• Tian Lan's avatar
    blk-mq: fix blk_mq_hw_ctx active request accounting · ddad5933
    Tian Lan authored
    The nr_active counter continues to increase over time which causes the
    blk_mq_get_tag to hang until the thread is rescheduled to a different
    core despite there are still tags available.
    
    kernel-stack
    
      INFO: task inboundIOReacto:3014879 blocked for more than 2 seconds
      Not tainted 6.1.15-amd64 #1 Debian 6.1.15~debian11
      "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
      task:inboundIOReacto state:D stack:0  pid:3014879 ppid:4557 flags:0x00000000
        Call Trace:
        <TASK>
        __schedule+0x351/0xa20
        scheduler+0x5d/0xe0
        io_schedule+0x42/0x70
        blk_mq_get_tag+0x11a/0x2a0
        ? dequeue_task_stop+0x70/0x70
        __blk_mq_alloc_requests+0x191/0x2e0
    
    kprobe output showing RQF_MQ_INFLIGHT bit is not cleared before
    __blk_mq_free_request being called.
    
      320    320  kworker/29:1H __blk_mq_free_request rq_flags 0x220c0 in-flight 1
             b'__blk_mq_free_request+0x1 [kernel]'
             b'bt_iter+0x50 [kernel]'
             b'blk_mq_queue_tag_busy_iter+0x318 [kernel]'
             b'blk_mq_timeout_work+0x7c [kernel]'
             b'process_one_work+0x1c4 [kernel]'
             b'worker_thread+0x4d [kernel]'
             b'kthread+0xe6 [kernel]'
             b'ret_from_fork+0x1f [kernel]'
    Signed-off-by: default avatarTian Lan <tian.lan@twosigma.com>
    Fixes: 2e315dc0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
    Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
    Link: https://lore.kernel.org/r/20230513221227.497327-1-tilan7663@gmail.comSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
    ddad5933
blk-mq.c 120 KB