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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

write to 0xffffffff87008330 of 4 bytes by interrupt on cpu 1:
 fprop_new_period+0x113/0x190 lib/flex_proportions.c:83
 writeout_period+0x55/0xe0 mm/page-writeback.c:610
 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
 __irq_exit_rcu kernel/softirq.c:637 [inline]
 irq_exit_rcu+0x37/0x70 kernel/softirq.c:649
 sysvec_apic_timer_interrupt+0x8d/0xb0 arch/x86/kernel/apic/apic.c:1097
 asm_sysvec_apic_timer_interrupt+0x12/0x20
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x37/0x60 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:404 [inline]
 __folio_start_writeback+0x407/0x5f0 mm/page-writeback.c:2877
 set_page_writeback+0x3d/0xe0 mm/folio-compat.c:78
 ext4_bio_write_page+0xfd/0x860 fs/ext4/page-io.c:449
 mpage_submit_page fs/ext4/inode.c:2090 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2336 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2475 [inline]
 ext4_writepages+0xe76/0x1a60 fs/ext4/inode.c:2804
 do_writepages+0x1cb/0x330 mm/page-writeback.c:2352
 filemap_fdatawrite_wbc mm/filemap.c:388 [inline]
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0x134/0x1d0 mm/filemap.c:779
 ext4_sync_file+0xad/0x570 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2732 [inline]
 ext4_buffered_write_iter+0x23f/0x280 fs/ext4/file.c:277
 ext4_file_write_iter+0x21a/0xd70
 call_write_iter include/linux/fs.h:2050 [inline]
 new_sync_write fs/read_write.c:504 [inline]
 vfs_write+0x755/0x8b0 fs/read_write.c:591
 ksys_write+0xd9/0x190 fs/read_write.c:644
 __do_sys_write fs/read_write.c:656 [inline]
 __se_sys_write fs/read_write.c:653 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:653
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x50 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff87008330 of 4 bytes by task 2011 on cpu 0:
 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:557 [inline]
 __wb_writeout_add mm/page-writeback.c:581 [inline]
 __folio_end_writeback+0x352/0x630 mm/page-writeback.c:2809
 folio_end_writeback+0x57/0x130 mm/filemap.c:1652
 end_page_writeback+0x3b/0xe0 mm/folio-compat.c:26
 ext4_finish_bio+0x30e/0x3f0 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+0x3e3/0x970 kernel/workqueue.c:2289
 worker_thread+0x638/0xaa0 kernel/workqueue.c:2436
 kthread+0x1bf/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0x00000039 -> 0x0000003a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2011 Comm: kworker/u4:7 Not tainted 5.18.0-rc1-syzkaller-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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