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AJvYcCW/tRhBlIJYBdS54VJEaCUHorn9Dnu2K6tBfm1n5SNqiwVekO0NepCZpDH5pyIWL+Fe3MoJuvcc6A==@kvack.org X-Gm-Message-State: AOJu0YymtgzGSWjqaEk7RWtTskQfs2Gr/HoxObXzNDtdfUvRtfrmF4K5 TT2khXrv1LNYYywxrV31rkiC52oFTNf6TX/p79vQFCQrB0TZyl/3maCu5q5dLhUD5vqV+xqRrVG wKZnVwR4IBvAQ8PahAkLZpN4ATEZkB37whIfM X-Google-Smtp-Source: AGHT+IHFoZwB9UJQ/W7UPJWTT6Mwf1OXIt2PanaSLVRWyM98+DOHGoOSiH002T//dMssG37gkEwNVD1jyiUDrfB47Us= X-Received: by 2002:a67:eada:0:b0:4a3:c32a:dfbf with SMTP id ada2fe7eead31-4a961b8080dmr9219748137.9.1730757889902; Mon, 04 Nov 2024 14:04:49 -0800 (PST) MIME-Version: 1.0 References: <20241025012304.2473312-1-shakeel.butt@linux.dev> <20241025012304.2473312-6-shakeel.butt@linux.dev> <20241104133834.e0e138038a111c2b0d20bdde@linux-foundation.org> In-Reply-To: <20241104133834.e0e138038a111c2b0d20bdde@linux-foundation.org> From: Yu Zhao Date: Mon, 4 Nov 2024 15:04:13 -0700 Message-ID: Subject: Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU To: Andrew Morton Cc: Shakeel Butt , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Hugh Dickins , Yosry Ahmed , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Meta kernel team Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Stat-Signature: 5yktp4kifi9ceobd35zfmafm6wjh4sos X-Rspamd-Queue-Id: 073C018001B X-Rspam-User: X-HE-Tag: 1730757867-952526 X-HE-Meta: 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 +z8fbXlb X3pUv4O8k/ZGb9iqR3ZeQIUKLwQO5kE5Y8vCbnfd4am7ieZW1M6P2FillglU3BrOBBa4INVWoMJO/mVkddrd0ibwbRAu/9uyIq6gSRWQmgi7jqjSO6VMPVEAX0awNG2jTxHoYBKK3JD1HmqqfDxrJAQ9YclQlE0WKtOupXIJBpOXDZFUk6sp3EcrtGMYqlUuKsX88UkUD3rm0y2mZCfl33umGEx3sHNDBdKnRl3sk9tXZwb7sFBSUXoM6dhYUXgrznbws8h1QevOH+T6Hr4o9Hb8TsWUugqNbMO8M2eSfcjSmhJhOBtBi4YWo2JmwiDpo5MY7gIG+a3Dnldx/54WyN0pjOQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Mon, Nov 4, 2024 at 2:38=E2=80=AFPM Andrew Morton wrote: > > On Mon, 4 Nov 2024 10:30:29 -0700 Yu Zhao wrote: > > > On Sat, Oct 26, 2024 at 09:26:04AM -0600, Yu Zhao wrote: > > > On Sat, Oct 26, 2024 at 12:34=E2=80=AFAM Shakeel Butt wrote: > > > > > > > > On Thu, Oct 24, 2024 at 06:23:02PM GMT, Shakeel Butt wrote: > > > > > While updating the generation of the folios, MGLRU requires that = the > > > > > folio's memcg association remains stable. With the charge migrati= on > > > > > deprecated, there is no need for MGLRU to acquire locks to keep t= he > > > > > folio and memcg association stable. > > > > > > > > > > Signed-off-by: Shakeel Butt > > > > > > > > Andrew, can you please apply the following fix to this patch after = your > > > > unused fixup? > > > > > > Thanks! > > > > syzbot caught the following: > > > > WARNING: CPU: 0 PID: 85 at mm/vmscan.c:3140 folio_update_gen+0x23d/0x= 250 mm/vmscan.c:3140 > > ... > > > > Andrew, can you please fix this in place? > > OK, but... > > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -3138,7 +3138,6 @@ static int folio_update_gen(struct folio *folio, = int gen) > > unsigned long new_flags, old_flags =3D READ_ONCE(folio->flags); > > > > VM_WARN_ON_ONCE(gen >=3D MAX_NR_GENS); > > - VM_WARN_ON_ONCE(!rcu_read_lock_held()); > > > > do { > > /* lru_gen_del_folio() has isolated this page? */ > > it would be good to know why this assertion is considered incorrect? The assertion was caused by the patch in this thread. It used to assert that a folio must be protected from charge migration. Charge migration is removed by this series, and as part of the effort, this patch removes the RCU lock. > And a link to the sysbot report? https://syzkaller.appspot.com/bug?extid=3D24f45b8beab9788e467e