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[73.179.220.136]) by smtp.gmail.com with ESMTPSA id j142-20020a819294000000b0056d1de0a154sm2173381ywg.37.2023.06.14.07.35.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jun 2023 07:35:55 -0700 (PDT) Date: Wed, 14 Jun 2023 10:35:54 -0400 From: Johannes Weiner To: Domenico Cerasuolo Cc: sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, yosryahmed@google.com, nphamcs@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH] mm: zswap: invaldiate entry after writeback Message-ID: References: <20230614143122.74471-1-cerasuolodomenico@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230614143122.74471-1-cerasuolodomenico@gmail.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0CE6C160020 X-Stat-Signature: ryecd6emzy4o4kmbisgbix7krceksy7t X-Rspam-User: X-HE-Tag: 1686753356-769681 X-HE-Meta: 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 xc8NVthY 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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@gmail.com> in mm-unstable + > commit f090b7949768("mm: zswap: support exclusive loads") that's in > mm-unstable as well. > > Suggested-by: Johannes Weiner > Signed-off-by: Domenico Cerasuolo Acked-by: Johannes Weiner Thanks Domenico!