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BUG: KCSAN: data-race in balance_dirty_pages / percpu_counter_add_batch

write to 0xffff8880b5c34490 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+0x4d1/0x790 mm/page-writeback.c:2736
 end_page_writeback+0x9e/0x190 mm/filemap.c:1339
 ext4_finish_bio+0x40d/0x520 fs/ext4/page-io.c:110
 ext4_end_bio+0xd2/0x310 fs/ext4/page-io.c:334
 bio_endio+0x3a8/0x4f0 block/bio.c:1818
 req_bio_endio block/blk-core.c:242 [inline]
 blk_update_request+0x427/0x7b0 block/blk-core.c:1462
 scsi_end_request+0x6b/0x3e0 drivers/scsi/scsi_lib.c:579
 scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:963
 scsi_finish_command+0x280/0x380 drivers/scsi/scsi.c:228
 scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1477
 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+0xa6/0x180 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x19
 constant_test_bit+0x1c/0x30 arch/x86/include/asm/bitops.h:211
 test_bit include/asm-generic/bitops-instrumented.h:255 [inline]
 mapping_use_writeback_tags include/linux/pagemap.h:97 [inline]
 __test_set_page_writeback+0x64/0x7d0 mm/page-writeback.c:2770
 set_page_writeback include/linux/page-flags.h:542 [inline]
 ext4_bio_write_page+0x157/0xb90 fs/ext4/page-io.c:424
 mpage_submit_page+0xeb/0x170 fs/ext4/inode.c:2222
 mpage_map_and_submit_buffers+0x331/0x520 fs/ext4/inode.c:2422
 mpage_map_and_submit_extent fs/ext4/inode.c:2556 [inline]
 ext4_writepages+0x1458/0x2300 fs/ext4/inode.c:2869
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __writeback_single_inode+0xaf/0x8e0 fs/fs-writeback.c:1449
 writeback_sb_inodes+0x4ba/0xa50 fs/fs-writeback.c:1713
 __writeback_inodes_wb+0xe8/0x1b0 fs/fs-writeback.c:1782
 wb_writeback+0x557/0x6a0 fs/fs-writeback.c:1891
 wb_check_background_flush fs/fs-writeback.c:1959 [inline]
 wb_do_writeback fs/fs-writeback.c:2047 [inline]
 wb_workfn+0x696/0x970 fs/fs-writeback.c:2075
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880b5c34490 of 8 bytes by task 18692 on cpu 0:
 wb_stat include/linux/backing-dev.h:88 [inline]
 wb_dirty_limits mm/page-writeback.c:1550 [inline]
 balance_dirty_pages+0x1247/0x1ba0 mm/page-writeback.c:1693
 balance_dirty_pages_ratelimited+0x752/0xb40 mm/page-writeback.c:1913
 generic_perform_write+0x22d/0x320 mm/filemap.c:3341
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3434
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [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/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18692 Comm: syz-executor.0 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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