[PATCH] nvme-fabrics: allow to queue requests for live queues

[Christoph Hellwig]

Dropped from nvme-5.9 to wait to the discussion to finish as I want
to send a PR to Jens today..

On Mon, Jul 27, 2020 at 10:35:23PM -0700, Sagi Grimberg wrote:
> Right now we are failing requests based on the controller
> state (which is checked inline in nvmf_check_ready) however
> we should definitely accept requests if the queue is live.
> 
> When entering controller reset, we transition the controller
> into NVME_CTRL_RESETTING, and then return BLK_STS_RESOURCE for
> non-mpath requests (have blk_noretry_request set).
> 
> This is also the case for NVME_REQ_USER for some reason, but
> there shouldn't be any reason for us to reject this I/O in a
> controller reset.
> 
> In a non-mpath setup, this means that the requests will simply
> be requeued over and over forever not allowing the q_usage_counter
> to drop its final reference, causing controller reset to hang
> if running concurrently with heavy I/O.
> 
> While we are at it, remove the redundant NVME_CTRL_NEW case, which
> should never see any I/O as it must first transition to
> NVME_CTRL_CONNECTING.
> 
> Fixes: 35897b920c8a ("nvme-fabrics: fix and refine state checks in __nvmf_check_ready")
> Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
> ---
>  drivers/nvme/host/fabrics.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
> index 4ec4829d6233..2e7838f42e36 100644
> --- a/drivers/nvme/host/fabrics.c
> +++ b/drivers/nvme/host/fabrics.c
> @@ -564,21 +564,13 @@ bool __nvmf_check_ready(struct nvme_ctrl *ctrl, struct request *rq,
>  {
>  	struct nvme_request *req = nvme_req(rq);
>  
> -	/*
> -	 * If we are in some state of setup or teardown only allow
> -	 * internally generated commands.
> -	 */
> -	if (!blk_rq_is_passthrough(rq) || (req->flags & NVME_REQ_USERCMD))
> -		return false;
> -
>  	/*
>  	 * Only allow commands on a live queue, except for the connect command,
>  	 * which is require to set the queue live in the appropinquate states.
>  	 */
>  	switch (ctrl->state) {
> -	case NVME_CTRL_NEW:
>  	case NVME_CTRL_CONNECTING:
> -		if (nvme_is_fabrics(req->cmd) &&
> +		if (blk_rq_is_passthrough(rq) && nvme_is_fabrics(req->cmd) &&
>  		    req->cmd->fabrics.fctype == nvme_fabrics_type_connect)
>  			return true;
>  		break;
> -- 
> 2.25.1
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