syzbot

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BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

read-write to 0xffff8881011ff948 of 8 bytes by task 36 on cpu 0:
 percpu_counter_add_batch+0xc9/0x140 lib/percpu_counter.c:96
 wb_stat_mod include/linux/backing-dev.h:66 [inline]
 __wb_writeout_add+0x45/0x1d0 mm/page-writeback.c:583
 __folio_end_writeback+0x215/0x4a0 mm/page-writeback.c:3042
 folio_end_writeback+0x74/0x1f0 mm/filemap.c:1632
 ext4_finish_bio+0x476/0x8e0 fs/ext4/page-io.c:144
 ext4_release_io_end+0x8c/0x1f0 fs/ext4/page-io.c:159
 ext4_end_io_end fs/ext4/page-io.c:193 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:258 [inline]
 ext4_end_io_rsv_work+0x2d3/0x370 fs/ext4/page-io.c:272
 process_one_work kernel/workqueue.c:3248 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3329
 worker_thread+0x526/0x720 kernel/workqueue.c:3409
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff8881011ff948 of 8 bytes by task 3829 on cpu 1:
 percpu_counter_read include/linux/percpu_counter.h:110 [inline]
 __wb_update_bandwidth+0x9b/0x5d0 mm/page-writeback.c:1484
 wb_update_bandwidth mm/page-writeback.c:1511 [inline]
 do_writepages+0x443/0x480 mm/page-writeback.c:2660
 filemap_fdatawrite_wbc+0xdb/0x100 mm/filemap.c:397
 __filemap_fdatawrite_range mm/filemap.c:430 [inline]
 __filemap_fdatawrite mm/filemap.c:436 [inline]
 filemap_flush+0x61/0x90 mm/filemap.c:463
 ext4_alloc_da_blocks+0x50/0x130 fs/ext4/inode.c:3069
 ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:169
 __fput+0x192/0x6f0 fs/file_table.c:422
 ____fput+0x15/0x20 fs/file_table.c:450
 task_work_run+0x13a/0x1a0 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x5d5/0x1710 kernel/exit.c:874
 do_group_exit+0x102/0x150 kernel/exit.c:1023
 get_signal+0xf2f/0x1080 kernel/signal.c:2909
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000097d0 -> 0x00000000000097e0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3829 Comm: syz.2.218 Not tainted 6.10.0-rc6-syzkaller-00041-g9903efbddba0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
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