syzbot

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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

write to 0xffffffff86dea2b0 of 4 bytes by interrupt on cpu 0:
 fprop_new_period+0x113/0x190 lib/flex_proportions.c:83
 writeout_period+0x55/0xe0 mm/page-writeback.c:622
 call_timer_fn+0x2e/0x240 kernel/time/timer.c:1421
 expire_timers+0x116/0x240 kernel/time/timer.c:1466
 __run_timers+0x368/0x410 kernel/time/timer.c:1734
 run_timer_softirq+0x56/0x60 kernel/time/timer.c:1749
 __do_softirq+0x158/0x2de kernel/softirq.c:558
 run_ksoftirqd+0x1f/0x30 kernel/softirq.c:921
 smpboot_thread_fn+0x308/0x4a0 kernel/smpboot.c:164
 kthread+0x1bf/0x1e0 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30

read to 0xffffffff86dea2b0 of 4 bytes by task 1851 on cpu 1:
 fprop_reflect_period_percpu+0x22/0x1a0 lib/flex_proportions.c:192
 __fprop_add_percpu lib/flex_proportions.c:223 [inline]
 __fprop_add_percpu_max+0x42/0x250 lib/flex_proportions.c:281
 wb_domain_writeout_add mm/page-writeback.c:569 [inline]
 __wb_writeout_add mm/page-writeback.c:593 [inline]
 __folio_end_writeback+0x2a7/0x580 mm/page-writeback.c:2825
 folio_end_writeback+0x57/0x130 mm/filemap.c:1644
 end_page_writeback+0x37/0x50 mm/folio-compat.c:25
 ext4_finish_bio+0x30e/0x360 fs/ext4/page-io.c:143
 ext4_release_io_end+0x5f/0x140 fs/ext4/page-io.c:158
 ext4_end_io_end fs/ext4/page-io.c:192 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:257 [inline]
 ext4_end_io_rsv_work+0x1f6/0x240 fs/ext4/page-io.c:271
 process_one_work+0x3f6/0x960 kernel/workqueue.c:2307
 worker_thread+0x616/0xa70 kernel/workqueue.c:2454
 kthread+0x1bf/0x1e0 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30

value changed: 0x00000015 -> 0x00000016

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1851 Comm: kworker/u4:5 Not tainted 5.17.0-rc5-syzkaller-00189-g53ab78cd6d5a-dirty #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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