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BUG: KCSAN: data-race in filemap_flush / xas_set_mark

write to 0xffff8881004c43a4 of 4 bytes by task 28 on cpu 1:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark+0x131/0x150 lib/xarray.c:893
 __folio_start_writeback+0x1e8/0x430 mm/page-writeback.c:3147
 __block_write_full_folio+0x506/0x8c0 fs/buffer.c:1899
 block_write_full_folio+0x293/0x2b0
 write_cache_pages+0x62/0x100 mm/page-writeback.c:2665
 blkdev_writepages+0x59/0x90 block/fops.c:458
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2708
 __writeback_single_inode+0x89/0x850 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x461/0xa30 fs/fs-writeback.c:1976
 __writeback_inodes_wb+0x9a/0x1a0 fs/fs-writeback.c:2047
 wb_writeback+0x274/0x640 fs/fs-writeback.c:2158
 wb_check_background_flush fs/fs-writeback.c:2228 [inline]
 wb_do_writeback fs/fs-writeback.c:2316 [inline]
 wb_workfn+0x67f/0x940 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3317
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3398
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff8881004c43a4 of 4 bytes by task 6893 on cpu 0:
 xa_marked include/linux/xarray.h:424 [inline]
 mapping_tagged include/linux/fs.h:540 [inline]
 filemap_fdatawrite_wbc mm/filemap.c:385 [inline]
 __filemap_fdatawrite_range mm/filemap.c:422 [inline]
 __filemap_fdatawrite mm/filemap.c:428 [inline]
 filemap_flush+0x9a/0x120 mm/filemap.c:455
 sync_blockdev_nowait+0x29/0x40 block/bdev.c:206
 sync_filesystem+0xe3/0x190 fs/sync.c:60
 generic_shutdown_super+0x46/0x220 fs/super.c:621
 kill_block_super+0x2a/0x70 fs/super.c:1710
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7368
 deactivate_locked_super+0x7d/0x1c0 fs/super.c:473
 deactivate_super+0x9f/0xb0 fs/super.c:506
 cleanup_mnt+0x268/0x2e0 fs/namespace.c:1413
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1420
 task_work_run+0x13a/0x1a0 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xa8/0x120 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x02000021 -> 0x04000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6893 Comm: syz-executor Not tainted 6.13.0-syzkaller-07644-gc2da8b3f914f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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