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

read-write to 0xffff88811aed7220 of 8 bytes by task 9614 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_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+0x384/0x4a0 mm/page-writeback.c:2712
 mark_buffer_dirty+0x11e/0x210 fs/buffer.c:1206
 folio_zero_new_buffers+0x28c/0x2e0 fs/buffer.c:2032
 block_write_end+0x200/0x210 fs/buffer.c:2289
 ext4_da_do_write_end fs/ext4/inode.c:3218 [inline]
 ext4_da_write_end+0x1d3/0x800 fs/ext4/inode.c:3292
 generic_perform_write+0x312/0x490 mm/filemap.c:4335
 ext4_buffered_write_iter+0x1ee/0x3c0 fs/ext4/file.c:299
 ext4_file_write_iter+0x387/0xf60 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811aed7220 of 8 bytes by task 9626 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:2064
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2332
 mpage_prepare_extent_to_map+0x308/0xc20 fs/ext4/inode.c:2639
 ext4_do_writepages+0x9f6/0x27e0 fs/ext4/inode.c:2930
 ext4_writepages+0x179/0x300 fs/ext4/inode.c:3026
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2598
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_flush_range+0xf1/0x130 mm/filemap.c:436
 generic_fadvise+0x312/0x430 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+0x29f4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:222
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x07ffffffffffffff -> 0x1fffffffffffffff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9626 Comm: syz.8.7201 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
EXT4-fs error (device loop8): ext4_validate_block_bitmap:441: comm syz.8.7201: bg 0: block 345: padding at end of block bitmap is not set
EXT4-fs (loop8): Remounting filesystem read-only