linux-kernel - Re: [PATCH] block: Fix default IO priority if there is no IO context

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Message-ID: <04e4aa4c-8d33-42ab-88cc-3dceadd6c9b1@kernel.org>
Date: Thu, 31 Jul 2025 14:22:00 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>, Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 Bart Van Assche <bvanassche@....org>
Subject: Re: [PATCH] block: Fix default IO priority if there is no IO context

On 7/31/25 1:49 PM, Guenter Roeck wrote:
> Upstream commit 53889bcaf536 ("block: make __get_task_ioprio() easier to
> read") changes the IO priority returned to the caller if no IO context
> is defined for the task. Prior to this commit, the returned IO priority
> was determined by task_nice_ioclass() and task_nice_ioprio(). Now it is
> always IOPRIO_DEFAULT, which translates to IOPRIO_CLASS_NONE with priority
> 0. However, task_nice_ioclass() returns IOPRIO_CLASS_IDLE, IOPRIO_CLASS_RT,
> or IOPRIO_CLASS_BE depending on the task scheduling policy, and
> task_nice_ioprio() returns a value determined by task_nice(). This causes
> regressions in test code checking the IO priority and class of IO
> operations on tasks with no IO context.
> 
> Fix the problem by returning the IO priority calculated from
> task_nice_ioclass() and task_nice_ioprio() if no IO context is defined
> to match earlier behavior.
> 
> Fixes: 53889bcaf536 ("block: make __get_task_ioprio() easier to read")
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Bart Van Assche <bvanassche@....org>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Looks good to me.

Reviewed-by: Damien Le Moal <dlemoal@...nel.org>


-- 
Damien Le Moal
Western Digital Research