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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

read-write to 0xffff88811a8d66b8 of 8 bytes by task 6953 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_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+0x43f/0x520 mm/page-writeback.c:2678
 mark_buffer_dirty+0x120/0x1f0 fs/buffer.c:1014
 folio_zero_new_buffers+0x272/0x2d0 fs/buffer.c:1917
 block_write_end+0xad/0xc0 fs/buffer.c:2177
 ext4_da_do_write_end fs/ext4/inode.c:3232 [inline]
 ext4_da_write_end+0xe9/0x6f0 fs/ext4/inode.c:3300
 generic_perform_write+0x314/0x490 mm/filemap.c:4395
 ext4_buffered_write_iter+0x2e3/0x480 fs/ext4/file.c:354
 ext4_file_write_iter+0x36e/0x1020 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57f/0x9a0 fs/read_write.c:687
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x154e/0x2550 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a8d66b8 of 8 bytes by task 6960 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
 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+0x105/0x140 mm/filemap.c:436
 generic_fadvise+0x333/0x450 mm/fadvise.c:114
 vfs_fadvise mm/fadvise.c:184 [inline]
 ksys_fadvise64_64 mm/fadvise.c:197 [inline]
 __do_sys_fadvise64 mm/fadvise.c:209 [inline]
 __se_sys_fadvise64 mm/fadvise.c:207 [inline]
 __x64_sys_fadvise64+0xcb/0x110 mm/fadvise.c:207
 x64_sys_call+0x2392/0x2550 arch/x86/include/generated/asm/syscalls_64.h:222
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x3fffffffffffffff -> 0xffffffffffffffff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6960 Comm: syz.0.1372 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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EXT4-fs error (device loop0): ext4_validate_block_bitmap:445: comm syz.0.1372: bg 0: block 345: padding at end of block bitmap is not set
EXT4-fs (loop0): Remounting filesystem read-only