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BUG: KCSAN: data-race in __xa_set_mark / find_get_pages_range_tag

write to 0xffff88811eea9b28 of 8 bytes by task 19379 on cpu 1:
 instrument_write include/linux/instrumented.h:42 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:79 [inline]
 __test_and_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:95 [inline]
 node_set_mark lib/xarray.c:93 [inline]
 xas_set_mark lib/xarray.c:879 [inline]
 __xa_set_mark+0x249/0x300 lib/xarray.c:1708
 __set_page_dirty+0x17e/0x1d0 fs/buffer.c:609
 mark_buffer_dirty+0x126/0x230 fs/buffer.c:1137
 mark_buffer_dirty_inode+0x48/0x1b0 fs/buffer.c:575
 __ext4_handle_dirty_metadata+0x1af/0x5a0 fs/ext4/ext4_jbd2.c:360
 ext4_getblk+0x255/0x2e0 fs/ext4/inode.c:866
 ext4_bread+0x3a/0x1f0 fs/ext4/inode.c:882
 ext4_append+0xda/0x1c0 fs/ext4/namei.c:67
 ext4_init_new_dir fs/ext4/namei.c:2764 [inline]
 ext4_mkdir+0x4b6/0xc90 fs/ext4/namei.c:2809
 vfs_mkdir+0x288/0x350 fs/namei.c:3649
 ovl_do_mkdir fs/overlayfs/overlayfs.h:150 [inline]
 ovl_mkdir_real fs/overlayfs/dir.c:146 [inline]
 ovl_create_real+0xe0/0x250 fs/overlayfs/dir.c:193
 ovl_workdir_create+0x200/0x350 fs/overlayfs/super.c:713
 ovl_get_indexdir fs/overlayfs/super.c:1369 [inline]
 ovl_fill_super+0x2595/0x3510 fs/overlayfs/super.c:1879
 mount_nodev+0x4f/0xd0 fs/super.c:1465
 ovl_mount+0x25/0x30 fs/overlayfs/super.c:1944
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4d/0x1a0 fs/super.c:1549
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x118d/0x1c70 fs/namespace.c:3203
 do_mount fs/namespace.c:3216 [inline]
 __do_sys_mount fs/namespace.c:3424 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3401
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3401
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811eea9b28 of 8 bytes by task 9062 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1625 [inline]
 xas_next_marked include/linux/xarray.h:1656 [inline]
 find_get_pages_range_tag+0x30c/0x5a0 mm/filemap.c:2074
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1161
 write_cache_pages+0x1f8/0x820 mm/page-writeback.c:2203
 generic_writepages+0x64/0xa0 mm/page-writeback.c:2337
 blkdev_writepages+0x19/0x20 fs/block_dev.c:1946
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 __filemap_fdatawrite mm/filemap.c:430 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:457
 __sync_blockdev+0x69/0x70 fs/block_dev.c:508
 __sync_filesystem fs/sync.c:40 [inline]
 sync_filesystem+0xcb/0x160 fs/sync.c:64
 ovl_sync_fs+0x74/0x90 fs/overlayfs/super.c:281
 __sync_filesystem fs/sync.c:39 [inline]
 sync_filesystem+0x112/0x160 fs/sync.c:67
 generic_shutdown_super+0x42/0x210 fs/super.c:448
 kill_anon_super+0x23/0x40 fs/super.c:1108
 deactivate_locked_super+0x6a/0xb0 fs/super.c:335
 deactivate_super+0x85/0x90 fs/super.c:366
 cleanup_mnt+0x277/0x2e0 fs/namespace.c:1118
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1125
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:165 [inline]
 exit_to_user_mode_prepare+0x1b2/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9062 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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