linux-kernel - [BUG] fs: ocfs2: possible ABBA deadlock in ocfs2_dio_end_io_write() and ocfs2_move

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Date:   Fri, 10 Dec 2021 16:37:31 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     mark@...heh.com, jlbec@...lplan.org, joseph.qi@...ux.alibaba.com
Cc:     ocfs2-devel@....oracle.com,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [BUG] fs: ocfs2: possible ABBA deadlock in ocfs2_dio_end_io_write()
 and ocfs2_move_extents()

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@...nghua.edu.cn>

Best wishes,
Jia-Ju Bai