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WARNING in set_mm_walk

syzbot syzbot 5 participants 8 messages Aug 11 – Aug 12

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author syzbot
#0 lore raw

Hello,

syzbot found the following issue on:

HEAD commit:    562bfb501c54 Merge tag 'integrity-v7.2-rc7' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a8cbb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-562bfb50.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9cbf6ef0490e/vmlinux-562bfb50.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7ee52864c79a/bzImage-562bfb50.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#1: kswapd0/110
Modules linked in:
CPU: 1 UID: 0 PID: 110 Comm: kswapd0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:set_mm_walk+0x210/0x270 mm/vmscan.c:3800
Code: 13 00 00 4d 8d 7d 08 e9 f7 fe ff ff e8 79 f5 2a 00 e9 b7 fe ff ff e8 7f 6b ba ff 90 0f 0b 90 e9 d2 fe ff ff e8 71 6b ba ff 90 <0f> 0b 90 e9 74 ff ff ff 4c 89 ff e8 80 f5 2a 00 e9 4e fe ff ff 48
RSP: 0018:ffffc900027772b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888024934a80 RCX: ffffffff824ff8e8
RDX: ffff888024934a80 RSI: ffffffff824ff96f RDI: ffff888024934a80
RBP: 0000000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000020000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc90002777c38 R14: 0000000000000001 R15: ffffc90002777c40
FS:  0000000000000000(0000) GS:ffff8880d5ed8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31923ffc CR3: 0000000109695000 CR4: 0000000000352ef0
DR0: 0000000000000005 DR1: 0000000000000005 DR2: 0000000020040004
DR3: 0000000000000056 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 try_to_inc_max_seq+0xf0/0x1090 mm/vmscan.c:4023
 try_to_shrink_lruvec+0x4bd/0x6b0 mm/vmscan.c:4977
 lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
 shrink_lruvec+0x31e/0x25b0 mm/vmscan.c:5888
 mem_cgroup_shrink_node+0x227/0x6a0 mm/vmscan.c:6753
 mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
 memcg1_soft_limit_reclaim+0x2d5/0x830 mm/memcontrol-v1.c:362
 balance_pgdat+0xa11/0x1f00 mm/vmscan.c:7177
 kswapd+0x556/0xb50 mm/vmscan.c:7462
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

---
This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

maintainer
#1 lore raw
Quoted 10 lines · On Mon, 10 Aug 2026 17:13:29 -0700 syzbot…

Hello,

syzbot found the following issue on:

HEAD commit:    562bfb501c54 Merge tag 'integrity-v7.2-rc7' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a8cbb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Thanks. One for the MGLRU develoeprs, it seems.

https://share.gemini.google/Wg4a5ns7E0LF might save a bit of time figuring this out.

Quoted 68 lines

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-562bfb50.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9cbf6ef0490e/vmlinux-562bfb50.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7ee52864c79a/bzImage-562bfb50.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#1: kswapd0/110

Modules linked in:
CPU: 1 UID: 0 PID: 110 Comm: kswapd0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:set_mm_walk+0x210/0x270 mm/vmscan.c:3800
Code: 13 00 00 4d 8d 7d 08 e9 f7 fe ff ff e8 79 f5 2a 00 e9 b7 fe ff ff e8 7f 6b ba ff 90 0f 0b 90 e9 d2 fe ff ff e8 71 6b ba ff 90 <0f> 0b 90 e9 74 ff ff ff 4c 89 ff e8 80 f5 2a 00 e9 4e fe ff ff 48
RSP: 0018:ffffc900027772b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888024934a80 RCX: ffffffff824ff8e8
RDX: ffff888024934a80 RSI: ffffffff824ff96f RDI: ffff888024934a80
RBP: 0000000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000020000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc90002777c38 R14: 0000000000000001 R15: ffffc90002777c40
FS:  0000000000000000(0000) GS:ffff8880d5ed8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31923ffc CR3: 0000000109695000 CR4: 0000000000352ef0
DR0: 0000000000000005 DR1: 0000000000000005 DR2: 0000000020040004
DR3: 0000000000000056 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 try_to_inc_max_seq+0xf0/0x1090 mm/vmscan.c:4023
 try_to_shrink_lruvec+0x4bd/0x6b0 mm/vmscan.c:4977
 lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
 shrink_lruvec+0x31e/0x25b0 mm/vmscan.c:5888
 mem_cgroup_shrink_node+0x227/0x6a0 mm/vmscan.c:6753
 mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
 memcg1_soft_limit_reclaim+0x2d5/0x830 mm/memcontrol-v1.c:362
 balance_pgdat+0xa11/0x1f00 mm/vmscan.c:7177
 kswapd+0x556/0xb50 mm/vmscan.c:7462
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

---
This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

#2 lore raw
Quoted 13 lines · Andrew Morton
Quoted 10 lines · On Mon, 10 Aug 2026 17:13:29 -0700 syzbot…

Hello,

syzbot found the following issue on:

HEAD commit:    562bfb501c54 Merge tag 'integrity-v7.2-rc7' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a8cbb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
Quoted 4 lines

Thanks. One for the MGLRU develoeprs, it seems.

https://share.gemini.google/Wg4a5ns7E0LF might save a bit of time figuring this out.

This is memcg-v1's soft limit which is deprecated. I am more inclined to simply remove this code instead of fixing it.

I will take a stab at removal.

Quoted 68 lines
Quoted 68 lines

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-562bfb50.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9cbf6ef0490e/vmlinux-562bfb50.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7ee52864c79a/bzImage-562bfb50.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#1: kswapd0/110

Modules linked in:
CPU: 1 UID: 0 PID: 110 Comm: kswapd0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:set_mm_walk+0x210/0x270 mm/vmscan.c:3800
Code: 13 00 00 4d 8d 7d 08 e9 f7 fe ff ff e8 79 f5 2a 00 e9 b7 fe ff ff e8 7f 6b ba ff 90 0f 0b 90 e9 d2 fe ff ff e8 71 6b ba ff 90 <0f> 0b 90 e9 74 ff ff ff 4c 89 ff e8 80 f5 2a 00 e9 4e fe ff ff 48
RSP: 0018:ffffc900027772b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888024934a80 RCX: ffffffff824ff8e8
RDX: ffff888024934a80 RSI: ffffffff824ff96f RDI: ffff888024934a80
RBP: 0000000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000020000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc90002777c38 R14: 0000000000000001 R15: ffffc90002777c40
FS:  0000000000000000(0000) GS:ffff8880d5ed8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31923ffc CR3: 0000000109695000 CR4: 0000000000352ef0
DR0: 0000000000000005 DR1: 0000000000000005 DR2: 0000000020040004
DR3: 0000000000000056 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 try_to_inc_max_seq+0xf0/0x1090 mm/vmscan.c:4023
 try_to_shrink_lruvec+0x4bd/0x6b0 mm/vmscan.c:4977
 lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
 shrink_lruvec+0x31e/0x25b0 mm/vmscan.c:5888
 mem_cgroup_shrink_node+0x227/0x6a0 mm/vmscan.c:6753
 mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
 memcg1_soft_limit_reclaim+0x2d5/0x830 mm/memcontrol-v1.c:362
 balance_pgdat+0xa11/0x1f00 mm/vmscan.c:7177
 kswapd+0x556/0xb50 mm/vmscan.c:7462
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

---
This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

#3 lore raw
Quoted 2 lines · Shakeel Butt

This is memcg-v1's soft limit which is deprecated. I am more inclined to simply remove this code instead of fixing it.

Love it :)

The best code is no code (sadly we have to have _some_ code :)

#4 lore raw
In reply to Shakeel Butt
Quoted 16 lines · Shakeel Butt
Quoted 15 lines · Andrew Morton
Quoted 10 lines · On Mon, 10 Aug 2026 17:13:29 -0700 syzbot…

Hello,

syzbot found the following issue on:

HEAD commit:    562bfb501c54 Merge tag 'integrity-v7.2-rc7' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a8cbb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Thanks. One for the MGLRU develoeprs, it seems.

Quoted 7 lines
Quoted 2 lines

https://share.gemini.google/Wg4a5ns7E0LF might save a bit of time figuring this out.

This is memcg-v1's soft limit which is deprecated. I am more inclined to simply remove this code instead of fixing it.

I will take a stab at removal.

MGLRU doesn't actually support memcg-v1's soft limit:

unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
gfp_t gfp_mask, unsigned long *total_scanned)

{
	......

        if (lru_gen_enabled())
                return 0;

	......
}

The call trace below likely showed up because the test repeatedly toggled MGLRU on and off, which isn't a normal operation and should be avoided in practice.

I also agree that removing the deprecated memcg-v1 soft limit is the better way forward.

Quoted 68 lines
Quoted 68 lines
Quoted 68 lines

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-562bfb50.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9cbf6ef0490e/vmlinux-562bfb50.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7ee52864c79a/bzImage-562bfb50.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#1: kswapd0/110

Modules linked in:
CPU: 1 UID: 0 PID: 110 Comm: kswapd0 Tainted: G             L      syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:set_mm_walk+0x210/0x270 mm/vmscan.c:3800
Code: 13 00 00 4d 8d 7d 08 e9 f7 fe ff ff e8 79 f5 2a 00 e9 b7 fe ff ff e8 7f 6b ba ff 90 0f 0b 90 e9 d2 fe ff ff e8 71 6b ba ff 90 <0f> 0b 90 e9 74 ff ff ff 4c 89 ff e8 80 f5 2a 00 e9 4e fe ff ff 48
RSP: 0018:ffffc900027772b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888024934a80 RCX: ffffffff824ff8e8
RDX: ffff888024934a80 RSI: ffffffff824ff96f RDI: ffff888024934a80
RBP: 0000000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000020000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc90002777c38 R14: 0000000000000001 R15: ffffc90002777c40
FS:  0000000000000000(0000) GS:ffff8880d5ed8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31923ffc CR3: 0000000109695000 CR4: 0000000000352ef0
DR0: 0000000000000005 DR1: 0000000000000005 DR2: 0000000020040004
DR3: 0000000000000056 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
  <TASK>
  try_to_inc_max_seq+0xf0/0x1090 mm/vmscan.c:4023
  try_to_shrink_lruvec+0x4bd/0x6b0 mm/vmscan.c:4977
  lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
  shrink_lruvec+0x31e/0x25b0 mm/vmscan.c:5888
  mem_cgroup_shrink_node+0x227/0x6a0 mm/vmscan.c:6753
  mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
  memcg1_soft_limit_reclaim+0x2d5/0x830 mm/memcontrol-v1.c:362
  balance_pgdat+0xa11/0x1f00 mm/vmscan.c:7177
  kswapd+0x556/0xb50 mm/vmscan.c:7462
  kthread+0x370/0x450 kernel/kthread.c:436
  ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
  </TASK>

---
This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

author syzbot
#5 lore raw
In reply to syzbot
syzbot has found a reproducer for the following issue on:

syzbot has found a reproducer for the following issue on:

HEAD commit:    f5bbbfec59b4 Merge tag 'probes-fixes-v7.2-rc7' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f44c79580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10d11149580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#2: kswapd0/111
Modules linked in:
CPU: 2 UID: 0 PID: 111 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:set_mm_walk+0x210/0x270 mm/vmscan.c:3800
Code: 13 00 00 4d 8d 7d 08 e9 f7 fe ff ff e8 19 f7 2a 00 e9 b7 fe ff ff e8 7f 68 ba ff 90 0f 0b 90 e9 d2 fe ff ff e8 71 68 ba ff 90 <0f> 0b 90 e9 74 ff ff ff 4c 89 ff e8 20 f7 2a 00 e9 4e fe ff ff 48
RSP: 0018:ffffc9000272f2b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888023f04a80 RCX: ffffffff82500a88
RDX: ffff888023f04a80 RSI: ffffffff82500b0f RDI: ffff888023f04a80
RBP: 0000000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000020000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc9000272fc38 R14: 0000000000000001 R15: ffffc9000272fc40
FS:  0000000000000000(0000) GS:ffff8880d5fec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005643a2ed4168 CR3: 000000003c7ec000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 try_to_inc_max_seq+0xf0/0x1090 mm/vmscan.c:4023
 try_to_shrink_lruvec+0x4bd/0x6b0 mm/vmscan.c:4977
 lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
 shrink_lruvec+0x31e/0x25b0 mm/vmscan.c:5888
 mem_cgroup_shrink_node+0x227/0x6a0 mm/vmscan.c:6753
 mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
 memcg1_soft_limit_reclaim+0x2d5/0x830 mm/memcontrol-v1.c:362
 balance_pgdat+0xa11/0x1f00 mm/vmscan.c:7177
 kswapd+0x556/0xb50 mm/vmscan.c:7462
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

maintainer
#6 lore raw
Quoted 10 lines · On Wed, 12 Aug 2026 05:26:24 -0700 syzbot…

syzbot has found a reproducer for the following issue on:

HEAD commit:    f5bbbfec59b4 Merge tag 'probes-fixes-v7.2-rc7' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f44c79580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10d11149580000
Quoted 6 lines

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#2: kswapd0/111

Thanks. Shakeel is working on a series which will fix this by removing the calling code. But it isn't a minor patch.

Shakeel, it would be good to have a backportable quick-fix to make this warning go away?

Quoted 29 lines
Modules linked in:
CPU: 2 UID: 0 PID: 111 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:set_mm_walk+0x210/0x270 mm/vmscan.c:3800
Code: 13 00 00 4d 8d 7d 08 e9 f7 fe ff ff e8 19 f7 2a 00 e9 b7 fe ff ff e8 7f 68 ba ff 90 0f 0b 90 e9 d2 fe ff ff e8 71 68 ba ff 90 <0f> 0b 90 e9 74 ff ff ff 4c 89 ff e8 20 f7 2a 00 e9 4e fe ff ff 48
RSP: 0018:ffffc9000272f2b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888023f04a80 RCX: ffffffff82500a88
RDX: ffff888023f04a80 RSI: ffffffff82500b0f RDI: ffff888023f04a80
RBP: 0000000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000020000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc9000272fc38 R14: 0000000000000001 R15: ffffc9000272fc40
FS:  0000000000000000(0000) GS:ffff8880d5fec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005643a2ed4168 CR3: 000000003c7ec000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 try_to_inc_max_seq+0xf0/0x1090 mm/vmscan.c:4023
 try_to_shrink_lruvec+0x4bd/0x6b0 mm/vmscan.c:4977
 lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
 shrink_lruvec+0x31e/0x25b0 mm/vmscan.c:5888
 mem_cgroup_shrink_node+0x227/0x6a0 mm/vmscan.c:6753
 mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
 memcg1_soft_limit_reclaim+0x2d5/0x830 mm/memcontrol-v1.c:362
 balance_pgdat+0xa11/0x1f00 mm/vmscan.c:7177
 kswapd+0x556/0xb50 mm/vmscan.c:7462
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
#7 lore raw
Quoted 19 lines · Andrew Morton
Quoted 10 lines · On Wed, 12 Aug 2026 05:26:24 -0700 syzbot…

syzbot has found a reproducer for the following issue on:

HEAD commit:    f5bbbfec59b4 Merge tag 'probes-fixes-v7.2-rc7' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f44c79580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=12ee2725d5fde63a9c96
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10d11149580000
Quoted 6 lines

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
------------[ cut here ]------------
current_is_kswapd()
WARNING: mm/vmscan.c:3800 at set_mm_walk+0x210/0x270 mm/vmscan.c:3800, CPU#2: kswapd0/111
Quoted 6 lines

Thanks. Shakeel is working on a series which will fix this by removing the calling code. But it isn't a minor patch.

Shakeel, it would be good to have a backportable quick-fix to make this warning go away?

Actually the first patch [1] of the series will fix this warning and we can backport just that patch to the older stable kernels.

Do you want me to send that patch as a standalone?

[1] https://lore.kernel.org/all/[email protected]/