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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff870d75c0 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:612
 call_timer_fn+0x2e/0x240 kernel/time/timer.c:1474
 expire_timers+0x116/0x240 kernel/time/timer.c:1519
 __run_timers+0x350/0x400 kernel/time/timer.c:1790
 run_timer_softirq+0x56/0x60 kernel/time/timer.c:1805
 __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
 __sanitizer_cov_trace_switch+0x50/0x100
 xas_retry include/linux/xarray.h:1506 [inline]
 find_get_entry mm/filemap.c:2007 [inline]
 find_lock_entries+0xb2/0x4b0 mm/filemap.c:2095
 truncate_inode_pages_range+0x118/0x870 mm/truncate.c:364
 truncate_inode_pages mm/truncate.c:452 [inline]
 truncate_inode_pages_final+0x54/0x60 mm/truncate.c:487
 ext4_evict_inode+0x27c/0xe90 fs/ext4/inode.c:221
 evict+0x1aa/0x410 fs/inode.c:664
 iput_final fs/inode.c:1747 [inline]
 iput+0x3f9/0x580 fs/inode.c:1773
 dentry_unlink_inode+0x22a/0x240 fs/dcache.c:401
 __dentry_kill+0x28b/0x450 fs/dcache.c:607
 dentry_kill+0x8d/0x1e0
 dput+0x11e/0x1f0 fs/dcache.c:913
 __fput+0x3bf/0x570 fs/file_table.c:328
 ____fput+0x11/0x20 fs/file_table.c:348
 task_work_run+0xde/0x110 kernel/task_work.c:179
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x5ad/0x1740 kernel/exit.c:820
 do_group_exit+0xfe/0x140 kernel/exit.c:950
 get_signal+0xb40/0xc60 kernel/signal.c:2858
 arch_do_signal_or_restart+0x87/0x2d0 arch/x86/kernel/signal.c:869
 exit_to_user_mode_loop+0x78/0x130 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x69/0x90 kernel/entry/common.c:203
 irqentry_exit_to_user_mode+0x5/0x10 kernel/entry/common.c:309
 irqentry_exit+0xe/0x40 kernel/entry/common.c:412
 exc_general_protection+0x321/0x4b0 arch/x86/kernel/traps.c:728
 asm_exc_general_protection+0x22/0x30 arch/x86/include/asm/idtentry.h:564

read to 0xffffffff870d75c0 of 4 bytes by task 8324 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:559 [inline]
 __wb_writeout_add+0x7e/0x1d0 mm/page-writeback.c:583
 __folio_end_writeback+0x246/0x4d0 mm/page-writeback.c:2932
 folio_end_writeback+0x57/0x130 mm/filemap.c:1613
 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:306

value changed: 0x00000083 -> 0x00000084

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8324 Comm: kworker/u4:21 Not tainted 6.1.0-rc7-syzkaller-00123-ga4412fdd49dc-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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