syzbot

EXT4-fs (loop5): mounted filesystem 76b65be2-f6da-4727-8c75-0525a5b65a09 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /49/file1 supports timestamps until 2038-01-19 (0x7fffffff)
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BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

read-write to 0xffff888102159948 of 8 bytes by task 56 on cpu 1:
 percpu_counter_add_batch+0x120/0x140 lib/percpu_counter.c:107
 wb_stat_mod include/linux/backing-dev.h:66 [inline]
 __wb_writeout_add+0x45/0x1d0 mm/page-writeback.c:584
 __folio_end_writeback+0x217/0x4a0 mm/page-writeback.c:3053
 folio_end_writeback+0xcd/0x3d0 mm/filemap.c:1648
 ext4_finish_bio+0x476/0x8f0 fs/ext4/page-io.c:144
 ext4_release_io_end+0x8c/0x1f0 fs/ext4/page-io.c:159
 ext4_end_io_end+0x19c/0x260 fs/ext4/page-io.c:210
 ext4_do_flush_completed_IO fs/ext4/page-io.c:287 [inline]
 ext4_end_io_rsv_work+0x155/0x1e0 fs/ext4/page-io.c:302
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4de/0xa20 kernel/workqueue.c:3319
 worker_thread+0x52c/0x710 kernel/workqueue.c:3400
 kthread+0x4b7/0x540 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888102159948 of 8 bytes by task 4708 on cpu 0:
 percpu_counter_read include/linux/percpu_counter.h:110 [inline]
 __wb_update_bandwidth+0x96/0x5d0 mm/page-writeback.c:1510
 wb_update_bandwidth mm/page-writeback.c:1537 [inline]
 do_writepages+0x44a/0x480 mm/page-writeback.c:2682
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x16e/0x2f0 mm/filemap.c:794
 generic_buffers_fsync_noflush+0x46/0x120 fs/buffer.c:600
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x1c3/0x6c0 fs/ext4/fsync.c:147
 vfs_fsync_range+0x116/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:2976 [inline]
 ext4_buffered_write_iter+0x358/0x3c0 fs/ext4/file.c:305
 ext4_file_write_iter+0x3b2/0xf80 include/linux/fs.h:-1
 aio_write+0x324/0x460 fs/aio.c:1633
 __io_submit_one fs/aio.c:-1 [inline]
 io_submit_one+0xb0c/0x1230 fs/aio.c:2052
 __do_sys_io_submit fs/aio.c:2111 [inline]
 __se_sys_io_submit+0xf7/0x280 fs/aio.c:2081
 __x64_sys_io_submit+0x43/0x50 fs/aio.c:2081
 x64_sys_call+0xa8b/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:210
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000010 -> 0x0000000000000020

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4708 Comm: syz.5.316 Not tainted 6.15.0-rc2-syzkaller-00257-gb5c6891b2c5b #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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