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Mon, 04 Nov 2024 14:08:46 -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: From: Yu Zhao Date: Mon, 4 Nov 2024 15:08:09 -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: rspam04 X-Rspamd-Queue-Id: D7BE71C0010 X-Stat-Signature: mksscoidsi7engpnfpz7u9yozn7o6xep X-Rspam-User: X-HE-Tag: 1730758066-333943 X-HE-Meta: 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 T8KI0db0 Diusayz773gcuOfzRrb+QRYSl3/6ZS6Lg6Z+JeSVpmMdEEfvWHGEybKkoLB6EDMizGj3GGrmTVWQHyT9LikZoNXqw3bQ5fvTImc3jodnze+TA+UtcNy3jAkvHhTE4KCx6n5oBOOWVy4F5KjTCH2P4LEwX22JypcXKzumAxAGRolpfy8fjTrhwTYRHOpt5lgDivizSV345WPyO9DdV23udqeIzXi5OgQZGRiJSx6PKH0ojcC6SFvOkDGto8L+mPo86Aaqo8lRq1f+Z8sojuBX9bPA8KsaTXEa1BjvmO+NeXKf/dS95PiMZJ6SGhh4mob5GMlFv3EqqcXXY/cgpm/OpxJkQBhETJ/l5UMy5GhguAH18b5Q= 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 3:04=E2=80=AFPM Yu Zhao wrote: > > 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 tha= t the > > > > > > folio's memcg association remains stable. With the charge migra= tion > > > > > > deprecated, there is no need for MGLRU to acquire locks to keep= the > > > > > > folio and memcg association stable. > > > > > > > > > > > > Signed-off-by: Shakeel Butt > > > > > > > > > > Andrew, can you please apply the following fix to this patch afte= r your > > > > > unused fixup? > > > > > > > > Thanks! > > > > > > syzbot caught the following: > > > > > > WARNING: CPU: 0 PID: 85 at mm/vmscan.c:3140 folio_update_gen+0x23d/= 0x250 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 Or this link would work better: https://lore.kernel.org/lkml/67294349.050a0220.701a.0010.GAE@google.com/