Re: [PATCH RFC 1/5] nvme: Let the blocklayer set timeouts for requests

[Mohamed Khalfella <mkhalfella@purestorage.com>]

On Thu 2026-02-12 13:09:47 +0100, Maurizio Lombardi wrote:
> From: "Heyne, Maximilian" <mheyne@amazon.de>
> 
> When initializing an nvme request which is about to be send to the block
> layer, we do not need to initialize its timeout. If it's left
> uninitialized at 0 the block layer will use the request queue's timeout
> in blk_add_timer (via nvme_start_request which is called from
> nvme_*_queue_rq). These timeouts are setup to either NVME_IO_TIMEOUT or
> NVME_ADMIN_TIMEOUT when the request queues were created.
> 
> Because the io_timeout of the IO queues can be modified via sysfs, the
> following situation can occur:
> 
> 1) NVME_IO_TIMEOUT = 30 (default module parameter)
> 2) nvme1n1 is probed. IO queues default timeout is 30 s
> 3) manually change the IO timeout to 90 s
>    echo 90000 > /sys/class/nvme/nvme1/nvme1n1/queue/io_timeout
> 4) Any call of __submit_sync_cmd on nvme1n1 to an IO queue will issue
>    commands with the 30 s timeout instead of the wanted 90 s which might
>    be more suitable for this device.
> 
> Commit 470e900c8036 ("nvme: refactor nvme_alloc_request") silently
> changed the behavior for ioctl's already because it unconditionally
> overrides the request's timeout that was set in nvme_init_request. If it
> was unset by the user of the ioctl if will be overridden with 0 meaning
> the block layer will pick the request queue's IO timeout.
> 
> Following up on that, this patch further improves the consistency of IO
> timeout usage. However, there are still uses of NVME_IO_TIMEOUT which
> could be inconsistent with what is set in the device's request_queue by
> the user.
> 
> Signed-off-by: Maximilian Heyne <mheyne@amazon.de>
> ---
>  drivers/nvme/host/core.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 7bf228df6001..b9315f0abf80 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -724,10 +724,8 @@ void nvme_init_request(struct request *req, struct nvme_command *cmd)
>  		struct nvme_ns *ns = req->q->disk->private_data;
>  
>  		logging_enabled = ns->head->passthru_err_log_enabled;
> -		req->timeout = NVME_IO_TIMEOUT;
>  	} else { /* no queuedata implies admin queue */
>  		logging_enabled = nr->ctrl->passthru_err_log_enabled;
> -		req->timeout = NVME_ADMIN_TIMEOUT;
>  	}
>  
>  	if (!logging_enabled)
> -- 
> 2.53.0
> 
> 

I wonder what was the impact of these lines given that req->timeout is
set to 0 by blk_mq_rq_ctx_init() when the request is allocated?


Reviewed-by: Mohamed Khalfella <mkhalfella@purestorage.com>