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BUG: KCSAN: data-race in balance_dirty_pages / percpu_counter_add_batch

write to 0xffff8880a6f83090 of 8 bytes by interrupt on cpu 1:
 percpu_counter_add_batch+0xca/0x150 lib/percpu_counter.c:91
 __add_wb_stat include/linux/backing-dev.h:73 [inline]
 dec_wb_stat include/linux/backing-dev.h:83 [inline]
 test_clear_page_writeback+0x4d4/0x790 mm/page-writeback.c:2736
 end_page_writeback+0x9e/0x190 mm/filemap.c:1339
 ext4_finish_bio+0x40d/0x520 fs/ext4/page-io.c:148
 ext4_end_bio+0xd2/0x2f0 fs/ext4/page-io.c:370
 bio_endio+0x2fa/0x400 block/bio.c:1821
 req_bio_endio block/blk-core.c:245 [inline]
 blk_update_request+0x427/0x7b0 block/blk-core.c:1464
 scsi_end_request+0x6b/0x360 drivers/scsi/scsi_lib.c:576
 scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:960
 scsi_finish_command+0x283/0x380 drivers/scsi/scsi.c:228
 scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1476
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 do_IRQ+0x81/0x130 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x21
 arch_local_irq_enable arch/x86/include/asm/paravirt.h:762 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:168 [inline]
 _raw_spin_unlock_irq+0x4e/0x80 kernel/locking/spinlock.c:199
 finish_lock_switch kernel/sched/core.c:3124 [inline]
 finish_task_switch+0x7b/0x260 kernel/sched/core.c:3224
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x30e/0x690 kernel/sched/core.c:4081
 schedule+0x4a/0x100 kernel/sched/core.c:4155
 worker_thread+0x1dc/0x800 kernel/workqueue.c:2431
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880a6f83090 of 8 bytes by task 12947 on cpu 0:
 wb_stat include/linux/backing-dev.h:88 [inline]
 wb_dirty_limits mm/page-writeback.c:1550 [inline]
 balance_dirty_pages+0x106d/0x1ba0 mm/page-writeback.c:1677
 balance_dirty_pages_ratelimited+0x703/0xa30 mm/page-writeback.c:1913
 generic_perform_write+0x22d/0x320 mm/filemap.c:3345
 ext4_buffered_write_iter+0x143/0x290 fs/ext4/file.c:252
 ext4_file_write_iter+0xf4/0xd40 fs/ext4/file.c:547
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12947 Comm: syz-executor.3 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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