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BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff888106ee3fd0 of 8 bytes by task 3780 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+0x91/0x180 lib/xarray.c:922
 __folio_start_writeback+0x23f/0x370 mm/page-writeback.c:3026
 ext4_bio_write_folio+0x5a2/0xa10 fs/ext4/page-io.c:541
 mpage_submit_folio fs/ext4/inode.c:2094 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2331 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2515 [inline]
 ext4_do_writepages+0x141a/0x2870 fs/ext4/inode.c:2938
 ext4_writepages+0x191/0x300 fs/ext4/inode.c:3032
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2560
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_flush_range mm/filemap.c:436 [inline]
 filemap_flush+0xee/0x130 mm/filemap.c:451
 ext4_alloc_da_blocks+0x54/0x100 fs/ext4/inode.c:3343
 ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:171
 __fput+0x29e/0x630 fs/file_table.c:512
 ____fput+0x1c/0x30 fs/file_table.c:540
 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:343 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106ee3fd0 of 8 bytes by task 3791 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x211/0x650 lib/xarray.c:1513
 find_get_entry mm/filemap.c:2087 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2353
 mpage_prepare_extent_to_map+0x32a/0xca0 fs/ext4/inode.c:2634
 ext4_do_writepages+0xa10/0x2870 fs/ext4/inode.c:2936
 ext4_writepages+0x191/0x300 fs/ext4/inode.c:3032
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2560
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_flush_range mm/filemap.c:436 [inline]
 filemap_flush+0xee/0x130 mm/filemap.c:451
 ext4_alloc_da_blocks+0x54/0x100 fs/ext4/inode.c:3343
 ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:171
 __fput+0x29e/0x630 fs/file_table.c:512
 ____fput+0x1c/0x30 fs/file_table.c:540
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 get_signal+0xdc1/0xf10 kernel/signal.c:2884
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x15d/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:343 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffff800000000 -> 0xfffffe0000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3791 Comm: syz.3.66 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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