[syzbot ci] Re: mm/swap, memcg: Introduce swap tiers for cgroup based swap control

[syzbot ci <syzbot+ci687e6f97bd3a602d@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v5] mm/swap, memcg: Introduce swap tiers for cgroup based swap control
https://lore.kernel.org/all/20260325175453.2523280-1-youngjun.park@lge.com
* [PATCH v5 1/4] mm: swap: introduce swap tier infrastructure
* [PATCH v5 2/4] mm: swap: associate swap devices with tiers
* [PATCH v5 3/4] mm: memcontrol: add interfaces for swap tier selection
* [PATCH v5 4/4] mm: swap: filter swap allocation by memcg tier mask

and found the following issue:
WARNING in folio_tier_effective_mask

Full report is available here:
https://ci.syzbot.org/series/6ed50ca2-a106-41e9-aa4d-7c46869e0011

***

WARNING in folio_tier_effective_mask

tree:      mm-new
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git
base:      6381a729fa7dda43574d93ab9c61cec516dd885b
arch:      amd64
compiler:  Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config:    https://ci.syzbot.org/builds/e5c66fa8-a7fd-4809-9564-448847b5f230/config
C repro:   https://ci.syzbot.org/findings/d64cc6fa-636a-40a0-b131-d02ce1129494/c_repro
syz repro: https://ci.syzbot.org/findings/d64cc6fa-636a-40a0-b131-d02ce1129494/syz_repro

------------[ cut here ]------------
debug_locks && !(rcu_read_lock_held() || lock_is_held(&(&cgroup_mutex)->dep_map))
WARNING: ./include/linux/memcontrol.h:377 at obj_cgroup_memcg include/linux/memcontrol.h:377 [inline], CPU#1: syz.0.17/5955
WARNING: ./include/linux/memcontrol.h:377 at folio_memcg include/linux/memcontrol.h:431 [inline], CPU#1: syz.0.17/5955
WARNING: ./include/linux/memcontrol.h:377 at folio_tier_effective_mask+0x175/0x210 mm/swap_tier.h:63, CPU#1: syz.0.17/5955
Modules linked in:
CPU: 1 UID: 0 PID: 5955 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:obj_cgroup_memcg include/linux/memcontrol.h:377 [inline]
RIP: 0010:folio_memcg include/linux/memcontrol.h:431 [inline]
RIP: 0010:folio_tier_effective_mask+0x175/0x210 mm/swap_tier.h:63
Code: 0f b6 04 20 84 c0 75 6b 8b 03 eb 0a e8 04 b8 9e ff b8 ff ff ff ff 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc cc e8 ec b7 9e ff 90 <0f> 0b 90 eb 9b 44 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c c2 fe ff ff
RSP: 0018:ffffc90004bee6d0 EFLAGS: 00010293
RAX: ffffffff8226dd04 RBX: ffff888113589280 RCX: ffff8881727b8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffea0006c62207 R09: 1ffffd4000d8c440
R10: dffffc0000000000 R11: fffff94000d8c441 R12: dffffc0000000000
R13: ffffea0006c62208 R14: ffffea0006c62200 R15: ffffea0006c62230
FS:  00005555771cb500(0000) GS:ffff8882a9462000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ed63fff CR3: 0000000112d86000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 swap_alloc_fast mm/swapfile.c:1355 [inline]
 folio_alloc_swap+0x392/0x13a0 mm/swapfile.c:1735
 shrink_folio_list+0x26a7/0x5250 mm/vmscan.c:1281
 reclaim_folio_list+0x100/0x460 mm/vmscan.c:2171
 reclaim_pages+0x45b/0x530 mm/vmscan.c:2208
 madvise_cold_or_pageout_pte_range+0x1ef5/0x2220 mm/madvise.c:563
 walk_pmd_range mm/pagewalk.c:142 [inline]
 walk_pud_range mm/pagewalk.c:233 [inline]
 walk_p4d_range mm/pagewalk.c:275 [inline]
 walk_pgd_range+0xfdc/0x1d90 mm/pagewalk.c:316
 __walk_page_range+0x14c/0x710 mm/pagewalk.c:424
 walk_page_range_vma_unsafe+0x309/0x410 mm/pagewalk.c:728
 madvise_pageout_page_range mm/madvise.c:622 [inline]
 madvise_pageout mm/madvise.c:647 [inline]
 madvise_vma_behavior+0x28b9/0x42c0 mm/madvise.c:1358
 madvise_walk_vmas+0x573/0xae0 mm/madvise.c:1713
 madvise_do_behavior+0x386/0x540 mm/madvise.c:1929
 do_madvise+0x1fa/0x2e0 mm/madvise.c:2022
 __do_sys_madvise mm/madvise.c:2031 [inline]
 __se_sys_madvise mm/madvise.c:2029 [inline]
 __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2029
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5e5af9c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff0c8e2708 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f5e5b215fa0 RCX: 00007f5e5af9c799
RDX: 0000000000000015 RSI: 0000000000600000 RDI: 0000200000000000
RBP: 00007f5e5b032c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5e5b215fac R14: 00007f5e5b215fa0 R15: 00007f5e5b215fa0
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@syzkaller.appspotmail.com

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