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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff86eeace0 of 4 bytes by interrupt on cpu 0:
 fprop_new_period+0xaa/0xe0 lib/flex_proportions.c:79
 writeout_period+0x59/0xe0 mm/page-writeback.c:613
 call_timer_fn+0x35/0x290 kernel/time/timer.c:1700
 expire_timers kernel/time/timer.c:1751 [inline]
 __run_timers+0x46c/0x650 kernel/time/timer.c:2022
 run_timer_softirq+0x31/0x40 kernel/time/timer.c:2037
 __do_softirq+0xc1/0x265 kernel/softirq.c:553
 invoke_softirq kernel/softirq.c:427 [inline]
 __irq_exit_rcu kernel/softirq.c:632 [inline]
 irq_exit_rcu+0x3b/0x90 kernel/softirq.c:644
 sysvec_apic_timer_interrupt+0x6d/0x80 arch/x86/kernel/apic/apic.c:1074
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x3d/0x50 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 rmqueue_bulk mm/page_alloc.c:2154 [inline]
 __rmqueue_pcplist+0x9c5/0xb30 mm/page_alloc.c:2698
 rmqueue_pcplist mm/page_alloc.c:2740 [inline]
 rmqueue mm/page_alloc.c:2777 [inline]
 get_page_from_freelist+0x3db/0x13c0 mm/page_alloc.c:3167
 __alloc_pages+0x193/0x340 mm/page_alloc.c:4426
 alloc_pages+0x3e1/0x4e0
 folio_alloc+0x1e/0x30 mm/mempolicy.c:2308
 filemap_alloc_folio+0x68/0x220 mm/filemap.c:976
 __filemap_get_folio+0x2ca/0x500 mm/filemap.c:1936
 ext4_da_write_begin+0x2eb/0x550 fs/ext4/inode.c:2881
 generic_perform_write+0x1c9/0x410 mm/filemap.c:3969
 ext4_buffered_write_iter+0x1f6/0x370 fs/ext4/file.c:299
 ext4_file_write_iter+0xd6/0x1200
 __kernel_write_iter+0x162/0x3c0 fs/read_write.c:517
 dump_emit_page fs/coredump.c:888 [inline]
 dump_user_range+0x25d/0x480 fs/coredump.c:915
 elf_core_dump+0x1a85/0x1ba0 fs/binfmt_elf.c:2142
 do_coredump+0x1029/0x1890 fs/coredump.c:764
 get_signal+0xda3/0x1090 kernel/signal.c:2878
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff86eeace0 of 4 bytes by task 1550 on cpu 1:
 fprop_reflect_period_percpu+0x22/0x1a0 lib/flex_proportions.c:188
 __fprop_add_percpu lib/flex_proportions.c:219 [inline]
 __fprop_add_percpu_max+0x58/0x180 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+0x264/0x4f0 mm/page-writeback.c:2964
 folio_end_writeback+0x5b/0x150 mm/filemap.c:1613
 ext4_finish_bio+0x45c/0x8c0 fs/ext4/page-io.c:145
 ext4_release_io_end+0x8c/0x1e0 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+0x2d3/0x360 fs/ext4/page-io.c:273
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

value changed: 0x0000003b -> 0x0000003c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1550 Comm: kworker/u4:5 Not tainted 6.6.0-rc3-syzkaller-00044-g633b47cb009d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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