syzbot

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BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff8881085bd468 of 8 bytes by task 10182 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_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:114 [inline]
 node_clear_mark lib/xarray.c:102 [inline]
 xas_clear_mark+0x90/0x180 lib/xarray.c:914
 __folio_start_writeback+0x2e8/0x450 mm/page-writeback.c:3078
 __block_write_full_folio+0x506/0x8d0 fs/buffer.c:1887
 block_write_full_folio+0x293/0x2b0
 write_cache_pages+0x62/0x100 mm/page-writeback.c:2569
 blkdev_writepages+0x59/0x90 block/fops.c:429
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2612
 filemap_fdatawrite_wbc+0xdb/0x100 mm/filemap.c:397
 __filemap_fdatawrite_range mm/filemap.c:430 [inline]
 __filemap_fdatawrite mm/filemap.c:436 [inline]
 filemap_flush+0x61/0x90 mm/filemap.c:463
 sync_blockdev_nowait+0x36/0x50 block/bdev.c:195
 sync_filesystem+0xe3/0x190 fs/sync.c:60
 generic_shutdown_super+0x42/0x210 fs/super.c:620
 kill_block_super+0x2a/0x70 fs/super.c:1675
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7327
 deactivate_locked_super+0x7d/0x1c0 fs/super.c:472
 deactivate_super+0x9f/0xb0 fs/super.c:505
 cleanup_mnt+0x272/0x2e0 fs/namespace.c:1267
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1274
 task_work_run+0x13a/0x1a0 kernel/task_work.c:180
 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:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xbe/0x130 kernel/entry/common.c:218
 do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881085bd468 of 8 bytes by task 5488 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1723 [inline]
 xas_find_marked+0x216/0x660 lib/xarray.c:1354
 find_get_entry+0x5d/0x290 mm/filemap.c:1968
 filemap_get_folios_tag+0x136/0x210 mm/filemap.c:2218
 writeback_get_folio mm/page-writeback.c:2419 [inline]
 writeback_iter+0x4b0/0x830 mm/page-writeback.c:2520
 write_cache_pages+0x4b/0x100 mm/page-writeback.c:2568
 blkdev_writepages+0x59/0x90 block/fops.c:429
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2612
 __writeback_single_inode+0x91/0x870 fs/fs-writeback.c:1650
 writeback_sb_inodes+0x4de/0xaa0 fs/fs-writeback.c:1941
 __writeback_inodes_wb+0x9a/0x1a0 fs/fs-writeback.c:2012
 wb_writeback+0x264/0x6f0 fs/fs-writeback.c:2119
 wb_check_background_flush fs/fs-writeback.c:2189 [inline]
 wb_do_writeback fs/fs-writeback.c:2277 [inline]
 wb_workfn+0x67f/0x940 fs/fs-writeback.c:2304
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x000000000000010f -> 0x000000000000010c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5488 Comm: kworker/u8:7 Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: writeback wb_workfn (flush-7:2)
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