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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff86ef9d80 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+0x37/0x2f0 kernel/time/timer.c:1700
 expire_timers kernel/time/timer.c:1751 [inline]
 __run_timers+0x448/0x630 kernel/time/timer.c:2038
 run_timer_softirq+0x31/0x40 kernel/time/timer.c:2053
 __do_softirq+0xc4/0x279 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:1076
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:649
 kcsan_setup_watchpoint+0x3fe/0x410 kernel/kcsan/core.c:705
 security_sid_to_context_core+0x49/0x2f0 security/selinux/ss/services.c:1320
 security_sid_to_context_force+0x2a/0x30 security/selinux/ss/services.c:1399
 selinux_inode_init_security+0x3f8/0x490 security/selinux/hooks.c:2949
 security_inode_init_security+0x124/0x290 security/security.c:1732
 ext4_init_security+0x34/0x40 fs/ext4/xattr_security.c:58
 __ext4_new_inode+0x2004/0x2270 fs/ext4/ialloc.c:1326
 ext4_symlink+0x242/0x590 fs/ext4/namei.c:3396
 vfs_symlink+0xc2/0x1a0 fs/namei.c:4470
 do_symlinkat+0xe3/0x340 fs/namei.c:4496
 __do_sys_symlinkat fs/namei.c:4512 [inline]
 __se_sys_symlinkat fs/namei.c:4509 [inline]
 __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4509
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffffffff86ef9d80 of 4 bytes by task 14603 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+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+0x21b/0x4a0 mm/page-writeback.c:2963
 folio_end_writeback+0x74/0x1f0 mm/filemap.c:1599
 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:2633 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2706
 worker_thread+0x525/0x730 kernel/workqueue.c:2787
 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:242

value changed: 0x00000099 -> 0x0000009a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 14603 Comm: kworker/u4:18 Not tainted 6.7.0-syzkaller-06264-g70d201a40823 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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