syzbot

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BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff8881338b26c8 of 8 bytes by task 15638 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+0x2e7/0x440 mm/page-writeback.c:3090
 __block_write_full_folio+0x53a/0x8f0 fs/buffer.c:1928
 block_write_full_folio+0x2c2/0x2e0 fs/buffer.c:-1
 blkdev_writepages+0x88/0x100 block/fops.c:483
 do_writepages+0x1c3/0x310 mm/page-writeback.c:2634
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 filemap_write_and_wait_range+0x144/0x340 mm/filemap.c:691
 filemap_write_and_wait include/linux/pagemap.h:68 [inline]
 sync_blockdev block/bdev.c:260 [inline]
 bdev_release+0xeb/0x3d0 block/bdev.c:1126
 blkdev_release+0x15/0x20 block/fops.c:699
 __fput+0x298/0x650 fs/file_table.c:468
 ____fput+0x1c/0x30 fs/file_table.c:496
 task_work_run+0x131/0x1a0 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe4/0x100 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881338b26c8 of 8 bytes by task 15636 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x218/0x620 lib/xarray.c:1510
 find_get_entry+0x5d/0x380 mm/filemap.c:2039
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2307
 writeback_get_folio mm/page-writeback.c:2461 [inline]
 writeback_iter+0x4bb/0x820 mm/page-writeback.c:2562
 blkdev_writepages+0xa7/0x100 block/fops.c:482
 do_writepages+0x1c3/0x310 mm/page-writeback.c:2634
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 __filemap_fdatawrite mm/filemap.c:425 [inline]
 filemap_fdatawrite+0xec/0x120 mm/filemap.c:430
 sync_bdevs+0x1a2/0x260 block/bdev.c:1300
 ksys_sync+0x81/0xe0 fs/sync.c:105
 __ia32_sys_sync+0xe/0x20 fs/sync.c:113
 x64_sys_call+0x2d10/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffff80000000000 -> 0xffffc00000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 15636 Comm: syz.0.4037 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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