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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88811a4ab228 of 8 bytes by task 3434 on cpu 0:
 instrument_read_write include/linux/instrumented.h:56 [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+0xf4/0x360 mm/page-writeback.c:2948
 folio_end_writeback_no_dropbehind+0x6d/0x1d0 mm/filemap.c:1661
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1687
 ext4_finish_bio+0x459/0x8b0 fs/ext4/page-io.c:145
 ext4_release_io_end+0x9f/0x1f0 fs/ext4/page-io.c:160
 ext4_end_io_end+0x18d/0x240 fs/ext4/page-io.c:211
 ext4_do_flush_completed_IO fs/ext4/page-io.c:291 [inline]
 ext4_end_io_rsv_work+0x15b/0x1f0 fs/ext4/page-io.c:306
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0x4de/0x9e0 kernel/workqueue.c:3358
 worker_thread+0x581/0x770 kernel/workqueue.c:3439
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88811a4ab228 of 8 bytes by task 4037 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2064 [inline]
 filemap_get_folios_tag+0xfa/0x510 mm/filemap.c:2332
 __filemap_fdatawait_range mm/filemap.c:523 [inline]
 file_write_and_wait_range+0x20c/0x2f0 mm/filemap.c:789
 generic_buffers_fsync_noflush+0x45/0x130 fs/buffer.c:607
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x1aa/0x6b0 fs/ext4/fsync.c:147
 vfs_fsync_range fs/sync.c:186 [inline]
 vfs_fsync fs/sync.c:200 [inline]
 do_fsync fs/sync.c:211 [inline]
 __do_sys_fdatasync fs/sync.c:221 [inline]
 __se_sys_fdatasync fs/sync.c:219 [inline]
 __x64_sys_fdatasync+0x83/0xe0 fs/sync.c:219
 x64_sys_call+0x2d1f/0x3020 arch/x86/include/generated/asm/syscalls_64.h:76
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00003ff800000000 -> 0x0000380000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4037 Comm: syz.1.131 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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