syzbot

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BUG: KCSAN: data-race in __wb_writeout_add / writeout_period

write to 0xffffffff86ea3420 of 8 bytes by interrupt on cpu 0:
 writeout_period+0xa6/0xe0 mm/page-writeback.c:613
 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+0x158/0x2e3 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:1106
 asm_sysvec_apic_timer_interrupt+0x1b/0x20
 kcsan_setup_watchpoint+0x3e9/0x3f0 kernel/kcsan/core.c:694
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:406 [inline]
 batadv_nc_worker+0x78/0xc00 net/batman-adv/network-coding.c:719
 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

read to 0xffffffff86ea3420 of 8 bytes by task 18682 on cpu 1:
 wb_domain_writeout_add mm/page-writeback.c:562 [inline]
 __wb_writeout_add+0x8a/0x1d0 mm/page-writeback.c:583
 __folio_end_writeback+0x2f4/0x540 mm/page-writeback.c:2902
 folio_end_writeback+0x57/0x130 mm/filemap.c:1646
 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

value changed: 0x0000000100014496 -> 0x00000001000145c2

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18682 Comm: kworker/u4:10 Not tainted 5.19.0-rc4-syzkaller-00219-g20855e4cb361-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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