linux-kernel - nvme-fc: Question about __nvme_fc_abort_outstanding

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Message-ID: <Z38nGkThjH59LFrf@ceto>
Date: Wed, 8 Jan 2025 17:32:10 -0800
From: Mohamed Khalfella <mkhalfella@...estorage.com>
To: James Smart <james.smart@...adcom.com>, Keith Busch <kbusch@...nel.org>,
	Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
	randyj@...estorage.com, jrani@...estorage.com
Subject: nvme-fc: Question about __nvme_fc_abort_outstanding_ios()

Hello,

I was looking at this code and I had a question about it.

drivers/nvme/host/fc.c
2473 static void
2474 __nvme_fc_abort_outstanding_ios(struct nvme_fc_ctrl *ctrl, bool start_queues)
2475 {
...
...
2503                 blk_mq_tagset_busy_iter(&ctrl->tag_set,
2504                                 nvme_fc_terminate_exchange, &ctrl->ctrl);
2505                 blk_mq_tagset_wait_completed_request(&ctrl->tag_set);

nvme_fc_terminate_exchange() calls __nvme_fc_abort_op() to abort all active
ops with status FCPOP_STATE_ACTIVE. I think these active ops map to in-flight
requests MQ_RQ_IN_FLIGHT. After blk_mq_tagset_busy_iter() returns it is not
guaranteed that all ops had done callback functions called on them. Some
of these requests might still be in-flight.

blk_mq_tagset_wait_completed_request() makes sure that we do not have pending
completed requests, but it does not check for in-flight requests?

Am I missing something obvious here?

Why we need blk_mq_tagset_wait_completed_request() here?
Is it possible to have in-flight requests after the function returns?

Should this call be moved to nvme_fc_delete_association() after all the
requests are aborted by LLDD?

Thanks,
Mohamed Khalfella