syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6077/1:b..l
	(detected by 1, t=10502 jiffies, g=32017, q=109 ncpus=2)
task:syz.2.500       state:R  running task     stack:25312 pid:6077  ppid:5866   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5241 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6558
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6870
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:653
RIP: 0010:lookup_page_ext mm/page_ext.c:275 [inline]
RIP: 0010:page_ext_get+0x17c/0x2a0 mm/page_ext.c:158
Code: 83 e5 7f 48 c1 e5 05 48 01 eb eb 0e e8 3d dd 9d ff eb 05 e8 36 dd 9d ff 31 db 48 83 c3 10 48 89 d8 48 c1 e8 03 42 80 3c 38 00 <74> 08 48 89 df e8 2a 58 f5 ff 4c 8b 3b e8 82 61 85 ff 89 c3 31 ff
RSP: 0018:ffffc9000310f638 EFLAGS: 00000246
RAX: 1ffff11027fff226 RBX: ffff88813fff9130 RCX: 0000000000040000
RDX: ffffc90003a11000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: 0000000000000120 R08: ffffffff81ecc25a R09: fffffbfff20e7445
R10: 0000000000000000 R11: dffffc0000000001 R12: 000000000004da14
R13: 0000000000000000 R14: ffffffff81ecc18c R15: dffffc0000000000
 __set_page_owner+0x32/0x390 mm/page_owner.c:192
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x18d/0x1b0 mm/page_alloc.c:2517
 prep_new_page mm/page_alloc.c:2524 [inline]
 get_page_from_freelist+0x322e/0x33b0 mm/page_alloc.c:4290
 __alloc_pages+0x28d/0x770 mm/page_alloc.c:5558
 relay_alloc_buf kernel/relay.c:121 [inline]
 relay_create_buf kernel/relay.c:162 [inline]
 relay_open_buf+0x285/0xd10 kernel/relay.c:384
 relay_open+0x395/0x8b0 kernel/relay.c:517
 do_blk_trace_setup+0x54a/0x970 kernel/trace/blktrace.c:591
 __blk_trace_setup kernel/trace/blktrace.c:631 [inline]
 blk_trace_ioctl+0x354/0x960 kernel/trace/blktrace.c:745
 blkdev_ioctl+0x1b9/0x760 block/ioctl.c:608
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9759f79e79
RSP: 002b:00007f975acff038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f975a115f80 RCX: 00007f9759f79e79
RDX: 0000000020000000 RSI: 00000000c0481273 RDI: 0000000000000003
RBP: 00007f9759fe7916 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f975a115f80 R15: 00007fff2c5e47d8
 </TASK>
rcu: rcu_preempt kthread starved for 10537 jiffies! g32017 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27064 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5241 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6558
 schedule+0xbf/0x180 kernel/sched/core.c:6634
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:567