ocfs2: fix possible deadlock between unlink and dio_end_io_write

ocfs2_unlink takes orphan dir inode_lock first and then ip_alloc_sem,
while in ocfs2_dio_end_io_write, it acquires these locks in reverse order.
This creates an ABBA lock ordering violation on lock classes
ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE] and
ocfs2_file_ip_alloc_sem_key.

Lock Chain #0 (orphan dir inode_lock -> ip_alloc_sem):
ocfs2_unlink
  ocfs2_prepare_orphan_dir
    ocfs2_lookup_lock_orphan_dir
      inode_lock(orphan_dir_inode) <- lock A
    __ocfs2_prepare_orphan_dir
      ocfs2_prepare_dir_for_insert
        ocfs2_extend_dir
	  ocfs2_expand_inline_dir
	    down_write(&oi->ip_alloc_sem) <- Lock B

Lock Chain #1 (ip_alloc_sem -> orphan dir inode_lock):
ocfs2_dio_end_io_write
  down_write(&oi->ip_alloc_sem) <- Lock B
  ocfs2_del_inode_from_orphan()
    inode_lock(orphan_dir_inode) <- Lock A

Deadlock Scenario:
  CPU0 (unlink)                     CPU1 (dio_end_io_write)
  ------                            ------
  inode_lock(orphan_dir_inode)
                                    down_write(ip_alloc_sem)
  down_write(ip_alloc_sem)
                                    inode_lock(orphan_dir_inode)

Since ip_alloc_sem is to protect allocation changes, which is unrelated
with operations in ocfs2_del_inode_from_orphan.  So move
ocfs2_del_inode_from_orphan out of ip_alloc_sem to fix the deadlock.

Link: https://lkml.kernel.org/r/20260306032211.1016452-1-joseph.qi@linux.alibaba.com
Reported-by: syzbot+67b90111784a3eac8c04@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=67b90111784a3eac8c04
Fixes: a86a72a4a4e0 ("ocfs2: take ip_alloc_sem in ocfs2_dio_get_block & ocfs2_dio_end_io_write")
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 17ba79f443ee736cb5225702c57d13f4019f3c52..09146b43d1f07ac0bb0192e6fa3d1980d7ac980a 100644 (file)
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2294,8 +2294,6 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
                goto out;
        }
 
-       down_write(&oi->ip_alloc_sem);
-
        /* Delete orphan before acquire i_rwsem. */
        if (dwc->dw_orphaned) {
                BUG_ON(dwc->dw_writer_pid != task_pid_nr(current));
@@ -2308,6 +2306,7 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
                        mlog_errno(ret);
        }
 
+       down_write(&oi->ip_alloc_sem);
        di = (struct ocfs2_dinode *)di_bh->b_data;
 
        ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);