Messages in this thread | | | Subject | Re: [PATCH V2 7/8] nvme: use blk_mq_queue_tag_inflight_iter | From | "jianchao.wang" <> | Date | Tue, 26 Mar 2019 09:17:24 +0800 |
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Hi Keith
On 3/25/19 9:49 PM, Keith Busch wrote: > On Mon, Mar 25, 2019 at 01:38:37PM +0800, Jianchao Wang wrote: >> blk_mq_tagset_inflight_iter is not safe that it could get stale request >> in tags->rqs[]. Use blk_mq_queue_tag_inflight_iter here. A new helper >> interface nvme_iterate_inflight_rqs is introduced to iterate >> all of the ns under a ctrl. > > Nak, NVMe only iterates tags when new requests can't enter, allocated > requests can't dispatch, and dispatched commands can't complete. So > it is perfectly safe to iterate if the driver takes reasonable steps > beforehand.
nvme_dev_disable just quiesce and freeze the request_queue, but not drain the enters. So there still could be someone escapes the queue freeze checking and tries to allocate request.
> Further, for M tags and N namespaces, we complete teardown > in O(M) time, but this makes in O(M*N) without gaining anything. >
Yes, it is indeed inefficient.
Thanks Jianchao
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