diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 6441e47d8a5e..7c22f5b8c535 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -514,6 +514,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 			put_page(page);
 			break;
 		}
+		add_size = min(em->start + em->len, page_end + 1) - cur;
 		free_extent_map(em);
 
 		if (page->index == end_index) {
@@ -526,7 +527,6 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 			}
 		}
 
-		add_size = min(em->start + em->len, page_end + 1) - cur;
 		ret = bio_add_page(orig_bio, page, add_size, offset_in_page(cur));
 		if (ret != add_size) {
 			unlock_extent(tree, cur, page_end, NULL);