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From: Shakeel Butt To: Andrew Morton Cc: Yu Zhao , 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 Subject: Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU Message-ID: <6uoqxdnchcsmjze4uosvdjh6ztxbvo63bs3tctjkzy47ryllwp@6wvnxdeghlru> References: <20241025012304.2473312-1-shakeel.butt@linux.dev> <20241025012304.2473312-6-shakeel.butt@linux.dev> <20241104133834.e0e138038a111c2b0d20bdde@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241104133834.e0e138038a111c2b0d20bdde@linux-foundation.org> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: D9ABC40005 X-Rspamd-Server: rspam11 X-Stat-Signature: xgqgw9wrdkjx6c9xyhxwksr6y1gccimu X-HE-Tag: 1730757833-312318 X-HE-Meta: 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 a2y/gT7O lZ40+tY6SFOXH9CIvM0tPRlflIFuB/X8iKqPuDxhFTYhLe/kcsp+Osg1aKdTPQaA86LgIeKHFvwbsAwjl4pDjlO14GRL2pPpcT0ccc3tOW4bILiPCV6svSnsjmUoLDK4WpipHPiPw8bOec9tqsvXb/bC+ZQhEfrM/GCOhre6zCWz0wlSWdtOuvUpekIPWShd6hdxb 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 04, 2024 at 01:38:34PM -0800, 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 AM 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 migration > > > > > 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 after 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 = READ_ONCE(folio->flags); > > > > VM_WARN_ON_ONCE(gen >= 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? > And a link to the sysbot report? So, this assertion is incorrect after this patch series that has removed the charge migration and has removed mem_cgroup_trylock_pages() / mem_cgroup_unlock_pages() from the caller of this function (folio_update_gen()).