[moderation] [bcachefs?] BUG: unable to handle kernel paging request in __btree_node_reclaim

Hello,

syzbot found the following issue on:

HEAD commit: 38fec10eb60d Linux 6.14
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15804de4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d0b5b6b74098b0ef
dashboard link: https://syzkaller.appspot.com/bug?extid=e406b82a42ab1a9482e9
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [[email protected] [email protected] [email protected]]

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-38fec10e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d34e40d2aad1/vmlinux-38fec10e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e290e3747399/bzImage-38fec10e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

BUG: unable to handle page fault for address: ffffe8fffd451040
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 1b03f067 P4D 1b03f067 PUD 1ed11067 PMD 49f70067 PTE 0
Oops: Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 75 Comm: kswapd0 Not tainted 6.14.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__btree_node_reclaim+0x647/0xa00 fs/bcachefs/btree_cache.c:444
Code: 00 49 8d 9f 48 b6 04 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 1c 0d e1 fd 48 8b 03 <65> 48 ff 40 40 0f 1f 44 00 00 e8 7a cd 79 fd 65 8b 1d 2f c4 bb 7b
RSP: 0018:ffffc9000106f270 EFLAGS: 00010246
RAX: 0000607fdd851000 RBX: ffff88804904b648 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 1db8f60c84bb244c RDI: 0000000000000000
RBP: 1db8f60c84bb244c R08: ffffffff84481215 R09: 1ffff11009433016
R10: dffffc0000000000 R11: ffffed1009433017 R12: ffff88804a198000
R13: ffffffff84480d4c R14: 1ffff11009433016 R15: ffff888049000000
FS: 0000000000000000(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe8fffd451040 CR3: 0000000040926000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
btree_node_reclaim fs/bcachefs/btree_cache.c:456 [inline]
bch2_btree_cache_scan+0x63e/0xec0 fs/bcachefs/btree_cache.c:525
do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
shrink_one+0x43b/0x850 mm/vmscan.c:4868
shrink_many mm/vmscan.c:4929 [inline]
lru_gen_shrink_node mm/vmscan.c:5007 [inline]
shrink_node+0x379b/0x3e20 mm/vmscan.c:5978
kswapd_shrink_node mm/vmscan.c:6807 [inline]
balance_pgdat mm/vmscan.c:6999 [inline]
kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
kthread+0x7a9/0x920 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Modules linked in:
CR2: ffffe8fffd451040
---[ end trace 0000000000000000 ]---
RIP: 0010:__btree_node_reclaim+0x647/0xa00 fs/bcachefs/btree_cache.c:444
Code: 00 49 8d 9f 48 b6 04 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 1c 0d e1 fd 48 8b 03 <65> 48 ff 40 40 0f 1f 44 00 00 e8 7a cd 79 fd 65 8b 1d 2f c4 bb 7b
RSP: 0018:ffffc9000106f270 EFLAGS: 00010246
RAX: 0000607fdd851000 RBX: ffff88804904b648 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 1db8f60c84bb244c RDI: 0000000000000000
RBP: 1db8f60c84bb244c R08: ffffffff84481215 R09: 1ffff11009433016
R10: dffffc0000000000 R11: ffffed1009433017 R12: ffff88804a198000
R13: ffffffff84480d4c R14: 1ffff11009433016 R15: ffff888049000000
FS: 0000000000000000(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe8fffd451040 CR3: 0000000040926000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 49 8d 9f 48 b6 04 00 lea 0x4b648(%r15),%rbx
7: 48 89 d8 mov %rbx,%rax
a: 48 c1 e8 03 shr $0x3,%rax
e: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
15: fc ff df
18: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1)
1c: 74 08 je 0x26
1e: 48 89 df mov %rbx,%rdi
21: e8 1c 0d e1 fd call 0xfde10d42
26: 48 8b 03 mov (%rbx),%rax
* 29: 65 48 ff 40 40 incq %gs:0x40(%rax) <-- trapping instruction
2e: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
33: e8 7a cd 79 fd call 0xfd79cdb2
38: 65 8b 1d 2f c4 bb 7b mov %gs:0x7bbbc42f(%rip),%ebx # 0x7bbbc46e


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