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>

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 23f6bad..f3b9d91 100644 (file)
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -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;