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AJvYcCUcdsSg02L6/dfPLXVoq5Che3UEvoXdd/WedLCuL/pdiEGIo5URkqEFJ/y/gyhPiin5PhDqCFNecw==@kvack.org X-Gm-Message-State: AOJu0Yw8vTntOAH1PC5HREK8Ji1m46B9UG7X1qTkSRKBCx88HXcGdVb8 PLPDsnrVtX5oreEJ7HyNP4mH09DssyrIWFbQ3R1AOEEh8GvUY1pVGj/KchtazGFKxOEjUF7zlrk eB/XsuMkzf5NhDW+amDt6plhFc2f7TLT2XLQh X-Google-Smtp-Source: AGHT+IEYwBGfTFm2L33SK9fmz4kJbVLbv8hDQ2e+YiLDLKjI0fPHMvWbn4/4Yh3eoZmDzBbd9BzfQBf8B2iidi0ERBQ= X-Received: by 2002:a05:622a:450a:b0:456:7ed1:c1cc with SMTP id d75a77b69052e-4567fcbf264mr58971cf.26.1724867366963; Wed, 28 Aug 2024 10:49:26 -0700 (PDT) MIME-Version: 1.0 References: <20240827230753.2073580-1-kinseyho@google.com> <20240827230753.2073580-4-kinseyho@google.com> In-Reply-To: <20240827230753.2073580-4-kinseyho@google.com> From: "T.J. Mercier" Date: Wed, 28 Aug 2024 10:49:12 -0700 Message-ID: Subject: Re: [PATCH mm-unstable v3 3/5] mm: increment gen # before restarting traversal To: Kinsey Ho Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Yosry Ahmed , Roman Gushchin , Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , Tejun Heo , Zefan Li , mkoutny@suse.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5C6334001F X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ern1ma7gkugkp4fa88668umk6dd6frem X-HE-Tag: 1724867368-641614 X-HE-Meta: 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 0ELuT7za 9uxc9CK/DrLlshK1TbSVI6F9KnhqBWySPmU+LNEgkAeA8uzD/TK18c04uC548i1K/eOrzJNbqBJOtBxx2dqY13mJD257ow10PYfoHJJ898HA28QStvHm4Kl8gCd9T8eKQu9Z1ylAryFh5O/dE8hVh/3/PE/wQAjlYkO3+gaAAwqr4DqJFzdvA2u34H9cj5OmZ2/Odzm1btrcQ/zIrKqBDRvwwf19rOCZ8gOET X-Bogosity: Ham, tests=bogofilter, spamicity=0.041203, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Aug 27, 2024 at 4:11=E2=80=AFPM Kinsey Ho wro= te: > > The generation number in struct mem_cgroup_reclaim_iter should be > incremented on every round-trip. Currently, it is possible for a > concurrent reclaimer to jump in at the end of the hierarchy, causing a > traversal restart (resetting the iteration position) without > incrementing the generation number. > > By resetting the position without incrementing the generation, it's > possible for another ongoing mem_cgroup_iter() thread to walk the tree > twice. > > Move the traversal restart such that the generation number is > incremented before the restart. > > Signed-off-by: Kinsey Ho Reviewed-by: T.J. Mercier