Btrfs: assert page dirty bit on extent buffer pages

Just in case that someone breaks the rule that pages are dirty as long
as eb is dirty. The next patch will dirty the pages conditionally.
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -5176,6 +5176,12 @@ int set_extent_buffer_dirty(struct extent_buffer *eb)
 
 	for (i = 0; i < num_pages; i++)
 		set_page_dirty(eb->pages[i]);
+
+#ifdef CONFIG_BTRFS_DEBUG
+	for (i = 0; i < num_pages; i++)
+		ASSERT(PageDirty(eb->pages[i]));
+#endif
+
 	return was_dirty;
 }