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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff86f5a010 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:571
 invoke_softirq kernel/softirq.c:445 [inline]
 __irq_exit_rcu+0x57/0xa0 kernel/softirq.c:650
 sysvec_apic_timer_interrupt+0x6d/0x80 arch/x86/kernel/apic/apic.c:1106
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
 kcsan_setup_watchpoint+0x3fe/0x410 kernel/kcsan/core.c:705
 crc32_body lib/crc32.c:112 [inline]
 crc32_le_generic lib/crc32.c:179 [inline]
 __crc32c_le_base+0x12b/0x520 lib/crc32.c:201
 chksum_update+0x32/0x50 crypto/crc32c_generic.c:88
 crypto_shash_update+0x136/0x1a0 crypto/shash.c:134
 ext4_chksum fs/ext4/ext4.h:2399 [inline]
 ext4_block_bitmap_csum_set+0x13e/0x250 fs/ext4/bitmap.c:91
 ext4_mb_mark_diskspace_used+0x793/0xa90 fs/ext4/mballoc.c:3857
 ext4_mb_new_blocks+0xa2b/0x2100 fs/ext4/mballoc.c:5861
 ext4_ext_map_blocks+0xe1f/0x36c0 fs/ext4/extents.c:4286
 ext4_map_blocks+0x738/0x1050 fs/ext4/inode.c:623
 _ext4_get_block+0x103/0x370 fs/ext4/inode.c:779
 ext4_get_block_unwritten+0x2a/0x30 fs/ext4/inode.c:810
 __block_write_begin_int+0x3b0/0xf50 fs/buffer.c:2064
 __block_write_begin+0x5e/0x110 fs/buffer.c:2114
 ext4_write_begin+0x41e/0xba0
 ext4_da_write_begin+0x1b6/0x550 fs/ext4/inode.c:2893
 generic_perform_write+0x1c3/0x3d0 mm/filemap.c:3929
 ext4_buffered_write_iter+0x234/0x3e0 fs/ext4/file.c:289
 ext4_file_write_iter+0xd7/0x10e0
 __kernel_write_iter+0x15c/0x380 fs/read_write.c:517
 dump_emit_page fs/coredump.c:888 [inline]
 dump_user_range+0x25d/0x490 fs/coredump.c:915
 elf_core_dump+0x1a73/0x1b90 fs/binfmt_elf.c:2142
 do_coredump+0x1029/0x1870 fs/coredump.c:764
 get_signal+0xd65/0xff0 kernel/signal.c:2862
 arch_do_signal_or_restart+0x89/0x2a0 arch/x86/kernel/signal.c:306
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 irqentry_exit_to_user_mode+0x9/0x20 kernel/entry/common.c:310
 irqentry_exit+0x12/0x40 kernel/entry/common.c:413
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

read to 0xffffffff86f5a010 of 4 bytes by task 33 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+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_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+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

value changed: 0x00000015 -> 0x00000016

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 33 Comm: kworker/u4:2 Not tainted 6.4.0-rc6-syzkaller-00269-g1b29d271614a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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