fix-incorrect-locking-in-move_extent_per_page

   1 ext4: fix incorrect locking in move_extent_per_page
   2
   3 From: Dmitry Monakhov <dmonakhov@openvz.org>
   4
   5 If we have to copy data we must drop i_data_sem because of
   6 get_blocks() will be called inside mext_page_mkuptodate(), but later we must
   7 reacquire it again because we are about to change extent's tree
   8
   9 Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
  10 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  11 Reviewed-by: Jan Kara <jack@suse.cz>
  12 ---
  13  fs/ext4/move_extent.c |    3 ++-
  14  1 files changed, 2 insertions(+), 1 deletions(-)
  15
  16 diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
  17 index 2484c7e..671a74b 100644
  18 --- a/fs/ext4/move_extent.c
  19 +++ b/fs/ext4/move_extent.c
  20 @@ -1013,10 +1013,11 @@ data_copy:
  21                 *err = -EBUSY;
  22                 goto unlock_pages;
  23         }
  24 -
  25 +       ext4_double_down_write_data_sem(orig_inode, donor_inode);
  26         replaced_count = mext_replace_branches(handle, orig_inode, donor_inode,
  27                                                orig_blk_offset,
  28                                                block_len_in_page, err);
  29 +       ext4_double_up_write_data_sem(orig_inode, donor_inode);
  30         if (*err) {
  31                 if (replaced_count) {
  32                         block_len_in_page = replaced_count;
  33 --
  34 1.7.1
  35
  36