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

read-write to 0xffff888107b66fd8 of 8 bytes by task 5968 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_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:99 [inline]
 node_set_mark lib/xarray.c:95 [inline]
 xas_set_mark lib/xarray.c:893 [inline]
 __xa_set_mark+0xd2/0x1a0 lib/xarray.c:2082
 __folio_mark_dirty+0x383/0x490 mm/page-writeback.c:2712
 mark_buffer_dirty+0x11e/0x200 fs/buffer.c:1206
 block_commit_write fs/buffer.c:2218 [inline]
 block_page_mkwrite+0x287/0x3c0 fs/buffer.c:2643
 ext4_page_mkwrite+0x859/0xb90 fs/ext4/inode.c:6689
 do_page_mkwrite mm/memory.c:3528 [inline]
 do_shared_fault mm/memory.c:5831 [inline]
 do_fault mm/memory.c:5893 [inline]
 do_pte_missing mm/memory.c:4401 [inline]
 handle_pte_fault mm/memory.c:6273 [inline]
 __handle_mm_fault mm/memory.c:6411 [inline]
 handle_mm_fault+0x18fb/0x3030 mm/memory.c:6580
 do_user_addr_fault+0x62f/0x1050 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffff888107b66fd8 of 8 bytes by task 2792 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry+0x5d/0x380 mm/filemap.c:2064
 filemap_get_folios_tag+0xb6/0x230 mm/filemap.c:2332
 mpage_prepare_extent_to_map+0x328/0xc50 fs/ext4/inode.c:2639
 ext4_do_writepages+0x9f6/0x2800 fs/ext4/inode.c:2930
 ext4_writepages+0x18f/0x320 fs/ext4/inode.c:3026
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2598
 __writeback_single_inode+0x80/0x7b0 fs/fs-writeback.c:1737
 writeback_sb_inodes+0x4f4/0xb70 fs/fs-writeback.c:2030
 __writeback_inodes_wb+0x94/0x1a0 fs/fs-writeback.c:2107
 wb_writeback+0x261/0x5b0 fs/fs-writeback.c:2218
 wb_check_old_data_flush fs/fs-writeback.c:2322 [inline]
 wb_do_writeback fs/fs-writeback.c:2375 [inline]
 wb_workfn+0x651/0x960 fs/fs-writeback.c:2403
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x581/0x770 kernel/workqueue.c:3421
 kthread+0x488/0x510 kernel/kthread.c:463
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x0000000000800000 -> 0x0000000000808001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2792 Comm: kworker/u8:12 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: writeback wb_workfn (flush-8:0)
==================================================================