linux-kernel - Re: [PATCH] mm: zswap: invaldiate entry after writeback

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Message-ID: <ZInQSg08lDyM_W-b@cmpxchg.org>
Date:   Wed, 14 Jun 2023 10:35:54 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Domenico Cerasuolo <cerasuolodomenico@...il.com>
Cc:     sjenning@...hat.com, ddstreet@...e.org, vitaly.wool@...sulko.com,
        yosryahmed@...gle.com, nphamcs@...il.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH] mm: zswap: invaldiate entry after writeback

On Wed, Jun 14, 2023 at 04:31:22PM +0200, Domenico Cerasuolo wrote:
> When an entry started writeback, it used to be invalidated with ref
> count logic alone, meaning that it would stay on the tree until all
> references were put. The problem with this behavior is that as soon as
> the writeback started, the ownership of the data held by the entry is
> passed to the swapcache and should not be left in zswap too.
> Currently there are no known issues because of this, but this change
> explicitly invalidates an entry that started writeback to reduce
> opportunities for future bugs.
> 
> This patch is a follow up on the series titled "mm: zswap: move
> writeback LRU from zpool to zswap" with message id
> <20230612093815.133504-1-cerasuolodomenico@...il.com> in mm-unstable +
> commit f090b7949768("mm: zswap: support exclusive loads") that's in
> mm-unstable as well.
> 
> Suggested-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@...il.com>

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

Thanks Domenico!