syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P8961/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=128857, q=2481 ncpus=2)
task:kworker/u10:6   state:R  running task     stack:23784 pid:8961  tgid:8961  ppid:2      task_flags:0x24248160 flags:0x00004000
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7288
 irqentry_exit+0x36/0x90 kernel/entry/common.c:197
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:page_ext_lookup+0x2a/0x50 mm/page_ext.c:509
Code: 66 0f 1f 00 53 48 89 fb 48 c1 e3 06 e8 5f f6 8e ff 48 c7 c0 70 04 f5 8d 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 <75> 10 48 03 1d 1d f2 c8 0b 48 89 df 5b e9 e4 f8 ff ff 48 c7 c7 70
RSP: 0018:ffffc900046eef60 EFLAGS: 00000246
RAX: 1ffffffff1bea08e RBX: 0000000001740b40 RCX: ffffffff822a7e3e
RDX: dffffc0000000000 RSI: ffffffff822c1231 RDI: 000000000005d02d
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000014270 R12: 00000000008e056e
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000e6050b
 page_ext_iter_begin include/linux/page_ext.h:132 [inline]
 __update_page_owner_free_handle.constprop.0+0xaa/0x4a0 mm/page_owner.c:272
 __reset_page_owner+0x93/0x1a0 mm/page_owner.c:309
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0x7d5/0x10f0 mm/page_alloc.c:2895
 discard_slab mm/slub.c:2753 [inline]
 __put_partials+0x165/0x1c0 mm/slub.c:3218
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:340
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4180 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_noprof+0x1cb/0x3b0 mm/slub.c:4236
 ext4_alloc_io_end_vec+0x2b/0x1c0 fs/ext4/page-io.c:60
 mpage_map_and_submit_extent fs/ext4/inode.c:2463 [inline]
 ext4_do_writepages+0x167b/0x3cf0 fs/ext4/inode.c:2931
 ext4_writepages+0x37a/0x7d0 fs/ext4/inode.c:3025
 do_writepages+0x27a/0x600 mm/page-writeback.c:2634
 __writeback_single_inode+0x160/0xfb0 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x60d/0xfa0 fs/fs-writeback.c:1976
 __writeback_inodes_wb+0xf8/0x2d0 fs/fs-writeback.c:2047
 wb_writeback+0x7f3/0xb70 fs/fs-writeback.c:2158
 wb_check_old_data_flush fs/fs-writeback.c:2262 [inline]
 wb_do_writeback fs/fs-writeback.c:2315 [inline]
 wb_workfn+0x8ca/0xbe0 fs/fs-writeback.c:2343
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3236
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>