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BUG: KCSAN: data-race in wq_worker_tick / wq_worker_tick

read-write to 0xffff8881001e0eb8 of 8 bytes by interrupt on cpu 1:
 wq_worker_tick+0x63/0x240 kernel/workqueue.c:1474
 sched_tick+0x116/0x260 kernel/sched/core.c:5677
 update_process_times+0x161/0x190 kernel/time/timer.c:2520
 tick_sched_handle kernel/time/tick-sched.c:276 [inline]
 tick_nohz_handler+0x250/0x2d0 kernel/time/tick-sched.c:297
 __run_hrtimer kernel/time/hrtimer.c:1791 [inline]
 __hrtimer_run_queues+0x221/0x5f0 kernel/time/hrtimer.c:1855
 hrtimer_interrupt+0x235/0x4a0 kernel/time/hrtimer.c:1917
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x5c/0x1d0 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0x6e/0x80 arch/x86/kernel/apic/apic.c:1049
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
 __sanitizer_cov_trace_pc+0x8/0x70 kernel/kcov.c:213
 ext4_ext_index_trans_blocks+0x15/0xc0 fs/ext4/extents.c:2397
 ext4_index_trans_blocks fs/ext4/inode.c:5733 [inline]
 ext4_meta_trans_blocks fs/ext4/inode.c:5759 [inline]
 ext4_da_writepages_trans_blocks fs/ext4/inode.c:2359 [inline]
 ext4_do_writepages+0x8e5/0x21d0 fs/ext4/inode.c:2718
 ext4_writepages+0x183/0x320 fs/ext4/inode.c:2828
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2656
 __writeback_single_inode+0x89/0x850 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x458/0xa10 fs/fs-writeback.c:1976
 wb_writeback+0x264/0x650 fs/fs-writeback.c:2156
 wb_do_writeback fs/fs-writeback.c:2303 [inline]
 wb_workfn+0x1aa/0x960 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4de/0xa20 kernel/workqueue.c:3319
 worker_thread+0x52c/0x710 kernel/workqueue.c:3400
 kthread+0x4b7/0x540 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read-write to 0xffff8881001e0eb8 of 8 bytes by interrupt on cpu 0:
 wq_worker_tick+0x63/0x240 kernel/workqueue.c:1474
 sched_tick+0x116/0x260 kernel/sched/core.c:5677
 update_process_times+0x161/0x190 kernel/time/timer.c:2520
 tick_sched_handle kernel/time/tick-sched.c:276 [inline]
 tick_nohz_handler+0x250/0x2d0 kernel/time/tick-sched.c:297
 __run_hrtimer kernel/time/hrtimer.c:1791 [inline]
 __hrtimer_run_queues+0x221/0x5f0 kernel/time/hrtimer.c:1855
 hrtimer_interrupt+0x235/0x4a0 kernel/time/hrtimer.c:1917
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x5c/0x1d0 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0x6e/0x80 arch/x86/kernel/apic/apic.c:1049
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
 __sanitizer_cov_trace_pc+0x0/0x70
 arch_static_branch arch/x86/include/asm/jump_label.h:36 [inline]
 page_fixed_fake_head include/linux/page-flags.h:206 [inline]
 page_is_fake_head include/linux/page-flags.h:238 [inline]
 page_ref_add_unless include/linux/page_ref.h:237 [inline]
 folio_ref_add_unless include/linux/page_ref.h:248 [inline]
 folio_try_get include/linux/page_ref.h:264 [inline]
 find_get_entry+0xc5/0x390 mm/filemap.c:2039
 filemap_get_folios_tag+0x13e/0x220 mm/filemap.c:2294
 mpage_prepare_extent_to_map+0x332/0xb80 fs/ext4/inode.c:2452
 ext4_do_writepages+0xa3b/0x21d0 fs/ext4/inode.c:2736
 ext4_writepages+0x183/0x320 fs/ext4/inode.c:2828
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2656
 __writeback_single_inode+0x89/0x850 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x458/0xa10 fs/fs-writeback.c:1976
 wb_writeback+0x264/0x650 fs/fs-writeback.c:2156
 wb_do_writeback fs/fs-writeback.c:2303 [inline]
 wb_workfn+0x1aa/0x960 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4de/0xa20 kernel/workqueue.c:3319
 worker_thread+0x52c/0x710 kernel/workqueue.c:3400
 kthread+0x4b7/0x540 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x000000000fd77b20 -> 0x000000000fd7a230

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10455 Comm: kworker/u8:53 Not tainted 6.14.0-syzkaller-12508-g92b71befc349 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: writeback wb_workfn (flush-7:5)
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