Re: [syzbot] [bcachefs?] WARNING in bch2_trans_srcu_unlock

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    f03359bca01b Merge tag 'for-6.9-rc6-tag' of git://git.kern..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11e60b38980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d2f00edef461175
dashboard link: https://syzkaller.appspot.com/bug?extid=1e515cab343dbe5aa38a
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11d42c70980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15ce8250980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e3ee5200440e/disk-f03359bc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c651e70b4ae3/vmlinux-f03359bc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/196f43b316ad/bzImage-f03359bc.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/4b5f0e6cc6de/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1e515cab343dbe5aa38a@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
btree trans held srcu lock (delaying memory reclaim) for 29 seconds
WARNING: CPU: 0 PID: 5076 at fs/bcachefs/btree_iter.c:2873 check_srcu_held_too_long fs/bcachefs/btree_iter.c:2871 [inline]
WARNING: CPU: 0 PID: 5076 at fs/bcachefs/btree_iter.c:2873 bch2_trans_srcu_unlock+0x4f1/0x600 fs/bcachefs/btree_iter.c:2887
Modules linked in:
CPU: 0 PID: 5076 Comm: syz-executor304 Not tainted 6.9.0-rc6-syzkaller-00131-gf03359bca01b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:check_srcu_held_too_long fs/bcachefs/btree_iter.c:2871 [inline]
RIP: 0010:bch2_trans_srcu_unlock+0x4f1/0x600 fs/bcachefs/btree_iter.c:2887
Code: 2b 1f 48 c1 eb 02 48 b9 c3 f5 28 5c 8f c2 f5 28 48 89 d8 48 f7 e1 48 c1 ea 02 48 c7 c7 40 26 11 8c 48 89 d6 e8 e0 a5 49 fd 90 <0f> 0b 90 90 e9 c0 fe ff ff 44 89 f9 80 e1 07 38 c1 0f 8c 38 fb ff
RSP: 0018:ffffc90003edf1b0 EFLAGS: 00010246
RAX: bf0e0aad7b822500 RBX: 00000000000002da RCX: ffff888029225a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000ffffac70 R08: ffffffff81588e32 R09: 1ffff1101728519a
R10: dffffc0000000000 R11: ffffed101728519b R12: dffffc0000000000
R13: 1ffff11003c1100d R14: 1ffff11003c11008 R15: ffff88801e088068
FS:  000055556aeb6380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000559d71bf4968 CR3: 000000001b6f2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 bch2_trans_begin+0x1482/0x1920 fs/bcachefs/btree_iter.c:2963
 __bchfs_fallocate fs/bcachefs/fs-io.c:608 [inline]
 bchfs_fallocate fs/bcachefs/fs-io.c:733 [inline]
 bch2_fallocate_dispatch+0x1181/0x3810 fs/bcachefs/fs-io.c:780
 vfs_fallocate+0x564/0x6c0 fs/open.c:330
 do_vfs_ioctl+0x2592/0x2e50 fs/ioctl.c:883
 __do_sys_ioctl fs/ioctl.c:902 [inline]
 __se_sys_ioctl+0x81/0x170 fs/ioctl.c:890
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f180396cb19
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe82aad958 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0073746e6576652e RCX: 00007f180396cb19
RDX: 0000000020000000 RSI: 0000000040305828 RDI: 0000000000000005
RBP: 652e79726f6d656d R08: 000055556aeb74c0 R09: 000055556aeb74c0
R10: 000055556aeb74c0 R11: 0000000000000246 R12: 00007ffe82aad980
R13: 00007ffe82aadba8 R14: 431bde82d7b634db R15: 00007f18039b503b
 </TASK>


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