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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff86eff0c0 of 4 bytes by interrupt on cpu 1:
 fprop_new_period+0xa6/0xd0 lib/flex_proportions.c:79
 writeout_period+0x55/0xe0 mm/page-writeback.c:613
 call_timer_fn+0x2e/0x240 kernel/time/timer.c:1700
 expire_timers+0x11f/0x260 kernel/time/timer.c:1751
 __run_timers+0x350/0x400 kernel/time/timer.c:2022
 run_timer_softirq+0x56/0x60 kernel/time/timer.c:2037
 __do_softirq+0xf2/0x2c7 kernel/softirq.c:571
 __irq_exit_rcu kernel/softirq.c:650 [inline]
 irq_exit_rcu+0x41/0x70 kernel/softirq.c:662
 sysvec_apic_timer_interrupt+0x8d/0xb0 arch/x86/kernel/apic/apic.c:1107
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649
 kcsan_setup_watchpoint+0x3e9/0x3f0 kernel/kcsan/core.c:696
 __fput+0x26/0x570 fs/file_table.c:296
 ____fput+0x11/0x20 fs/file_table.c:348
 task_work_run+0xde/0x110 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x124/0x130 kernel/entry/common.c:171
 exit_to_user_mode_prepare kernel/entry/common.c:203 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x6a/0x90 kernel/entry/common.c:296
 do_syscall_64+0x37/0x70 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff86eff0c0 of 4 bytes by task 4745 on cpu 0:
 fprop_reflect_period_percpu+0x22/0x1a0 lib/flex_proportions.c:188
 __fprop_add_percpu lib/flex_proportions.c:219 [inline]
 __fprop_add_percpu_max+0x54/0x180 lib/flex_proportions.c:277
 wb_domain_writeout_add mm/page-writeback.c:560 [inline]
 __wb_writeout_add+0x7e/0x1d0 mm/page-writeback.c:584
 __folio_end_writeback+0x246/0x4d0 mm/page-writeback.c:3044
 folio_end_writeback+0x57/0x130 mm/filemap.c:1614
 end_page_writeback+0x3b/0xe0 mm/folio-compat.c:26
 ext4_finish_bio+0x421/0x520 fs/ext4/page-io.c:145
 ext4_release_io_end+0x98/0x200 fs/ext4/page-io.c:160
 ext4_end_io_end fs/ext4/page-io.c:194 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:259 [inline]
 ext4_end_io_rsv_work+0x319/0x3a0 fs/ext4/page-io.c:273
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x0000016f -> 0x00000170

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4745 Comm: kworker/u4:1 Not tainted 6.2.0-rc1-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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