syzbot

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BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

read-write to 0xffff888102315148 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
 end_buffer_async_write+0x156/0x1f0 fs/buffer.c:419
 end_bio_bh_io_sync+0x76/0xa0 fs/buffer.c:2776
 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+0x74/0xb0 block/blk-mq.c:1231
 handle_softirqs+0xba/0x290 kernel/softirq.c:579
 do_softirq+0x5d/0x90 kernel/softirq.c:480
 __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:407
 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline]
 _raw_spin_unlock_bh+0x36/0x40 kernel/locking/spinlock.c:210
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 batadv_nc_purge_paths+0x22b/0x270 net/batman-adv/network-coding.c:471
 batadv_nc_worker+0x3d8/0xae0 net/batman-adv/network-coding.c:720
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888102315148 of 8 bytes by task 10369 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+0x54/0x80 mm/page-writeback.c:1536
 wb_update_bandwidth_workfn+0x1c/0x30 mm/backing-dev.c:507
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x000000000000c0f0 -> 0x000000000000c110

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10369 Comm: kworker/u8:53 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Workqueue: writeback wb_update_bandwidth_workfn
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