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

read-write to 0xffff88811acd4228 of 8 bytes by task 5103 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+0x42c/0x520 mm/page-writeback.c:2689
 mark_buffer_dirty+0x120/0x1f0 fs/buffer.c:1116
 block_commit_write fs/buffer.c:2196 [inline]
 block_write_end+0x12d/0x210 fs/buffer.c:2272
 ext4_da_do_write_end fs/ext4/inode.c:3241 [inline]
 ext4_da_write_end+0x1e4/0x7b0 fs/ext4/inode.c:3311
 generic_perform_write+0x314/0x490 mm/filemap.c:4379
 ext4_buffered_write_iter+0x2e2/0x480 fs/ext4/file.c:316
 ext4_file_write_iter+0x38e/0xef0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57d/0x990 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+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811acd4228 of 8 bytes by task 5086 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:2081 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2348
 mpage_prepare_extent_to_map+0x2f8/0xc00 fs/ext4/inode.c:2656
 ext4_do_writepages+0x9e5/0x2720 fs/ext4/inode.c:2947
 ext4_writepages+0x18f/0x300 fs/ext4/inode.c:3043
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 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+0x242b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:222
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x03ffffffffffffff -> 0x3fffffffffffffff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5086 Comm: syz.1.354 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
==================================================================
EXT4-fs error (device loop1): ext4_validate_block_bitmap:441: comm syz.1.354: bg 0: block 345: padding at end of block bitmap is not set
EXT4-fs (loop1): Remounting filesystem read-only