linux-kernel - [syzbot ci] Re: Separate compound page from folio

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Message-ID: <697c68b3.a70a0220.9914.0032.GAE@google.com>
Date: Fri, 30 Jan 2026 00:15:47 -0800
From: syzbot ci <syzbot+ci7f632827e1b1c91b@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, apopple@...dia.com, axboe@...nel.dk, 
	balbirs@...dia.com, baohua@...nel.org, baolin.wang@...ux.alibaba.com, 
	david@...nel.org, dev.jain@....com, hannes@...xchg.org, 
	io-uring@...r.kernel.org, jackmanb@...gle.com, jgg@...dia.com, 
	lance.yang@...ux.dev, liam.howlett@...cle.com, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, lorenzo.stoakes@...cle.com, mhocko@...e.com, 
	muchun.song@...ux.dev, npache@...hat.com, osalvador@...e.de, rppt@...nel.org, 
	ryan.roberts@....com, surenb@...gle.com, vbabka@...e.cz, willy@...radead.org, 
	ziy@...dia.com
Cc: syzbot@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: [syzbot ci] Re: Separate compound page from folio

syzbot ci has tested the following series

[v1] Separate compound page from folio
https://lore.kernel.org/all/20260130034818.472804-1-ziy@nvidia.com
* [RFC PATCH 1/5] io_uring: allocate folio in io_mem_alloc_compound() and function rename
* [RFC PATCH 2/5] mm/huge_memory: use page_rmappable_folio() to convert after-split folios
* [RFC PATCH 3/5] mm/hugetlb: set large_rmappable on hugetlb and avoid deferred_list handling
* [RFC PATCH 4/5] mm: only use struct page in compound_nr() and compound_order()
* [RFC PATCH 5/5] mm: code separation for compound page and folio

and found the following issue:
WARNING in __folio_large_mapcount_sanity_checks

Full report is available here:
https://ci.syzbot.org/series/f64f0297-d388-4cfa-b3be-f05819d0ce34

***

WARNING in __folio_large_mapcount_sanity_checks

tree:      mm-new
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git
base:      0241748f8b68fc2bf637f4901b9d7ca660d177ca
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/76dc5ea6-0ff5-410b-8b1f-72e5607a704e/config
C repro:   https://ci.syzbot.org/findings/a308f1d6-69e2-4ebc-80a9-b51d9dc02851/c_repro
syz repro: https://ci.syzbot.org/findings/a308f1d6-69e2-4ebc-80a9-b51d9dc02851/syz_repro

------------[ cut here ]------------
diff > folio_large_nr_pages(folio)
WARNING: ./include/linux/rmap.h:148 at __folio_large_mapcount_sanity_checks+0x499/0x6b0 include/linux/rmap.h:148, CPU#1: syz.0.17/5988
Modules linked in:
CPU: 1 UID: 0 PID: 5988 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:__folio_large_mapcount_sanity_checks+0x499/0x6b0 include/linux/rmap.h:148
Code: 5f 5d e9 4a 4e 64 09 cc e8 84 d8 aa ff 90 0f 0b 90 e9 82 fc ff ff e8 76 d8 aa ff 90 0f 0b 90 e9 8f fc ff ff e8 68 d8 aa ff 90 <0f> 0b 90 e9 b8 fc ff ff e8 5a d8 aa ff 90 0f 0b 90 e9 f2 fc ff ff
RSP: 0018:ffffc900040e72f8 EFLAGS: 00010293
RAX: ffffffff8217c0f8 RBX: ffffea0006ef5c00 RCX: ffff888105fdba80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffea0006ef5c07 R09: 1ffffd4000ddeb80
R10: dffffc0000000000 R11: fffff94000ddeb81 R12: 0000000000000001
R13: 0000000000000000 R14: 1ffffd4000ddeb8f R15: ffffea0006ef5c78
FS:  00005555867b3500(0000) GS:ffff8882a9923000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000000c0 CR3: 0000000103ab0000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 folio_add_return_large_mapcount include/linux/rmap.h:184 [inline]
 __folio_add_rmap mm/rmap.c:1377 [inline]
 __folio_add_file_rmap mm/rmap.c:1696 [inline]
 folio_add_file_rmap_ptes+0x4c2/0xe60 mm/rmap.c:1722
 insert_page_into_pte_locked+0x5ab/0x910 mm/memory.c:2378
 insert_page+0x186/0x2d0 mm/memory.c:2398
 packet_mmap+0x360/0x530 net/packet/af_packet.c:4622
 vfs_mmap include/linux/fs.h:2053 [inline]
 mmap_file mm/internal.h:167 [inline]
 __mmap_new_file_vma mm/vma.c:2468 [inline]
 __mmap_new_vma mm/vma.c:2532 [inline]
 __mmap_region mm/vma.c:2759 [inline]
 mmap_region+0x18fe/0x2240 mm/vma.c:2837
 do_mmap+0xc39/0x10c0 mm/mmap.c:559
 vm_mmap_pgoff+0x2c9/0x4f0 mm/util.c:581
 ksys_mmap_pgoff+0x51e/0x760 mm/mmap.c:605
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5d7399acb9
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:00007ffe9f3eea78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f5d73c15fa0 RCX: 00007f5d7399acb9
RDX: 0000000000000002 RSI: 0000000000030000 RDI: 0000200000000000
RBP: 00007f5d73a08bf7 R08: 0000000000000003 R09: 0000000000000000
R10: 0000000000000011 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5d73c15fac R14: 00007f5d73c15fa0 R15: 00007f5d73c15fa0
 </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@...kaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@...glegroups.com.