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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88815787ad98 of 8 bytes by task 6205 on cpu 1:
 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:2971
 folio_end_writeback_no_dropbehind+0x6d/0x1d0 mm/filemap.c:1667
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1693
 ext4_finish_bio+0x454/0x770 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+0x15b/0x1f0 fs/ext4/page-io.c:305
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88815787ad98 of 8 bytes by task 6934 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x211/0x650 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2082 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2349
 __filemap_fdatawait_range mm/filemap.c:524 [inline]
 filemap_write_and_wait_range+0x1f5/0x370 mm/filemap.c:693
 ext4_insert_range+0x1b8/0x650 fs/ext4/extents.c:5660
 ext4_fallocate+0x2f0/0x320 fs/ext4/extents.c:4919
 vfs_fallocate+0x3ac/0x400 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0x7a/0xd0 fs/open.c:365
 x64_sys_call+0x298e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:286
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00007fffffffff00 -> 0x00007ffffffff800

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6934 Comm: syz.4.812 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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