return ret;
}

int btrfs_set_bit_hook(struct inode *inode, u64 start, u64 end,
                       unsigned long old, unsigned long bits)
{
        unsigned long flags;
        if (!(old & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                spin_lock_irqsave(&root->fs_info->delalloc_lock, flags);
                BTRFS_I(inode)->delalloc_bytes += end - start + 1;
                root->fs_info->delalloc_bytes += end - start + 1;
                spin_unlock_irqrestore(&root->fs_info->delalloc_lock, flags);
        }
        return 0;
}

int btrfs_clear_bit_hook(struct inode *inode, u64 start, u64 end,
                         unsigned long old, unsigned long bits)
{
        if ((old & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                unsigned long flags;

                spin_lock_irqsave(&root->fs_info->delalloc_lock, flags);
                if (end - start + 1 > root->fs_info->delalloc_bytes) {
                        printk("warning: delalloc account %Lu %Lu\n",
                               end - start + 1, root->fs_info->delalloc_bytes);
                        root->fs_info->delalloc_bytes = 0;
                        BTRFS_I(inode)->delalloc_bytes = 0;
                } else {
                        root->fs_info->delalloc_bytes -= end - start + 1;
                        BTRFS_I(inode)->delalloc_bytes -= end - start + 1;
                }
                spin_unlock_irqrestore(&root->fs_info->delalloc_lock, flags);
        }
        return 0;
}

int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
                         size_t size, struct bio *bio)
{
        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
        struct btrfs_mapping_tree *map_tree;
        u64 logical = bio->bi_sector << 9;
        u64 length = 0;
        u64 map_length;
        int ret;

        length = bio->bi_size;
        map_tree = &root->fs_info->mapping_tree;
        map_length = length;
        ret = btrfs_map_block(map_tree, READ, logical,
                              &map_length, NULL, 0);

        if (map_length < length + size) {
                return 1;
        }
        return 0;
}

int __btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
                          int mirror_num)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        ret = btrfs_csum_one_bio(root, inode, bio);
        BUG_ON(ret);

        return btrfs_map_bio(root, rw, bio, mirror_num, 1);
}

int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
                          int mirror_num)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
        BUG_ON(ret);

        if (!(rw & (1 << BIO_RW))) {
                goto mapit;
        }

        return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
                                   inode, rw, bio, mirror_num,
                                   __btrfs_submit_bio_hook);
mapit:
        return btrfs_map_bio(root, rw, bio, mirror_num, 0);
}

static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
                             struct inode *inode, u64 file_offset,
                             struct list_head *list)
{
        struct list_head *cur;
        struct btrfs_ordered_sum *sum;

        btrfs_set_trans_block_group(trans, inode);
        list_for_each(cur, list) {
                sum = list_entry(cur, struct btrfs_ordered_sum, list);
                mutex_lock(&BTRFS_I(inode)->csum_mutex);
                btrfs_csum_file_blocks(trans, BTRFS_I(inode)->root,
                                       inode, sum);
                mutex_unlock(&BTRFS_I(inode)->csum_mutex);
        }
        return 0;
}

struct btrfs_writepage_fixup {
        struct page *page;
        struct btrfs_work work;
};

/* see btrfs_writepage_start_hook for details on why this is required */
void btrfs_writepage_fixup_worker(struct btrfs_work *work)
{
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_ordered_extent *ordered;
        struct page *page;
        struct inode *inode;
        u64 page_start;
        u64 page_end;

        fixup = container_of(work, struct btrfs_writepage_fixup, work);
        page = fixup->page;
again:
        lock_page(page);
        if (!page->mapping || !PageDirty(page) || !PageChecked(page)) {
                ClearPageChecked(page);
                goto out_page;
        }

        inode = page->mapping->host;
        page_start = page_offset(page);
        page_end = page_offset(page) + PAGE_CACHE_SIZE - 1;

        lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end, GFP_NOFS);

        /* already ordered? We're done */
        if (test_range_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
                             EXTENT_ORDERED, 0)) {
                goto out;
        }

        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent(&BTRFS_I(inode)->io_tree, page_start,
                              page_end, GFP_NOFS);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                goto again;
        }

        set_extent_delalloc(&BTRFS_I(inode)->io_tree, page_start, page_end,
                            GFP_NOFS);
        ClearPageChecked(page);
out:
        unlock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end, GFP_NOFS);
out_page:
        unlock_page(page);
        page_cache_release(page);
}

/*
 * There are a few paths in the higher layers of the kernel that directly
 * set the page dirty bit without asking the filesystem if it is a
 * good idea.  This causes problems because we want to make sure COW
 * properly happens and the data=ordered rules are followed.
 *
 * In our case any range that doesn't have the EXTENT_ORDERED bit set
 * hasn't been properly setup for IO.  We kick off an async process
 * to fix it up.  The async helper will wait for ordered extents, set
 * the delalloc bit and make it safe to write the page.
 */
int btrfs_writepage_start_hook(struct page *page, u64 start, u64 end)
{
        struct inode *inode = page->mapping->host;
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        ret = test_range_bit(&BTRFS_I(inode)->io_tree, start, end,
                             EXTENT_ORDERED, 0);
        if (ret)
                return 0;

        if (PageChecked(page))
                return -EAGAIN;

        fixup = kzalloc(sizeof(*fixup), GFP_NOFS);
        if (!fixup)
                return -EAGAIN;

        SetPageChecked(page);
        page_cache_get(page);
        fixup->work.func = btrfs_writepage_fixup_worker;
        fixup->page = page;
        btrfs_queue_worker(&root->fs_info->fixup_workers, &fixup->work);
        return -EAGAIN;
}

static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        struct btrfs_ordered_extent *ordered_extent;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_map *em;
        struct extent_map *em_orig;
        u64 alloc_hint = 0;
        u64 clear_start;
        u64 clear_end;
        struct list_head list;
        struct btrfs_key ins;
        struct rb_node *rb;
        int ret;

        ret = btrfs_dec_test_ordered_pending(inode, start, end - start + 1);
        if (!ret)
                return 0;

        trans = btrfs_join_transaction(root, 1);

        ordered_extent = btrfs_lookup_ordered_extent(inode, start);
        BUG_ON(!ordered_extent);

        lock_extent(io_tree, ordered_extent->file_offset,
                    ordered_extent->file_offset + ordered_extent->len - 1,
                    GFP_NOFS);

        INIT_LIST_HEAD(&list);

        ins.objectid = ordered_extent->start;
        ins.offset = ordered_extent->len;
        ins.type = BTRFS_EXTENT_ITEM_KEY;

        ret = btrfs_alloc_reserved_extent(trans, root, root->root_key.objectid,
                                          trans->transid, inode->i_ino,
                                          ordered_extent->file_offset, &ins);
        BUG_ON(ret);

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

        spin_lock(&em_tree->lock);
        clear_start = ordered_extent->file_offset;
        clear_end = ordered_extent->file_offset + ordered_extent->len;
        em = lookup_extent_mapping(em_tree, clear_start,
                                   ordered_extent->len);
        em_orig = em;
        while(em && clear_start < extent_map_end(em) && clear_end > em->start) {
                clear_bit(EXTENT_FLAG_PINNED, &em->flags);
                rb = rb_next(&em->rb_node);
                if (!rb)
                        break;
                em = rb_entry(rb, struct extent_map, rb_node);
        }
        free_extent_map(em_orig);
        spin_unlock(&em_tree->lock);

        ret = btrfs_drop_extents(trans, root, inode,
                                 ordered_extent->file_offset,
                                 ordered_extent->file_offset +
                                 ordered_extent->len,
                                 ordered_extent->file_offset, &alloc_hint);
        BUG_ON(ret);
        ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
                                       ordered_extent->file_offset,
                                       ordered_extent->start,
                                       ordered_extent->len,
                                       ordered_extent->len, 0);
        BUG_ON(ret);

        btrfs_drop_extent_cache(inode, ordered_extent->file_offset,
                                ordered_extent->file_offset +
                                ordered_extent->len - 1);
        mutex_unlock(&BTRFS_I(inode)->extent_mutex);

        inode->i_blocks += ordered_extent->len >> 9;
        unlock_extent(io_tree, ordered_extent->file_offset,
                    ordered_extent->file_offset + ordered_extent->len - 1,
                    GFP_NOFS);
        add_pending_csums(trans, inode, ordered_extent->file_offset,
                          &ordered_extent->list);

        btrfs_ordered_update_i_size(inode, ordered_extent);
        btrfs_remove_ordered_extent(inode, ordered_extent);

        /* once for us */
        btrfs_put_ordered_extent(ordered_extent);
        /* once for the tree */
        btrfs_put_ordered_extent(ordered_extent);

        btrfs_update_inode(trans, root, inode);
        btrfs_end_transaction(trans, root);
        return 0;
}

int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
                                struct extent_state *state, int uptodate)
{
        return btrfs_finish_ordered_io(page->mapping->host, start, end);
}

int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
{
        int ret = 0;
        struct inode *inode = page->mapping->host;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_csum_item *item;
        struct btrfs_path *path = NULL;
        u32 csum;

        if (btrfs_test_opt(root, NODATASUM) ||
            btrfs_test_flag(inode, NODATASUM))
                return 0;

        /*
         * It is possible there is an ordered extent that has
         * not yet finished for this range in the file.  If so,
         * that extent will have a csum cached, and it will insert
         * the sum after all the blocks in the extent are fully
         * on disk.  So, look for an ordered extent and use the
         * sum if found.  We have to do this before looking in the
         * btree because csum items are pre-inserted based on
         * the file size.  btrfs_lookup_csum might find an item
         * that still hasn't been fully filled.
         */
        ret = btrfs_find_ordered_sum(inode, start, &csum);
        if (ret == 0)
                goto found;

        ret = 0;
        path = btrfs_alloc_path();
        item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, start, 0);
        if (IS_ERR(item)) {
                ret = PTR_ERR(item);
                /* a csum that isn't present is a preallocated region. */
                if (ret == -ENOENT || ret == -EFBIG)
                        ret = 0;
                csum = 0;
                printk("no csum found for inode %lu start %Lu\n", inode->i_ino,
                       start);
                goto out;
        }
        read_extent_buffer(path->nodes[0], &csum, (unsigned long)item,
                           BTRFS_CRC32_SIZE);
found:
        set_state_private(io_tree, start, csum);
out:
        if (path)
                btrfs_free_path(path);
        return ret;
}

struct io_failure_record {
        struct page *page;
        u64 start;
        u64 len;
        u64 logical;
        int last_mirror;
};

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

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

                spin_lock(&em_tree->lock);
                em = lookup_extent_mapping(em_tree, start, failrec->len);
                if (em->start > start || em->start + em->len < start) {
                        free_extent_map(em);
                        em = NULL;
                }
                spin_unlock(&em_tree->lock);

                if (!em || IS_ERR(em)) {
                        kfree(failrec);
                        return -EIO;
                }
                logical = start - em->start;
                logical = em->block_start + logical;
                failrec->logical = logical;
                free_extent_map(em);
                set_extent_bits(failure_tree, start, end, EXTENT_LOCKED |
                                EXTENT_DIRTY, GFP_NOFS);
                set_state_private(failure_tree, start,
                                 (u64)(unsigned long)failrec);
        } else {
                failrec = (struct io_failure_record *)(unsigned long)private;
        }
        num_copies = btrfs_num_copies(
                              &BTRFS_I(inode)->root->fs_info->mapping_tree,
                              failrec->logical, failrec->len);
        failrec->last_mirror++;
        if (!state) {
                spin_lock_irq(&BTRFS_I(inode)->io_tree.lock);
                state = find_first_extent_bit_state(&BTRFS_I(inode)->io_tree,
                                                    failrec->start,
                                                    EXTENT_LOCKED);
                if (state && state->start != failrec->start)
                        state = NULL;
                spin_unlock_irq(&BTRFS_I(inode)->io_tree.lock);
        }
        if (!state || failrec->last_mirror > num_copies) {
                set_state_private(failure_tree, failrec->start, 0);
                clear_extent_bits(failure_tree, failrec->start,
                                  failrec->start + failrec->len - 1,
                                  EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
                kfree(failrec);
                return -EIO;
        }
        bio = bio_alloc(GFP_NOFS, 1);
        bio->bi_private = state;
        bio->bi_end_io = failed_bio->bi_end_io;
        bio->bi_sector = failrec->logical >> 9;
        bio->bi_bdev = failed_bio->bi_bdev;
        bio->bi_size = 0;
        bio_add_page(bio, page, failrec->len, start - page_offset(page));
        if (failed_bio->bi_rw & (1 << BIO_RW))
                rw = WRITE;
        else
                rw = READ;

        BTRFS_I(inode)->io_tree.ops->submit_bio_hook(inode, rw, bio,
                                                      failrec->last_mirror);
        return 0;
}

int btrfs_clean_io_failures(struct inode *inode, u64 start)
{
        u64 private;
        u64 private_failure;
        struct io_failure_record *failure;
        int ret;

        private = 0;
        if (count_range_bits(&BTRFS_I(inode)->io_failure_tree, &private,
                             (u64)-1, 1, EXTENT_DIRTY)) {
                ret = get_state_private(&BTRFS_I(inode)->io_failure_tree,
                                        start, &private_failure);
                if (ret == 0) {
                        failure = (struct io_failure_record *)(unsigned long)
                                   private_failure;
                        set_state_private(&BTRFS_I(inode)->io_failure_tree,
                                          failure->start, 0);
                        clear_extent_bits(&BTRFS_I(inode)->io_failure_tree,
                                          failure->start,
                                          failure->start + failure->len - 1,
                                          EXTENT_DIRTY | EXTENT_LOCKED,
                                          GFP_NOFS);
                        kfree(failure);
                }
        }
        return 0;
}

int btrfs_readpage_end_io_hook(struct page *page, u64 start, u64 end,
                               struct extent_state *state)
{
        size_t offset = start - ((u64)page->index << PAGE_CACHE_SHIFT);
        struct inode *inode = page->mapping->host;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        char *kaddr;
        u64 private = ~(u32)0;
        int ret;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u32 csum = ~(u32)0;
        unsigned long flags;

        if (btrfs_test_opt(root, NODATASUM) ||
            btrfs_test_flag(inode, NODATASUM))
                return 0;
        if (state && state->start == start) {
                private = state->private;
                ret = 0;
        } else {
                ret = get_state_private(io_tree, start, &private);
        }
        local_irq_save(flags);
        kaddr = kmap_atomic(page, KM_IRQ0);
        if (ret) {
                goto zeroit;
        }
        csum = btrfs_csum_data(root, kaddr + offset, csum,  end - start + 1);
        btrfs_csum_final(csum, (char *)&csum);
        if (csum != private) {
                goto zeroit;
        }
        kunmap_atomic(kaddr, KM_IRQ0);
        local_irq_restore(flags);

        /* if the io failure tree for this inode is non-empty,
         * check to see if we've recovered from a failed IO
         */
        btrfs_clean_io_failures(inode, start);
        return 0;

zeroit:
        printk("btrfs csum failed ino %lu off %llu csum %u private %Lu\n",
               page->mapping->host->i_ino, (unsigned long long)start, csum,
               private);
        memset(kaddr + offset, 1, end - start + 1);
        flush_dcache_page(page);
        kunmap_atomic(kaddr, KM_IRQ0);
        local_irq_restore(flags);
        if (private == 0)
                return 0;
        return -EIO;
}

/*
 * This creates an orphan entry for the given inode in case something goes
 * wrong in the middle of an unlink/truncate.
 */
int btrfs_orphan_add(struct btrfs_trans_handle *trans, struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        spin_lock(&root->orphan_lock);

        /* already on the orphan list, we're good */
        if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
                spin_unlock(&root->orphan_lock);
                return 0;
        }

        list_add(&BTRFS_I(inode)->i_orphan, &root->orphan_list);

        spin_unlock(&root->orphan_lock);

        /*
         * insert an orphan item to track this unlinked/truncated file
         */
        ret = btrfs_insert_orphan_item(trans, root, inode->i_ino);

        return ret;
}

/*
 * We have done the truncate/delete so we can go ahead and remove the orphan
 * item for this particular inode.
 */
int btrfs_orphan_del(struct btrfs_trans_handle *trans, struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        spin_lock(&root->orphan_lock);

        if (list_empty(&BTRFS_I(inode)->i_orphan)) {
                spin_unlock(&root->orphan_lock);
                return 0;
        }

        list_del_init(&BTRFS_I(inode)->i_orphan);
        if (!trans) {
                spin_unlock(&root->orphan_lock);
                return 0;
        }

        spin_unlock(&root->orphan_lock);

        ret = btrfs_del_orphan_item(trans, root, inode->i_ino);

        return ret;
}

/*
 * this cleans up any orphans that may be left on the list from the last use
 * of this root.
 */
void btrfs_orphan_cleanup(struct btrfs_root *root)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_item *item;
        struct btrfs_key key, found_key;
        struct btrfs_trans_handle *trans;
        struct inode *inode;
        int ret = 0, nr_unlink = 0, nr_truncate = 0;

        /* don't do orphan cleanup if the fs is readonly. */
        if (root->inode->i_sb->s_flags & MS_RDONLY)
                return;

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

        key.objectid = BTRFS_ORPHAN_OBJECTID;
        btrfs_set_key_type(&key, BTRFS_ORPHAN_ITEM_KEY);
        key.offset = (u64)-1;

        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, root->inode);

        while (1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0) {
                        printk(KERN_ERR "Error searching slot for orphan: %d"
                               "\n", ret);
                        break;
                }

                /*
                 * if ret == 0 means we found what we were searching for, which
                 * is weird, but possible, so only screw with path if we didnt
                 * find the key and see if we have stuff that matches
                 */
                if (ret > 0) {
                        if (path->slots[0] == 0)
                                break;
                        path->slots[0]--;
                }

                /* pull out the item */
                leaf = path->nodes[0];
                item = btrfs_item_nr(leaf, path->slots[0]);
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                /* make sure the item matches what we want */
                if (found_key.objectid != BTRFS_ORPHAN_OBJECTID)
                        break;
                if (btrfs_key_type(&found_key) != BTRFS_ORPHAN_ITEM_KEY)
                        break;

                /* release the path since we're done with it */
                btrfs_release_path(root, path);

                /*
                 * this is where we are basically btrfs_lookup, without the
                 * crossing root thing.  we store the inode number in the
                 * offset of the orphan item.
                 */
                inode = btrfs_iget_locked(root->inode->i_sb,
                                          found_key.offset, root);
                if (!inode)
                        break;

                if (inode->i_state & I_NEW) {
                        BTRFS_I(inode)->root = root;

                        /* have to set the location manually */
                        BTRFS_I(inode)->location.objectid = inode->i_ino;
                        BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
                        BTRFS_I(inode)->location.offset = 0;

                        btrfs_read_locked_inode(inode);
                        unlock_new_inode(inode);
                }

                /*
                 * add this inode to the orphan list so btrfs_orphan_del does
                 * the proper thing when we hit it
                 */
                spin_lock(&root->orphan_lock);
                list_add(&BTRFS_I(inode)->i_orphan, &root->orphan_list);
                spin_unlock(&root->orphan_lock);

                /*
                 * if this is a bad inode, means we actually succeeded in
                 * removing the inode, but not the orphan record, which means
                 * we need to manually delete the orphan since iput will just
                 * do a destroy_inode
                 */
                if (is_bad_inode(inode)) {
                        btrfs_orphan_del(trans, inode);
                        iput(inode);
                        continue;
                }

                /* if we have links, this was a truncate, lets do that */
                if (inode->i_nlink) {
                        nr_truncate++;
                        btrfs_truncate(inode);
                } else {
                        nr_unlink++;
                }

                /* this will do delete_inode and everything for us */
                iput(inode);
        }

        if (nr_unlink)
                printk(KERN_INFO "btrfs: unlinked %d orphans\n", nr_unlink);
        if (nr_truncate)
                printk(KERN_INFO "btrfs: truncated %d orphans\n", nr_truncate);

        btrfs_free_path(path);
        btrfs_end_transaction(trans, root);
}

void btrfs_read_locked_inode(struct inode *inode)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_inode_item *inode_item;
        struct btrfs_timespec *tspec;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key location;
        u64 alloc_group_block;
        u32 rdev;
        int ret;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        memcpy(&location, &BTRFS_I(inode)->location, sizeof(location));

        ret = btrfs_lookup_inode(NULL, root, path, &location, 0);
        if (ret)
                goto make_bad;

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

        inode->i_mode = btrfs_inode_mode(leaf, inode_item);
        inode->i_nlink = btrfs_inode_nlink(leaf, inode_item);
        inode->i_uid = btrfs_inode_uid(leaf, inode_item);
        inode->i_gid = btrfs_inode_gid(leaf, inode_item);
        btrfs_i_size_write(inode, btrfs_inode_size(leaf, inode_item));

        tspec = btrfs_inode_atime(inode_item);
        inode->i_atime.tv_sec = btrfs_timespec_sec(leaf, tspec);
        inode->i_atime.tv_nsec = btrfs_timespec_nsec(leaf, tspec);

        tspec = btrfs_inode_mtime(inode_item);
        inode->i_mtime.tv_sec = btrfs_timespec_sec(leaf, tspec);
        inode->i_mtime.tv_nsec = btrfs_timespec_nsec(leaf, tspec);

        tspec = btrfs_inode_ctime(inode_item);
        inode->i_ctime.tv_sec = btrfs_timespec_sec(leaf, tspec);
        inode->i_ctime.tv_nsec = btrfs_timespec_nsec(leaf, tspec);

        inode->i_blocks = btrfs_inode_nblocks(leaf, inode_item);
        inode->i_generation = btrfs_inode_generation(leaf, inode_item);
        inode->i_rdev = 0;
        rdev = btrfs_inode_rdev(leaf, inode_item);

        BTRFS_I(inode)->index_cnt = (u64)-1;

        alloc_group_block = btrfs_inode_block_group(leaf, inode_item);
        BTRFS_I(inode)->block_group = btrfs_lookup_block_group(root->fs_info,
                                                       alloc_group_block);
        BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);
        if (!BTRFS_I(inode)->block_group) {
                BTRFS_I(inode)->block_group = btrfs_find_block_group(root,
                                                 NULL, 0,
                                                 BTRFS_BLOCK_GROUP_METADATA, 0);
        }
        btrfs_free_path(path);
        inode_item = NULL;

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                inode->i_mapping->a_ops = &btrfs_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                break;
        case S_IFDIR:
                inode->i_fop = &btrfs_dir_file_operations;
                if (root == root->fs_info->tree_root)
                        inode->i_op = &btrfs_dir_ro_inode_operations;
                else
                        inode->i_op = &btrfs_dir_inode_operations;
                break;
        case S_IFLNK:
                inode->i_op = &btrfs_symlink_inode_operations;
                inode->i_mapping->a_ops = &btrfs_symlink_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                break;
        default:
                init_special_inode(inode, inode->i_mode, rdev);
                break;
        }
        return;

make_bad:
        btrfs_free_path(path);
        make_bad_inode(inode);
}

static void fill_inode_item(struct extent_buffer *leaf,
                            struct btrfs_inode_item *item,
                            struct inode *inode)
{
        btrfs_set_inode_uid(leaf, item, inode->i_uid);
        btrfs_set_inode_gid(leaf, item, inode->i_gid);
        btrfs_set_inode_size(leaf, item, BTRFS_I(inode)->disk_i_size);
        btrfs_set_inode_mode(leaf, item, inode->i_mode);
        btrfs_set_inode_nlink(leaf, item, inode->i_nlink);

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

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

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

        btrfs_set_inode_nblocks(leaf, item, inode->i_blocks);
        btrfs_set_inode_generation(leaf, item, inode->i_generation);
        btrfs_set_inode_rdev(leaf, item, inode->i_rdev);
        btrfs_set_inode_flags(leaf, item, BTRFS_I(inode)->flags);
        btrfs_set_inode_block_group(leaf, item,
                                    BTRFS_I(inode)->block_group->key.objectid);
}

int noinline btrfs_update_inode(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct inode *inode)
{
        struct btrfs_inode_item *inode_item;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        ret = btrfs_lookup_inode(trans, root, path,
                                 &BTRFS_I(inode)->location, 1);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto failed;
        }

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

        fill_inode_item(leaf, inode_item, inode);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_set_inode_last_trans(trans, inode);
        ret = 0;
failed:
        btrfs_free_path(path);
        return ret;
}


static int btrfs_unlink_trans(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct inode *dir,
                              struct dentry *dentry)
{
        struct btrfs_path *path;
        const char *name = dentry->d_name.name;
        int name_len = dentry->d_name.len;
        int ret = 0;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        u64 index;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto err;
        }

        di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
                                    name, name_len, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto err;
        }
        if (!di) {
                ret = -ENOENT;
                goto err;
        }
        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        if (ret)
                goto err;
        btrfs_release_path(root, path);

        ret = btrfs_del_inode_ref(trans, root, name, name_len,
                                  dentry->d_inode->i_ino,
                                  dentry->d_parent->d_inode->i_ino, &index);
        if (ret) {
                printk("failed to delete reference to %.*s, "
                       "inode %lu parent %lu\n", name_len, name,
                       dentry->d_inode->i_ino,
                       dentry->d_parent->d_inode->i_ino);
                goto err;
        }

        di = btrfs_lookup_dir_index_item(trans, root, path, dir->i_ino,
                                         index, name, name_len, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto err;
        }
        if (!di) {
                ret = -ENOENT;
                goto err;
        }
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        btrfs_release_path(root, path);

        dentry->d_inode->i_ctime = dir->i_ctime;
err:
        btrfs_free_path(path);
        if (!ret) {
                btrfs_i_size_write(dir, dir->i_size - name_len * 2);
                dir->i_mtime = dir->i_ctime = CURRENT_TIME;
                btrfs_update_inode(trans, root, dir);
#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
                dentry->d_inode->i_nlink--;
#else
                drop_nlink(dentry->d_inode);
#endif
                ret = btrfs_update_inode(trans, root, dentry->d_inode);
                dir->i_sb->s_dirt = 1;
        }
        return ret;
}

static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
{
        struct btrfs_root *root;
        struct btrfs_trans_handle *trans;
        struct inode *inode = dentry->d_inode;
        int ret;
        unsigned long nr = 0;

        root = BTRFS_I(dir)->root;

        ret = btrfs_check_free_space(root, 1, 1);
        if (ret)
                goto fail;

        trans = btrfs_start_transaction(root, 1);

        btrfs_set_trans_block_group(trans, dir);
        ret = btrfs_unlink_trans(trans, root, dir, dentry);

        if (inode->i_nlink == 0)
                ret = btrfs_orphan_add(trans, inode);

        nr = trans->blocks_used;

        btrfs_end_transaction_throttle(trans, root);
fail:
        btrfs_btree_balance_dirty(root, nr);
        return ret;
}

static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;
        int err = 0;
        int ret;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;
        unsigned long nr = 0;

        if (inode->i_size > BTRFS_EMPTY_DIR_SIZE) {
                return -ENOTEMPTY;
        }

        ret = btrfs_check_free_space(root, 1, 1);
        if (ret)
                goto fail;

        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, dir);

        err = btrfs_orphan_add(trans, inode);
        if (err)
                goto fail_trans;

        /* now the directory is empty */
        err = btrfs_unlink_trans(trans, root, dir, dentry);
        if (!err) {
                btrfs_i_size_write(inode, 0);
        }

fail_trans:
        nr = trans->blocks_used;
        ret = btrfs_end_transaction_throttle(trans, root);
fail:
        btrfs_btree_balance_dirty(root, nr);

        if (ret && !err)
                err = ret;
        return err;
}

/*
 * this can truncate away extent items, csum items and directory items.
 * It starts at a high offset and removes keys until it can't find
 * any higher than i_size.
 *
 * csum items that cross the new i_size are truncated to the new size
 * as well.
 *
 * min_type is the minimum key type to truncate down to.  If set to 0, this
 * will kill all the items on this inode, including the INODE_ITEM_KEY.
 */
static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   struct inode *inode,
                                   u32 min_type)
{
        int ret;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u32 found_type;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        u64 extent_start = 0;
        u64 extent_num_bytes = 0;
        u64 item_end = 0;
        u64 root_gen = 0;
        u64 root_owner = 0;
        int found_extent;
        int del_item;
        int pending_del_nr = 0;
        int pending_del_slot = 0;
        int extent_type = -1;
        u64 mask = root->sectorsize - 1;

        btrfs_drop_extent_cache(inode, inode->i_size & (~mask), (u64)-1);
        path = btrfs_alloc_path();
        path->reada = -1;
        BUG_ON(!path);

        /* FIXME, add redo link to tree so we don't leak on crash */
        key.objectid = inode->i_ino;
        key.offset = (u64)-1;
        key.type = (u8)-1;

        btrfs_init_path(path);
search_again:
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0) {
                goto error;
        }
        if (ret > 0) {
                BUG_ON(path->slots[0] == 0);
                path->slots[0]--;
        }

        while(1) {
                fi = NULL;
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                found_type = btrfs_key_type(&found_key);

                if (found_key.objectid != inode->i_ino)
                        break;

                if (found_type < min_type)
                        break;

                item_end = found_key.offset;
                if (found_type == BTRFS_EXTENT_DATA_KEY) {
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        extent_type = btrfs_file_extent_type(leaf, fi);
                        if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                                item_end +=
                                    btrfs_file_extent_num_bytes(leaf, fi);
                        } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                                struct btrfs_item *item = btrfs_item_nr(leaf,
                                                                path->slots[0]);
                                item_end += btrfs_file_extent_inline_len(leaf,
                                                                         item);
                        }
                        item_end--;
                }
                if (found_type == BTRFS_CSUM_ITEM_KEY) {
                        ret = btrfs_csum_truncate(trans, root, path,
                                                  inode->i_size);
                        BUG_ON(ret);
                }
                if (item_end < inode->i_size) {
                        if (found_type == BTRFS_DIR_ITEM_KEY) {
                                found_type = BTRFS_INODE_ITEM_KEY;
                        } else if (found_type == BTRFS_EXTENT_ITEM_KEY) {
                                found_type = BTRFS_CSUM_ITEM_KEY;
                        } else if (found_type == BTRFS_EXTENT_DATA_KEY) {
                                found_type = BTRFS_XATTR_ITEM_KEY;
                        } else if (found_type == BTRFS_XATTR_ITEM_KEY) {
                                found_type = BTRFS_INODE_REF_KEY;
                        } else if (found_type) {
                                found_type--;
                        } else {
                                break;
                        }
                        btrfs_set_key_type(&key, found_type);
                        goto next;
                }
                if (found_key.offset >= inode->i_size)
                        del_item = 1;
                else
                        del_item = 0;
                found_extent = 0;

                /* FIXME, shrink the extent if the ref count is only 1 */
                if (found_type != BTRFS_EXTENT_DATA_KEY)
                        goto delete;

                if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                        u64 num_dec;
                        extent_start = btrfs_file_extent_disk_bytenr(leaf, fi);
                        if (!del_item) {
                                u64 orig_num_bytes =
                                        btrfs_file_extent_num_bytes(leaf, fi);
                                extent_num_bytes = inode->i_size -
                                        found_key.offset + root->sectorsize - 1;
                                extent_num_bytes = extent_num_bytes &
                                        ~((u64)root->sectorsize - 1);
                                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                         extent_num_bytes);
                                num_dec = (orig_num_bytes -
                                           extent_num_bytes);
                                if (extent_start != 0)
                                        dec_i_blocks(inode, num_dec);
                                btrfs_mark_buffer_dirty(leaf);
                        } else {
                                extent_num_bytes =
                                        btrfs_file_extent_disk_num_bytes(leaf,
                                                                         fi);
                                /* FIXME blocksize != 4096 */
                                num_dec = btrfs_file_extent_num_bytes(leaf, fi);
                                if (extent_start != 0) {
                                        found_extent = 1;
                                        dec_i_blocks(inode, num_dec);
                                }
                                root_gen = btrfs_header_generation(leaf);
                                root_owner = btrfs_header_owner(leaf);
                        }
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        if (!del_item) {
                                u32 newsize = inode->i_size - found_key.offset;
                                dec_i_blocks(inode, item_end + 1 -
                                            found_key.offset - newsize);
                                newsize =
                                    btrfs_file_extent_calc_inline_size(newsize);
                                ret = btrfs_truncate_item(trans, root, path,
                                                          newsize, 1);
                                BUG_ON(ret);
                        } else {
                                dec_i_blocks(inode, item_end + 1 -
                                             found_key.offset);
                        }
                }
delete:
                if (del_item) {
                        if (!pending_del_nr) {
                                /* no pending yet, add ourselves */
                                pending_del_slot = path->slots[0];
                                pending_del_nr = 1;
                        } else if (pending_del_nr &&
                                   path->slots[0] + 1 == pending_del_slot) {
                                /* hop on the pending chunk */
                                pending_del_nr++;
                                pending_del_slot = path->slots[0];
                        } else {
                                printk("bad pending slot %d pending_del_nr %d pending_del_slot %d\n", path->slots[0], pending_del_nr, pending_del_slot);
                        }
                } else {
                        break;
                }
                if (found_extent) {
                        ret = btrfs_free_extent(trans, root, extent_start,
                                                extent_num_bytes,
                                                root_owner,
                                                root_gen, inode->i_ino,
                                                found_key.offset, 0);
                        BUG_ON(ret);
                }
next:
                if (path->slots[0] == 0) {
                        if (pending_del_nr)
                                goto del_pending;
                        btrfs_release_path(root, path);
                        goto search_again;
                }

                path->slots[0]--;
                if (pending_del_nr &&
                    path->slots[0] + 1 != pending_del_slot) {
                        struct btrfs_key debug;
del_pending:
                        btrfs_item_key_to_cpu(path->nodes[0], &debug,
                                              pending_del_slot);
                        ret = btrfs_del_items(trans, root, path,
                                              pending_del_slot,
                                              pending_del_nr);
                        BUG_ON(ret);
                        pending_del_nr = 0;
                        btrfs_release_path(root, path);
                        goto search_again;
                }
        }
        ret = 0;
error:
        if (pending_del_nr) {
                ret = btrfs_del_items(trans, root, path, pending_del_slot,
                                      pending_del_nr);
        }
        btrfs_free_path(path);
        inode->i_sb->s_dirt = 1;
        return ret;
}

/*
 * taken from block_truncate_page, but does cow as it zeros out
 * any bytes left in the last page in the file.
 */
static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
{
        struct inode *inode = mapping->host;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        char *kaddr;
        u32 blocksize = root->sectorsize;
        pgoff_t index = from >> PAGE_CACHE_SHIFT;
        unsigned offset = from & (PAGE_CACHE_SIZE-1);
        struct page *page;
        int ret = 0;
        u64 page_start;
        u64 page_end;

        if ((offset & (blocksize - 1)) == 0)
                goto out;

        ret = -ENOMEM;
again:
        page = grab_cache_page(mapping, index);
        if (!page)
                goto out;

        page_start = page_offset(page);
        page_end = page_start + PAGE_CACHE_SIZE - 1;

        if (!PageUptodate(page)) {
                ret = btrfs_readpage(NULL, page);
                lock_page(page);
                if (page->mapping != mapping) {
                        unlock_page(page);
                        page_cache_release(page);
                        goto again;
                }
                if (!PageUptodate(page)) {
                        ret = -EIO;
                        goto out_unlock;
                }
        }
        wait_on_page_writeback(page);

        lock_extent(io_tree, page_start, page_end, GFP_NOFS);
        set_page_extent_mapped(page);

        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
                unlock_page(page);
                page_cache_release(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        set_extent_delalloc(&BTRFS_I(inode)->io_tree, page_start,
                            page_end, GFP_NOFS);
        ret = 0;
        if (offset != PAGE_CACHE_SIZE) {
                kaddr = kmap(page);
                memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        unlock_extent(io_tree, page_start, page_end, GFP_NOFS);

out_unlock:
        unlock_page(page);
        page_cache_release(page);
out:
        return ret;
}

static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = dentry->d_inode;
        int err;

        err = inode_change_ok(inode, attr);
        if (err)
                return err;

        if (S_ISREG(inode->i_mode) &&
            attr->ia_valid & ATTR_SIZE && attr->ia_size > inode->i_size) {
                struct btrfs_trans_handle *trans;
                struct btrfs_root *root = BTRFS_I(inode)->root;
                struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;

                u64 mask = root->sectorsize - 1;
                u64 hole_start = (inode->i_size + mask) & ~mask;
                u64 block_end = (attr->ia_size + mask) & ~mask;
                u64 hole_size;
                u64 alloc_hint = 0;

                if (attr->ia_size <= hole_start)
                        goto out;

                err = btrfs_check_free_space(root, 1, 0);
                if (err)
                        goto fail;

                btrfs_truncate_page(inode->i_mapping, inode->i_size);

                hole_size = block_end - hole_start;
                btrfs_wait_ordered_range(inode, hole_start, hole_size);
                lock_extent(io_tree, hole_start, block_end - 1, GFP_NOFS);

                trans = btrfs_start_transaction(root, 1);
                btrfs_set_trans_block_group(trans, inode);
                mutex_lock(&BTRFS_I(inode)->extent_mutex);
                err = btrfs_drop_extents(trans, root, inode,
                                         hole_start, block_end, hole_start,
                                         &alloc_hint);

                if (alloc_hint != EXTENT_MAP_INLINE) {
                        err = btrfs_insert_file_extent(trans, root,
                                                       inode->i_ino,
                                                       hole_start, 0, 0,
                                                       hole_size, 0);
                        btrfs_drop_extent_cache(inode, hole_start,
                                                (u64)-1);
                        btrfs_check_file(root, inode);
                }
                mutex_unlock(&BTRFS_I(inode)->extent_mutex);
                btrfs_end_transaction(trans, root);
                unlock_extent(io_tree, hole_start, block_end - 1, GFP_NOFS);
                if (err)
                        return err;
        }
out:
        err = inode_setattr(inode, attr);

        if (!err && ((attr->ia_valid & ATTR_MODE)))
                err = btrfs_acl_chmod(inode);
fail:
        return err;
}

void btrfs_delete_inode(struct inode *inode)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        unsigned long nr;
        int ret;

        truncate_inode_pages(&inode->i_data, 0);
        if (is_bad_inode(inode)) {
                btrfs_orphan_del(NULL, inode);
                goto no_delete;
        }
        btrfs_wait_ordered_range(inode, 0, (u64)-1);

        btrfs_i_size_write(inode, 0);
        trans = btrfs_start_transaction(root, 1);

        btrfs_set_trans_block_group(trans, inode);
        ret = btrfs_truncate_in_trans(trans, root, inode, 0);
        if (ret) {
                btrfs_orphan_del(NULL, inode);
                goto no_delete_lock;
        }

        btrfs_orphan_del(trans, inode);

        nr = trans->blocks_used;
        clear_inode(inode);

        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root, nr);
        return;

no_delete_lock:
        nr = trans->blocks_used;
        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root, nr);
no_delete:
        clear_inode(inode);
}

/*
 * this returns the key found in the dir entry in the location pointer.
 * If no dir entries were found, location->objectid is 0.
 */
static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry,
                               struct btrfs_key *location)
{
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        struct btrfs_dir_item *di;
        struct btrfs_path *path;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int ret = 0;

        if (namelen == 1 && strcmp(name, ".") == 0) {
                location->objectid = dir->i_ino;
                location->type = BTRFS_INODE_ITEM_KEY;
                location->offset = 0;
                return 0;
        }
        path = btrfs_alloc_path();
        BUG_ON(!path);

        if (namelen == 2 && strcmp(name, "..") == 0) {
                struct btrfs_key key;
                struct extent_buffer *leaf;
                u32 nritems;
                int slot;

                key.objectid = dir->i_ino;
                btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
                key.offset = 0;
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                BUG_ON(ret == 0);
                ret = 0;

                leaf = path->nodes[0];
                slot = path->slots[0];
                nritems = btrfs_header_nritems(leaf);
                if (slot >= nritems)
                        goto out_err;

                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (key.objectid != dir->i_ino ||
                    key.type != BTRFS_INODE_REF_KEY) {
                        goto out_err;
                }
                location->objectid = key.offset;
                location->type = BTRFS_INODE_ITEM_KEY;
                location->offset = 0;
                goto out;
        }

        di = btrfs_lookup_dir_item(NULL, root, path, dir->i_ino, name,
                                    namelen, 0);
        if (IS_ERR(di))
                ret = PTR_ERR(di);
        if (!di || IS_ERR(di)) {
                goto out_err;
        }
        btrfs_dir_item_key_to_cpu(path->nodes[0], di, location);
out:
        btrfs_free_path(path);
        return ret;
out_err:
        location->objectid = 0;
        goto out;
}

/*
 * when we hit a tree root in a directory, the btrfs part of the inode
 * needs to be changed to reflect the root directory of the tree root.  This
 * is kind of like crossing a mount point.
 */
static int fixup_tree_root_location(struct btrfs_root *root,
                             struct btrfs_key *location,
                             struct btrfs_root **sub_root,
                             struct dentry *dentry)
{
        struct btrfs_path *path;
        struct btrfs_root_item *ri;

        if (btrfs_key_type(location) != BTRFS_ROOT_ITEM_KEY)
                return 0;
        if (location->objectid == BTRFS_ROOT_TREE_OBJECTID)
                return 0;

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

        *sub_root = btrfs_read_fs_root(root->fs_info, location,
                                        dentry->d_name.name,
                                        dentry->d_name.len);
        if (IS_ERR(*sub_root))
                return PTR_ERR(*sub_root);

        ri = &(*sub_root)->root_item;
        location->objectid = btrfs_root_dirid(ri);
        btrfs_set_key_type(location, BTRFS_INODE_ITEM_KEY);
        location->offset = 0;

        btrfs_free_path(path);
        return 0;
}

static int btrfs_init_locked_inode(struct inode *inode, void *p)
{
        struct btrfs_iget_args *args = p;
        inode->i_ino = args->ino;
        BTRFS_I(inode)->root = args->root;
        BTRFS_I(inode)->delalloc_bytes = 0;
        BTRFS_I(inode)->disk_i_size = 0;
        BTRFS_I(inode)->index_cnt = (u64)-1;
        extent_map_tree_init(&BTRFS_I(inode)->extent_tree, GFP_NOFS);
        extent_io_tree_init(&BTRFS_I(inode)->io_tree,
                             inode->i_mapping, GFP_NOFS);
        extent_io_tree_init(&BTRFS_I(inode)->io_failure_tree,
                             inode->i_mapping, GFP_NOFS);
        btrfs_ordered_inode_tree_init(&BTRFS_I(inode)->ordered_tree);
        mutex_init(&BTRFS_I(inode)->csum_mutex);
        mutex_init(&BTRFS_I(inode)->extent_mutex);
        return 0;
}

static int btrfs_find_actor(struct inode *inode, void *opaque)
{
        struct btrfs_iget_args *args = opaque;
        return (args->ino == inode->i_ino &&
                args->root == BTRFS_I(inode)->root);
}

struct inode *btrfs_ilookup(struct super_block *s, u64 objectid,
                            u64 root_objectid)
{
        struct btrfs_iget_args args;
        args.ino = objectid;
        args.root = btrfs_lookup_fs_root(btrfs_sb(s)->fs_info, root_objectid);

        if (!args.root)
                return NULL;

        return ilookup5(s, objectid, btrfs_find_actor, (void *)&args);
}

struct inode *btrfs_iget_locked(struct super_block *s, u64 objectid,
                                struct btrfs_root *root)
{
        struct inode *inode;
        struct btrfs_iget_args args;
        args.ino = objectid;
        args.root = root;

        inode = iget5_locked(s, objectid, btrfs_find_actor,
                             btrfs_init_locked_inode,
                             (void *)&args);
        return inode;
}

static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
                                   struct nameidata *nd)
{
        struct inode * inode;
        struct btrfs_inode *bi = BTRFS_I(dir);
        struct btrfs_root *root = bi->root;
        struct btrfs_root *sub_root = root;
        struct btrfs_key location;
        int ret, do_orphan = 0;

        if (dentry->d_name.len > BTRFS_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        ret = btrfs_inode_by_name(dir, dentry, &location);

        if (ret < 0)
                return ERR_PTR(ret);

        inode = NULL;
        if (location.objectid) {
                ret = fixup_tree_root_location(root, &location, &sub_root,
                                                dentry);
                if (ret < 0)
                        return ERR_PTR(ret);
                if (ret > 0)
                        return ERR_PTR(-ENOENT);

                inode = btrfs_iget_locked(dir->i_sb, location.objectid,
                                          sub_root);
                if (!inode)
                        return ERR_PTR(-EACCES);
                if (inode->i_state & I_NEW) {
                        /* the inode and parent dir are two different roots */
                        if (sub_root != root) {
                                igrab(inode);
                                sub_root->inode = inode;
                                do_orphan = 1;
                        }
                        BTRFS_I(inode)->root = sub_root;
                        memcpy(&BTRFS_I(inode)->location, &location,
                               sizeof(location));
                        btrfs_read_locked_inode(inode);
                        unlock_new_inode(inode);
                }
        }

        if (unlikely(do_orphan))
                btrfs_orphan_cleanup(sub_root);

        return d_splice_alias(inode, dentry);
}

static unsigned char btrfs_filetype_table[] = {
        DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
};

static int btrfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
        struct inode *inode = filp->f_dentry->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_item *item;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_path *path;
        int ret;
        u32 nritems;
        struct extent_buffer *leaf;
        int slot;
        int advance;
        unsigned char d_type;
        int over = 0;
        u32 di_cur;
        u32 di_total;
        u32 di_len;
        int key_type = BTRFS_DIR_INDEX_KEY;
        char tmp_name[32];
        char *name_ptr;
        int name_len;

        /* FIXME, use a real flag for deciding about the key type */
        if (root->fs_info->tree_root == root)
                key_type = BTRFS_DIR_ITEM_KEY;

        /* special case for "." */
        if (filp->f_pos == 0) {
                over = filldir(dirent, ".", 1,
                               1, inode->i_ino,
                               DT_DIR);
                if (over)
                        return 0;
                filp->f_pos = 1;
        }

        key.objectid = inode->i_ino;
        path = btrfs_alloc_path();
        path->reada = 2;

        /* special case for .., just use the back ref */
        if (filp->f_pos == 1) {
                btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
                key.offset = 0;
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                BUG_ON(ret == 0);
                leaf = path->nodes[0];
                slot = path->slots[0];
                nritems = btrfs_header_nritems(leaf);
                if (slot >= nritems) {
                        btrfs_release_path(root, path);
                        goto read_dir_items;
                }
                btrfs_item_key_to_cpu(leaf, &found_key, slot);
                btrfs_release_path(root, path);
                if (found_key.objectid != key.objectid ||
                    found_key.type != BTRFS_INODE_REF_KEY)
                        goto read_dir_items;
                over = filldir(dirent, "..", 2,
                               2, found_key.offset, DT_DIR);
                if (over)
                        goto nopos;
                filp->f_pos = 2;
        }

read_dir_items:
        btrfs_set_key_type(&key, key_type);
        key.offset = filp->f_pos;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;
        advance = 0;
        while(1) {
                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
                slot = path->slots[0];
                if (advance || slot >= nritems) {
                        if (slot >= nritems -1) {
                                ret = btrfs_next_leaf(root, path);
                                if (ret)
                                        break;
                                leaf = path->nodes[0];
                                nritems = btrfs_header_nritems(leaf);
                                slot = path->slots[0];
                        } else {
                                slot++;
                                path->slots[0]++;
                        }
                }
                advance = 1;
                item = btrfs_item_nr(leaf, slot);
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                if (found_key.objectid != key.objectid)
                        break;
                if (btrfs_key_type(&found_key) != key_type)
                        break;
                if (found_key.offset < filp->f_pos)
                        continue;

                filp->f_pos = found_key.offset;
                advance = 1;
                di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
                di_cur = 0;
                di_total = btrfs_item_size(leaf, item);
                while(di_cur < di_total) {
                        struct btrfs_key location;

                        name_len = btrfs_dir_name_len(leaf, di);
                        if (name_len < 32) {
                                name_ptr = tmp_name;
                        } else {
                                name_ptr = kmalloc(name_len, GFP_NOFS);
                                BUG_ON(!name_ptr);
                        }
                        read_extent_buffer(leaf, name_ptr,
                                           (unsigned long)(di + 1), name_len);

                        d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
                        btrfs_dir_item_key_to_cpu(leaf, di, &location);
                        over = filldir(dirent, name_ptr, name_len,
                                       found_key.offset,
                                       location.objectid,
                                       d_type);

                        if (name_ptr != tmp_name)
                                kfree(name_ptr);

                        if (over)
                                goto nopos;
                        di_len = btrfs_dir_name_len(leaf, di) +
                                btrfs_dir_data_len(leaf, di) +sizeof(*di);
                        di_cur += di_len;
                        di = (struct btrfs_dir_item *)((char *)di + di_len);
                }
        }
        if (key_type == BTRFS_DIR_INDEX_KEY)
                filp->f_pos = INT_LIMIT(typeof(filp->f_pos));
        else
                filp->f_pos++;
nopos:
        ret = 0;
err:
        btrfs_free_path(path);
        return ret;
}

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

        if (wait) {
                trans = btrfs_join_transaction(root, 1);
                btrfs_set_trans_block_group(trans, inode);
                ret = btrfs_commit_transaction(trans, root);
        }
        return ret;
}

/*
 * This is somewhat expensive, updating the tree every time the
 * inode changes.  But, it is most likely to find the inode in cache.
 * FIXME, needs more benchmarking...there are no reasons other than performance
 * to keep or drop this code.
 */
void btrfs_dirty_inode(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;

        trans = btrfs_join_transaction(root, 1);
        btrfs_set_trans_block_group(trans, inode);
        btrfs_update_inode(trans, root, inode);
        btrfs_end_transaction(trans, root);
}

static int btrfs_set_inode_index_count(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key key, found_key;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        key.objectid = inode->i_ino;
        btrfs_set_key_type(&key, BTRFS_DIR_INDEX_KEY);
        key.offset = (u64)-1;

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

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        /* FIXME: we should be able to handle this */
        if (ret == 0)
                goto out;
        ret = 0;

        /*
         * MAGIC NUMBER EXPLANATION:
         * since we search a directory based on f_pos we have to start at 2
         * since '.' and '..' have f_pos of 0 and 1 respectively, so everybody
         * else has to start at 2
         */
        if (path->slots[0] == 0) {
                BTRFS_I(inode)->index_cnt = 2;
                goto out;
        }

        path->slots[0]--;

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

        if (found_key.objectid != inode->i_ino ||
            btrfs_key_type(&found_key) != BTRFS_DIR_INDEX_KEY) {
                BTRFS_I(inode)->index_cnt = 2;
                goto out;
        }

        BTRFS_I(inode)->index_cnt = found_key.offset + 1;
out:
        btrfs_free_path(path);
        return ret;
}

static int btrfs_set_inode_index(struct inode *dir, struct inode *inode)
{
        int ret = 0;

        if (BTRFS_I(dir)->index_cnt == (u64)-1) {
                ret = btrfs_set_inode_index_count(dir);
                if (ret)
                        return ret;
        }

        BTRFS_I(inode)->index = BTRFS_I(dir)->index_cnt;
        BTRFS_I(dir)->index_cnt++;

        return ret;
}

static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct inode *dir,
                                     const char *name, int name_len,
                                     u64 ref_objectid,
                                     u64 objectid,
                                     struct btrfs_block_group_cache *group,
                                     int mode)
{
        struct inode *inode;
        struct btrfs_inode_item *inode_item;
        struct btrfs_block_group_cache *new_inode_group;
        struct btrfs_key *location;
        struct btrfs_path *path;
        struct btrfs_inode_ref *ref;
        struct btrfs_key key[2];
        u32 sizes[2];
        unsigned long ptr;
        int ret;
        int owner;

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

        inode = new_inode(root->fs_info->sb);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        if (dir) {
                ret = btrfs_set_inode_index(dir, inode);
                if (ret)
                        return ERR_PTR(ret);
        } else {
                BTRFS_I(inode)->index = 0;
        }
        /*
         * index_cnt is ignored for everything but a dir,
         * btrfs_get_inode_index_count has an explanation for the magic
         * number
         */
        BTRFS_I(inode)->index_cnt = 2;

        extent_map_tree_init(&BTRFS_I(inode)->extent_tree, GFP_NOFS);
        extent_io_tree_init(&BTRFS_I(inode)->io_tree,
                             inode->i_mapping, GFP_NOFS);
        extent_io_tree_init(&BTRFS_I(inode)->io_failure_tree,
                             inode->i_mapping, GFP_NOFS);
        btrfs_ordered_inode_tree_init(&BTRFS_I(inode)->ordered_tree);
        mutex_init(&BTRFS_I(inode)->csum_mutex);
        mutex_init(&BTRFS_I(inode)->extent_mutex);
        BTRFS_I(inode)->delalloc_bytes = 0;
        BTRFS_I(inode)->disk_i_size = 0;
        BTRFS_I(inode)->root = root;

        if (mode & S_IFDIR)
                owner = 0;
        else
                owner = 1;
        new_inode_group = btrfs_find_block_group(root, group, 0,
                                       BTRFS_BLOCK_GROUP_METADATA, owner);
        if (!new_inode_group) {
                printk("find_block group failed\n");
                new_inode_group = group;
        }
        BTRFS_I(inode)->block_group = new_inode_group;
        BTRFS_I(inode)->flags = 0;

        key[0].objectid = objectid;
        btrfs_set_key_type(&key[0], BTRFS_INODE_ITEM_KEY);
        key[0].offset = 0;

        key[1].objectid = objectid;
        btrfs_set_key_type(&key[1], BTRFS_INODE_REF_KEY);
        key[1].offset = ref_objectid;

        sizes[0] = sizeof(struct btrfs_inode_item);
        sizes[1] = name_len + sizeof(*ref);

        ret = btrfs_insert_empty_items(trans, root, path, key, sizes, 2);
        if (ret != 0)
                goto fail;

        if (objectid > root->highest_inode)
                root->highest_inode = objectid;

        inode->i_uid = current->fsuid;
        inode->i_gid = current->fsgid;
        inode->i_mode = mode;
        inode->i_ino = objectid;
        inode->i_blocks = 0;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                  struct btrfs_inode_item);
        fill_inode_item(path->nodes[0], inode_item, inode);

        ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
                             struct btrfs_inode_ref);
        btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
        btrfs_set_inode_ref_index(path->nodes[0], ref, BTRFS_I(inode)->index);
        ptr = (unsigned long)(ref + 1);
        write_extent_buffer(path->nodes[0], name, ptr, name_len);

        btrfs_mark_buffer_dirty(path->nodes[0]);
        btrfs_free_path(path);

        location = &BTRFS_I(inode)->location;
        location->objectid = objectid;
        location->offset = 0;
        btrfs_set_key_type(location, BTRFS_INODE_ITEM_KEY);

        insert_inode_hash(inode);
        return inode;
fail:
        if (dir)
                BTRFS_I(dir)->index_cnt--;
        btrfs_free_path(path);
        return ERR_PTR(ret);
}

static inline u8 btrfs_inode_type(struct inode *inode)
{
        return btrfs_type_by_mode[(inode->i_mode & S_IFMT) >> S_SHIFT];
}

static int btrfs_add_link(struct btrfs_trans_handle *trans,
                            struct dentry *dentry, struct inode *inode,
                            int add_backref)
{
        int ret;
        struct btrfs_key key;
        struct btrfs_root *root = BTRFS_I(dentry->d_parent->d_inode)->root;
        struct inode *parent_inode = dentry->d_parent->d_inode;

        key.objectid = inode->i_ino;
        btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
        key.offset = 0;

        ret = btrfs_insert_dir_item(trans, root,
                                    dentry->d_name.name, dentry->d_name.len,
                                    dentry->d_parent->d_inode->i_ino,
                                    &key, btrfs_inode_type(inode),
                                    BTRFS_I(inode)->index);
        if (ret == 0) {
                if (add_backref) {
                        ret = btrfs_insert_inode_ref(trans, root,
                                             dentry->d_name.name,
                                             dentry->d_name.len,
                                             inode->i_ino,
                                             parent_inode->i_ino,
                                             BTRFS_I(inode)->index);
                }
                btrfs_i_size_write(parent_inode, parent_inode->i_size +
                                   dentry->d_name.len * 2);
                parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
                ret = btrfs_update_inode(trans, root,
                                         dentry->d_parent->d_inode);
        }
        return ret;
}

static int btrfs_add_nondir(struct btrfs_trans_handle *trans,
                            struct dentry *dentry, struct inode *inode,
                            int backref)
{
        int err = btrfs_add_link(trans, dentry, inode, backref);
        if (!err) {
                d_instantiate(dentry, inode);
                return 0;
        }
        if (err > 0)
                err = -EEXIST;
        return err;
}

static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
                        int mode, dev_t rdev)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        u64 objectid;
        unsigned long nr = 0;

        if (!new_valid_dev(rdev))
                return -EINVAL;

        err = btrfs_check_free_space(root, 1, 0);
        if (err)
                goto fail;

        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, dir);

        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
        if (err) {
                err = -ENOSPC;
                goto out_unlock;
        }

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len,
                                dentry->d_parent->d_inode->i_ino, objectid,
                                BTRFS_I(dir)->block_group, mode);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_unlock;

        err = btrfs_init_acl(inode, dir);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }

        btrfs_set_trans_block_group(trans, inode);
        err = btrfs_add_nondir(trans, dentry, inode, 0);
        if (err)
                drop_inode = 1;
        else {
                inode->i_op = &btrfs_special_inode_operations;
                init_special_inode(inode, inode->i_mode, rdev);
                btrfs_update_inode(trans, root, inode);
        }
        dir->i_sb->s_dirt = 1;
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);
out_unlock:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
fail:
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int btrfs_create(struct inode *dir, struct dentry *dentry,
                        int mode, struct nameidata *nd)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        unsigned long nr = 0;
        u64 objectid;

        err = btrfs_check_free_space(root, 1, 0);
        if (err)
                goto fail;
        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, dir);

        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
        if (err) {
                err = -ENOSPC;
                goto out_unlock;
        }

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len,
                                dentry->d_parent->d_inode->i_ino,
                                objectid, BTRFS_I(dir)->block_group, mode);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_unlock;

        err = btrfs_init_acl(inode, dir);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }

        btrfs_set_trans_block_group(trans, inode);
        err = btrfs_add_nondir(trans, dentry, inode, 0);
        if (err)
                drop_inode = 1;
        else {
                inode->i_mapping->a_ops = &btrfs_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                extent_map_tree_init(&BTRFS_I(inode)->extent_tree, GFP_NOFS);
                extent_io_tree_init(&BTRFS_I(inode)->io_tree,
                                     inode->i_mapping, GFP_NOFS);
                extent_io_tree_init(&BTRFS_I(inode)->io_failure_tree,
                                     inode->i_mapping, GFP_NOFS);
                mutex_init(&BTRFS_I(inode)->csum_mutex);
                mutex_init(&BTRFS_I(inode)->extent_mutex);
                BTRFS_I(inode)->delalloc_bytes = 0;
                BTRFS_I(inode)->disk_i_size = 0;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                btrfs_ordered_inode_tree_init(&BTRFS_I(inode)->ordered_tree);
        }
        dir->i_sb->s_dirt = 1;
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);
out_unlock:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
fail:
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
                      struct dentry *dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = old_dentry->d_inode;
        unsigned long nr = 0;
        int err;
        int drop_inode = 0;

        if (inode->i_nlink == 0)
                return -ENOENT;

#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
        inode->i_nlink++;
#else
        inc_nlink(inode);
#endif
        err = btrfs_check_free_space(root, 1, 0);
        if (err)
                goto fail;
        err = btrfs_set_inode_index(dir, inode);
        if (err)
                goto fail;

        trans = btrfs_start_transaction(root, 1);

        btrfs_set_trans_block_group(trans, dir);
        atomic_inc(&inode->i_count);

        err = btrfs_add_nondir(trans, dentry, inode, 1);

        if (err)
                drop_inode = 1;

        dir->i_sb->s_dirt = 1;
        btrfs_update_inode_block_group(trans, dir);
        err = btrfs_update_inode(trans, root, inode);

        if (err)
                drop_inode = 1;

        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
fail:
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        struct inode *inode = NULL;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int err = 0;
        int drop_on_err = 0;
        u64 objectid = 0;
        unsigned long nr = 1;

        err = btrfs_check_free_space(root, 1, 0);
        if (err)
                goto out_unlock;

        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, dir);

        if (IS_ERR(trans)) {
                err = PTR_ERR(trans);
                goto out_unlock;
        }

        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
        if (err) {
                err = -ENOSPC;
                goto out_unlock;
        }

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len,
                                dentry->d_parent->d_inode->i_ino, objectid,
                                BTRFS_I(dir)->block_group, S_IFDIR | mode);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out_fail;
        }

        drop_on_err = 1;

        err = btrfs_init_acl(inode, dir);
        if (err)
                goto out_fail;

        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;
        btrfs_set_trans_block_group(trans, inode);

        btrfs_i_size_write(inode, 0);
        err = btrfs_update_inode(trans, root, inode);
        if (err)
                goto out_fail;

        err = btrfs_add_link(trans, dentry, inode, 0);
        if (err)
                goto out_fail;

        d_instantiate(dentry, inode);
        drop_on_err = 0;
        dir->i_sb->s_dirt = 1;
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);

out_fail:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);

out_unlock:
        if (drop_on_err)
                iput(inode);
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int merge_extent_mapping(struct extent_map_tree *em_tree,
                                struct extent_map *existing,
                                struct extent_map *em,
                                u64 map_start, u64 map_len)
{
        u64 start_diff;

        BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
        start_diff = map_start - em->start;
        em->start = map_start;
        em->len = map_len;
        if (em->block_start < EXTENT_MAP_LAST_BYTE)
                em->block_start += start_diff;
        return add_extent_mapping(em_tree, em);
}

struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
                                    size_t pg_offset, u64 start, u64 len,
                                    int create)
{
        int ret;
        int err = 0;
        u64 bytenr;
        u64 extent_start = 0;
        u64 extent_end = 0;
        u64 objectid = inode->i_ino;
        u32 found_type;
        struct btrfs_path *path = NULL;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_extent_item *item;
        struct extent_buffer *leaf;
        struct btrfs_key found_key;
        struct extent_map *em = NULL;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_trans_handle *trans = NULL;

again:
        spin_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, len);
        if (em)
                em->bdev = root->fs_info->fs_devices->latest_bdev;
        spin_unlock(&em_tree->lock);

        if (em) {
                if (em->start > start || em->start + em->len <= start)
                        free_extent_map(em);
                else if (em->block_start == EXTENT_MAP_INLINE && page)
                        free_extent_map(em);
                else
                        goto out;
        }
        em = alloc_extent_map(GFP_NOFS);
        if (!em) {
                err = -ENOMEM;
                goto out;
        }
        em->bdev = root->fs_info->fs_devices->latest_bdev;
        em->start = EXTENT_MAP_HOLE;
        em->len = (u64)-1;

        if (!path) {
                path = btrfs_alloc_path();
                BUG_ON(!path);
        }

        ret = btrfs_lookup_file_extent(trans, root, path,
                                       objectid, start, trans != NULL);
        if (ret < 0) {
                err = ret;
                goto out;
        }

        if (ret != 0) {
                if (path->slots[0] == 0)
                        goto not_found;
                path->slots[0]--;
        }

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0],
                              struct btrfs_file_extent_item);
        /* are we inside the extent that was found? */
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
        found_type = btrfs_key_type(&found_key);
        if (found_key.objectid != objectid ||
            found_type != BTRFS_EXTENT_DATA_KEY) {
                goto not_found;
        }

        found_type = btrfs_file_extent_type(leaf, item);
        extent_start = found_key.offset;
        if (found_type == BTRFS_FILE_EXTENT_REG) {
                extent_end = extent_start +
                       btrfs_file_extent_num_bytes(leaf, item);
                err = 0;
                if (start < extent_start || start >= extent_end) {
                        em->start = start;
                        if (start < extent_start) {
                                if (start + len <= extent_start)
                                        goto not_found;
                                em->len = extent_end - extent_start;
                        } else {
                                em->len = len;
                        }
                        goto not_found_em;
                }
                bytenr = btrfs_file_extent_disk_bytenr(leaf, item);
                if (bytenr == 0) {
                        em->start = extent_start;
                        em->len = extent_end - extent_start;
                        em->block_start = EXTENT_MAP_HOLE;
                        goto insert;
                }
                bytenr += btrfs_file_extent_offset(leaf, item);
                em->block_start = bytenr;
                em->start = extent_start;
                em->len = extent_end - extent_start;
                goto insert;
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                u64 page_start;
                unsigned long ptr;
                char *map;
                size_t size;
                size_t extent_offset;
                size_t copy_size;

                size = btrfs_file_extent_inline_len(leaf, btrfs_item_nr(leaf,
                                                    path->slots[0]));
                extent_end = (extent_start + size + root->sectorsize - 1) &
                        ~((u64)root->sectorsize - 1);
                if (start < extent_start || start >= extent_end) {
                        em->start = start;
                        if (start < extent_start) {
                                if (start + len <= extent_start)
                                        goto not_found;
                                em->len = extent_end - extent_start;
                        } else {
                                em->len = len;
                        }
                        goto not_found_em;
                }
                em->block_start = EXTENT_MAP_INLINE;

                if (!page) {
                        em->start = extent_start;
                        em->len = size;
                        goto out;
                }

                page_start = page_offset(page) + pg_offset;
                extent_offset = page_start - extent_start;
                copy_size = min_t(u64, PAGE_CACHE_SIZE - pg_offset,
                                size - extent_offset);
                em->start = extent_start + extent_offset;
                em->len = (copy_size + root->sectorsize - 1) &
                        ~((u64)root->sectorsize - 1);
                map = kmap(page);
                ptr = btrfs_file_extent_inline_start(item) + extent_offset;
                if (create == 0 && !PageUptodate(page)) {
                        read_extent_buffer(leaf, map + pg_offset, ptr,
                                           copy_size);
                        flush_dcache_page(page);
                } else if (create && PageUptodate(page)) {
                        if (!trans) {
                                kunmap(page);
                                free_extent_map(em);
                                em = NULL;
                                btrfs_release_path(root, path);
                                trans = btrfs_join_transaction(root, 1);
                                goto again;
                        }
                        write_extent_buffer(leaf, map + pg_offset, ptr,
                                            copy_size);
                        btrfs_mark_buffer_dirty(leaf);
                }
                kunmap(page);
                set_extent_uptodate(io_tree, em->start,
                                    extent_map_end(em) - 1, GFP_NOFS);
                goto insert;
        } else {
                printk("unkknown found_type %d\n", found_type);
                WARN_ON(1);
        }
not_found:
        em->start = start;
        em->len = len;
not_found_em:
        em->block_start = EXTENT_MAP_HOLE;
insert:
        btrfs_release_path(root, path);
        if (em->start > start || extent_map_end(em) <= start) {
                printk("bad extent! em: [%Lu %Lu] passed [%Lu %Lu]\n", em->start, em->len, start, len);
                err = -EIO;
                goto out;
        }

        err = 0;
        spin_lock(&em_tree->lock);
        ret = add_extent_mapping(em_tree, em);
        /* it is possible that someone inserted the extent into the tree
         * while we had the lock dropped.  It is also possible that
         * an overlapping map exists in the tree
         */
        if (ret == -EEXIST) {
                struct extent_map *existing;

                ret = 0;

                existing = lookup_extent_mapping(em_tree, start, len);
                if (existing && (existing->start > start ||
                    existing->start + existing->len <= start)) {
                        free_extent_map(existing);
                        existing = NULL;
                }
                if (!existing) {
                        existing = lookup_extent_mapping(em_tree, em->start,
                                                         em->len);
                        if (existing) {
                                err = merge_extent_mapping(em_tree, existing,
                                                           em, start,
                                                           root->sectorsize);
                                free_extent_map(existing);
                                if (err) {
                                        free_extent_map(em);
                                        em = NULL;
                                }
                        } else {
                                err = -EIO;
                                printk("failing to insert %Lu %Lu\n",
                                       start, len);
                                free_extent_map(em);
                                em = NULL;
                        }
                } else {
                        free_extent_map(em);
                        em = existing;
                        err = 0;
                }
        }
        spin_unlock(&em_tree->lock);
out:
        if (path)
                btrfs_free_path(path);
        if (trans) {
                ret = btrfs_end_transaction(trans, root);
                if (!err) {
                        err = ret;
                }
        }
        if (err) {
                free_extent_map(em);
                WARN_ON(1);
                return ERR_PTR(err);
        }
        return em;
}

#if 0 /* waiting for O_DIRECT reads */
static int btrfs_get_block(struct inode *inode, sector_t iblock,
                        struct buffer_head *bh_result, int create)
{
        struct extent_map *em;
        u64 start = (u64)iblock << inode->i_blkbits;
        struct btrfs_multi_bio *multi = NULL;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u64 len;
        u64 logical;
        u64 map_length;
        int ret = 0;

        em = btrfs_get_extent(inode, NULL, 0, start, bh_result->b_size, 0);

        if (!em || IS_ERR(em))
                goto out;

        if (em->start > start || em->start + em->len <= start) {
            goto out;
        }

        if (em->block_start == EXTENT_MAP_INLINE) {
                ret = -EINVAL;
                goto out;
        }

        len = em->start + em->len - start;
        len = min_t(u64, len, INT_LIMIT(typeof(bh_result->b_size)));

        if (em->block_start == EXTENT_MAP_HOLE ||
            em->block_start == EXTENT_MAP_DELALLOC) {
                bh_result->b_size = len;
                goto out;
        }

        logical = start - em->start;
        logical = em->block_start + logical;

        map_length = len;
        ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
                              logical, &map_length, &multi, 0);
        BUG_ON(ret);
        bh_result->b_blocknr = multi->stripes[0].physical >> inode->i_blkbits;
        bh_result->b_size = min(map_length, len);

        bh_result->b_bdev = multi->stripes[0].dev->bdev;
        set_buffer_mapped(bh_result);
        kfree(multi);
out:
        free_extent_map(em);
        return ret;
}
#endif

static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
                        const struct iovec *iov, loff_t offset,
                        unsigned long nr_segs)
{
        return -EINVAL;
#if 0
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;

        if (rw == WRITE)
                return -EINVAL;

        return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
                                  offset, nr_segs, btrfs_get_block, NULL);
#endif
}

static sector_t btrfs_bmap(struct address_space *mapping, sector_t iblock)
{
        return extent_bmap(mapping, iblock, btrfs_get_extent);
}

int btrfs_readpage(struct file *file, struct page *page)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_read_full_page(tree, page, btrfs_get_extent);
}

static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct extent_io_tree *tree;


        if (current->flags & PF_MEMALLOC) {
                redirty_page_for_writepage(wbc, page);
                unlock_page(page);
                return 0;
        }
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
}

int btrfs_writepages(struct address_space *mapping,
                     struct writeback_control *wbc)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(mapping->host)->io_tree;
        return extent_writepages(tree, mapping, btrfs_get_extent, wbc);
}

static int
btrfs_readpages(struct file *file, struct address_space *mapping,
                struct list_head *pages, unsigned nr_pages)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(mapping->host)->io_tree;
        return extent_readpages(tree, mapping, pages, nr_pages,
                                btrfs_get_extent);
}
static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        struct extent_io_tree *tree;
        struct extent_map_tree *map;
        int ret;

        tree = &BTRFS_I(page->mapping->host)->io_tree;
        map = &BTRFS_I(page->mapping->host)->extent_tree;
        ret = try_release_extent_mapping(map, tree, page, gfp_flags);
        if (ret == 1) {
                ClearPagePrivate(page);
                set_page_private(page, 0);
                page_cache_release(page);
        }
        return ret;
}

static int btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        return __btrfs_releasepage(page, gfp_flags);
}

static void btrfs_invalidatepage(struct page *page, unsigned long offset)
{
        struct extent_io_tree *tree;
        struct btrfs_ordered_extent *ordered;
        u64 page_start = page_offset(page);
        u64 page_end = page_start + PAGE_CACHE_SIZE - 1;

        wait_on_page_writeback(page);
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        if (offset) {
                btrfs_releasepage(page, GFP_NOFS);
                return;
        }

        lock_extent(tree, page_start, page_end, GFP_NOFS);
        ordered = btrfs_lookup_ordered_extent(page->mapping->host,
                                           page_offset(page));
        if (ordered) {
                /*
                 * IO on this page will never be started, so we need
                 * to account for any ordered extents now
                 */
                clear_extent_bit(tree, page_start, page_end,
                                 EXTENT_DIRTY | EXTENT_DELALLOC |
                                 EXTENT_LOCKED, 1, 0, GFP_NOFS);
                btrfs_finish_ordered_io(page->mapping->host,
                                        page_start, page_end);
                btrfs_put_ordered_extent(ordered);
                lock_extent(tree, page_start, page_end, GFP_NOFS);
        }
        clear_extent_bit(tree, page_start, page_end,
                 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
                 EXTENT_ORDERED,
                 1, 1, GFP_NOFS);
        __btrfs_releasepage(page, GFP_NOFS);

        ClearPageChecked(page);
        if (PagePrivate(page)) {
                ClearPagePrivate(page);
                set_page_private(page, 0);
                page_cache_release(page);
        }
}

/*
 * btrfs_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
 * vmtruncate() writes the inode size before removing pages, once we have the
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
 */
int btrfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
{
        struct inode *inode = fdentry(vma->vm_file)->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        char *kaddr;
        unsigned long zero_start;
        loff_t size;
        int ret;
        u64 page_start;
        u64 page_end;

        ret = btrfs_check_free_space(root, PAGE_CACHE_SIZE, 0);
        if (ret)
                goto out;

        ret = -EINVAL;
again:
        lock_page(page);
        size = i_size_read(inode);
        page_start = page_offset(page);
        page_end = page_start + PAGE_CACHE_SIZE - 1;

        if ((page->mapping != inode->i_mapping) ||
            (page_start >= size)) {
                /* page got truncated out from underneath us */
                goto out_unlock;
        }
        wait_on_page_writeback(page);

        lock_extent(io_tree, page_start, page_end, GFP_NOFS);
        set_page_extent_mapped(page);

        /*
         * we can't set the delalloc bits if there are pending ordered
         * extents.  Drop our locks and wait for them to finish
         */
        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        set_extent_delalloc(&BTRFS_I(inode)->io_tree, page_start,
                            page_end, GFP_NOFS);
        ret = 0;

        /* page is wholly or partially inside EOF */
        if (page_start + PAGE_CACHE_SIZE > size)
                zero_start = size & ~PAGE_CACHE_MASK;
        else
                zero_start = PAGE_CACHE_SIZE;

        if (zero_start != PAGE_CACHE_SIZE) {
                kaddr = kmap(page);
                memset(kaddr + zero_start, 0, PAGE_CACHE_SIZE - zero_start);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        unlock_extent(io_tree, page_start, page_end, GFP_NOFS);

out_unlock:
        unlock_page(page);
out:
        return ret;
}

static void btrfs_truncate(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;
        struct btrfs_trans_handle *trans;
        unsigned long nr;
        u64 mask = root->sectorsize - 1;

        if (!S_ISREG(inode->i_mode))
                return;
        if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
                return;

        btrfs_truncate_page(inode->i_mapping, inode->i_size);
        btrfs_wait_ordered_range(inode, inode->i_size & (~mask), (u64)-1);

        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, inode);
        btrfs_i_size_write(inode, inode->i_size);

        ret = btrfs_orphan_add(trans, inode);
        if (ret)
                goto out;
        /* FIXME, add redo link to tree so we don't leak on crash */
        ret = btrfs_truncate_in_trans(trans, root, inode,
                                      BTRFS_EXTENT_DATA_KEY);
        btrfs_update_inode(trans, root, inode);

        ret = btrfs_orphan_del(trans, inode);
        BUG_ON(ret);

out:
        nr = trans->blocks_used;
        ret = btrfs_end_transaction_throttle(trans, root);
        BUG_ON(ret);
        btrfs_btree_balance_dirty(root, nr);
}

/*
 * Invalidate a single dcache entry at the root of the filesystem.
 * Needed after creation of snapshot or subvolume.
 */
void btrfs_invalidate_dcache_root(struct btrfs_root *root, char *name,
                                  int namelen)
{
        struct dentry *alias, *entry;
        struct qstr qstr;

        alias = d_find_alias(root->fs_info->sb->s_root->d_inode);
        if (alias) {
                qstr.name = name;
                qstr.len = namelen;
                /* change me if btrfs ever gets a d_hash operation */
                qstr.hash = full_name_hash(qstr.name, qstr.len);
                entry = d_lookup(alias, &qstr);
                dput(alias);
                if (entry) {
                        d_invalidate(entry);
                        dput(entry);
                }
        }
}

int btrfs_create_subvol_root(struct btrfs_root *new_root,
                struct btrfs_trans_handle *trans, u64 new_dirid,
                struct btrfs_block_group_cache *block_group)
{
        struct inode *inode;

        inode = btrfs_new_inode(trans, new_root, NULL, "..", 2, new_dirid,
                                new_dirid, block_group, S_IFDIR | 0700);
        if (IS_ERR(inode))
                return PTR_ERR(inode);
        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;
        new_root->inode = inode;

        inode->i_nlink = 1;
        btrfs_i_size_write(inode, 0);

        return btrfs_update_inode(trans, new_root, inode);
}

unsigned long btrfs_force_ra(struct address_space *mapping,
                              struct file_ra_state *ra, struct file *file,
                              pgoff_t offset, pgoff_t last_index)
{
        pgoff_t req_size = last_index - offset + 1;

#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,23)
        offset = page_cache_readahead(mapping, ra, file, offset, req_size);
        return offset;
#else
        page_cache_sync_readahead(mapping, ra, file, offset, req_size);
        return offset + req_size;
#endif
}

struct inode *btrfs_alloc_inode(struct super_block *sb)
{
        struct btrfs_inode *ei;

        ei = kmem_cache_alloc(btrfs_inode_cachep, GFP_NOFS);
        if (!ei)
                return NULL;
        ei->last_trans = 0;
        btrfs_ordered_inode_tree_init(&ei->ordered_tree);
        ei->i_acl = BTRFS_ACL_NOT_CACHED;
        ei->i_default_acl = BTRFS_ACL_NOT_CACHED;
        INIT_LIST_HEAD(&ei->i_orphan);
        return &ei->vfs_inode;
}

void btrfs_destroy_inode(struct inode *inode)
{
        struct btrfs_ordered_extent *ordered;
        WARN_ON(!list_empty(&inode->i_dentry));
        WARN_ON(inode->i_data.nrpages);

        if (BTRFS_I(inode)->i_acl &&
            BTRFS_I(inode)->i_acl != BTRFS_ACL_NOT_CACHED)
                posix_acl_release(BTRFS_I(inode)->i_acl);
        if (BTRFS_I(inode)->i_default_acl &&
            BTRFS_I(inode)->i_default_acl != BTRFS_ACL_NOT_CACHED)
                posix_acl_release(BTRFS_I(inode)->i_default_acl);

        spin_lock(&BTRFS_I(inode)->root->orphan_lock);
        if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
                printk(KERN_ERR "BTRFS: inode %lu: inode still on the orphan"
                       " list\n", inode->i_ino);
                dump_stack();
        }
        spin_unlock(&BTRFS_I(inode)->root->orphan_lock);

        while(1) {
                ordered = btrfs_lookup_first_ordered_extent(inode, (u64)-1);
                if (!ordered)
                        break;
                else {
                        printk("found ordered extent %Lu %Lu\n",
                               ordered->file_offset, ordered->len);
                        btrfs_remove_ordered_extent(inode, ordered);
                        btrfs_put_ordered_extent(ordered);
                        btrfs_put_ordered_extent(ordered);
                }
        }
        btrfs_drop_extent_cache(inode, 0, (u64)-1);
        kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
}

#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
static void init_once(struct kmem_cache * cachep, void *foo)
#else
static void init_once(void * foo, struct kmem_cache * cachep,
                      unsigned long flags)
#endif
{
        struct btrfs_inode *ei = (struct btrfs_inode *) foo;

        inode_init_once(&ei->vfs_inode);
}

void btrfs_destroy_cachep(void)
{
        if (btrfs_inode_cachep)
                kmem_cache_destroy(btrfs_inode_cachep);
        if (btrfs_trans_handle_cachep)
                kmem_cache_destroy(btrfs_trans_handle_cachep);
        if (btrfs_transaction_cachep)
                kmem_cache_destroy(btrfs_transaction_cachep);
        if (btrfs_bit_radix_cachep)
                kmem_cache_destroy(btrfs_bit_radix_cachep);
        if (btrfs_path_cachep)
                kmem_cache_destroy(btrfs_path_cachep);
}

struct kmem_cache *btrfs_cache_create(const char *name, size_t size,
                                       unsigned long extra_flags,
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
                                       void (*ctor)(struct kmem_cache *, void *)
#else
                                       void (*ctor)(void *, struct kmem_cache *,
                                                    unsigned long)
#endif
                                     )
{
        return kmem_cache_create(name, size, 0, (SLAB_RECLAIM_ACCOUNT |
                                 SLAB_MEM_SPREAD | extra_flags), ctor
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,23)
                                 ,NULL
#endif
                                );
}

int btrfs_init_cachep(void)
{
        btrfs_inode_cachep = btrfs_cache_create("btrfs_inode_cache",
                                          sizeof(struct btrfs_inode),
                                          0, init_once);
        if (!btrfs_inode_cachep)
                goto fail;
        btrfs_trans_handle_cachep =
                        btrfs_cache_create("btrfs_trans_handle_cache",
                                           sizeof(struct btrfs_trans_handle),
                                           0, NULL);
        if (!btrfs_trans_handle_cachep)
                goto fail;
        btrfs_transaction_cachep = btrfs_cache_create("btrfs_transaction_cache",
                                             sizeof(struct btrfs_transaction),
                                             0, NULL);
        if (!btrfs_transaction_cachep)
                goto fail;
        btrfs_path_cachep = btrfs_cache_create("btrfs_path_cache",
                                         sizeof(struct btrfs_path),
                                         0, NULL);
        if (!btrfs_path_cachep)
                goto fail;
        btrfs_bit_radix_cachep = btrfs_cache_create("btrfs_radix", 256,
                                              SLAB_DESTROY_BY_RCU, NULL);
        if (!btrfs_bit_radix_cachep)
                goto fail;
        return 0;
fail:
        btrfs_destroy_cachep();
        return -ENOMEM;
}

static int btrfs_getattr(struct vfsmount *mnt,
                         struct dentry *dentry, struct kstat *stat)
{
        struct inode *inode = dentry->d_inode;
        generic_fillattr(inode, stat);
        stat->blksize = PAGE_CACHE_SIZE;
        stat->blocks = inode->i_blocks + (BTRFS_I(inode)->delalloc_bytes >> 9);
        return 0;
}

static int btrfs_rename(struct inode * old_dir, struct dentry *old_dentry,
                           struct inode * new_dir,struct dentry *new_dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(old_dir)->root;
        struct inode *new_inode = new_dentry->d_inode;
        struct inode *old_inode = old_dentry->d_inode;
        struct timespec ctime = CURRENT_TIME;
        int ret;

        if (S_ISDIR(old_inode->i_mode) && new_inode &&
            new_inode->i_size > BTRFS_EMPTY_DIR_SIZE) {
                return -ENOTEMPTY;
        }

        ret = btrfs_check_free_space(root, 1, 0);
        if (ret)
                goto out_unlock;

        trans = btrfs_start_transaction(root, 1);

        btrfs_set_trans_block_group(trans, new_dir);

        old_dentry->d_inode->i_nlink++;
        old_dir->i_ctime = old_dir->i_mtime = ctime;
        new_dir->i_ctime = new_dir->i_mtime = ctime;
        old_inode->i_ctime = ctime;

        ret = btrfs_unlink_trans(trans, root, old_dir, old_dentry);
        if (ret)
                goto out_fail;

        if (new_inode) {
                new_inode->i_ctime = CURRENT_TIME;
                ret = btrfs_unlink_trans(trans, root, new_dir, new_dentry);
                if (ret)
                        goto out_fail;
                if (new_inode->i_nlink == 0) {
                        ret = btrfs_orphan_add(trans, new_inode);
                        if (ret)
                                goto out_fail;
                }
        }
        ret = btrfs_set_inode_index(new_dir, old_inode);
        if (ret)
                goto out_fail;

        ret = btrfs_add_link(trans, new_dentry, old_inode, 1);
        if (ret)
                goto out_fail;

out_fail:
        btrfs_end_transaction(trans, root);
out_unlock:
        return ret;
}

static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                         const char *symname)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        u64 objectid;
        int name_len;
        int datasize;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        struct extent_buffer *leaf;
        unsigned long nr = 0;

        name_len = strlen(symname) + 1;
        if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
                return -ENAMETOOLONG;

        err = btrfs_check_free_space(root, 1, 0);
        if (err)
                goto out_fail;

        trans = btrfs_start_transaction(root, 1);
        btrfs_set_trans_block_group(trans, dir);

        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
        if (err) {
                err = -ENOSPC;
                goto out_unlock;
        }

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len,
                                dentry->d_parent->d_inode->i_ino, objectid,
                                BTRFS_I(dir)->block_group, S_IFLNK|S_IRWXUGO);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_unlock;

        err = btrfs_init_acl(inode, dir);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }

        btrfs_set_trans_block_group(trans, inode);
        err = btrfs_add_nondir(trans, dentry, inode, 0);
        if (err)
                drop_inode = 1;
        else {
                inode->i_mapping->a_ops = &btrfs_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                extent_map_tree_init(&BTRFS_I(inode)->extent_tree, GFP_NOFS);
                extent_io_tree_init(&BTRFS_I(inode)->io_tree,
                                     inode->i_mapping, GFP_NOFS);
                extent_io_tree_init(&BTRFS_I(inode)->io_failure_tree,
                                     inode->i_mapping, GFP_NOFS);
                mutex_init(&BTRFS_I(inode)->csum_mutex);
                mutex_init(&BTRFS_I(inode)->extent_mutex);
                BTRFS_I(inode)->delalloc_bytes = 0;
                BTRFS_I(inode)->disk_i_size = 0;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                btrfs_ordered_inode_tree_init(&BTRFS_I(inode)->ordered_tree);
        }
        dir->i_sb->s_dirt = 1;
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);
        if (drop_inode)
                goto out_unlock;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        key.objectid = inode->i_ino;
        key.offset = 0;
        btrfs_set_key_type(&key, BTRFS_EXTENT_DATA_KEY);
        datasize = btrfs_file_extent_calc_inline_size(name_len);
        err = btrfs_insert_empty_item(trans, root, path, &key,
                                      datasize);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei,
                                   BTRFS_FILE_EXTENT_INLINE);
        ptr = btrfs_file_extent_inline_start(ei);
        write_extent_buffer(leaf, symname, ptr, name_len);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_free_path(path);

        inode->i_op = &btrfs_symlink_inode_operations;
        inode->i_mapping->a_ops = &btrfs_symlink_aops;
        inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
        btrfs_i_size_write(inode, name_len - 1);
        err = btrfs_update_inode(trans, root, inode);
        if (err)
                drop_inode = 1;

out_unlock:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
out_fail:
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int btrfs_set_page_dirty(struct page *page)
{
        return __set_page_dirty_nobuffers(page);
}

static int btrfs_permission(struct inode *inode, int mask,
                            struct nameidata *nd)
{
        if (btrfs_test_flag(inode, READONLY) && (mask & MAY_WRITE))
                return -EACCES;
        return generic_permission(inode, mask, btrfs_check_acl);
}

static struct inode_operations btrfs_dir_inode_operations = {
        .lookup         = btrfs_lookup,
        .create         = btrfs_create,
        .unlink         = btrfs_unlink,
        .link           = btrfs_link,
        .mkdir          = btrfs_mkdir,
        .rmdir          = btrfs_rmdir,
        .rename         = btrfs_rename,
        .symlink        = btrfs_symlink,
        .setattr        = btrfs_setattr,
        .mknod          = btrfs_mknod,
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = generic_removexattr,
        .permission     = btrfs_permission,
};
static struct inode_operations btrfs_dir_ro_inode_operations = {
        .lookup         = btrfs_lookup,
        .permission     = btrfs_permission,
};
static struct file_operations btrfs_dir_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .readdir        = btrfs_readdir,
        .unlocked_ioctl = btrfs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = btrfs_ioctl,
#endif
        .release        = btrfs_release_file,
};

static struct extent_io_ops btrfs_extent_io_ops = {
        .fill_delalloc = run_delalloc_range,
        .submit_bio_hook = btrfs_submit_bio_hook,
        .merge_bio_hook = btrfs_merge_bio_hook,
        .readpage_io_hook = btrfs_readpage_io_hook,
        .readpage_end_io_hook = btrfs_readpage_end_io_hook,
        .writepage_end_io_hook = btrfs_writepage_end_io_hook,
        .writepage_start_hook = btrfs_writepage_start_hook,
        .readpage_io_failed_hook = btrfs_io_failed_hook,
        .set_bit_hook = btrfs_set_bit_hook,
        .clear_bit_hook = btrfs_clear_bit_hook,
};

static struct address_space_operations btrfs_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .writepages     = btrfs_writepages,
        .readpages      = btrfs_readpages,
        .sync_page      = block_sync_page,
        .bmap           = btrfs_bmap,
        .direct_IO      = btrfs_direct_IO,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
        .set_page_dirty = btrfs_set_page_dirty,
};

static struct address_space_operations btrfs_symlink_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
};

static struct inode_operations btrfs_file_inode_operations = {
        .truncate       = btrfs_truncate,
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = generic_removexattr,
        .permission     = btrfs_permission,
};
static struct inode_operations btrfs_special_inode_operations = {
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .permission     = btrfs_permission,
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = generic_removexattr,
};
static struct inode_operations btrfs_symlink_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = page_follow_link_light,
        .put_link       = page_put_link,
        .permission     = btrfs_permission,
};