484  * forward/backward merge with existing mappings.  The extent_map struct passed
638  * Helper for btrfs_get_extent.  Given an existing extent in the tree,
639  * the existing extent is the nearest extent to map_start,
644 					 struct extent_map *existing,  in merge_extent_mapping()  argument
657 	if (existing->start > map_start) {  in merge_extent_mapping()
658 		next = existing;  in merge_extent_mapping()
661 		prev = existing;  in merge_extent_mapping()
690  * a) Returning the existing extent in @em_in if @start is within the
691  *    existing em.
692  * b) Merge the existing extent with @em_in passed in.
717 		struct extent_map *existing;  in btrfs_add_extent_mapping()  local
719 		existing = search_extent_mapping(&inode->extent_tree, start, len);  in btrfs_add_extent_mapping()
721 		trace_btrfs_handle_em_exist(fs_info, existing, em, start, len);  in btrfs_add_extent_mapping()
724 		 * existing will always be non-NULL, since there must be  in btrfs_add_extent_mapping()
727 		if (start >= existing->start &&  in btrfs_add_extent_mapping()
728 		    start < extent_map_end(existing)) {  in btrfs_add_extent_mapping()
730 			*em_in = existing;  in btrfs_add_extent_mapping()
737 			 * The existing extent map is the one nearest to  in btrfs_add_extent_mapping()
740 			ret = merge_extent_mapping(inode, existing, em, start);  in btrfs_add_extent_mapping()
745 "extent map merge error existing [%llu, %llu) with em [%llu, %llu) start %llu",  in btrfs_add_extent_mapping()
746 					   existing->start, extent_map_end(existing),  in btrfs_add_extent_mapping()
749 			free_extent_map(existing);  in btrfs_add_extent_mapping()