• Junxiao Bi's avatar
    ocfs2: fix journal commit deadlock · 136f49b9
    Junxiao Bi authored
    For buffer write, page lock will be got in write_begin and released in
    write_end, in ocfs2_write_end_nolock(), before it unlock the page in
    ocfs2_free_write_ctxt(), it calls ocfs2_run_deallocs(), this will ask
    for the read lock of journal->j_trans_barrier.  Holding page lock and
    ask for journal->j_trans_barrier breaks the locking order.
    
    This will cause a deadlock with journal commit threads, ocfs2cmt will
    get write lock of journal->j_trans_barrier first, then it wakes up
    kjournald2 to do the commit work, at last it waits until done.  To
    commit journal, kjournald2 needs flushing data first, it needs get the
    cache page lock.
    
    Since some ocfs2 cluster locks are holding by write process, this
    deadlock may hung the whole cluster.
    
    unlock pages before ocfs2_run_deallocs() can fix the locking order, also
    put unlock before ocfs2_commit_trans() to make page lock is unlocked
    before j_trans_barrier to preserve unlocking order.
    Signed-off-by: default avatarJunxiao Bi <junxiao.bi@oracle.com>
    Reviewed-by: default avatarWengang Wang <wen.gang.wang@oracle.com>
    Cc: <stable@vger.kernel.org>
    Reviewed-by: default avatarMark Fasheh <mfasheh@suse.de>
    Cc: Joel Becker <jlbec@evilplan.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    136f49b9
aops.c 52.8 KB