INFO: task can't die in iterate_supers (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a1f92694 Add linux-next specific files for 20210518
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12cd5268300000
kernel config: https://syzkaller.appspot.com/x/.config?x=d612e75ffd53a6d3
dashboard link: https://syzkaller.appspot.com/bug?extid=7cfbdf2e4ef08fac5722
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7cfbdf...@syzkaller.appspotmail.com

INFO: task syz-executor.1:30358 can't die for more than 143 seconds.
task:syz-executor.1 state:D stack:29336 pid:30358 ppid: 8452 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4688 [inline]
__schedule+0xb38/0x58c0 kernel/sched/core.c:5945
schedule+0xcf/0x270 kernel/sched/core.c:6024
rwsem_down_read_slowpath+0x4ca/0x980 kernel/locking/rwsem.c:992
__down_read_common kernel/locking/rwsem.c:1213 [inline]
__down_read kernel/locking/rwsem.c:1222 [inline]
down_read+0xe4/0x440 kernel/locking/rwsem.c:1355
iterate_supers+0xdb/0x290 fs/super.c:693
ksys_sync+0x86/0x150 fs/sync.c:114
__do_sys_sync+0xa/0x10 fs/sync.c:125
do_syscall_64+0x31/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665d9
RSP: 002b:00007fd6d39d7188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007fffb951a9af R14: 00007fd6d39d7300 R15: 0000000000022000
INFO: task syz-executor.1:30363 can't die for more than 143 seconds.
task:syz-executor.1 state:D stack:27320 pid:30363 ppid: 8452 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4688 [inline]
__schedule+0xb38/0x58c0 kernel/sched/core.c:5945
schedule+0xcf/0x270 kernel/sched/core.c:6024
rwsem_down_read_slowpath+0x4ca/0x980 kernel/locking/rwsem.c:992
__down_read_common kernel/locking/rwsem.c:1213 [inline]
__down_read kernel/locking/rwsem.c:1222 [inline]
down_read+0xe4/0x440 kernel/locking/rwsem.c:1355
iterate_supers+0xdb/0x290 fs/super.c:693
ksys_sync+0x86/0x150 fs/sync.c:114
__do_sys_sync+0xa/0x10 fs/sync.c:125
do_syscall_64+0x31/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665d9
RSP: 002b:00007fd6d39b6188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c038
R13: 00007fffb951a9af R14: 00007fd6d39b6300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by ksoftirqd/1/19:
#0: ffff8880b9d35718 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2b/0x120 kernel/sched/core.c:460
1 lock held by khungtaskd/1622:
#0: ffffffff8c17afe0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6333
1 lock held by in:imklog/8138:
#0: ffff88801c434370 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
2 locks held by syz-executor.0/29322:
#0: ffff88807edaa0e0 (&type->s_umount_key#90/1){+.+.}-{3:3}, at: alloc_super+0x1dd/0xab0 fs/super.c:229
#1: ffff88808032c090 (&client->mount_mutex){+.+.}-{3:3}, at: ceph_real_mount fs/ceph/super.c:929 [inline]
#1: ffff88808032c090 (&client->mount_mutex){+.+.}-{3:3}, at: ceph_get_tree+0x6fb/0x1750 fs/ceph/super.c:1098
1 lock held by syz-executor.0/29385:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29484:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29556:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29649:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29714:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29781:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29873:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/29946:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30000:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30063:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30129:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30167:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30246:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30326:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.1/30358:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: iterate_supers+0xdb/0x290 fs/super.c:693
1 lock held by syz-executor.1/30363:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: iterate_supers+0xdb/0x290 fs/super.c:693
1 lock held by syz-executor.0/30391:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389
1 lock held by syz-executor.0/30429:
#0: ffff88807edaa0e0 (&type->s_umount_key#94){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:389

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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.