Btrfs: fix off-by-one error of the reserved size of btrfs_allocate()

alloc_end is not the real end of the current extent, it is the start of the
next adjoining extent. So we needn't +1 when calculating the size the space
that is about to be reserved.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index a43d0aef6ee1..8e3d6788d6dd 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2072,7 +2072,7 @@ static long btrfs_fallocate(struct file *file, int mode,
          * Make sure we have enough space before we do the
          * allocation.
          */
-        ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start + 1);
+        ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start);
         if (ret)
                 return ret;
 
@@ -2179,7 +2179,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 out:
         mutex_unlock(&inode->i_mutex);
         /* Let go of our reservation. */
-        btrfs_free_reserved_data_space(inode, alloc_end - alloc_start + 1);
+        btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
         return ret;
 }