INFO: rcu detected stall in vfs_fallocate

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=152f1274080000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=c44ac76f65d49cdc59d4
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c44ac7...@syzkaller.appspotmail.com

IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 0, t=10502 jiffies, g=121001, q=318)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4295027035-4295016532), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.1 R running task 27880 9615 11169 0x00000000
Call Trace:
<IRQ>
sched_show_task.cold+0x332/0x396 kernel/sched/core.c:5337
print_other_cpu_stall kernel/rcu/tree.c:1430 [inline]
check_cpu_stall kernel/rcu/tree.c:1557 [inline]
__rcu_pending kernel/rcu/tree.c:3293 [inline]
rcu_pending kernel/rcu/tree.c:3336 [inline]
rcu_check_callbacks.cold+0xb37/0xe19 kernel/rcu/tree.c:2682
update_process_times+0x2a/0x70 kernel/time/timer.c:1650
tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:168
tick_sched_timer+0xfc/0x290 kernel/time/tick-sched.c:1278
__run_hrtimer kernel/time/hrtimer.c:1465 [inline]
__hrtimer_run_queues+0x3f6/0xe60 kernel/time/hrtimer.c:1527
hrtimer_interrupt+0x326/0x9e0 kernel/time/hrtimer.c:1585
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1071 [inline]
smp_apic_timer_interrupt+0x10c/0x550 arch/x86/kernel/apic/apic.c:1096
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
</IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:97
Code: ff 48 89 df e8 11 dd 35 00 e9 ab fe ff ff 4c 89 ef e8 04 dd 35 00 e9 23 fe ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <48> 8b 34 24 65 48 8b 04 25 c0 df 01 00 65 8b 15 cc 59 9f 7e 81 e2
RSP: 0018:ffff8880515df240 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000002 RBX: 0000000000000001 RCX: ffffffff83771e23
RDX: 0000000000000001 RSI: ffff8880947a2300 RDI: 0000000000000005
RBP: ffffffff88b3e120 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff88b3e0e0 R14: dffffc0000000000 R15: 0000000000000000
check_preemption_disabled+0x3c/0x280 lib/smp_processor_id.c:25
__pv_queued_spin_lock_slowpath+0xe2/0xae0 kernel/locking/qspinlock.c:389
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:679 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:53 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:88 [inline]
do_raw_spin_lock+0x189/0x220 kernel/locking/spinlock_debug.c:113
spin_lock include/linux/spinlock.h:329 [inline]
ext4_lock_group fs/ext4/ext4.h:3022 [inline]
ext4_mb_discard_group_preallocations+0xada/0x12c0 fs/ext4/mballoc.c:3943
ext4_mb_discard_preallocations fs/ext4/mballoc.c:4478 [inline]
ext4_mb_new_blocks+0x1d1d/0x4370 fs/ext4/mballoc.c:4593
ext4_ext_map_blocks+0x2aa2/0x7390 fs/ext4/extents.c:4493
ext4_map_blocks+0x7a2/0x1a50 fs/ext4/inode.c:657
ext4_alloc_file_blocks.isra.0+0x2ca/0xa70 fs/ext4/extents.c:4720
ext4_fallocate+0x7cf/0x2150 fs/ext4/extents.c:5005
vfs_fallocate+0x487/0x9a0 fs/open.c:308
ioctl_preallocate+0x186/0x200 fs/ioctl.c:482
file_ioctl fs/ioctl.c:498 [inline]
do_vfs_ioctl+0x1060/0x12e0 fs/ioctl.c:688
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7ff2e4b77209
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff2e34cb168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff2e4c8a030 RCX: 00007ff2e4b77209
RDX: 0000000020000040 RSI: 000000004030582a RDI: 0000000000000005
RBP: 00007ff2e4bd1161 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd4c88ccef R14: 00007ff2e34cb300 R15: 0000000000022000
rcu: rcu_preempt kthread starved for 10553 jiffies! g121001 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 29208 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
schedule_timeout+0x4cf/0xfe0 kernel/time/timer.c:1818
rcu_gp_kthread+0xdad/0x21c0 kernel/rcu/tree.c:2202
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.