linux-kernel - Re: [RFC PATCH 1/9] mm: zswap: always shrink in zswap_store() if zswap_pool_reached

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240328190900.GD7597@cmpxchg.org>
Date: Thu, 28 Mar 2024 15:09:00 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Nhat Pham <nphamcs@...il.com>,
	Chengming Zhou <chengming.zhou@...ux.dev>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/9] mm: zswap: always shrink in zswap_store() if
 zswap_pool_reached_full

On Mon, Mar 25, 2024 at 11:50:09PM +0000, Yosry Ahmed wrote:
> The cleanup code in zswap_store() is not pretty, particularly the
> 'shrink' label at the bottom that ends up jumping between cleanup
> labels.
> 
> Instead of having a dedicated label to shrink the pool, just use
> zswap_pool_reached_full directly to figure out if the pool needs
> shrinking. zswap_pool_reached_full should be true if and only if the
> pool needs shrinking.
> 
> The only caveat is that the value of zswap_pool_reached_full may be
> changed by concurrent zswap_store() calls between checking the limit and
> testing zswap_pool_reached_full in the cleanup code. This is fine
> because:
> - If zswap_pool_reached_full was true during limit checking then became
>   false during the cleanup code, then someone else already took care of
>   shrinking the pool and there is no need to queue the worker. That
>   would be a good change.
> - If zswap_pool_reached_full was false during limit checking then became
>   true during the cleanup code, then someone else hit the limit
>   meanwhile. In this case, both threads will try to queue the worker,
>   but it never gets queued more than once anyway. Also, calling
>   queue_work() multiple times when the limit is hit could already happen
>   today, so this isn't a significant change in any way.
> 
> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>

Acked-by: Johannes Weiner <hannes@...xchg.org>