syzbot

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BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

read-write to 0xffff8881011ee920 of 8 bytes by task 4474 on cpu 0:
 percpu_counter_add_batch+0x120/0x140 lib/percpu_counter.c:107
 wb_stat_mod include/linux/backing-dev.h:66 [inline]
 folio_account_dirtied mm/page-writeback.c:2749 [inline]
 __folio_mark_dirty+0x27f/0x4e0 mm/page-writeback.c:2797
 mark_buffer_dirty+0x134/0x230 fs/buffer.c:1205
 __block_commit_write fs/buffer.c:2199 [inline]
 block_write_end+0x16d/0x300 fs/buffer.c:2275
 ext4_write_end+0x177/0x820 fs/ext4/inode.c:1318
 ext4_da_write_end+0xa8/0x860 fs/ext4/inode.c:3090
 generic_perform_write+0x36e/0x580 mm/filemap.c:4035
 ext4_buffered_write_iter+0x1f6/0x380 fs/ext4/file.c:299
 ext4_file_write_iter+0x29f/0xe30
 do_iter_readv_writev+0x3b0/0x470
 vfs_writev+0x2e0/0x880 fs/read_write.c:971
 do_pwritev fs/read_write.c:1072 [inline]
 __do_sys_pwritev2 fs/read_write.c:1131 [inline]
 __se_sys_pwritev2+0x10c/0x1d0 fs/read_write.c:1122
 __x64_sys_pwritev2+0x78/0x90 fs/read_write.c:1122
 x64_sys_call+0x271f/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:329
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881011ee920 of 8 bytes by task 3282 on cpu 1:
 percpu_counter_read include/linux/percpu_counter.h:110 [inline]
 __wb_update_bandwidth+0x83/0x5d0 mm/page-writeback.c:1528
 wb_update_bandwidth+0x55/0x80 mm/page-writeback.c:1556
 wb_update_bandwidth_workfn+0x1c/0x30 mm/backing-dev.c:507
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x6e0 kernel/workqueue.c:3389
 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

value changed: 0x0000000000000030 -> 0x0000000000000040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3282 Comm: kworker/u8:6 Not tainted 6.11.0-rc5-syzkaller-00015-g3e9bff3bbe13 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: writeback wb_update_bandwidth_workfn
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