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

read-write to 0xffff88810727bd88 of 8 bytes by task 19372 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+0x3b7/0x4b0 mm/page-writeback.c:2689
 mark_buffer_dirty+0x120/0x1f0 fs/buffer.c:1110
 block_commit_write fs/buffer.c:2115 [inline]
 block_write_end+0x12d/0x210 fs/buffer.c:2191
 ext4_da_do_write_end fs/ext4/inode.c:3240 [inline]
 ext4_da_write_end+0x1d3/0x7b0 fs/ext4/inode.c:3310
 generic_perform_write+0x311/0x490 mm/filemap.c:4346
 ext4_buffered_write_iter+0x304/0x4c0 fs/ext4/file.c:316
 ext4_file_write_iter+0x380/0xfa0 fs/ext4/file.c:-1
 iter_file_splice_write+0x6c4/0xa80 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1159
 splice_direct_to_actor+0x311/0x670 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x382/0x650 fs/read_write.c:1372
 __do_sys_sendfile64 fs/read_write.c:1433 [inline]
 __se_sys_sendfile64 fs/read_write.c:1419 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
 x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810727bd88 of 8 bytes by task 7924 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2070 [inline]
 filemap_get_folios_tag+0xfa/0x430 mm/filemap.c:2338
 mpage_prepare_extent_to_map+0x328/0xc50 fs/ext4/inode.c:2655
 ext4_do_writepages+0x9f6/0x2770 fs/ext4/inode.c:2946
 ext4_writepages+0x18f/0x320 fs/ext4/inode.c:3042
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2575
 __writeback_single_inode+0x7f/0x650 fs/fs-writeback.c:1764
 writeback_sb_inodes+0x4dd/0xaa0 fs/fs-writeback.c:2056
 __writeback_inodes_wb+0x94/0x1a0 fs/fs-writeback.c:2132
 wb_writeback+0x261/0x560 fs/fs-writeback.c:2243
 wb_check_start_all fs/fs-writeback.c:2369 [inline]
 wb_do_writeback fs/fs-writeback.c:2395 [inline]
 wb_workfn+0x4d1/0x930 fs/fs-writeback.c:2428
 process_one_work kernel/workqueue.c:3302 [inline]
 process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3385
 worker_thread+0x58a/0x780 kernel/workqueue.c:3466
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x000000000007fffe -> 0x00000000001ffffe

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7924 Comm: kworker/u8:15 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: writeback wb_workfn (flush-7:9)
==================================================================
EXT4-fs error (device loop9): ext4_validate_block_bitmap:441: comm kworker/u8:15: bg 0: block 345: padding at end of block bitmap is not set
EXT4-fs (loop9): Remounting filesystem read-only