On 2023/11/14 07:57, Bart Van Assche wrote: > On 11/13/23 07:05, Chengming Zhou wrote: >> Ok, I reviewed the code of virtio_queue_rqs(), found the main difference >> is that request won't fail after blk_mq_start_request(). >> >> But in null_blk case, the request will fail after blk_mq_start_request(), >> return BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE. If we return these rqs >> back to the block layer core, they will be queued individually once again. >> So caused the warning. > > I think it is safe to move the blk_mq_start_request() call under the if-block > that decides whether or not to requeue a request in null_queue_rq() > Right! And null_handle_throttled() in null_handle_cmd() may also return the BLK_STS_DEV_RESOURCE, it's also needed to put in null_queue_rq() and before the blk_mq_start_request(). Then request must return BLK_STS_OK after blk_mq_start_request(). Thanks!
