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BUG: KCSAN: data-race in __folio_end_writeback / writeout_period

write to 0xffffffff86dc4130 of 8 bytes by interrupt on cpu 1:
 writeout_period+0xa6/0xe0 mm/page-writeback.c:623
 call_timer_fn+0x2e/0x240 kernel/time/timer.c:1421
 expire_timers+0x116/0x240 kernel/time/timer.c:1466
 __run_timers+0x368/0x410 kernel/time/timer.c:1734
 run_timer_softirq+0x56/0x60 kernel/time/timer.c:1749
 __do_softirq+0x158/0x2de kernel/softirq.c:558
 __irq_exit_rcu kernel/softirq.c:637 [inline]
 irq_exit_rcu+0x37/0x70 kernel/softirq.c:649
 sysvec_apic_timer_interrupt+0x8d/0xb0 arch/x86/kernel/apic/apic.c:1097
 asm_sysvec_apic_timer_interrupt+0x12/0x20
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
 _raw_spin_unlock_irq+0x2a/0x50 kernel/locking/spinlock.c:202
 spin_unlock_irq include/linux/spinlock.h:399 [inline]
 __filemap_add_folio+0x2ca/0x4d0 mm/filemap.c:952
 filemap_add_folio+0x6b/0x150 mm/filemap.c:999
 __filemap_get_folio+0x4c4/0x690 mm/filemap.c:1962
 pagecache_get_page+0x26/0xe0 mm/folio-compat.c:125
 grab_cache_page_write_begin+0x3f/0x50 mm/folio-compat.c:139
 ext4_da_write_begin+0x292/0x4b0 fs/ext4/inode.c:2958
 generic_perform_write+0x1c8/0x400 mm/filemap.c:3754
 ext4_buffered_write_iter+0x196/0x290 fs/ext4/file.c:269
 ext4_file_write_iter+0x22b/0xdc0
 call_write_iter include/linux/fs.h:2162 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:725
 do_iter_write+0x192/0x5c0 fs/read_write.c:851
 vfs_iter_write+0x4c/0x70 fs/read_write.c:892
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x675/0xc40 fs/read_write.c:1245
 __do_sys_sendfile64 fs/read_write.c:1310 [inline]
 __se_sys_sendfile64 fs/read_write.c:1296 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1296
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff86dc4130 of 8 bytes by task 29234 on cpu 0:
 wb_domain_writeout_add mm/page-writeback.c:572 [inline]
 __wb_writeout_add mm/page-writeback.c:593 [inline]
 __folio_end_writeback+0x2b3/0x580 mm/page-writeback.c:2821
 folio_end_writeback+0x57/0x130 mm/filemap.c:1605
 end_page_writeback+0x37/0x50 mm/folio-compat.c:25
 ext4_finish_bio+0x30e/0x360 fs/ext4/page-io.c:143
 ext4_release_io_end+0x5f/0x140 fs/ext4/page-io.c:158
 ext4_end_io_end fs/ext4/page-io.c:192 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:257 [inline]
 ext4_end_io_rsv_work+0x1f6/0x240 fs/ext4/page-io.c:271
 process_one_work+0x3fc/0x980 kernel/workqueue.c:2298
 worker_thread+0x616/0xa70 kernel/workqueue.c:2445
 kthread+0x2c7/0x2e0 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30

value changed: 0x000000010000004d -> 0x0000000100000179

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29234 Comm: kworker/u4:23 Not tainted 5.16.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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