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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff88402f38 of 4 bytes by interrupt on cpu 1:
 fprop_new_period+0xaa/0xe0 lib/flex_proportions.c:79
 writeout_period+0x59/0xe0 mm/page-writeback.c:613
 call_timer_fn+0x3a/0x300 kernel/time/timer.c:1793
 expire_timers kernel/time/timer.c:1844 [inline]
 __run_timers kernel/time/timer.c:2418 [inline]
 __run_timer_base+0x417/0x640 kernel/time/timer.c:2429
 run_timer_base kernel/time/timer.c:2438 [inline]
 run_timer_softirq+0x45/0x70 kernel/time/timer.c:2449
 __do_softirq+0xc8/0x285 kernel/softirq.c:554
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu kernel/softirq.c:633 [inline]
 irq_exit_rcu+0x3c/0x90 kernel/softirq.c:645
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0x73/0x80 arch/x86/kernel/apic/apic.c:1043
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
 _raw_spin_unlock_irq+0x2f/0x50 kernel/locking/spinlock.c:202
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 delete_from_page_cache_batch+0x503/0x710 mm/filemap.c:344
 truncate_inode_pages_range+0x1c5/0x6b0 mm/truncate.c:359
 truncate_inode_pages mm/truncate.c:439 [inline]
 truncate_inode_pages_final+0x55/0x60 mm/truncate.c:474
 ext4_evict_inode+0x174/0xdd0 fs/ext4/inode.c:193
 evict+0x1ae/0x420 fs/inode.c:667
 iput_final fs/inode.c:1741 [inline]
 iput+0x432/0x5c0 fs/inode.c:1767
 do_unlinkat+0x282/0x4c0 fs/namei.c:4406
 __do_sys_unlink fs/namei.c:4447 [inline]
 __se_sys_unlink fs/namei.c:4445 [inline]
 __x64_sys_unlink+0x30/0x40 fs/namei.c:4445
 x64_sys_call+0x286b/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88402f38 of 4 bytes by task 16593 on cpu 0:
 fprop_reflect_period_percpu+0x22/0x1a0 lib/flex_proportions.c:111
 __fprop_add_percpu lib/flex_proportions.c:142 [inline]
 __fprop_add_percpu_max+0x58/0x180 lib/flex_proportions.c:200
 wb_domain_writeout_add mm/page-writeback.c:560 [inline]
 __wb_writeout_add+0x7e/0x1e0 mm/page-writeback.c:584
 __folio_end_writeback+0x21b/0x4a0 mm/page-writeback.c:3017
 folio_end_writeback+0x74/0x1f0 mm/filemap.c:1608
 ext4_finish_bio+0x47b/0x8f0 fs/ext4/page-io.c:145
 ext4_release_io_end+0x8c/0x1f0 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+0x2d3/0x370 fs/ext4/page-io.c:273
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000075 -> 0x00000076

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16593 Comm: kworker/u8:7 Tainted: G        W          6.9.0-rc4-syzkaller-00031-g96fca68c4fbf #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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