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BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

write to 0xffff888102919140 of 8 bytes by task 1842 on cpu 0:
 percpu_counter_add_batch+0xb4/0x130 lib/percpu_counter.c:91
 wb_stat_mod include/linux/backing-dev.h:70 [inline]
 __wb_writeout_add mm/page-writeback.c:592 [inline]
 __folio_end_writeback+0x274/0x580 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

read to 0xffff888102919140 of 8 bytes by task 6238 on cpu 1:
 percpu_counter_read include/linux/percpu_counter.h:72 [inline]
 __wb_update_bandwidth+0x9f/0x420 mm/page-writeback.c:1353
 wb_update_bandwidth mm/page-writeback.c:1380 [inline]
 do_writepages+0x306/0x330 mm/page-writeback.c:2386
 filemap_fdatawrite_wbc mm/filemap.c:407 [inline]
 __filemap_fdatawrite_range mm/filemap.c:440 [inline]
 __filemap_fdatawrite mm/filemap.c:446 [inline]
 filemap_flush+0xd7/0x100 mm/filemap.c:473
 ext4_release_file+0x4b/0x160 fs/ext4/file.c:141
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x160/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xd0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000019f60 -> 0x0000000000019f80

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6238 Comm: syz-executor.2 Not tainted 5.16.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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