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Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 1/8] mm: use zone lock guard in reserve_highatomic_pageblock() Message-ID: <20260428114721.GV3102624@noisy.programming.kicks-ass.net> References: <20260306095336.a79fcc869a7f6d2b2e97501b@linux-foundation.org> <20260306130052.7da8eab3@gandalf.local.home> <20260307131641.GX606826@noisy.programming.kicks-ass.net> <20260309164516.GE606826@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: i4fzrw4wpfdaf3f3md6s9d1w37sdos6r X-Rspamd-Queue-Id: C5F74A000B X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1777376849-709583 X-HE-Meta: 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 IWSG0OLD ueOH+vAUhsirmE2IdLqDSZ+7to+THMaXl5lmUNXr4jzL+c9Ktnt7+pJ4xJv2fyQOiijOuzDSj1keMg7E53tl1p3NnvY34c9ECibSC3ww2vo2joiWhGBidSalYpuOJPz3KDU639LsVuv9fJ223G1/c+zHuTiADpXAU8e/4MgBSmljxBBMM6HQOIo66LtQav1dmKtwwKo/GUdWZkWVXoidlRa/N6W0n5hjpRFvArrxFw9M+JpYhsuTf7yBaYpmoq9SlEVf/HBY1naJy8HUYHbEKasXsXBbw2uBnDO2zauAkxD/GzMlq+ykTdiWPuddoOax1qIzjnqJjG68zCf+xbhOr6r37Zg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 28, 2026 at 10:58:41AM +0000, Dmitry Ilvokhin wrote: > I re-tested my original patchset after rebasing and can still reproduce > the regression (though smaller). It appears to depend on compiler > inlining decisions: in some cases the compiler is able to deduplicate > the cleanup path across multiple return sites, while in others it is > not. I'm confused, all this has __always_inline on. And the compilers should be able to track the assignment of the variable and eliminate the test themselves if value-tracking excludes NULL. > Given that, I think we can go further than just removing > __GUARD_IS_ERR(). It should be possible to eliminate this branch > entirely and simplify the cleanup flow. > > https://lore.kernel.org/all/20260427165037.205337-1-d@ilvokhin.com/ > > Reposting here to increase visibility, as several people involved in > this code have participated in this thread already. > > Any feedback would be appreciated. This would require very careful audit of all the current users, it's had this behaviour from the start.