xfs: don't hold buffer locks across sync transaction commit in xfs_sync_sb_buf

xfs_sync_sb_buf() holds sb/rtsb buffer locks across a synchronous
xfs_trans_commit(), which flushes the CIL push workqueue internally.
If shutdown occurs during the CIL push, xfs_buf_item_unpin() needs to
lock these buffers to fail them, causing a deadlock:

  setlabel:          holds buf lock -> flush_workqueue(xfs-cil)
  CIL push worker:   xfs_buf_item_unpin -> xfs_buf_lock(same buf)

Remove the xfs_trans_bhold() calls so that commit releases the buffer
locks normally.  After the sync commit, re-acquire the buffers via
mp->m_sb_bp / mp->m_rtsb_bp for the on-disk writeback.

Fixes: f7664b31975b ("xfs: implement online get/set fs label")
Reported-by: syzbot+837bcd54843dd6262f2f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=837bcd54843dd6262f2f
Cc: stable@vger.kernel.org
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

0 files changed, 0 insertions, 0 deletions