syzbot

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BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff888129a1c228 of 8 bytes by task 37 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+0x8c/0x180 lib/xarray.c:914
 __folio_start_writeback+0x31d/0x4b0 mm/page-writeback.c:3026
 __block_write_full_folio+0x528/0x8a0 fs/buffer.c:1901
 block_write_full_page+0x2d3/0x390
 blkdev_writepage+0x24/0x30 block/fops.c:415
 writepage_cb+0x36/0xc0 mm/page-writeback.c:2537
 write_cache_pages+0x38d/0x740 mm/page-writeback.c:2474
 do_writepages+0x20f/0x340 mm/page-writeback.c:2558
 __writeback_single_inode+0x91/0x860 fs/fs-writeback.c:1625
 writeback_sb_inodes+0x514/0xad0 fs/fs-writeback.c:1916
 __writeback_inodes_wb+0x9a/0x1a0 fs/fs-writeback.c:1987
 wb_writeback+0x264/0x6e0 fs/fs-writeback.c:2094
 wb_check_background_flush fs/fs-writeback.c:2164 [inline]
 wb_do_writeback fs/fs-writeback.c:2252 [inline]
 wb_workfn+0x67f/0x8d0 fs/fs-writeback.c:2279
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

read to 0xffff888129a1c228 of 8 bytes by task 3091 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:1960
 filemap_get_folios_tag+0x136/0x210 mm/filemap.c:2210
 write_cache_pages+0x20d/0x740 mm/page-writeback.c:2429
 do_writepages+0x20f/0x340 mm/page-writeback.c:2558
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:387
 __filemap_fdatawrite_range mm/filemap.c:420 [inline]
 __filemap_fdatawrite mm/filemap.c:426 [inline]
 filemap_flush+0x95/0xc0 mm/filemap.c:453
 sync_blockdev_nowait+0x36/0x50 block/bdev.c:186
 sync_filesystem+0xe0/0x180 fs/sync.c:60
 generic_shutdown_super+0x42/0x210 fs/super.c:669
 kill_block_super+0x2a/0x60 fs/super.c:1667
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7330
 deactivate_locked_super+0x7a/0x1c0 fs/super.c:484
 deactivate_super+0x9b/0xb0 fs/super.c:517
 cleanup_mnt+0x272/0x2e0 fs/namespace.c:1256
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1263
 task_work_run+0x135/0x1a0 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xd6/0xe0 kernel/entry/common.c:171
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296
 do_syscall_64+0x50/0x110 arch/x86/entry/common.c:88
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000207 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3091 Comm: syz-executor.0 Not tainted 6.7.0-rc4-syzkaller-00009-gbee0e7762ad2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
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EXT4-fs (loop0): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop0): unmounting filesystem 00000000-0000-0000-0000-000000000000.