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b=HS7YjAe0WuuJf++7+e1yek2cH/BMiQtp43ZcCP+dD4Y3M5NFATlRdfpmojwnoA6cc +wf7BMjYx6qoelFhPLjQoAkzbIeszS5cg/mo1mcTwFG/CxT582IXLRfMJXs3DYNseX VZqdyHvBHOxZJAMgFmt8Xz3HiuL+GfhbY46twIgeyHFBVazl7/bSDQNBLLBOg6Eh9X FrSbFzGiM7JA82lZY3DwhfJ91xIVaVMAEjCR6HY2GFP5gN0M0+rfuh9nytg173Lzf+ /mAcMlpNokgD1OzHUBHM1ekpjZPjabsnZSzOP3nd/6c4nUNB7QRqeHHWWlrpHit97l qaL2saihF9SBA== Received: by mail-qv1-f51.google.com with SMTP id 6a1803df08f44-8a032383008so68153496d6.1 for ; Tue, 14 Apr 2026 14:00:08 -0700 (PDT) X-Forwarded-Encrypted: i=1; AFNElJ+eWX9qV48kKJL+Chk+2m1QmUiAPg98QHV6q1N1mglE+EhUP1U2Uzr8XzZ/9uoU9t7Lf9ZwmGPojQ==@kvack.org X-Gm-Message-State: AOJu0YzLKYvfPAPMd/gM8M+Y94AouYnr8xkFZSKvUt2ubKGeXxowJWt6 nX0oXft9drdG3rKjKMM0vyPg9vNiuTkFe0PKTQl0HUvltd77wBn7qnlO8V1Zvqv3AYv1PEWWO2x Oiuf0gQf6/+w05+O4n6ziJE90Bmx4BF4= X-Received: by 2002:a05:6214:da4:b0:8ad:bccd:94cf with SMTP id 6a1803df08f44-8adbccd95c9mr73153366d6.18.1776200407210; Tue, 14 Apr 2026 14:00:07 -0700 (PDT) MIME-Version: 1.0 References: <20260414065206.3236176-1-arnd@kernel.org> In-Reply-To: <20260414065206.3236176-1-arnd@kernel.org> From: Barry Song Date: Wed, 15 Apr 2026 04:59:53 +0800 X-Gmail-Original-Message-ID: X-Gm-Features: AQROBzD5UaAc4n9tOLGFa-kWgR7p4d77lr5y8E1TxejXmChGVIRzd3Ozk2hXIN8 Message-ID: Subject: Re: [PATCH] [v2] mm/vmscan: avoid false-positive -Wuninitialized warning To: Arnd Bergmann Cc: Andrew Morton , Johannes Weiner , Arnd Bergmann , Kairui Song , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , David Hildenbrand , Michal Hocko , Lorenzo Stoakes , Muchun Song , Baolin Wang , Davidlohr Bueso , Koichiro Den , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6CF724001D X-Stat-Signature: 4uq8t64gm8e78fsxi6gm7bw3byz5h3yj X-Rspam-User: X-HE-Tag: 1776200409-464209 X-HE-Meta: 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 QeCyQcwx 8BRkJHrwGGDlObe4QxxtKKhdGe42THw1wVTurUVBdMxIJyyd3ccwvgzTKrYkqbpvg4xr4g7T6stFML+s1tnh+fellaKwco6paIrvaZm0q98QruFSuy3R9Fxas6l3iryMImx7JVBB3hAsq06OWuhnfg5WC74X6mHdzKoNCrgoLTV6uV+vjeAxfyo74cQk5zZykpcCQLwOfhLBcKqTRJiiGqB6picN5P61O1rs6bLtqw+GVb2kIRS2A4rhDRWGCKexkWkkvsvaUVpNcKf4NP6wjRw8dTTveY838we2ElJJ1fbUsF9+BRKPBE7B1vH6vfexPwqHAJBtPskCd5kM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 14, 2026 at 2:52=E2=80=AFPM Arnd Bergmann wro= te: > > From: Arnd Bergmann > > When the -fsanitize=3Dbounds 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= =3Duninitialized] > > 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/CAJHvVcjtFW86o5FoQC8MMEXCHAC0FviggaQsd5= EmiCHP+1fBpg@mail.gmail.com/ > Signed-off-by: Arnd Bergmann > --- > v2: replace the earlier more invasive cleanup with a trivial > workaround Reviewed-by: Barry Song