rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P12/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=13965, q=371 ncpus=2)
task:kworker/u8:0    state:R  running task     stack:20728 pid:12    tgid:12    ppid:2      task_flags:0x24248160 flags:0x00080000
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5257 [inline]
 __schedule+0x14bc/0x5000 kernel/sched/core.c:6864
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7191
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x16c/0x340 kernel/locking/lockdep.c:5872
Code: 00 00 00 00 9c 8f 44 24 30 f7 44 24 30 00 02 00 00 0f 85 cd 00 00 00 f7 44 24 08 00 02 00 00 74 01 fb 65 48 8b 05 74 17 23 11 <48> 3b 44 24 58 0f 85 e5 00 00 00 48 83 c4 60 5b 41 5c 41 5d 41 5e
RSP: 0018:ffffc900001164d8 EFLAGS: 00000206
RAX: 6b3f5b780bf8d600 RBX: 0000000000000000 RCX: 6b3f5b780bf8d600
RDX: 0000000010a5b866 RSI: ffffffff8dc7e873 RDI: ffffffff8be1e760
RBP: ffffffff827ecc7e R08: ffffffff827ecc7e R09: ffffffff8e3419e0
R10: dffffc0000000000 R11: ffffed100ee330e8 R12: 0000000000000002
R13: ffffffff8e3419e0 R14: 0000000000000000 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 ext4_mb_use_preallocated+0x8df/0x13f0 fs/ext4/mballoc.c:5061
 ext4_mb_new_blocks+0x5a1/0x46a0 fs/ext4/mballoc.c:6308
 ext4_ext_map_blocks+0x1877/0x69c0 fs/ext4/extents.c:4383
 ext4_map_create_blocks fs/ext4/inode.c:613 [inline]
 ext4_map_blocks+0x82c/0x16f0 fs/ext4/inode.c:816
 mpage_map_one_extent fs/ext4/inode.c:2380 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2474 [inline]
 ext4_do_writepages+0x222f/0x4500 fs/ext4/inode.c:2932
 ext4_writepages+0x203/0x350 fs/ext4/inode.c:3026
 do_writepages+0x32e/0x550 mm/page-writeback.c:2598
 __writeback_single_inode+0x133/0x1240 fs/fs-writeback.c:1737
 writeback_sb_inodes+0x93a/0x1870 fs/fs-writeback.c:2030
 __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:2107
 wb_writeback+0x43f/0xaa0 fs/fs-writeback.c:2218
 wb_check_old_data_flush fs/fs-writeback.c:2322 [inline]
 wb_do_writeback fs/fs-writeback.c:2375 [inline]
 wb_workfn+0xad2/0xed0 fs/fs-writeback.c:2403
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: rcu_preempt kthread starved for 10553 jiffies! g13965 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:27464 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5257 [inline]
 __schedule+0x14bc/0x5000 kernel/sched/core.c:6864
 __schedule_loop kernel/sched/core.c:6946 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6961
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 6066 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0033:0x7fc4a724e817
Code: 5f c3 90 48 83 ec 18 89 fe 31 c0 bf e7 00 00 00 e8 2e 0f 14 00 c7 44 24 0c 00 00 00 00 66 0f 1f 44 00 00 8b 44 24 0c 83 c0 01 <89> 44 24 0c eb f3 0f 1f 00 55 53 48 89 fb 48 81 ec d8 00 00 00 48
RSP: 002b:00007fc4a829c580 EFLAGS: 00000202
RAX: 000000001b638991 RBX: 000000000000000b RCX: ffffffffffffffa8
RDX: 00007fc4a732b8ef RSI: 0000000000000000 RDI: 000000000000000b
RBP: 00007fc4a75e5fa0 R08: 0000000000000000 R09: 000000000000000b
R10: 00007fc4a829cb40 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc4a75e6038 R14: 00007ffeb7cb8a40 R15: 00007ffeb7cb8b28
FS:  00007fc4a829d6c0 GS:  0000000000000000