linux-kernel - Re: [PATCH v2 2/2] ublk: introduce and use ublk_set

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Message-ID: <aGfKsZgztW53svl-@fedora>
Date: Fri, 4 Jul 2025 20:36:01 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Uday Shankar <ushankar@...estorage.com>
Cc: Jens Axboe <axboe@...nel.dk>,
	Caleb Sander Mateos <csander@...estorage.com>,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] ublk: introduce and use ublk_set_canceling helper

On Thu, Jul 03, 2025 at 11:41:08PM -0600, Uday Shankar wrote:
> For performance reasons (minimizing the number of cache lines accessed
> in the hot path), we store the "canceling" state redundantly - there is
> one flag in the device, which can be considered the source of truth, and
> per-queue copies of that flag. This redundancy can cause confusion, and
> opens the door to bugs where the state is set inconsistently. Try to
> guard against these bugs by introducing a ublk_set_canceling helper
> which is the sole mutator of both the per-device and per-queue canceling
> state. This helper always sets the state consistently. Use the helper in
> all places where we need to modify the canceling state.
> 
> No functional changes are expected.
> 
> Signed-off-by: Uday Shankar <ushankar@...estorage.com>

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

thanks,
Ming