==================================================================
BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88811ae6f900 of 8 bytes by task 52 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+0xe7/0x530 mm/page-writeback.c:2960
 folio_end_writeback_no_dropbehind+0x6d/0x200 mm/filemap.c:1672
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1698
 ext4_finish_bio+0x454/0x770 fs/ext4/page-io.c:137
 ext4_release_io_end+0x9f/0x1f0 fs/ext4/page-io.c:151
 ext4_end_io_end+0x18d/0x240 fs/ext4/page-io.c:202
 ext4_do_flush_completed_IO fs/ext4/page-io.c:282 [inline]
 ext4_end_io_rsv_work+0x15b/0x1f0 fs/ext4/page-io.c:297
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3470
 worker_thread+0x569/0x750 kernel/workqueue.c:3551
 kthread+0x223/0x270 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 0xffff88811ae6f900 of 8 bytes by task 3307 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x211/0x650 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2087 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2353
 __filemap_fdatawait_range mm/filemap.c:523 [inline]
 filemap_fdatawait_keep_errors+0x6c/0x190 mm/filemap.c:626
 wait_sb_inodes fs/fs-writeback.c:2920 [inline]
 sync_inodes_sb+0x424/0x4d0 fs/fs-writeback.c:3053
 sync_filesystem+0x108/0x190 fs/sync.c:64
 generic_shutdown_super+0x4c/0x220 fs/super.c:748
 kill_block_super+0x2d/0xb0 fs/super.c:1918
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7527
 deactivate_locked_super+0x75/0x200 fs/super.c:603
 deactivate_super+0x9a/0xb0 fs/super.c:632
 cleanup_mnt+0x2c3/0x340 fs/namespace.c:1317
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1324
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x1e4/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffff80000 -> 0xffffffffffc00000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3307 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================