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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88811a21dd90 of 8 bytes by task 3685 on cpu 0:
 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:2100
 __folio_end_writeback+0xf7/0x410 mm/page-writeback.c:2998
 folio_end_writeback+0x71/0x3d0 mm/filemap.c:1673
 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:290 [inline]
 ext4_end_io_rsv_work+0x151/0x1e0 fs/ext4/page-io.c:305
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88811a21dd90 of 8 bytes by task 6901 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x218/0x620 lib/xarray.c:1510
 find_get_entry+0x5d/0x380 mm/filemap.c:2052
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2320
 __filemap_fdatawait_range mm/filemap.c:533 [inline]
 filemap_fdatawait_keep_errors+0x6c/0x180 mm/filemap.c:636
 wait_sb_inodes fs/fs-writeback.c:2754 [inline]
 sync_inodes_sb+0x39c/0x440 fs/fs-writeback.c:2876
 sync_filesystem+0x102/0x190 fs/sync.c:64
 generic_shutdown_super+0x44/0x210 fs/super.c:622
 kill_block_super+0x2a/0x70 fs/super.c:1723
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7401
 deactivate_locked_super+0x75/0x1c0 fs/super.c:474
 deactivate_super+0x97/0xa0 fs/super.c:507
 cleanup_mnt+0x269/0x2e0 fs/namespace.c:1318
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1325
 task_work_run+0x12e/0x1a0 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xed/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffffffffffff -> 0xffffffffffffc000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6901 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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EXT4-fs (loop9): unmounting filesystem 00000000-0000-0000-0000-000000000000.