• Jianchao Wang's avatar
    blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter · f5bbbbe4
    Jianchao Wang authored
    For blk-mq, part_in_flight/rw will invoke blk_mq_in_flight/rw to
    account the inflight requests. It will access the queue_hw_ctx and
    nr_hw_queues w/o any protection. When updating nr_hw_queues and
    blk_mq_in_flight/rw occur concurrently, panic comes up.
    
    Before update nr_hw_queues, the q will be frozen. So we could use
    q_usage_counter to avoid the race. percpu_ref_is_zero is used here
    so that we will not miss any in-flight request. The access to
    nr_hw_queues and queue_hw_ctx in blk_mq_queue_tag_busy_iter are
    under rcu critical section, __blk_mq_update_nr_hw_queues could use
    synchronize_rcu to ensure the zeroed q_usage_counter to be globally
    visible.
    Signed-off-by: default avatarJianchao Wang <jianchao.w.wang@oracle.com>
    Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    f5bbbbe4
blk-mq.c 77.3 KB