[syzbot] [bcachefs?] WARNING in bch2_fs_journal_stop

[syzbot] [bcachefs?] WARNING in bch2_fs_journal_stop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    975f3b6da180 Merge tag 'for-6.10-rc7-tag' of git://git.ker..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11b17221980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=42a432cfd0e579e0
dashboard link: https://syzkaller.appspot.com/bug?extid=4093905737cf289b6b38
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=17460766980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=130028f6980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/62ced967be02/disk-975f3b6d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c237fa04e1d4/vmlinux-975f3b6d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/47f6105ecbe2/bzImage-975f3b6d.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/02b246be7736/mount_0.gz

The issue was bisected to:

commit f7643bc9749f270d487c32dc35b578575bf1adb0
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date:   Wed Apr 17 05:26:02 2024 +0000

    bcachefs: make btree read errors silent during scan

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10381495980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12381495980000
console output: https://syzkaller.appspot.com/x/log.txt?x=14381495980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4093905737cf289b6b38@syzkaller.appspotmail.com
Fixes: f7643bc9749f ("bcachefs: make btree read errors silent during scan")

bcachefs (loop0): flushing journal and stopping allocators, journal seq 13
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 13
------------[ cut here ]------------
journal shutdown error: cur seq 13 but last empty seq 14
WARNING: CPU: 0 PID: 5081 at fs/bcachefs/journal.c:1191 bch2_fs_journal_stop+0x5f3/0x630 fs/bcachefs/journal.c:1187
Modules linked in:
CPU: 0 PID: 5081 Comm: syz-executor334 Not tainted 6.10.0-rc7-syzkaller-00244-g975f3b6da180 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
RIP: 0010:bch2_fs_journal_stop+0x5f3/0x630 fs/bcachefs/journal.c:1187
Code: 44 24 18 42 80 3c 20 00 48 8b 5c 24 20 74 08 48 89 df e8 20 a2 c7 fd 48 8b 13 48 c7 c7 a0 34 13 8c 4c 89 f6 e8 8e 51 27 fd 90 <0f> 0b 90 90 e9 e4 fe ff ff 44 89 f1 80 e1 07 38 c1 0f 8c 7f fc ff
RSP: 0018:ffffc90003cc7780 EFLAGS: 00010246
RAX: 9ce99195b516ba00 RBX: ffff8880772caaa0 RCX: ffff88801ab3bc00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003cc78c0 R08: ffffffff815857a2 R09: 1ffff1101728519a
R10: dffffc0000000000 R11: ffffed101728519b R12: dffffc0000000000
R13: ffff8880772ca440 R14: 000000000000000d R15: 1ffff1100ee59488
FS:  000055557822d380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd538a8b68 CR3: 000000002bf54000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __bch2_fs_read_only+0x30c/0x430 fs/bcachefs/super.c:291
 bch2_fs_read_only+0xb52/0x1210 fs/bcachefs/super.c:356
 __bch2_fs_stop+0x105/0x540 fs/bcachefs/super.c:617
 generic_shutdown_super+0x136/0x2d0 fs/super.c:642
 bch2_kill_sb+0x41/0x50 fs/bcachefs/fs.c:2052
 deactivate_locked_super+0xc4/0x130 fs/super.c:473
 cleanup_mnt+0x41f/0x4b0 fs/namespace.c:1267
 task_work_run+0x24f/0x310 kernel/task_work.c:180
 ptrace_notify+0x2d2/0x380 kernel/signal.c:2402
 ptrace_report_syscall include/linux/ptrace.h:415 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
 syscall_exit_work+0xc6/0x190 kernel/entry/common.c:173
 syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline]
 syscall_exit_to_user_mode+0x273/0x360 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa2d3adf307
Code: 08 00 48 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffd538a9318 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007fa2d3adf307
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd538a93d0
RBP: 00007ffd538a93d0 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000206 R12: 00007ffd538aa430
R13: 000055557822e6c0 R14: 0000000000000001 R15: 431bde82d7b634db
 </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 syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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

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.

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

Re: [syzbot] [PATCH] bcachefs: WARNING in bch2_fs_journal_stop

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] bcachefs: WARNING in bch2_fs_journal_stop
Author: cam.alvarez.i@gmail.com

#syz test
last_seq and last_empty_seq suffered from an off by one error when the
journal has no entries.

The indexes were fixed and an assertion is added to check that the
last_empty_seq is always kept under the next valid seq number.

Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
---
 fs/bcachefs/journal.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index 10b19791ec98..7bbbf4b149e9 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -1201,7 +1201,7 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
 	struct journal_replay *i, **_i;
 	struct genradix_iter iter;
 	bool had_entries = false;
-	u64 last_seq = cur_seq, nr, seq;
+        u64 last_written_seq = cur_seq - 1, last_seq = cur_seq - 1, nr, seq;
 
 	genradix_for_each_reverse(&c->journal_entries, iter, _i) {
 		i = *_i;
@@ -1209,11 +1209,11 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
 		if (journal_replay_ignore(i))
 			continue;
 
-		last_seq = le64_to_cpu(i->j.last_seq);
+		last_written_seq = le64_to_cpu(i->j.last_seq);
 		break;
 	}
 
-	nr = cur_seq - last_seq;
+	nr = cur_seq - last_written_seq;
 
 	if (nr + 1 > j->pin.size) {
 		free_fifo(&j->pin);
@@ -1224,14 +1224,14 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
 		}
 	}
 
-	j->replay_journal_seq	= last_seq;
+	j->replay_journal_seq	= last_written_seq;
 	j->replay_journal_seq_end = cur_seq;
-	j->last_seq_ondisk	= last_seq;
-	j->flushed_seq_ondisk	= cur_seq - 1;
-	j->seq_ondisk		= cur_seq - 1;
-	j->pin.front		= last_seq;
+	j->last_seq_ondisk	= last_written_seq;
+	j->flushed_seq_ondisk	= last_seq;
+	j->seq_ondisk		= last_seq;
+	j->pin.front		= last_written_seq;
 	j->pin.back		= cur_seq;
-	atomic64_set(&j->seq, cur_seq - 1);
+	atomic64_set(&j->seq, last_seq);
 
 	fifo_for_each_entry_ptr(p, &j->pin, seq)
 		journal_pin_list_init(p, 1);
@@ -1261,7 +1261,10 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
 	}
 
 	if (!had_entries)
-		j->last_empty_seq = cur_seq;
+		j->last_empty_seq = last_seq;
+
+	WARN(j->last_empty_seq >= cur_seq, "journal startup error: last empty seq %llu is higher or equal than the next seq number to be used (%llu)",
+	      j->last_empty_seq, cur_seq);
 
 	spin_lock(&j->lock);
 
-- 
2.34.1

Re: [syzbot] [bcachefs?] WARNING in bch2_fs_journal_stop

[Kent Overstreet]

#syz fix: bcachefs: Fix warning in bch2_fs_journal_stop()

Re: [syzbot] [bcachefs?] WARNING in bch2_fs_journal_stop

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+4093905737cf289b6b38@syzkaller.appspotmail.com
Tested-by: syzbot+4093905737cf289b6b38@syzkaller.appspotmail.com

Tested on:

commit:         e2f710f9 Merge tag 'ata-6.11-rc1' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=131258ce980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a2f87f8b8afcec45
dashboard link: https://syzkaller.appspot.com/bug?extid=4093905737cf289b6b38
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=168ee43d980000

Note: testing is done by a robot and is best-effort only.