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Thu, 17 Sep 2026 01:51:04 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 X-ThreadId: ACGBcqtoOIMw Date: Thu, 17 Sep 2026 07:50:43 +0200 From: "Arnd Bergmann" To: "Andrew Morton" , "Arnd Bergmann" , "Johannes Weiner" , "David Hildenbrand (Red Hat)" , "Michal Hocko" , "Qi Zheng" , "Shakeel Butt" , "Lorenzo Stoakes" , "Kairui Song" , "Barry Song" , "Axel Rasmussen" , "Yuanchu Xie" , "Wei Xu" , "Baoquan He" , "Baolin Wang" , "Ridong Chen" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Message-Id: <75939625-482c-464f-83fb-fa12d3e1d79c@app.fastmail.com> In-Reply-To: <20260916163044.3daa3811d9b2bf7d958f1f27@linux-foundation.org> References: <20260916083456.4136132-1-arnd@kernel.org> <20260916162816.39f0f33f6a48d30a71be3575@linux-foundation.org> <20260916163044.3daa3811d9b2bf7d958f1f27@linux-foundation.org> Subject: Re: [PATCH] mm/vmscan: avoid false-positive -Wuninitialized warning, again Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Stat-Signature: 7x364sdehkjo6r81n54n8uubiexttynk X-Rspam-User: X-Rspamd-Queue-Id: 9E86F180004 X-Rspamd-Server: rspam03 X-HE-Tag: 1789624274-525370 X-HE-Meta: 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 KXD/3s5r V6S8f0lWxQlpbkhf061htB81CpazWrmca76NJe17p/dfrf75TRvUMeFuyEjNLmCSrPRyI6QBTNayRYw0bjesBRyaYk1W3h8cLzK5bP2Kl7Rv0Iv7PVqF5xYAutDfrecsnczWDpf49KKg1cnBDFrgaIgWwcr4vpEBrmlM/2J8QI5zeBI4jw2UbR67j474xQ22SGsygYW5WEyn63jpJKJeCzaXf6Xivp+MIc5HvwEWILO7HgOvsmn7COkYLucY2tFlj6QA7icvqV6YnXb4Uc5W6r1j1E2FY3u3C5bOl Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 17, 2026, at 01:30, Andrew Morton wrote: > On Wed, 16 Sep 2026 16:28:16 -0700 Andrew Morton wrote: >> > >> > --- a/mm/vmscan.c >> > +++ b/mm/vmscan.c >> > @@ -3274,8 +3274,10 @@ struct ctrl_pos { >> > int gain; >> > }; >> > >> > -static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier_min, >> > - int tier_max, int gain, struct ctrl_pos *pos) >> > +/* __noipa works around gcc-16 warning for uninitizled use of pos->refaulted */ >> > +static __noipa void read_ctrl_pos(struct lruvec *lruvec, int type, >> > + int tier_min, int tier_max, int gain, >> > + struct ctrl_pos *pos) >> > { >> > int i; >> > struct lru_gen_folio *lrugen = &lruvec->lrugen; >> >> Current code has changed here somewhat, but I expect the error is still >> there. I fixed that "uninitizled" while in there. Altered patch is >> below. > > > Then the build blew up in unexpected ways. gcc-15.2.0. > > The failure looks like a legit min() signedness thing which has been > there quite a while. I'm thinking that __noipa surfaced this for some > reason? Right, I now saw the same thing here on the current linux-next. What I found now is that the __noipa is only needed on top of "mm/mglru: use explicit tier range in read_ctrl_pos()", which was in next-20260915 but disappeared in next-20260916. This patch also removed the min(). I think the reason why __noipa causes the warning about min() is that it prevents the constant propagation into read_ctrl_pos() and in turn the hack that suppresses warning about mixed types in minmax.h when both sides are constant. Is the mglru series currently expected to make it into 7.4? If not, I would withdraw my __noipa and hope that the next round of changes to read_ctrl_pos() does not run into this problem again. Arnd