syzbot

INFO: task syz-executor233:5852 blocked for more than 143 seconds.
      Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor233 state:D stack:19816 pid:5852  tgid:5852  ppid:5851   task_flags:0x440140 flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x168f/0x4c70 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6860
 __closure_sync+0x163/0x220 lib/closure.c:146
 bch2_wait_on_allocator fs/bcachefs/alloc_foreground.h:256 [inline]
 __bch2_write+0x324b/0x39b0 fs/bcachefs/io_write.c:1575
 closure_queue include/linux/closure.h:270 [inline]
 closure_call include/linux/closure.h:432 [inline]
 bch2_writepage_do_io fs/bcachefs/fs-io-buffered.c:494 [inline]
 bch2_writepages+0x269/0x360 fs/bcachefs/fs-io-buffered.c:677
 do_writepages+0x3ae/0x7b0 mm/page-writeback.c:2656
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x22c/0x330 mm/filemap.c:794
 bch2_fsync+0x127/0x330 fs/bcachefs/fs-io.c:243
 generic_write_sync include/linux/fs.h:2976 [inline]
 bch2_write_iter+0x2822/0x2b90 fs/bcachefs/fs-io-buffered.c:1097
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x548/0xa90 fs/read_write.c:684
 ksys_pwrite64 fs/read_write.c:791 [inline]
 __do_sys_pwrite64 fs/read_write.c:799 [inline]
 __se_sys_pwrite64 fs/read_write.c:796 [inline]
 __x64_sys_pwrite64+0x193/0x220 fs/read_write.c:796
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f007bce2b19
RSP: 002b:00007fffc41f35a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 0000200000000040 RCX: 00007f007bce2b19
RDX: 000000000000fdef RSI: 0000200000000140 RDI: 0000000000000004
RBP: 00007f007bd655f0 R08: 000055557375d4c0 R09: 000055557375d4c0
R10: 000000000000fecc R11: 0000000000000246 R12: 00007fffc41f35d0
R13: 00007fffc41f37f8 R14: 431bde82d7b634db R15: 00007f007bd2b03b
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6764
2 locks held by getty/5579:
 #0: ffff888034a5a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000333b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
1 lock held by syz-executor233/5852:
 #0: ffff8880308ee420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3041 [inline]
 #0: ffff8880308ee420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x211/0xa90 fs/read_write.c:680
2 locks held by bch-copygc/loop/5862:

=============================================

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:274 [inline]
 watchdog+0xfee/0x1030 kernel/hung_task.c:437
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5862 Comm: bch-copygc/loop Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:check_kcov_mode kernel/kcov.c:194 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:246 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp1+0x37/0x90 kernel/kcov.c:300
Code: 08 00 72 92 65 8b 0d d8 2d b2 10 81 e1 00 01 ff 00 74 11 81 f9 00 01 00 00 75 5b 83 ba 3c 16 00 00 00 74 52 8b 8a 18 16 00 00 <83> f9 03 75 47 48 8b 8a 20 16 00 00 44 8b 8a 1c 16 00 00 49 c1 e1
RSP: 0018:ffffc900041ef128 EFLAGS: 00000246
RAX: ffffffff841e29dd RBX: 0000000000000001 RCX: 0000000000000000
RDX: ffff8880733c9e00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffc900041ef027 R09: 0000000000000000
R10: ffffc900041ef000 R11: fffff5200083de05 R12: 00000000ffffffff
R13: ffff88807326c328 R14: 1ffff1100e64d865 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888126100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcea9c91e80 CR3: 000000000dd36000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 btree_node_locked fs/bcachefs/btree_locking.h:64 [inline]
 bch2_btree_path_verify_locks+0x49d/0xba0 fs/bcachefs/btree_locking.c:872
 bch2_btree_path_traverse_one+0x1b4f/0x2430 fs/bcachefs/btree_iter.c:1224
 bch2_btree_path_traverse fs/bcachefs/btree_iter.h:248 [inline]
 bch2_btree_iter_peek_slot+0x772/0x1f00 fs/bcachefs/btree_iter.c:2763
 __bch2_bkey_get_iter fs/bcachefs/btree_iter.h:591 [inline]
 bch2_bkey_get_iter fs/bcachefs/btree_iter.h:605 [inline]
 bch2_bucket_is_movable fs/bcachefs/movinggc.c:82 [inline]
 bch2_copygc_get_buckets fs/bcachefs/movinggc.c:169 [inline]
 bch2_copygc+0x9e4/0x3cf0 fs/bcachefs/movinggc.c:221
 bch2_copygc_thread+0x8c9/0xd40 fs/bcachefs/movinggc.c:405
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.232 msecs