KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0fa8ee0d Merge branch 'for-linus' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=101308f2500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e9a6e9171a00e85a
dashboard link: https://syzkaller.appspot.com/bug?extid=7a110c0628ede1f0e1b0
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org]

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+7a110c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff8830b820 of 4 bytes by interrupt on cpu 0:
fprop_new_period+0xd7/0x130 lib/flex_proportions.c:83
writeout_period+0x55/0xe0 mm/page-writeback.c:628
call_timer_fn+0x2e/0x240 kernel/time/timer.c:1410
expire_timers+0x116/0x260 kernel/time/timer.c:1455
__run_timers+0x338/0x3d0 kernel/time/timer.c:1747
run_timer_softirq+0x2d/0x30 kernel/time/timer.c:1762
__do_softirq+0x12c/0x2b1 kernel/softirq.c:298
run_ksoftirqd+0x13/0x20 kernel/softirq.c:653
smpboot_thread_fn+0x34f/0x520 kernel/smpboot.c:165
kthread+0x1fa/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffffffff8830b820 of 4 bytes by task 8 on cpu 1:
fprop_reflect_period_percpu+0x22/0x1a0 lib/flex_proportions.c:192
__fprop_inc_percpu+0x1a/0x80 lib/flex_proportions.c:222
__fprop_inc_percpu_max+0x3f/0x190 lib/flex_proportions.c:271
wb_domain_writeout_inc mm/page-writeback.c:575 [inline]
__wb_writeout_inc+0x54/0x1a0 mm/page-writeback.c:599
test_clear_page_writeback+0x2fa/0x450 mm/page-writeback.c:2745
end_page_writeback+0xa7/0x110 mm/filemap.c:1487
ext4_finish_bio+0x429/0x490 fs/ext4/page-io.c:146
ext4_release_io_end+0x98/0x200 fs/ext4/page-io.c:161
ext4_end_io_end fs/ext4/page-io.c:195 [inline]
ext4_do_flush_completed_IO fs/ext4/page-io.c:260 [inline]
ext4_end_io_rsv_work+0x306/0x360 fs/ext4/page-io.c:274
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
worker_thread+0x635/0xb90 kernel/workqueue.c:2418
kthread+0x1fa/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8 Comm: kworker/u4:0 Not tainted 5.10.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
==================================================================


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[syzbot]

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