syzbot

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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

read-write to 0xffff88811b584d90 of 8 bytes by task 6361 on cpu 1:
 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+0x383/0x4a0 mm/page-writeback.c:2668
 mark_buffer_dirty+0x120/0x220 fs/buffer.c:1203
 folio_zero_new_buffers+0x28c/0x2e0 fs/buffer.c:2029
 block_write_end+0x200/0x210 fs/buffer.c:2286
 ext4_da_do_write_end fs/ext4/inode.c:3211 [inline]
 ext4_da_write_end+0x1d3/0x810 fs/ext4/inode.c:3285
 generic_perform_write+0x311/0x490 mm/filemap.c:4335
 ext4_buffered_write_iter+0x1ee/0x3c0 fs/ext4/file.c:300
 ext4_file_write_iter+0x380/0xfa0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:688
 ksys_write+0xdc/0x1a0 fs/read_write.c:740
 __do_sys_write fs/read_write.c:751 [inline]
 __se_sys_write fs/read_write.c:748 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:748
 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b584d90 of 8 bytes by task 6369 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2064 [inline]
 filemap_get_folios_tag+0xfa/0x510 mm/filemap.c:2332
 mpage_prepare_extent_to_map+0x328/0xc50 fs/ext4/inode.c:2632
 ext4_do_writepages+0xa07/0x2840 fs/ext4/inode.c:2923
 ext4_writepages+0x18f/0x320 fs/ext4/inode.c:3019
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2554
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_flush_range+0x105/0x140 mm/filemap.c:436
 generic_fadvise+0x338/0x460 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000007f -> 0x00000000000003ff

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6369 Comm: syz.3.743 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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EXT4-fs error (device loop3): ext4_validate_block_bitmap:441: comm syz.3.743: bg 0: block 345: padding at end of block bitmap is not set
EXT4-fs (loop3): Remounting filesystem read-only