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b=WB/8VhxdRz0CoWK0Rl2C/CMFrU3rpY5l+wyYucwIia92gA+3bT3lnnNL/NsVJA6ymRO1XVIlk5vfdtmHGGmcY2ORSh7wsH1s09AvEFfYCjrNK0nliJn1Q84j98dyufyeL94sabHVDiMrrGOyGMQUQTgXUOOpMxZ4hHkjgF3xFa8= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R491e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037033178;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=19;SR=0;TI=SMTPD_---0X12xEIY_1776220065; Received: from 30.74.144.121(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X12xEIY_1776220065 cluster:ay36) by smtp.aliyun-inc.com; Wed, 15 Apr 2026 10:27:46 +0800 Message-ID: <7d5bc512-f3ed-40dc-991d-70cfed32b6f7@linux.alibaba.com> Date: Wed, 15 Apr 2026 10:27:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] [v2] mm/vmscan: avoid false-positive -Wuninitialized warning To: Arnd Bergmann , Andrew Morton , Johannes Weiner Cc: Arnd Bergmann , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , David Hildenbrand , Michal Hocko , Lorenzo Stoakes , Muchun Song , Davidlohr Bueso , Koichiro Den , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260414065206.3236176-1-arnd@kernel.org> From: Baolin Wang In-Reply-To: <20260414065206.3236176-1-arnd@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E76B54000A X-Stat-Signature: x1uwr73oa9o4bb9tfyaxibogso18rxbb X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1776220071-781604 X-HE-Meta: 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 0NG/Uyja FQTErw/cOiELSWtkDYGtO39Nw3Avku+t+QGyRGDjLfuUc+MhAqXb4qNHyODrIo5BaFQ+PPpZ1Wp+SaOBudEsYpegGjkSx1/tpqyFxmL6tYmv/NMr1iTn8XTiPIeg3CBqGH2wU1RyqtneeoFADzrMtbdF7BfAlrOu4sASI0Hrh6rwAwHeFReeyqAmjqAksnS2BWmEFFkTAZZvcxlmcYcR9tHsJho26M+Hhm4hdAzxio4inKKck4eMHyiabWzdxLKImd5wJWCg4AwnngryCrXY16W4jtr1zoHa5KgZyYmrUeA359hrLuT8eVZIjXZfmISGrul8eOdKdjAtC6z1OdOendCtgfSsZpwIYp+eC Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/14/26 2:51 PM, Arnd Bergmann wrote: > From: Arnd Bergmann > > When the -fsanitize=bounds sanitizer is enabled, gcc-16 sometimes runs > into a corner case in the read_ctrl_pos() pos function, where it sees > possible undefined behavior from the 'tier' index overflowing, presumably > in the case that this was called with a negative tier: > > In function 'get_tier_idx', > inlined from 'isolate_folios' at mm/vmscan.c:4671:14: > mm/vmscan.c: In function 'isolate_folios': > mm/vmscan.c:4645:29: error: 'pv.refaulted' is used uninitialized [-Werror=uninitialized] > > Part of the problem seems to be that read_ctrl_pos() has unusual calling > conventions since commit 37a260870f2c ("mm/mglru: rework type selection") > where passing MAX_NR_TIERS makes it accumulate all tiers but passing a > smaller positive number makes it read a single tier instead. > > Shut up the warning by adding a fake initialization to the two instances > of this variable that can run into that corner case. > > Link: https://lore.kernel.org/all/CAJHvVcjtFW86o5FoQC8MMEXCHAC0FviggaQsd5EmiCHP+1fBpg@mail.gmail.com/ > Signed-off-by: Arnd Bergmann > --- > v2: replace the earlier more invasive cleanup with a trivial > workaround > --- LGTM. Reviewed-by: Baolin Wang