• Bart Van Assche's avatar
    dm: Fix a race condition related to stopping and starting queues · 7b17c2f7
    Bart Van Assche authored
    Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request()
    calls have stopped before setting the "queue stopped" flag. This
    allows to remove the "queue stopped" test from dm_mq_queue_rq() and
    dm_mq_requeue_request(). This patch fixes a race condition because
    dm_mq_queue_rq() is called without holding the queue lock and hence
    BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is
    in progress. This patch prevents that the following hang occurs
    sporadically when using dm-mq:
    
    INFO: task systemd-udevd:10111 blocked for more than 480 seconds.
    Call Trace:
     [<ffffffff8161f397>] schedule+0x37/0x90
     [<ffffffff816239ef>] schedule_timeout+0x27f/0x470
     [<ffffffff8161e76f>] io_schedule_timeout+0x9f/0x110
     [<ffffffff8161fb36>] bit_wait_io+0x16/0x60
     [<ffffffff8161f929>] __wait_on_bit_lock+0x49/0xa0
     [<ffffffff8114fe69>] __lock_page+0xb9/0xc0
     [<ffffffff81165d90>] truncate_inode_pages_range+0x3e0/0x760
     [<ffffffff81166120>] truncate_inode_pages+0x10/0x20
     [<ffffffff81212a20>] kill_bdev+0x30/0x40
     [<ffffffff81213d41>] __blkdev_put+0x71/0x360
     [<ffffffff81214079>] blkdev_put+0x49/0x170
     [<ffffffff812141c0>] blkdev_close+0x20/0x30
     [<ffffffff811d48e8>] __fput+0xe8/0x1f0
     [<ffffffff811d4a29>] ____fput+0x9/0x10
     [<ffffffff810842d3>] task_work_run+0x83/0xb0
     [<ffffffff8106606e>] do_exit+0x3ee/0xc40
     [<ffffffff8106694b>] do_group_exit+0x4b/0xc0
     [<ffffffff81073d9a>] get_signal+0x2ca/0x940
     [<ffffffff8101bf43>] do_signal+0x23/0x660
     [<ffffffff810022b3>] exit_to_usermode_loop+0x73/0xb0
     [<ffffffff81002cb0>] syscall_return_slowpath+0xb0/0xc0
     [<ffffffff81624e33>] entry_SYSCALL_64_fastpath+0xa6/0xa8
    Signed-off-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
    Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
    Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
    Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    7b17c2f7
dm-rq.c 24.3 KB