ocfs2: Use struct ocfs2_extent_tree in ocfs2_num_free_extents().

ocfs2_num_free_extents() re-implements the logic of
ocfs2_get_extent_tree().  Now that ocfs2_get_extent_tree() does not
allocate, let's use it in ocfs2_num_free_extents() to simplify the code.

The inode validation code in ocfs2_num_free_extents() is not needed.
All callers are passing in pre-validated inodes.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/alloc.c

@@ -618,34 +618,13 @@ int ocfs2_num_free_extents(struct ocfs2_super *osb,
 	struct ocfs2_extent_block *eb;
 	struct buffer_head *eb_bh = NULL;
 	u64 last_eb_blk = 0;
+	struct ocfs2_extent_tree et;
 
 	mlog_entry_void();
 
-	if (type == OCFS2_DINODE_EXTENT) {
-		struct ocfs2_dinode *fe =
-				(struct ocfs2_dinode *)root_bh->b_data;
-		if (!OCFS2_IS_VALID_DINODE(fe)) {
-			OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, fe);
-			retval = -EIO;
-			goto bail;
-		}
-
-		if (fe->i_last_eb_blk)
-			last_eb_blk = le64_to_cpu(fe->i_last_eb_blk);
-		el = &fe->id2.i_list;
-	} else if (type == OCFS2_XATTR_VALUE_EXTENT) {
-		struct ocfs2_xattr_value_root *xv =
-			(struct ocfs2_xattr_value_root *) obj;
-
-		last_eb_blk = le64_to_cpu(xv->xr_last_eb_blk);
-		el = &xv->xr_list;
-	} else if (type == OCFS2_XATTR_TREE_EXTENT) {
-		struct ocfs2_xattr_block *xb =
-			(struct ocfs2_xattr_block *)root_bh->b_data;
-
-		last_eb_blk = le64_to_cpu(xb->xb_attrs.xb_root.xt_last_eb_blk);
-		el = &xb->xb_attrs.xb_root.xt_list;
-	}
+	ocfs2_get_extent_tree(&et, inode, root_bh, type, obj);
+	el = et.et_root_el;
+	last_eb_blk = ocfs2_et_get_last_eb_blk(&et);
 
 	if (last_eb_blk) {
 		retval = ocfs2_read_block(osb, last_eb_blk,
@@ -665,6 +644,7 @@ bail:
 	if (eb_bh)
 		brelse(eb_bh);
 
+	ocfs2_put_extent_tree(&et);
 	mlog_exit(retval);
 	return retval;
 }