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Date: Tue, 4 Jun 2024 23:12:54 +0800
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Subject: Re: [syzbot] [f2fs?] INFO: task hung in f2fs_balance_fs
To: syzbot <syzbot+8b85865808c8908a0d8c@syzkaller.appspotmail.com>,
 jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net,
 linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
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References: <0000000000000bf86505f7c6bf0c@google.com>
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From: Chao Yu <chao@kernel.org>
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#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git wip

On 2023/3/26 13:17, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    4bdec23f971b Merge tag 'hwmon-for-v6.3-rc4' of git://git.k..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=177bdf41c80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ea09b0836073ee4
> dashboard link: https://syzkaller.appspot.com/bug?extid=8b85865808c8908a0d8c
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1320ef41c80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100b561ec80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d61c34161317/disk-4bdec23f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6f84b5727488/vmlinux-4bdec23f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/1279076a5b70/bzImage-4bdec23f.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/c38a9411ccc2/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8b85865808c8908a0d8c@syzkaller.appspotmail.com
> 
> INFO: task kworker/u4:4:56 blocked for more than 143 seconds.
>        Not tainted 6.3.0-rc3-syzkaller-00322-g4bdec23f971b #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:kworker/u4:4    state:D stack:26464 pid:56    ppid:2      flags:0x00004000
> Workqueue: writeback wb_workfn (flush-7:0)
> Call Trace:
>   <TASK>
>   context_switch kernel/sched/core.c:5304 [inline]
>   __schedule+0xc91/0x5770 kernel/sched/core.c:6622
>   schedule+0xde/0x1a0 kernel/sched/core.c:6698
>   schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6757
>   rwsem_down_write_slowpath+0x3e2/0x1220 kernel/locking/rwsem.c:1178
>   __down_write_common kernel/locking/rwsem.c:1306 [inline]
>   __down_write kernel/locking/rwsem.c:1315 [inline]
>   down_write+0x1d2/0x200 kernel/locking/rwsem.c:1574
>   f2fs_down_write fs/f2fs/f2fs.h:2207 [inline]
>   f2fs_balance_fs+0x54e/0x6c0 fs/f2fs/segment.c:427
>   f2fs_write_inode+0x582/0xe00 fs/f2fs/inode.c:760
>   write_inode fs/fs-writeback.c:1453 [inline]
>   __writeback_single_inode+0x9f8/0xdc0 fs/fs-writeback.c:1665
>   writeback_sb_inodes+0x54d/0xe70 fs/fs-writeback.c:1891
>   __writeback_inodes_wb+0xc6/0x280 fs/fs-writeback.c:1962
>   wb_writeback+0x7e9/0xa50 fs/fs-writeback.c:2067
>   wb_check_old_data_flush fs/fs-writeback.c:2167 [inline]
>   wb_do_writeback fs/fs-writeback.c:2220 [inline]
>   wb_workfn+0x765/0xfc0 fs/fs-writeback.c:2248
>   process_one_work+0x991/0x15c0 kernel/workqueue.c:2390
>   worker_thread+0x669/0x1090 kernel/workqueue.c:2537
>   kthread+0x2e8/0x3a0 kernel/kthread.c:376
>   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
>   </TASK>
> 
> Showing all locks held in the system:
> 1 lock held by rcu_tasks_kthre/12:
>   #0: ffffffff8c794b70 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x31/0xd80 kernel/rcu/tasks.h:510
> 1 lock held by rcu_tasks_trace/13:
>   #0: ffffffff8c794870 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x31/0xd80 kernel/rcu/tasks.h:510
> 1 lock held by khungtaskd/28:
>   #0: ffffffff8c7956c0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x340 kernel/locking/lockdep.c:6495
> 4 locks held by kworker/u4:4/56:
>   #0: ffff88801750f138 ((wq_completion)writeback){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>   #0: ffff88801750f138 ((wq_completion)writeback){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
>   #0: ffff88801750f138 ((wq_completion)writeback){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline]
>   #0: ffff88801750f138 ((wq_completion)writeback){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:639 [inline]
>   #0: ffff88801750f138 ((wq_completion)writeback){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:666 [inline]
>   #0: ffff88801750f138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x87a/0x15c0 kernel/workqueue.c:2361
>   #1: ffffc90001577da8 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x15c0 kernel/workqueue.c:2365
>   #2: ffff8880244ae0e0 (&type->s_umount_key#44){.+.+}-{3:3}, at: trylock_super+0x21/0x110 fs/super.c:414
>   #3: ffff8880200f12a8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2207 [inline]
>   #3: ffff8880200f12a8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x54e/0x6c0 fs/f2fs/segment.c:427
> 2 locks held by getty/4755:
>   #0: ffff88802be78098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x26/0x80 drivers/tty/tty_ldisc.c:244
>   #1: ffffc900015a02f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xef4/0x13e0 drivers/tty/n_tty.c:2177
> 3 locks held by syz-executor470/5084:
> 1 lock held by syz-executor470/5814:
> 
> =============================================
> 
> NMI backtrace for cpu 1
> CPU: 1 PID: 28 Comm: khungtaskd Not tainted 6.3.0-rc3-syzkaller-00322-g4bdec23f971b #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> Call Trace:
>   <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
>   nmi_cpu_backtrace+0x29c/0x350 lib/nmi_backtrace.c:113
>   nmi_trigger_cpumask_backtrace+0x2a4/0x300 lib/nmi_backtrace.c:62
>   trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
>   check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
>   watchdog+0xe16/0x1090 kernel/hung_task.c:379
>   kthread+0x2e8/0x3a0 kernel/kthread.c:376
>   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
>   </TASK>
> Sending NMI from CPU 1 to CPUs 0:
> NMI backtrace for cpu 0
> CPU: 0 PID: 5814 Comm: syz-executor470 Not tainted 6.3.0-rc3-syzkaller-00322-g4bdec23f971b #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> RIP: 0010:__sanitizer_cov_trace_pc+0x3b/0x70 kernel/kcov.c:207
> Code: 81 e1 00 01 00 00 65 48 8b 14 25 80 b8 03 00 a9 00 01 ff 00 74 0e 85 c9 74 35 8b 82 74 15 00 00 85 c0 74 2b 8b 82 50 15 00 00 <83> f8 02 75 20 48 8b 8a 58 15 00 00 8b 92 54 15 00 00 48 8b 01 48
> RSP: 0018:ffffc9000444f8b8 EFLAGS: 00000246
> RAX: 0000000000000000 RBX: ffff88802bb0af58 RCX: 0000000000000000
> RDX: ffff888026079d40 RSI: ffffffff81b30401 RDI: 0000000000000001
> RBP: ffffea0001b5f3c0 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: ffffc9000444fa48 R15: 0000000000000001
> FS:  00007ff4d3fdc700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ff4cfbbb000 CR3: 00000000294d8000 CR4: 0000000000350ef0
> Call Trace:
>   <TASK>
>   truncate_inode_folio+0x51/0x70 mm/truncate.c:197
>   shmem_undo_range+0x33e/0x1340 mm/shmem.c:942
>   shmem_truncate_range mm/shmem.c:1041 [inline]
>   shmem_evict_inode+0x32f/0xb60 mm/shmem.c:1156
>   evict+0x2ed/0x6b0 fs/inode.c:665
>   iput_final fs/inode.c:1748 [inline]
>   iput.part.0+0x50a/0x740 fs/inode.c:1774
>   iput+0x5c/0x80 fs/inode.c:1764
>   dentry_unlink_inode+0x2b1/0x460 fs/dcache.c:401
>   __dentry_kill+0x3c0/0x640 fs/dcache.c:607
>   dentry_kill fs/dcache.c:733 [inline]
>   dput+0x865/0xe10 fs/dcache.c:913
>   __fput+0x3cc/0xa90 fs/file_table.c:329
>   task_work_run+0x16f/0x270 kernel/task_work.c:179
>   ptrace_notify+0x118/0x140 kernel/signal.c:2354
>   ptrace_report_syscall include/linux/ptrace.h:411 [inline]
>   ptrace_report_syscall_exit include/linux/ptrace.h:473 [inline]
>   syscall_exit_work kernel/entry/common.c:251 [inline]
>   syscall_exit_to_user_mode_prepare+0x129/0x220 kernel/entry/common.c:278
>   __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
>   syscall_exit_to_user_mode+0xd/0x50 kernel/entry/common.c:296
>   do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7ff4d3feca4b
> Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 03 fd ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 41 fd ff ff 8b 44
> RSP: 002b:00007ff4d3fdc160 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007ff4d3feca4b
> RDX: 0000000000000010 RSI: 0000000000004c00 RDI: 0000000000000003
> RBP: 0000000000000004 R08: 0000000000000000 R09: 00000000000105f8
> R10: 0000000000000000 R11: 0000000000000293 R12: 00007ff4d3fdc6b8
> R13: 00007ff4d3fdc190 R14: 00007ff4d3fdc1d0 R15: 0000000000000010
>   </TASK>
>