Btrfs: extent_map optimizations to cut down on CPU usage

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 52a8b93..f1dc28d 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -75,7 +75,7 @@
 	char *kaddr;
 	unsigned long map_start;
 	unsigned long map_len;
-	struct page *last_page;
+	struct page *first_page;
 	struct list_head lru;
 	atomic_t refs;
 	int flags;