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From: Yosry Ahmed <yosryahmed@google.com>
Date: Thu, 4 Apr 2024 16:36:03 -0700
Message-ID: <CAJD7tkakCEg9zkwCrBr8GyObO7b9KOD6rUgyqniFN+YTCePd0A@mail.gmail.com>
Subject: Re: [syzbot] [cgroups?] [mm?] WARNING in __mod_memcg_lruvec_state
To: Andrew Morton <akpm@linux-foundation.org>
Cc: syzbot <syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com>, 
	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, shakeel.butt@linux.dev, 
	syzkaller-bugs@googlegroups.com, Yu Zhao <yuzhao@google.com>
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On Wed, Apr 3, 2024 at 6:08=E2=80=AFPM Andrew Morton <akpm@linux-foundation=
org> wrote:
>
> On Tue, 02 Apr 2024 01:03:26 -0700 syzbot <syzbot+9319a4268a640e26b72b@sy=
zkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    317c7bc0ef03 Merge tag 'mmc-v6.9-rc1' of git://git.kern=
el...
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=3D15fd40c5180=
000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=3Df64ec427e98=
bccd7
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3D9319a4268a640=
e26b72b
> > compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for=
 Debian) 2.40
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets=
/7bc7510fe41f/non_bootable_disk-317c7bc0.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/efab473d72c0/vmli=
nux-317c7bc0.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/5ba3f56d362d=
/bzImage-317c7bc0.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the co=
mmit:
> > Reported-by: syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com
> >
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 30105 at mm/memcontrol.c:865 __mod_memcg_lruvec_st=
ate+0x3fa/0x550 mm/memcontrol.c:865
> > Modules linked in:
> > CPU: 0 PID: 30105 Comm: syz-executor.2 Not tainted 6.9.0-rc1-syzkaller-=
00178-g317c7bc0ef03 #0
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-=
1.16.2-1 04/01/2014
> > RIP: 0010:__mod_memcg_lruvec_state+0x3fa/0x550 mm/memcontrol.c:865
> > Code: 45 85 e4 75 1d 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc=
 cc cc b8 00 04 00 00 e9 80 fd ff ff 89 c6 e9 a0 fd ff ff 90 <0f> 0b 90 e9 =
a7 fc ff ff 48 c7 c7 18 43 e1 8f e8 32 51 f8 ff e9 5e
> > RSP: 0018:ffffc900034beef8 EFLAGS: 00010202
> > RAX: 0000000000000292 RBX: 0000000000000001 RCX: 1ffffffff1fc2863
> > RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888024b92bc8
> > RBP: ffff888024b92000 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
> > R13: ffff88801c326000 R14: 0000000000000001 R15: ffff888024b92000
> > FS:  00007f0811bf96c0(0000) GS:ffff88806b000000(0000) knlGS:00000000000=
00000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 000000000cfff1dd CR3: 000000003e4e2000 CR4: 0000000000350ef0
> > DR0: 0000000000000031 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  <TASK>
> >  __update_lru_size include/linux/mm_inline.h:47 [inline]
> >  lru_gen_update_size include/linux/mm_inline.h:199 [inline]
> >  lru_gen_add_folio+0x62d/0xe80 include/linux/mm_inline.h:262
> >  lruvec_add_folio include/linux/mm_inline.h:323 [inline]
> >  lru_add_fn+0x3fc/0xd80 mm/swap.c:215
> >  folio_batch_move_lru+0x243/0x400 mm/swap.c:233
>
> Well it beats me.  I assume we failed to update for a new case.  I'll
> toss this into -next to perhaps shed a bit of light.
>
> --- a/mm/memcontrol.c~__mod_memcg_lruvec_state-enhance-diagnostics
> +++ a/mm/memcontrol.c
> @@ -860,10 +860,12 @@ void __mod_memcg_lruvec_state(struct lru
>                 case NR_ANON_THPS:
>                 case NR_SHMEM_PMDMAPPED:
>                 case NR_FILE_PMDMAPPED:
> -                       WARN_ON_ONCE(!in_task());
> +                       if (WARN_ON_ONCE(!in_task()))
> +                               pr_warn("stat item index: %d\n", idx);
>                         break;
>                 default:
> -                       VM_WARN_ON_IRQS_ENABLED();
> +                       if (VM_WARN_ON_IRQS_ENABLED())
> +                               pr_warn("stat item index: %d\n", idx);

Line 865 from this commit should be this warning (i.e. warning because
IRQs are enabled). This also makes sense because __update_lru_size()
should not be updating any of the above stats.

folio_batch_move_lru() in the above call stack should be acquiring the
lock with IRQs disabled though, so I am not sure what's going on from
a quick look.

Adding Yu Zhao here.