Merge commit 'v2.6.29-rc1' into timers/hrtimers

Conflicts:
	kernel/time/tick-common.c

1 files changed, 831 insertions, 0 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
new file mode 100644
index 000000000000..964652435fd1
--- /dev/null
+++ b/fs/btrfs/file-item.c
@@ -0,0 +1,831 @@
+/*
+ * 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/bio.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "print-tree.h"
+
+#define MAX_CSUM_ITEMS(r, size) ((((BTRFS_LEAF_DATA_SIZE(r) - \
+                                   sizeof(struct btrfs_item) * 2) / \
+                                  size) - 1))
+
+#define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
+                                   sizeof(struct btrfs_ordered_sum)) / \
+                                   sizeof(struct btrfs_sector_sum) * \
+                                   (r)->sectorsize - (r)->sectorsize)
+
+int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
+                             struct btrfs_root *root,
+                             u64 objectid, u64 pos,
+                             u64 disk_offset, u64 disk_num_bytes,
+                             u64 num_bytes, u64 offset, u64 ram_bytes,
+                             u8 compression, u8 encryption, u16 other_encoding)
+{
+        int ret = 0;
+        struct btrfs_file_extent_item *item;
+        struct btrfs_key file_key;
+        struct btrfs_path *path;
+        struct extent_buffer *leaf;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        file_key.objectid = objectid;
+        file_key.offset = pos;
+        btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
+
+        ret = btrfs_insert_empty_item(trans, root, path, &file_key,
+                                      sizeof(*item));
+        if (ret < 0)
+                goto out;
+        BUG_ON(ret);
+        leaf = path->nodes[0];
+        item = btrfs_item_ptr(leaf, path->slots[0],
+                              struct btrfs_file_extent_item);
+        btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
+        btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
+        btrfs_set_file_extent_offset(leaf, item, offset);
+        btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
+        btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
+        btrfs_set_file_extent_generation(leaf, item, trans->transid);
+        btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
+        btrfs_set_file_extent_compression(leaf, item, compression);
+        btrfs_set_file_extent_encryption(leaf, item, encryption);
+        btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
+
+        btrfs_mark_buffer_dirty(leaf);
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
+                                          struct btrfs_root *root,
+                                          struct btrfs_path *path,
+                                          u64 bytenr, int cow)
+{
+        int ret;
+        struct btrfs_key file_key;
+        struct btrfs_key found_key;
+        struct btrfs_csum_item *item;
+        struct extent_buffer *leaf;
+        u64 csum_offset = 0;
+        u16 csum_size =
+                btrfs_super_csum_size(&root->fs_info->super_copy);
+        int csums_in_item;
+
+        file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+        file_key.offset = bytenr;
+        btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
+        ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
+        if (ret < 0)
+                goto fail;
+        leaf = path->nodes[0];
+        if (ret > 0) {
+                ret = 1;
+                if (path->slots[0] == 0)
+                        goto fail;
+                path->slots[0]--;
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
+                        goto fail;
+
+                csum_offset = (bytenr - found_key.offset) >>
+                                root->fs_info->sb->s_blocksize_bits;
+                csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
+                csums_in_item /= csum_size;
+
+                if (csum_offset >= csums_in_item) {
+                        ret = -EFBIG;
+                        goto fail;
+                }
+        }
+        item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
+        item = (struct btrfs_csum_item *)((unsigned char *)item +
+                                          csum_offset * csum_size);
+        return item;
+fail:
+        if (ret > 0)
+                ret = -ENOENT;
+        return ERR_PTR(ret);
+}
+
+
+int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
+                             struct btrfs_root *root,
+                             struct btrfs_path *path, u64 objectid,
+                             u64 offset, int mod)
+{
+        int ret;
+        struct btrfs_key file_key;
+        int ins_len = mod < 0 ? -1 : 0;
+        int cow = mod != 0;
+
+        file_key.objectid = objectid;
+        file_key.offset = offset;
+        btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
+        ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
+        return ret;
+}
+
+
+int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
+                          struct bio *bio, u32 *dst)
+{
+        u32 sum;
+        struct bio_vec *bvec = bio->bi_io_vec;
+        int bio_index = 0;
+        u64 offset;
+        u64 item_start_offset = 0;
+        u64 item_last_offset = 0;
+        u64 disk_bytenr;
+        u32 diff;
+        u16 csum_size =
+                btrfs_super_csum_size(&root->fs_info->super_copy);
+        int ret;
+        struct btrfs_path *path;
+        struct btrfs_csum_item *item = NULL;
+        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+
+        path = btrfs_alloc_path();
+        if (bio->bi_size > PAGE_CACHE_SIZE * 8)
+                path->reada = 2;
+
+        WARN_ON(bio->bi_vcnt <= 0);
+
+        disk_bytenr = (u64)bio->bi_sector << 9;
+        while (bio_index < bio->bi_vcnt) {
+                offset = page_offset(bvec->bv_page) + bvec->bv_offset;
+                ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
+                if (ret == 0)
+                        goto found;
+
+                if (!item || disk_bytenr < item_start_offset ||
+                    disk_bytenr >= item_last_offset) {
+                        struct btrfs_key found_key;
+                        u32 item_size;
+
+                        if (item)
+                                btrfs_release_path(root, path);
+                        item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
+                                                 path, disk_bytenr, 0);
+                        if (IS_ERR(item)) {
+                                ret = PTR_ERR(item);
+                                if (ret == -ENOENT || ret == -EFBIG)
+                                        ret = 0;
+                                sum = 0;
+                                if (BTRFS_I(inode)->root->root_key.objectid ==
+                                    BTRFS_DATA_RELOC_TREE_OBJECTID) {
+                                        set_extent_bits(io_tree, offset,
+                                                offset + bvec->bv_len - 1,
+                                                EXTENT_NODATASUM, GFP_NOFS);
+                                } else {
+                                        printk(KERN_INFO "btrfs no csum found "
+                                               "for inode %lu start %llu\n",
+                                               inode->i_ino,
+                                               (unsigned long long)offset);
+                                }
+                                item = NULL;
+                                btrfs_release_path(root, path);
+                                goto found;
+                        }
+                        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+                                              path->slots[0]);
+
+                        item_start_offset = found_key.offset;
+                        item_size = btrfs_item_size_nr(path->nodes[0],
+                                                       path->slots[0]);
+                        item_last_offset = item_start_offset +
+                                (item_size / csum_size) *
+                                root->sectorsize;
+                        item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                              struct btrfs_csum_item);
+                }
+                /*
+                 * this byte range must be able to fit inside
+                 * a single leaf so it will also fit inside a u32
+                 */
+                diff = disk_bytenr - item_start_offset;
+                diff = diff / root->sectorsize;
+                diff = diff * csum_size;
+
+                read_extent_buffer(path->nodes[0], &sum,
+                                   ((unsigned long)item) + diff,
+                                   csum_size);
+found:
+                if (dst)
+                        *dst++ = sum;
+                else
+                        set_state_private(io_tree, offset, sum);
+                disk_bytenr += bvec->bv_len;
+                bio_index++;
+                bvec++;
+        }
+        btrfs_free_path(path);
+        return 0;
+}
+
+int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
+                             struct list_head *list)
+{
+        struct btrfs_key key;
+        struct btrfs_path *path;
+        struct extent_buffer *leaf;
+        struct btrfs_ordered_sum *sums;
+        struct btrfs_sector_sum *sector_sum;
+        struct btrfs_csum_item *item;
+        unsigned long offset;
+        int ret;
+        size_t size;
+        u64 csum_end;
+        u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+
+        key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+        key.offset = start;
+        key.type = BTRFS_EXTENT_CSUM_KEY;
+
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (ret < 0)
+                goto fail;
+        if (ret > 0 && path->slots[0] > 0) {
+                leaf = path->nodes[0];
+                btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
+                if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
+                    key.type == BTRFS_EXTENT_CSUM_KEY) {
+                        offset = (start - key.offset) >>
+                                 root->fs_info->sb->s_blocksize_bits;
+                        if (offset * csum_size <
+                            btrfs_item_size_nr(leaf, path->slots[0] - 1))
+                                path->slots[0]--;
+                }
+        }
+
+        while (start <= end) {
+                leaf = path->nodes[0];
+                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+                        ret = btrfs_next_leaf(root, path);
+                        if (ret < 0)
+                                goto fail;
+                        if (ret > 0)
+                                break;
+                        leaf = path->nodes[0];
+                }
+
+                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+                if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+                    key.type != BTRFS_EXTENT_CSUM_KEY)
+                        break;
+
+                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+                if (key.offset > end)
+                        break;
+
+                if (key.offset > start)
+                        start = key.offset;
+
+                size = btrfs_item_size_nr(leaf, path->slots[0]);
+                csum_end = key.offset + (size / csum_size) * root->sectorsize;
+                if (csum_end <= start) {
+                        path->slots[0]++;
+                        continue;
+                }
+
+                csum_end = min(csum_end, end + 1);
+                item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                      struct btrfs_csum_item);
+                while (start < csum_end) {
+                        size = min_t(size_t, csum_end - start,
+                                        MAX_ORDERED_SUM_BYTES(root));
+                        sums = kzalloc(btrfs_ordered_sum_size(root, size),
+                                        GFP_NOFS);
+                        BUG_ON(!sums);
+
+                        sector_sum = sums->sums;
+                        sums->bytenr = start;
+                        sums->len = size;
+
+                        offset = (start - key.offset) >>
+                                root->fs_info->sb->s_blocksize_bits;
+                        offset *= csum_size;
+
+                        while (size > 0) {
+                                read_extent_buffer(path->nodes[0],
+                                                &sector_sum->sum,
+                                                ((unsigned long)item) +
+                                                offset, csum_size);
+                                sector_sum->bytenr = start;
+
+                                size -= root->sectorsize;
+                                start += root->sectorsize;
+                                offset += csum_size;
+                                sector_sum++;
+                        }
+                        list_add_tail(&sums->list, list);
+                }
+                path->slots[0]++;
+        }
+        ret = 0;
+fail:
+        btrfs_free_path(path);
+        return ret;
+}
+
+int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
+                       struct bio *bio, u64 file_start, int contig)
+{
+        struct btrfs_ordered_sum *sums;
+        struct btrfs_sector_sum *sector_sum;
+        struct btrfs_ordered_extent *ordered;
+        char *data;
+        struct bio_vec *bvec = bio->bi_io_vec;
+        int bio_index = 0;
+        unsigned long total_bytes = 0;
+        unsigned long this_sum_bytes = 0;
+        u64 offset;
+        u64 disk_bytenr;
+
+        WARN_ON(bio->bi_vcnt <= 0);
+        sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
+        if (!sums)
+                return -ENOMEM;
+
+        sector_sum = sums->sums;
+        disk_bytenr = (u64)bio->bi_sector << 9;
+        sums->len = bio->bi_size;
+        INIT_LIST_HEAD(&sums->list);
+
+        if (contig)
+                offset = file_start;
+        else
+                offset = page_offset(bvec->bv_page) + bvec->bv_offset;
+
+        ordered = btrfs_lookup_ordered_extent(inode, offset);
+        BUG_ON(!ordered);
+        sums->bytenr = ordered->start;
+
+        while (bio_index < bio->bi_vcnt) {
+                if (!contig)
+                        offset = page_offset(bvec->bv_page) + bvec->bv_offset;
+
+                if (!contig && (offset >= ordered->file_offset + ordered->len ||
+                    offset < ordered->file_offset)) {
+                        unsigned long bytes_left;
+                        sums->len = this_sum_bytes;
+                        this_sum_bytes = 0;
+                        btrfs_add_ordered_sum(inode, ordered, sums);
+                        btrfs_put_ordered_extent(ordered);
+
+                        bytes_left = bio->bi_size - total_bytes;
+
+                        sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
+                                       GFP_NOFS);
+                        BUG_ON(!sums);
+                        sector_sum = sums->sums;
+                        sums->len = bytes_left;
+                        ordered = btrfs_lookup_ordered_extent(inode, offset);
+                        BUG_ON(!ordered);
+                        sums->bytenr = ordered->start;
+                }
+
+                data = kmap_atomic(bvec->bv_page, KM_USER0);
+                sector_sum->sum = ~(u32)0;
+                sector_sum->sum = btrfs_csum_data(root,
+                                                  data + bvec->bv_offset,
+                                                  sector_sum->sum,
+                                                  bvec->bv_len);
+                kunmap_atomic(data, KM_USER0);
+                btrfs_csum_final(sector_sum->sum,
+                                 (char *)&sector_sum->sum);
+                sector_sum->bytenr = disk_bytenr;
+
+                sector_sum++;
+                bio_index++;
+                total_bytes += bvec->bv_len;
+                this_sum_bytes += bvec->bv_len;
+                disk_bytenr += bvec->bv_len;
+                offset += bvec->bv_len;
+                bvec++;
+        }
+        this_sum_bytes = 0;
+        btrfs_add_ordered_sum(inode, ordered, sums);
+        btrfs_put_ordered_extent(ordered);
+        return 0;
+}
+
+/*
+ * helper function for csum removal, this expects the
+ * key to describe the csum pointed to by the path, and it expects
+ * the csum to overlap the range [bytenr, len]
+ *
+ * The csum should not be entirely contained in the range and the
+ * range should not be entirely contained in the csum.
+ *
+ * This calls btrfs_truncate_item with the correct args based on the
+ * overlap, and fixes up the key as required.
+ */
+static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
+                                      struct btrfs_root *root,
+                                      struct btrfs_path *path,
+                                      struct btrfs_key *key,
+                                      u64 bytenr, u64 len)
+{
+        struct extent_buffer *leaf;
+        u16 csum_size =
+                btrfs_super_csum_size(&root->fs_info->super_copy);
+        u64 csum_end;
+        u64 end_byte = bytenr + len;
+        u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
+        int ret;
+
+        leaf = path->nodes[0];
+        csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
+        csum_end <<= root->fs_info->sb->s_blocksize_bits;
+        csum_end += key->offset;
+
+        if (key->offset < bytenr && csum_end <= end_byte) {
+                /*
+                 *         [ bytenr - len ]
+                 *         [   ]
+                 *   [csum     ]
+                 *   A simple truncate off the end of the item
+                 */
+                u32 new_size = (bytenr - key->offset) >> blocksize_bits;
+                new_size *= csum_size;
+                ret = btrfs_truncate_item(trans, root, path, new_size, 1);
+                BUG_ON(ret);
+        } else if (key->offset >= bytenr && csum_end > end_byte &&
+                   end_byte > key->offset) {
+                /*
+                 *         [ bytenr - len ]
+                 *                 [ ]
+                 *                 [csum     ]
+                 * we need to truncate from the beginning of the csum
+                 */
+                u32 new_size = (csum_end - end_byte) >> blocksize_bits;
+                new_size *= csum_size;
+
+                ret = btrfs_truncate_item(trans, root, path, new_size, 0);
+                BUG_ON(ret);
+
+                key->offset = end_byte;
+                ret = btrfs_set_item_key_safe(trans, root, path, key);
+                BUG_ON(ret);
+        } else {
+                BUG();
+        }
+        return 0;
+}
+
+/*
+ * deletes the csum items from the csum tree for a given
+ * range of bytes.
+ */
+int btrfs_del_csums(struct btrfs_trans_handle *trans,
+                    struct btrfs_root *root, u64 bytenr, u64 len)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        u64 end_byte = bytenr + len;
+        u64 csum_end;
+        struct extent_buffer *leaf;
+        int ret;
+        u16 csum_size =
+                btrfs_super_csum_size(&root->fs_info->super_copy);
+        int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
+
+        root = root->fs_info->csum_root;
+
+        path = btrfs_alloc_path();
+
+        while (1) {
+                key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+                key.offset = end_byte - 1;
+                key.type = BTRFS_EXTENT_CSUM_KEY;
+
+                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+                if (ret > 0) {
+                        if (path->slots[0] == 0)
+                                goto out;
+                        path->slots[0]--;
+                }
+                leaf = path->nodes[0];
+                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+
+                if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+                    key.type != BTRFS_EXTENT_CSUM_KEY) {
+                        break;
+                }
+
+                if (key.offset >= end_byte)
+                        break;
+
+                csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
+                csum_end <<= blocksize_bits;
+                csum_end += key.offset;
+
+                /* this csum ends before we start, we're done */
+                if (csum_end <= bytenr)
+                        break;
+
+                /* delete the entire item, it is inside our range */
+                if (key.offset >= bytenr && csum_end <= end_byte) {
+                        ret = btrfs_del_item(trans, root, path);
+                        BUG_ON(ret);
+                        if (key.offset == bytenr)
+                                break;
+                } else if (key.offset < bytenr && csum_end > end_byte) {
+                        unsigned long offset;
+                        unsigned long shift_len;
+                        unsigned long item_offset;
+                        /*
+                         *        [ bytenr - len ]
+                         *     [csum                ]
+                         *
+                         * Our bytes are in the middle of the csum,
+                         * we need to split this item and insert a new one.
+                         *
+                         * But we can't drop the path because the
+                         * csum could change, get removed, extended etc.
+                         *
+                         * The trick here is the max size of a csum item leaves
+                         * enough room in the tree block for a single
+                         * item header.  So, we split the item in place,
+                         * adding a new header pointing to the existing
+                         * bytes.  Then we loop around again and we have
+                         * a nicely formed csum item that we can neatly
+                         * truncate.
+                         */
+                        offset = (bytenr - key.offset) >> blocksize_bits;
+                        offset *= csum_size;
+
+                        shift_len = (len >> blocksize_bits) * csum_size;
+
+                        item_offset = btrfs_item_ptr_offset(leaf,
+                                                            path->slots[0]);
+
+                        memset_extent_buffer(leaf, 0, item_offset + offset,
+                                             shift_len);
+                        key.offset = bytenr;
+
+                        /*
+                         * btrfs_split_item returns -EAGAIN when the
+                         * item changed size or key
+                         */
+                        ret = btrfs_split_item(trans, root, path, &key, offset);
+                        BUG_ON(ret && ret != -EAGAIN);
+
+                        key.offset = end_byte - 1;
+                } else {
+                        ret = truncate_one_csum(trans, root, path,
+                                                &key, bytenr, len);
+                        BUG_ON(ret);
+                        if (key.offset < bytenr)
+                                break;
+                }
+                btrfs_release_path(root, path);
+        }
+out:
+        btrfs_free_path(path);
+        return 0;
+}
+
+int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           struct btrfs_ordered_sum *sums)
+{
+        u64 bytenr;
+        int ret;
+        struct btrfs_key file_key;
+        struct btrfs_key found_key;
+        u64 next_offset;
+        u64 total_bytes = 0;
+        int found_next;
+        struct btrfs_path *path;
+        struct btrfs_csum_item *item;
+        struct btrfs_csum_item *item_end;
+        struct extent_buffer *leaf = NULL;
+        u64 csum_offset;
+        struct btrfs_sector_sum *sector_sum;
+        u32 nritems;
+        u32 ins_size;
+        char *eb_map;
+        char *eb_token;
+        unsigned long map_len;
+        unsigned long map_start;
+        u16 csum_size =
+                btrfs_super_csum_size(&root->fs_info->super_copy);
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        sector_sum = sums->sums;
+again:
+        next_offset = (u64)-1;
+        found_next = 0;
+        file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+        file_key.offset = sector_sum->bytenr;
+        bytenr = sector_sum->bytenr;
+        btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
+
+        item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
+        if (!IS_ERR(item)) {
+                leaf = path->nodes[0];
+                ret = 0;
+                goto found;
+        }
+        ret = PTR_ERR(item);
+        if (ret == -EFBIG) {
+                u32 item_size;
+                /* we found one, but it isn't big enough yet */
+                leaf = path->nodes[0];
+                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+                if ((item_size / csum_size) >=
+                    MAX_CSUM_ITEMS(root, csum_size)) {
+                        /* already at max size, make a new one */
+                        goto insert;
+                }
+        } else {
+                int slot = path->slots[0] + 1;
+                /* we didn't find a csum item, insert one */
+                nritems = btrfs_header_nritems(path->nodes[0]);
+                if (path->slots[0] >= nritems - 1) {
+                        ret = btrfs_next_leaf(root, path);
+                        if (ret == 1)
+                                found_next = 1;
+                        if (ret != 0)
+                                goto insert;
+                        slot = 0;
+                }
+                btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
+                if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+                    found_key.type != BTRFS_EXTENT_CSUM_KEY) {
+                        found_next = 1;
+                        goto insert;
+                }
+                next_offset = found_key.offset;
+                found_next = 1;
+                goto insert;
+        }
+
+        /*
+         * at this point, we know the tree has an item, but it isn't big
+         * enough yet to put our csum in.  Grow it
+         */
+        btrfs_release_path(root, path);
+        ret = btrfs_search_slot(trans, root, &file_key, path,
+                                csum_size, 1);
+        if (ret < 0)
+                goto fail_unlock;
+
+        if (ret > 0) {
+                if (path->slots[0] == 0)
+                        goto insert;
+                path->slots[0]--;
+        }
+
+        leaf = path->nodes[0];
+        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+        csum_offset = (bytenr - found_key.offset) >>
+                        root->fs_info->sb->s_blocksize_bits;
+
+        if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
+            found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+            csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
+                goto insert;
+        }
+
+        if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
+            csum_size) {
+                u32 diff = (csum_offset + 1) * csum_size;
+
+                /*
+                 * is the item big enough already?  we dropped our lock
+                 * before and need to recheck
+                 */
+                if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
+                        goto csum;
+
+                diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
+                if (diff != csum_size)
+                        goto insert;
+
+                ret = btrfs_extend_item(trans, root, path, diff);
+                BUG_ON(ret);
+                goto csum;
+        }
+
+insert:
+        btrfs_release_path(root, path);
+        csum_offset = 0;
+        if (found_next) {
+                u64 tmp = total_bytes + root->sectorsize;
+                u64 next_sector = sector_sum->bytenr;
+                struct btrfs_sector_sum *next = sector_sum + 1;
+
+                while (tmp < sums->len) {
+                        if (next_sector + root->sectorsize != next->bytenr)
+                                break;
+                        tmp += root->sectorsize;
+                        next_sector = next->bytenr;
+                        next++;
+                }
+                tmp = min(tmp, next_offset - file_key.offset);
+                tmp >>= root->fs_info->sb->s_blocksize_bits;
+                tmp = max((u64)1, tmp);
+                tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
+                ins_size = csum_size * tmp;
+        } else {
+                ins_size = csum_size;
+        }
+        ret = btrfs_insert_empty_item(trans, root, path, &file_key,
+                                      ins_size);
+        if (ret < 0)
+                goto fail_unlock;
+        if (ret != 0) {
+                WARN_ON(1);
+                goto fail_unlock;
+        }
+csum:
+        leaf = path->nodes[0];
+        item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
+        ret = 0;
+        item = (struct btrfs_csum_item *)((unsigned char *)item +
+                                          csum_offset * csum_size);
+found:
+        item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
+        item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
+                                      btrfs_item_size_nr(leaf, path->slots[0]));
+        eb_token = NULL;
+        cond_resched();
+next_sector:
+
+        if (!eb_token ||
+           (unsigned long)item + csum_size >= map_start + map_len) {
+                int err;
+
+                if (eb_token)
+                        unmap_extent_buffer(leaf, eb_token, KM_USER1);
+                eb_token = NULL;
+                err = map_private_extent_buffer(leaf, (unsigned long)item,
+                                                csum_size,
+                                                &eb_token, &eb_map,
+                                                &map_start, &map_len, KM_USER1);
+                if (err)
+                        eb_token = NULL;
+        }
+        if (eb_token) {
+                memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
+                       &sector_sum->sum, csum_size);
+        } else {
+                write_extent_buffer(leaf, &sector_sum->sum,
+                                    (unsigned long)item, csum_size);
+        }
+
+        total_bytes += root->sectorsize;
+        sector_sum++;
+        if (total_bytes < sums->len) {
+                item = (struct btrfs_csum_item *)((char *)item +
+                                                  csum_size);
+                if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
+                    sector_sum->bytenr) {
+                        bytenr = sector_sum->bytenr;
+                        goto next_sector;
+                }
+        }
+        if (eb_token) {
+                unmap_extent_buffer(leaf, eb_token, KM_USER1);
+                eb_token = NULL;
+        }
+        btrfs_mark_buffer_dirty(path->nodes[0]);
+        cond_resched();
+        if (total_bytes < sums->len) {
+                btrfs_release_path(root, path);
+                goto again;
+        }
+out:
+        btrfs_free_path(path);
+        return ret;
+
+fail_unlock:
+        goto out;
+}