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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88811b827fd8 of 8 bytes by task 12 on cpu 1:
 instrument_read_write include/linux/instrumented.h:55 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
 ___test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:114 [inline]
 node_clear_mark lib/xarray.c:102 [inline]
 xas_clear_mark lib/xarray.c:922 [inline]
 __xa_clear_mark+0xf5/0x1e0 lib/xarray.c:2094
 __folio_end_writeback+0x177/0x470 mm/page-writeback.c:3047
 folio_end_writeback+0xb6/0x3a0 mm/filemap.c:1648
 ext4_finish_bio+0x459/0x8c0 fs/ext4/page-io.c:144
 ext4_release_io_end+0x9f/0x1f0 fs/ext4/page-io.c:159
 ext4_end_io_end+0x18d/0x240 fs/ext4/page-io.c:210
 ext4_do_flush_completed_IO fs/ext4/page-io.c:287 [inline]
 ext4_end_io_rsv_work+0x151/0x1e0 fs/ext4/page-io.c:302
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 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 0xffff88811b827fd8 of 8 bytes by task 9329 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1746 [inline]
 xas_find_marked+0x218/0x620 lib/xarray.c:1510
 find_get_entry+0x5d/0x380 mm/filemap.c:2027
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2295
 __filemap_fdatawait_range mm/filemap.c:530 [inline]
 filemap_fdatawait_keep_errors+0x6c/0x180 mm/filemap.c:633
 wait_sb_inodes fs/fs-writeback.c:2714 [inline]
 sync_inodes_sb+0x39c/0x440 fs/fs-writeback.c:2836
 sync_filesystem+0x102/0x190 fs/sync.c:64
 generic_shutdown_super+0x44/0x210 fs/super.c:621
 kill_block_super+0x2a/0x70 fs/super.c:1710
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7393
 deactivate_locked_super+0x72/0x1c0 fs/super.c:473
 deactivate_super+0x97/0xa0 fs/super.c:506
 cleanup_mnt+0x269/0x2e0 fs/namespace.c:1435
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1442
 task_work_run+0x12e/0x1a0 kernel/task_work.c:227
 resume_user_mode_work+0x6a/0x70 include/linux/resume_user_mode.h:50
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x77/0xb0 kernel/entry/common.c:218
 do_syscall_64+0xdd/0x1a0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00003ffe00000000 -> 0x00003fc000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9329 Comm: syz-executor Not tainted 6.15.0-rc4-syzkaller-00147-gebd297a2affa #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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