Received-SPF: pass (google.com: domain of linux-kernel+bounces-170130-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Precedence: bulk
MIME-Version: 1.0
References: <0000000000007545d00615188a03@google.com> <0000000000001b9d500617c8b23c@google.com>
 <ZjjlLcjHuQoV-7gh@google.com> <gbsy4rpt3fbcspuepstk6tzzwd3mrosuba7ufm7phopwor4pyb@ucxrvdw6nly3>
In-Reply-To: <gbsy4rpt3fbcspuepstk6tzzwd3mrosuba7ufm7phopwor4pyb@ucxrvdw6nly3>
From: Yosry Ahmed <yosryahmed@google.com>
Date: Mon, 6 May 2024 09:12:53 -0700
Message-ID: <CAJD7tkYVa5WQ=rSWYbm6EwAVJFjQE4iGsue8aOA80j6OHO6iQQ@mail.gmail.com>
Subject: Re: [syzbot] [mm?] [cgroups?] WARNING in __mod_memcg_lruvec_state
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: syzbot <syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com>, 
	akpm@linux-foundation.org, cgroups@vger.kernel.org, hannes@cmpxchg.org, 
	linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, 
	muchun.song@linux.dev, roman.gushchin@linux.dev, 
	syzkaller-bugs@googlegroups.com, yuzhao@google.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Mon, May 6, 2024 at 8:59=E2=80=AFAM Shakeel Butt <shakeel.butt@linux.dev=
> wrote:
>
> On Mon, May 06, 2024 at 02:11:57PM +0000, Yosry Ahmed wrote:
> > On Mon, May 06, 2024 at 06:03:29AM -0700, syzbot wrote:
> > > syzbot has found a reproducer for the following issue on:
> > >
> > > HEAD commit:    2b84edefcad1 Add linux-next specific files for 202405=
06
> > > git tree:       linux-next
> > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=3D1164931f1=
80000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=3Db499929e4=
aaba1af
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=3D9319a4268a6=
40e26b72b
> > > compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for=
 Debian) 2.40
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=3D123d5d1=
f180000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D165274509=
80000
> > >
> > > Downloadable assets:
> > > disk image: https://storage.googleapis.com/syzbot-assets/6a22cf95ee14=
/disk-2b84edef.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/f5c45b515282/vm=
linux-2b84edef.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/9bf98258a6=
62/bzImage-2b84edef.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the =
commit:
> > > Reported-by: syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com
> > >
> > > ------------[ cut here ]------------
> > > __mod_memcg_lruvec_state: missing stat item 25
> > > WARNING: CPU: 0 PID: 5091 at mm/memcontrol.c:999 __mod_memcg_lruvec_s=
tate+0x18c/0x430 mm/memcontrol.c:999
> >
> > This doesn't seem to be the same issue as the original one syzbot
> > reported. It's the same function but a different warning. I am not sure
> > how to tell syzbot that.
> >
> > Anyway, this warning is the one newly introduced by Shakeel. It is
> > firing because NR_SHMEM_PMDMAPPED and/or NR_FILE_PMDMAPPED are being
> > updated using __lruvec_stat_mod_folio(), which also updates the memcg
> > stats. However, these stats are not exported per-memcg.
> >
> > I think the following should fix it.
> >
>
> Hey Yosry, can you please post your patch with the signoff? The patch
> looks good and you can put my ack on it.

Will do. I noticed we also update these stats from
__folio_remove_rmap(). I will send a patch fixing these as well, so
I'll not include your Ack for that as it will be different.