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Tue, 20 Oct 2026 19:02:08 -0700 (PDT) Date: Wed, 21 Oct 2026 10:01:35 +0800 From: Wenwu Hou To: Yosry Ahmed Cc: hannes@cmpxchg.org, nphamcs@gmail.com, chengming.zhou@linux.dev, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm: zswap: set zswap_ever_enabled when enabling zswap at runtime Message-ID: References: <20261020122942.3477541-1-hwenwur@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 857901C0004 X-Stat-Signature: m6enxwabw73kupbd8msmhzspttsrejoe X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792548131-681093 X-HE-Meta: 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 4IGNnE5m 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Oct 20, 2026 at 08:57:15AM -0700, Yosry Ahmed wrote: > On Tue, Oct 20, 2026 at 5:30 AM Wenwu Hou wrote: > > > > zswap can end up enabled without zswap_ever_enabled being set, which > > leads to data corruption. With CONFIG_ZSWAP_DEFAULT_ON=n: > > > > 1. zswap_setup() fails to create the initial pool. Setup still counts > > as successful, but zswap_has_pool stays false. > > 2. The user writes a compressor name to > > /sys/module/zswap/parameters/compressor. > > zswap_compressor_param_set() creates a pool and sets > > zswap_has_pool = true, but never enables the zswap_ever_enabled > > static key. > > 3. The user runs "echo Y > /sys/module/zswap/parameters/enabled". > > 4. zswap_store() now stores pages in zswap, and swap_writeout() skips > > writing them to the swap device. > > 5. On swap-in, zswap_load() first checks zswap_never_enabled(). It > > returns true, so zswap_load() reports that the page is not in zswap. > > The page is then read from the swap device, which holds stale data. > > > > Fix this by enabling zswap_ever_enabled in zswap_enabled_param_set() > > before zswap_enabled becomes true. > > Wasn't this fixed by > https://lore.kernel.org/linux-mm/20260906133601.3563324-1-xialonglong2025@163.com/? Yes, please drop this one, sorry for the noise.