linux-kernel - Re: [PATCH] ublk: remove unnecessary ubq checks

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Message-ID: <aABFAg563W1g_4QS@fedora>
Date: Thu, 17 Apr 2025 08:02:10 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Caleb Sander Mateos <csander@...estorage.com>
Cc: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ublk: remove unnecessary ubq checks

On Wed, Apr 16, 2025 at 11:01:53AM -0600, Caleb Sander Mateos wrote:
> ublk_init_queues() ensures that all nr_hw_queues queues are initialized,
> with each ublk_queue's q_id set to its index. And ublk_init_queues() is
> called before ublk_add_chdev(), which creates the cdev. Is is therefore
> impossible for the !ubq || ub_cmd->q_id != ubq->q_id condition to hit in
> __ublk_ch_uring_cmd(). Remove it to avoids some branches in the I/O path.
> 
> Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
> ---
>  drivers/block/ublk_drv.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index cdb1543fa4a9..bc86231f5e27 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1947,13 +1947,10 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
>  
>  	if (ub_cmd->q_id >= ub->dev_info.nr_hw_queues)
>  		goto out;
>  
>  	ubq = ublk_get_queue(ub, ub_cmd->q_id);
> -	if (!ubq || ub_cmd->q_id != ubq->q_id)
> -		goto out;
> -

Looks correct, ubq->q_id is always same with the index passed to
ublk_get_queue().

Reviewed-by: Ming Lei <ming.lei@...hat.com>


Thanks,
Ming