Btrfs: properly check free space for tree balancing

btrfs_insert_empty_items takes the space needed by the btrfs_item
structure into account when calculating the required free space.

So the tree balancing code shouldn't add sizeof(struct btrfs_item)
to the size when checking the free space. This patch removes these
superfluous additions.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 7acadf3b742a..cc6e0b6de949 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -300,6 +300,10 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 
                 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;
+                }
 
                 size = min(csum_end, end + 1) - start;
                 sums = kzalloc(btrfs_ordered_sum_size(root, size), GFP_NOFS);