[BUG] fs: ocfs2: possible ABBA deadlock in ocfs2_dio_end_io_write() and ocfs2_move_extents()

[Jia-Ju Bai]

Hello,

My static analysis tool reports a possible ABBA deadlock in the ocfs2 
module in Linux 5.10:

ocfs2_dio_end_io_write()
  down_write(&oi->ip_alloc_sem); --> Line 2322 (Lock A)
  ocfs2_del_inode_from_orphan()
    inode_lock(orphan_dir_inode);  --> Line 2701 (Lock B)

ocfs2_move_extents()
  inode_lock(inode); --> Line 916 (Lock B)
  down_write(&OCFS2_I(inode)->ip_alloc_sem); --> Line 936 (Lock A)

When ocfs2_dio_end_io_write() and ocfs2_move_extents() are concurrently 
executed, the deadlocks can occur.

I am not quite sure whether this possible deadlock is real and how to 
fix it if it is real.
Any feedback would be appreciated, thanks :)

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>


Best wishes,
Jia-Ju Bai