ext4: fix incorrect locking in move_extent_per_page

If we have to copy data we must drop i_data_sem because of
get_blocks() will be called inside mext_page_mkuptodate(), but later we must
reacquire it again because we are about to change extent's tree

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 2484c7ec6a72..671a74b14fd7 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -1013,10 +1013,11 @@ data_copy:
                 *err = -EBUSY;
                 goto unlock_pages;
         }
-
+        ext4_double_down_write_data_sem(orig_inode, donor_inode);
         replaced_count = mext_replace_branches(handle, orig_inode, donor_inode,
                                                orig_blk_offset,
                                                block_len_in_page, err);
+        ext4_double_up_write_data_sem(orig_inode, donor_inode);
         if (*err) {
                 if (replaced_count) {
                         block_len_in_page = replaced_count;