syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P3850/1:b..l P4875/1:b..l
	(detected by 0, t=10502 jiffies, g=20173, q=631 ncpus=2)
task:ext4lazyinit    state:R  running task     stack:26816 pid:4875  ppid:2      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:lock_acquire+0x26f/0x5a0 kernel/locking/lockdep.c:5666
Code: 2b 00 74 08 4c 89 f7 e8 3f ac 77 00 f6 44 24 61 02 0f 85 84 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc90004c0f780 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff92000981efc RCX: 1ffff92000981e9c
RDX: dffffc0000000000 RSI: ffffffff8b0c14c0 RDI: ffffffff8b5d6dc0
RBP: ffffc90004c0f8c8 R08: dffffc0000000000 R09: fffffbfff223b845
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92000981ef8
R13: dffffc0000000000 R14: ffffc90004c0f7e0 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 mapping_get_entry mm/filemap.c:1850 [inline]
 __filemap_get_folio+0x171/0xe80 mm/filemap.c:1915
 pagecache_get_page+0x28/0x250 mm/folio-compat.c:110
 find_get_page_flags include/linux/pagemap.h:602 [inline]
 __find_get_block_slow fs/buffer.c:202 [inline]
 __find_get_block+0x3d8/0x1120 fs/buffer.c:1307
 __getblk_slow fs/buffer.c:1034 [inline]
 __getblk_gfp+0x146/0xa20 fs/buffer.c:1333
 sb_getblk include/linux/buffer_head.h:356 [inline]
 ext4_read_block_bitmap_nowait+0x1ff/0x980 fs/ext4/balloc.c:482
 ext4_mb_prefetch+0x46d/0x640 fs/ext4/mballoc.c:2587
 ext4_run_li_request fs/ext4/super.c:3655 [inline]
 ext4_lazyinit_thread+0x54d/0x1ad0 fs/ext4/super.c:3781
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
task:kworker/u4:13   state:R  running task     stack:21464 pid:3850  ppid:2      flags:0x00004000
Workqueue: bat_events batadv_mcast_mla_update
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5241 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6558
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:6727
 preempt_schedule+0xd9/0xe0 kernel/sched/core.c:6751
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 irq_work_queue+0xe7/0x150 kernel/irq_work.c:115
 __kfence_alloc+0x226/0x370 mm/kfence/core.c:1024
 kfence_alloc include/linux/kfence.h:128 [inline]
 slab_alloc_node mm/slub.c:3322 [inline]
 __kmem_cache_alloc_node+0x1fa/0x260 mm/slub.c:3437
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:557 [inline]
 batadv_mcast_mla_softif_get_ipv4 net/batman-adv/multicast.c:374 [inline]
 batadv_mcast_mla_softif_get net/batman-adv/multicast.c:501 [inline]
 __batadv_mcast_mla_update net/batman-adv/multicast.c:879 [inline]
 batadv_mcast_mla_update+0xbd7/0x3c80 net/batman-adv/multicast.c:916
 process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
 worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: rcu_preempt kthread starved for 9569 jiffies! g20173 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:567