syzbot

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BUG: KCSAN: data-race in fprop_reflect_period_percpu / fprop_reflect_period_percpu

write to 0xffff888101ace9c0 of 4 bytes by task 3872 on cpu 1:
 fprop_reflect_period_percpu+0x17c/0x1a0 lib/flex_proportions.c:211
 fprop_fraction_percpu+0x98/0x150 lib/flex_proportions.c:233
 __wb_calc_thresh mm/page-writeback.c:872 [inline]
 wb_calc_thresh mm/page-writeback.c:892 [inline]
 wb_over_bg_thresh+0x1f8/0x750 mm/page-writeback.c:2098
 wb_check_background_flush fs/fs-writeback.c:2126 [inline]
 wb_do_writeback fs/fs-writeback.c:2224 [inline]
 wb_workfn+0x643/0x8d0 fs/fs-writeback.c:2251
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2405
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2552
 kthread+0x1d7/0x210 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

read to 0xffff888101ace9c0 of 4 bytes by interrupt on cpu 0:
 fprop_reflect_period_percpu+0x32/0x1a0 lib/flex_proportions.c:192
 __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+0x26f/0x500 mm/page-writeback.c:2983
 folio_end_writeback+0x5b/0x150 mm/filemap.c:1618
 ext4_finish_bio+0x3f2/0x870 fs/ext4/page-io.c:145
 ext4_end_bio+0x189/0x2b0
 bio_endio+0x35f/0x400 block/bio.c:1608
 req_bio_endio block/blk-mq.c:761 [inline]
 blk_update_request+0x41c/0x950 block/blk-mq.c:906
 blk_mq_end_request+0x31/0x1e0 block/blk-mq.c:1023
 lo_complete_rq+0xce/0x160 drivers/block/loop.c:370
 blk_complete_reqs block/blk-mq.c:1101 [inline]
 blk_done_softirq+0x73/0xa0 block/blk-mq.c:1106
 __do_softirq+0xc1/0x265 kernel/softirq.c:571
 run_ksoftirqd+0x17/0x20 kernel/softirq.c:939
 smpboot_thread_fn+0x30a/0x4a0 kernel/smpboot.c:164
 kthread+0x1d7/0x210 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x0000022d -> 0x0000022e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 6.4.0-rc4-syzkaller-00031-g8b817fded42d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
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