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

read-write to 0xffff88811a4d5478 of 8 bytes by task 3521 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+0x91/0x180 lib/xarray.c:922
 __folio_start_writeback+0x270/0x370 mm/page-writeback.c:3055
 __block_write_full_folio+0x53a/0x8f0 fs/buffer.c:1928
 block_write_full_folio+0x2c1/0x2e0 fs/buffer.c:-1
 blkdev_writepages+0x88/0x100 block/fops.c:487
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2598
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 filemap_write_and_wait_range+0x166/0x370 mm/filemap.c:684
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev block/bdev.c:277 [inline]
 bdev_release+0xeb/0x3d0 block/bdev.c:1143
 blkdev_release+0x15/0x20 block/fops.c:706
 __fput+0x29b/0x650 fs/file_table.c:468
 ____fput+0x1c/0x30 fs/file_table.c:496
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x466/0x1590 kernel/exit.c:971
 do_group_exit+0x138/0x140 kernel/exit.c:1112
 __do_sys_exit_group kernel/exit.c:1123 [inline]
 __se_sys_exit_group kernel/exit.c:1121 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1121
 x64_sys_call+0x2fff/0x3000 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a4d5478 of 8 bytes by task 3007 on cpu 1:
 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+0x15f/0x230 mm/filemap.c:2332
 writeback_get_folio mm/page-writeback.c:2455 [inline]
 writeback_iter+0x4bb/0x810 mm/page-writeback.c:2556
 blkdev_writepages+0xa7/0x100 block/fops.c:486
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2598
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 filemap_write_and_wait_range+0x166/0x370 mm/filemap.c:684
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev+0x35/0x50 block/bdev.c:277
 bdev_disk_changed+0xdb/0xcb0 block/partitions/core.c:656
 blkdev_get_whole+0x1f5/0x2d0 block/bdev.c:765
 bdev_open+0x280/0x7e0 block/bdev.c:974
 bdev_file_open_by_dev+0x1e6/0x250 block/bdev.c:1076
 disk_scan_partitions+0x148/0x1b0 block/genhd.c:387
 blkdev_common_ioctl+0x1236/0x20b0 block/ioctl.c:707
 blkdev_ioctl+0x31f/0x460 block/ioctl.c:786
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffff80000000000 -> 0xffff000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3007 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
 loop1: p2 < > p3 < p5 > p4
loop1: partition table partially beyond EOD, truncated
loop1: p2 start 4278190080 is beyond EOD, truncated
loop1: p4 size 8192 extends beyond EOD, truncated
loop1: p5 size 8192 extends beyond EOD, truncated