[syzbot] [bcachefs?] possible deadlock in bch2_btree_roots_to_journal_entries

[syzbot] [bcachefs?] possible deadlock in bch2_btree_roots_to_journal_entries

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    0e1980c40b6e Add linux-next specific files for 20240531
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=165e4206980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9c3ca4e54577b88
dashboard link: https://syzkaller.appspot.com/bug?extid=49f73403c9dd50916299
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=165bfa9a980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10dc7ef2980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/44fb1d8b5978/disk-0e1980c4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a66ce5caf0b2/vmlinux-0e1980c4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8992fc8fe046/bzImage-0e1980c4.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/6e6980c5e9d0/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/84607f339774/mount_1.gz

The issue was bisected to:

commit 228e1c91ae5ec44f38aa8852aa3953005badce82
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date:   Wed Dec 27 23:31:46 2023 +0000

    bcachefs: KEY_TYPE_accounting

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10de95fc980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12de95fc980000
console output: https://syzkaller.appspot.com/x/log.txt?x=14de95fc980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+49f73403c9dd50916299@syzkaller.appspotmail.com
Fixes: 228e1c91ae5e ("bcachefs: KEY_TYPE_accounting")

bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 15
bcachefs (loop0): shutdown complete, journal seq 16
bcachefs (loop0): marking filesystem clean
======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc1-next-20240531-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor537/5091 is trying to acquire lock:
ffff888077801a60 (&c->btree_root_lock){+.+.}-{3:3}, at: bch2_btree_roots_to_journal_entries+0xbb/0x980 fs/bcachefs/btree_update_interior.c:2633

but task is already holding lock:
ffff888077800918 (&c->sb_lock){+.+.}-{3:3}, at: bch2_fs_mark_clean+0x35/0x9f0 fs/bcachefs/sb-clean.c:287

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&c->sb_lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5817
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       bch2_gc_mark_key+0xb3e/0x1050 fs/bcachefs/btree_gc.c:602
       bch2_gc_btree fs/bcachefs/btree_gc.c:650 [inline]
       bch2_gc_btrees fs/bcachefs/btree_gc.c:699 [inline]
       bch2_check_allocations+0xa1db/0xb9d0 fs/bcachefs/btree_gc.c:1121
       bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:183
       bch2_run_recovery_passes+0x19e/0x820 fs/bcachefs/recovery_passes.c:226
       bch2_fs_recovery+0x238b/0x3730 fs/bcachefs/recovery.c:846
       bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1017
       bch2_fs_open+0xa8d/0xdf0 fs/bcachefs/super.c:2113
       bch2_mount fs/bcachefs/fs.c:1908 [inline]
       bch2_fs_get_tree+0x75e/0x14d0 fs/bcachefs/fs.c:2069
       vfs_get_tree+0x90/0x2a0 fs/super.c:1780
       do_new_mount+0x2be/0xb40 fs/namespace.c:3352
       do_mount fs/namespace.c:3692 [inline]
       __do_sys_mount fs/namespace.c:3898 [inline]
       __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&c->btree_root_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3159 [inline]
       check_prevs_add kernel/locking/lockdep.c:3278 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3902
       __lock_acquire+0x1359/0x2000 kernel/locking/lockdep.c:5194
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5817
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       bch2_btree_roots_to_journal_entries+0xbb/0x980 fs/bcachefs/btree_update_interior.c:2633
       bch2_fs_mark_clean+0x4a9/0x9f0 fs/bcachefs/sb-clean.c:314
       bch2_fs_read_only+0x1115/0x1220 fs/bcachefs/super.c:367
       __bch2_fs_stop+0x105/0x540 fs/bcachefs/super.c:601
       generic_shutdown_super+0x136/0x2d0 fs/super.c:642
       bch2_kill_sb+0x41/0x50 fs/bcachefs/fs.c:2025
       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+0x273/0x370 kernel/entry/common.c:218
       do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&c->sb_lock);
                               lock(&c->btree_root_lock);
                               lock(&c->sb_lock);
  lock(&c->btree_root_lock);

 *** DEADLOCK ***

3 locks held by syz-executor537/5091:
 #0: ffff88807fdf00e0 (&type->s_umount_key#44){+.+.}-{3:3}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88807fdf00e0 (&type->s_umount_key#44){+.+.}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88807fdf00e0 (&type->s_umount_key#44){+.+.}-{3:3}, at: deactivate_super+0xb5/0xf0 fs/super.c:505
 #1: ffff888077800278 (&c->state_lock){+.+.}-{3:3}, at: __bch2_fs_stop+0xfd/0x540 fs/bcachefs/super.c:600
 #2: ffff888077800918 (&c->sb_lock){+.+.}-{3:3}, at: bch2_fs_mark_clean+0x35/0x9f0 fs/bcachefs/sb-clean.c:287

stack backtrace:
CPU: 0 PID: 5091 Comm: syz-executor537 Not tainted 6.10.0-rc1-next-20240531-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2075
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2204
 check_prev_add kernel/locking/lockdep.c:3159 [inline]
 check_prevs_add kernel/locking/lockdep.c:3278 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3902
 __lock_acquire+0x1359/0x2000 kernel/locking/lockdep.c:5194
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5817
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 bch2_btree_roots_to_journal_entries+0xbb/0x980 fs/bcachefs/btree_update_interior.c:2633
 bch2_fs_mark_clean+0x4a9/0x9f0 fs/bcachefs/sb-clean.c:314
 bch2_fs_read_only+0x1115/0x1220 fs/bcachefs/super.c:367
 __bch2_fs_stop+0x105/0x540 fs/bcachefs/super.c:601
 generic_shutdown_super+0x136/0x2d0 fs/super.c:642
 bch2_kill_sb+0x41/0x50 fs/bcachefs/fs.c:2025
 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+0x273/0x370 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f61d2db54c7
Code: 07 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:00007ffd384f1498 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 000000000000e4de RCX: 00007f61d2db54c7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd384f1550
RBP: 00007ffd384f1550 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000202 R12: 00007ffd384f25c0
R13: 000055557a8f46c0 R14: 431bde82d7b634db R15: 00007ffd384f25e0
 </TASK>
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 14
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 14
bcachefs (loop0): shutdown complete, journal seq 15
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 15
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 15
bcachefs (loop0): shutdown complete, journal seq 16
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 14
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 14
bcachefs (loop0): shutdown complete, journal seq 15
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 14
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 14
bcachefs (loop0): shutdown complete, journal seq 15
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 15
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 15
bcachefs (loop0): shutdown complete, journal seq 16
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 14
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 14
bcachefs (loop0): shutdown complete, journal seq 15
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 15
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 15
bcachefs (loop0): shutdown complete, journal seq 16
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 15
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 15
bcachefs (loop0): shutdown complete, journal seq 16
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 14
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 14
bcachefs (loop0): shutdown complete, journal seq 15


---
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Re: [syzbot] possible deadlock in bch2_btree_roots_to_journal_entries

[syzbot]

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

***

Subject: possible deadlock in bch2_btree_roots_to_journal_entries
Author: kent.overstreet@linux.dev

#syz fix: bcachefs: bch2_gc_btree() should not use btree_root_lock