Re: [Devel] [PATCH hci-8.1 5/7] drivers/md/dm-qcow2: implement per-qio fast processing

From: Konstantin Khorenko <khorenko@virtuozzo.com>
To: Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1 5/7] drivers/md/dm-qcow2: implement per-qio fast processing
Date: Wed, 04 Nov 2026 22:35:09 +0100	[thread overview]
Message-ID: <179382810904.2794215.166433010351657971.b4-review@b4> (raw)
In-Reply-To: <20261029140346.465768-6-andrey.zhadchenko@virtuozzo.com>

I won't apply this version, please send v2 with the changes below.

On Thu, 29 Oct 2026 17:03:44 +0300, Andrey Zhadchenko wrote:
> +static void qio_try_fast(struct qio *qio, struct list_head *deferred_qios)
> +{
> +	list_del(&qio->link);
> +
> +	if (process_one_qio(qio->qcow2, qio, true))
> +		list_add(&qio->link, deferred_qios);
> +}

Items 1 and 7 of the cover letter reply.

This patch is where the race of item 1 becomes live: from here on
process_one_qio() runs in parallel with do_qcow2_work(), and a write
can reach perform_rw_mapped() after the main kwork switched its L2 page
to writeback. The details are in the reply to patch 2.

Sashiko's list_add() remark holds, please use list_add_tail() or say
why the reversed order is fine.

-- 
Konstantin Khorenko,
Virtuozzo Linux Kernel Team

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