INFO: task can't die in grab_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bc09acc9 Add linux-next specific files for 20200812
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=167a131c900000
kernel config: https://syzkaller.appspot.com/x/.config?x=2055bd0d83d5ee16
dashboard link: https://syzkaller.appspot.com/bug?extid=db0c06ff59429269db90
compiler: gcc (GCC) 10.1.0-syz 20200507
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+db0c06...@syzkaller.appspotmail.com

INFO: task syz-executor.4:27742 can't die for more than 143 seconds.
syz-executor.4 D28880 27742 27202 0x00004004
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0x8e5/0x21e0 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
rwsem_down_write_slowpath+0x603/0xc60 kernel/locking/rwsem.c:1235
__down_write kernel/locking/rwsem.c:1389 [inline]
down_write+0x137/0x150 kernel/locking/rwsem.c:1532
grab_super+0x59/0x260 fs/super.c:391
sget_fc+0x24c/0x770 fs/super.c:563
ceph_get_tree+0x5ce/0x15f0 fs/ceph/super.c:1076
vfs_get_tree+0x89/0x2f0 fs/super.c:1549
do_new_mount fs/namespace.c:2912 [inline]
path_mount+0x1287/0x1e20 fs/namespace.c:3230
do_mount fs/namespace.c:3243 [inline]
__do_sys_mount fs/namespace.c:3451 [inline]
__se_sys_mount fs/namespace.c:3428 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3428
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d189
Code: Bad RIP value.
RSP: 002b:00007f5e7fc96c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000020480 RCX: 000000000045d189
RDX: 0000000020000140 RSI: 00000000200000c0 RDI: 0000000020000040
RBP: 000000000118cf90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffc24a0b81f R14: 00007f5e7fc979c0 R15: 000000000118cf4c

Showing all locks held in the system:
1 lock held by khungtaskd/1155:
#0: ffffffff89c66c40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5825
2 locks held by syz-executor.4/27637:
#0: ffff88803dba60e0 (&type->s_umount_key#59/1){+.+.}-{3:3}, at: alloc_super+0x1ba/0xa80 fs/super.c:230
#1: ffff88804d14c090 (&client->mount_mutex){+.+.}-{3:3}, at: ceph_real_mount fs/ceph/super.c:925 [inline]
#1: ffff88804d14c090 (&client->mount_mutex){+.+.}-{3:3}, at: ceph_get_tree+0x6d1/0x15f0 fs/ceph/super.c:1094
1 lock held by syz-executor.4/27699:
#0: ffff88803dba60e0 (&type->s_umount_key#60){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:391
1 lock held by syz-executor.4/27742:
#0: ffff88803dba60e0 (&type->s_umount_key#60){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:391
1 lock held by syz-executor.4/27792:
#0: ffff88803dba60e0 (&type->s_umount_key#60){++++}-{3:3}, at: grab_super+0x59/0x260 fs/super.c:391
1 lock held by syz-executor.5/31789:
#0: ffff88803dba60e0 (&type->s_umount_key#60){++++}-{3:3}, at: iterate_supers+0xdb/0x290 fs/super.c:694
1 lock held by syz-executor.5/31794:
#0: ffff88803dba60e0 (&type->s_umount_key#60){++++}-{3:3}, at: iterate_supers+0xdb/0x290 fs/super.c:694

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[syzbot]

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