Btrfs: Take the extent lock before dropping the delalloc bits

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 1a47251a9d4d..51466dcd44e0 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -765,9 +765,13 @@ static int prepare_pages(struct btrfs_root *root, struct file *file,
         if (start_pos < inode->i_size) {
                 u64 last_pos;
                 last_pos = (index + num_pages) << PAGE_CACHE_SHIFT;
+                lock_extent(&BTRFS_I(inode)->io_tree,
+                            start_pos, last_pos - 1, GFP_NOFS);
                 clear_extent_bits(&BTRFS_I(inode)->io_tree, start_pos,
                                   last_pos - 1, EXTENT_DIRTY | EXTENT_DELALLOC,
                                   GFP_NOFS);
+                unlock_extent(&BTRFS_I(inode)->io_tree,
+                              start_pos, last_pos - 1, GFP_NOFS);
         }
         return 0;
 }