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BUG: KCSAN: data-race in __xa_set_mark / find_get_pages_range_tag

write to 0xffff8880bb54f8e8 of 8 bytes by task 14299 on cpu 0:
 instrument_write include/linux/instrumented.h:42 [inline]
 __test_and_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:71 [inline]
 node_set_mark lib/xarray.c:93 [inline]
 xas_set_mark lib/xarray.c:879 [inline]
 __xa_set_mark+0x233/0x330 lib/xarray.c:1708
 __set_page_dirty+0x17e/0x1d0 fs/buffer.c:609
 mark_buffer_dirty+0x12e/0x260 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_xattr_block_set+0x1b84/0x1ff0 fs/ext4/xattr.c:2101
 ext4_xattr_set_handle+0x9bb/0xfd0 fs/ext4/xattr.c:2390
 ext4_xattr_set+0x17c/0x220 fs/ext4/xattr.c:2490
 ext4_xattr_trusted_set+0x36/0x40 fs/ext4/xattr_trusted.c:37
 __vfs_setxattr+0x2be/0x2f0 fs/xattr.c:177
 __vfs_setxattr_noperm+0xf4/0x380 fs/xattr.c:208
 __vfs_setxattr_locked+0x194/0x1b0 fs/xattr.c:266
 vfs_setxattr+0x99/0x1b0 fs/xattr.c:283
 ovl_do_setxattr fs/overlayfs/overlayfs.h:176 [inline]
 ovl_check_setxattr+0x8a/0xe0 fs/overlayfs/util.c:585
 ovl_set_origin fs/overlayfs/copy_up.c:349 [inline]
 ovl_copy_up_inode+0x23f/0x3c0 fs/overlayfs/copy_up.c:519
 ovl_copy_up_tmpfile fs/overlayfs/copy_up.c:658 [inline]
 ovl_do_copy_up fs/overlayfs/copy_up.c:738 [inline]
 ovl_copy_up_one fs/overlayfs/copy_up.c:886 [inline]
 ovl_copy_up_flags+0xe95/0x15f0 fs/overlayfs/copy_up.c:931
 ovl_copy_up+0x13/0x20 fs/overlayfs/copy_up.c:978
 ovl_link+0x4c/0x1c0 fs/overlayfs/dir.c:702
 vfs_link+0x4e5/0x670 fs/namei.c:4073
 do_linkat+0x49e/0x5a0 fs/namei.c:4141
 __do_sys_link fs/namei.c:4170 [inline]
 __se_sys_link fs/namei.c:4168 [inline]
 __x64_sys_link+0x3a/0x40 fs/namei.c:4168
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bb54f8e8 of 8 bytes by task 10924 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1625 [inline]
 xas_next_marked include/linux/xarray.h:1656 [inline]
 find_get_pages_range_tag+0x30c/0x5b0 mm/filemap.c:1976
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1122
 write_cache_pages+0x1f8/0x840 mm/page-writeback.c:2203
 generic_writepages+0x64/0xa0 mm/page-writeback.c:2337
 blkdev_writepages+0x19/0x20 fs/block_dev.c:1948
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19b/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:479
 __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
 delayed_mntput+0x39/0x60 fs/namespace.c:1135
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10924 Comm: kworker/1:11 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events delayed_mntput
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