syzbot

rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 	0-....: (10499 ticks this GP) idle=9aa/1/0x4000000000000002 softirq=228629/228629 fqs=5234 
	(t=10500 jiffies g=268537 q=551)
NMI backtrace for cpu 0
CPU: 0 PID: 18777 Comm: syz-executor.3 Not tainted 5.2.0+ #37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
 nmi_cpu_backtrace+0xb0/0x1a0 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x14c/0x240 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
 rcu_pending kernel/rcu/tree.c:2736 [inline]
 rcu_sched_clock_irq+0x7e3/0xfb0 kernel/rcu/tree.c:2183
 update_process_times+0x114/0x170 kernel/time/timer.c:1639
 tick_sched_handle kernel/time/tick-sched.c:167 [inline]
 tick_sched_timer+0x257/0x410 kernel/time/tick-sched.c:1296
 __run_hrtimer kernel/time/hrtimer.c:1389 [inline]
 __hrtimer_run_queues+0x471/0x8c0 kernel/time/hrtimer.c:1451
 hrtimer_interrupt+0x36c/0xd80 kernel/time/hrtimer.c:1509
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1068 [inline]
 smp_apic_timer_interrupt+0xc2/0x220 arch/x86/kernel/apic/apic.c:1093
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:828
 </IRQ>
RIP: 0010:check_kcov_mode kernel/kcov.c:79 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:123 [inline]
RIP: 0010:__sanitizer_cov_trace_cmp8+0x21/0x80 kernel/kcov.c:169
Code: 2e 0f 1f 84 00 00 00 00 00 4c 8b 04 24 65 48 8b 14 25 40 fd 01 00 65 8b 05 e8 30 8b 7e a9 00 01 1f 00 75 61 8b 82 a8 12 00 00 <83> f8 03 75 56 48 8b 8a b0 12 00 00 44 8b 8a ac 12 00 00 49 c1 e1
RSP: 0018:ffff88809877e680 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: 0000000000000002 RCX: ffff88809a240440
RDX: ffff88809a240440 RSI: 0000000000000040 RDI: 0000000000000002
RBP: ffff88809877e6b8 R08: ffffffff8362f4a7 R09: ffffffff819af834
R10: ffff88809a240440 R11: 0000000000000004 R12: 0000000000000002
R13: dffffc0000000000 R14: 0000000000000040 R15: ffffffff88fdcbf0
 cpumask_next+0x4a/0x60 lib/cpumask.c:22
 lruvec_page_state_local include/linux/memcontrol.h:660 [inline]
 lruvec_lru_size+0xb1/0x400 mm/vmscan.c:364
 get_scan_count+0x319/0x14a0 mm/vmscan.c:2405
 shrink_node_memcg+0x1a1/0x1120 mm/vmscan.c:2462
 shrink_node+0x468/0x17a0 mm/vmscan.c:2707
 shrink_zones+0x2d8/0x940 mm/vmscan.c:2940
 do_try_to_free_pages+0x21e/0x930 mm/vmscan.c:2998
 try_to_free_mem_cgroup_pages+0x3d1/0x6c0 mm/vmscan.c:3300
 try_charge+0x6aa/0x17b0 mm/memcontrol.c:2399
 __memcg_kmem_charge_memcg+0x78/0x180 mm/memcontrol.c:2781
 memcg_kmem_charge_memcg include/linux/memcontrol.h:1314 [inline]
 memcg_charge_slab mm/slab.h:304 [inline]
 charge_slab_page mm/slab.h:425 [inline]
 kmem_getpages+0x411/0x970 mm/slab.c:1372
 cache_grow_begin+0x7e/0x2c0 mm/slab.c:2599
 fallback_alloc+0x134/0x1c0 mm/slab.c:3146
 ____cache_alloc_node+0x22a/0x250 mm/slab.c:3214
 __do_cache_alloc mm/slab.c:3283 [inline]
 slab_alloc mm/slab.c:3311 [inline]
 kmem_cache_alloc+0x157/0x2e0 mm/slab.c:3483
 ext4_alloc_inode+0x1f/0x560 fs/ext4/super.c:1073
 alloc_inode fs/inode.c:227 [inline]
 iget_locked+0x182/0x8a0 fs/inode.c:1181
 __ext4_iget+0x2f0/0x47b0 fs/ext4/inode.c:4866
 ext4_lookup+0x61f/0xd30 fs/ext4/namei.c:1700
 __lookup_slow+0x2d8/0x410 fs/namei.c:1669
 lookup_slow fs/namei.c:1686 [inline]
 mountpoint_last fs/namei.c:2663 [inline]
 path_mountpoint+0x29f/0x750 fs/namei.c:2693
 filename_mountpoint+0x221/0x670 fs/namei.c:2715
 user_path_mountpoint_at+0x39/0x50 fs/namei.c:2745
 ksys_umount+0x169/0x10a0 fs/namespace.c:1680
 __do_sys_umount fs/namespace.c:1706 [inline]
 __se_sys_umount fs/namespace.c:1704 [inline]
 __x64_sys_umount+0x5a/0x70 fs/namespace.c:1704
 do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c257
Code: 64 89 04 25 d0 02 00 00 58 5f ff d0 48 89 c7 e8 2f be ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 9d 8d fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe85e54cf8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045c257
RDX: 0000000000403520 RSI: 0000000000000002 RDI: 00007ffe85e54da0
RBP: 0000000000000008 R08: 0000000000000000 R09: 000000000000000e
R10: 000000000000000a R11: 0000000000000206 R12: 00007ffe85e55e30
R13: 0000555556ab4940 R14: 0000000000000000 R15: 00007ffe85e55e30