Commit 834d3710 authored Mar 13, 2019 by James Smart Committed by Jens Axboe Mar 13, 2019

nvme-fc: reject reconnect if io queue count is reduced to zero



If:

 - A successful connect has occurred with an io queue count greater than
   zero and namespaces detected and running.
 - An error or something occurs which causes a termination of the prior
   association and then starts a reconnect,
 - The reconnect then creates a new controller, but for whatever reason,
   nvme_set_queue_count() results in io queue count set to zero.  This
   will skip io queue and tag set changes.
 - But... the controller will transition to live, calling
   nvme_start_ctrl, which calls nvme_start_queues(), which then releases
   I/Os into the transport which then sends them to the driver.

As there are no queues, things eventually hit the driver looking for a
handle, which was cleared when the original controller was reset, and it
can't proceed. Worst case, things progress, but everything fails.

In the failing scenario, the nvme_set_features(NVME_FEAT_NUM_QUEUES)
command actually failed with a NVME_SC_INTERNAL error.  For some reason,
although nvme_set_queue_count() saw the error and set io queue count to
zero, it doesn't return a failure status to the transport, which allows
the transport to continue using the controller.

Fix the problem by simply rejecting the new association if at least 1
I/O queue can't be created. The association reject will fail the
reconnect attempt and fall into the reconnect retry policy.

Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 06f3d71e

drivers/nvme/host/fc.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -2475,6 +2475,7 @@ static int
		nvme_fc_recreate_io_queues(struct nvme_fc_ctrl *ctrl)
		{
		struct nvmf_ctrl_options *opts = ctrl->ctrl.opts;
		u32 prior_ioq_cnt = ctrl->ctrl.queue_count - 1;
		unsigned int nr_io_queues;
		int ret;

		@@ -2487,6 +2488,13 @@ nvme_fc_recreate_io_queues(struct nvme_fc_ctrl *ctrl)
		return ret;
		}

		if (!nr_io_queues && prior_ioq_cnt) {
		dev_info(ctrl->ctrl.device,
		"Fail Reconnect: At least 1 io queue "
		"required (was %d)\n", prior_ioq_cnt);
		return -ENOSPC;
		}

		ctrl->ctrl.queue_count = nr_io_queues + 1;
		/* check for io queues existing */
		if (ctrl->ctrl.queue_count == 1)
		@@ -2500,6 +2508,10 @@ nvme_fc_recreate_io_queues(struct nvme_fc_ctrl *ctrl)
		if (ret)
		goto out_delete_hw_queues;

		if (prior_ioq_cnt != nr_io_queues)
		dev_info(ctrl->ctrl.device,
		"reconnect: revising io queue count from %d to %d\n",
		prior_ioq_cnt, nr_io_queues);
		blk_mq_update_nr_hw_queues(&ctrl->tag_set, nr_io_queues);

		return 0;

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