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BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

read-write to 0xffff8881001f7948 of 8 bytes by interrupt on cpu 1:
 percpu_counter_add_batch+0x110/0x130 lib/percpu_counter.c:107
 wb_stat_mod include/linux/backing-dev.h:66 [inline]
 __wb_writeout_add+0x42/0x1b0 mm/page-writeback.c:585
 __folio_end_writeback+0x200/0x470 mm/page-writeback.c:3028
 folio_end_writeback+0x71/0x3d0 mm/filemap.c:1660
 ext4_finish_bio+0x459/0x8c0 fs/ext4/page-io.c:144
 ext4_end_bio+0x298/0x3b0 fs/ext4/page-io.c:-1
 bio_endio+0x37e/0x420 block/bio.c:1651
 blk_update_request+0x336/0x730 block/blk-mq.c:989
 blk_mq_end_request+0x26/0x50 block/blk-mq.c:1151
 lo_complete_rq+0x98/0x140 drivers/block/loop.c:314
 blk_complete_reqs block/blk-mq.c:1226 [inline]
 blk_done_softirq+0x77/0xb0 block/blk-mq.c:1231
 handle_softirqs+0xba/0x290 kernel/softirq.c:622
 run_ksoftirqd+0x1c/0x30 kernel/softirq.c:1063
 smpboot_thread_fn+0x328/0x530 kernel/smpboot.c:160
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881001f7948 of 8 bytes by task 31 on cpu 0:
 percpu_counter_read include/linux/percpu_counter.h:110 [inline]
 __wb_update_bandwidth+0x98/0x5d0 mm/page-writeback.c:1509
 wb_update_bandwidth mm/page-writeback.c:1536 [inline]
 do_writepages+0x2dd/0x310 mm/page-writeback.c:2657
 __writeback_single_inode+0x80/0x7c0 fs/fs-writeback.c:1719
 writeback_sb_inodes+0x48f/0xa30 fs/fs-writeback.c:2015
 wb_writeback+0x252/0x5c0 fs/fs-writeback.c:2195
 wb_do_writeback fs/fs-writeback.c:2342 [inline]
 wb_workfn+0x194/0x910 fs/fs-writeback.c:2382
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000000000000b0 -> 0x00000000000000c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 31 Comm: kworker/u8:1 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: writeback wb_workfn (flush-7:1)
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