xfs: check for cow blocks before trying to clear them

There's no point in allocating a transaction and locking the inode in
preparation to clear cow blocks if there actually are any cow fork
extents.  Therefore, move the xfs_reflink_cancel_cow_range hunk to
xfs_inactive and check the cow ifp first.  This makes inode reclamation
run faster.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/xfs_inode.c

@@ -1872,6 +1872,7 @@ xfs_inactive(
 	xfs_inode_t	*ip)
 {
 	struct xfs_mount	*mp;
+	struct xfs_ifork	*cow_ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
 	int			error;
 	int			truncate = 0;
 
@@ -1892,6 +1893,10 @@ xfs_inactive(
 	if (mp->m_flags & XFS_MOUNT_RDONLY)
 		return;
 
+	/* Try to clean out the cow blocks if there are any. */
+	if (xfs_is_reflink_inode(ip) && cow_ifp->if_bytes > 0)
+		xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, true);
+
 	if (VFS_I(ip)->i_nlink != 0) {
 		/*
 		 * force is true because we are evicting an inode from the

fs/xfs/xfs_super.c

@@ -972,7 +972,6 @@ xfs_fs_destroy_inode(
 	struct inode		*inode)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
-	int			error;
 
 	trace_xfs_destroy_inode(ip);
 
@@ -980,14 +979,6 @@ xfs_fs_destroy_inode(
 	XFS_STATS_INC(ip->i_mount, vn_rele);
 	XFS_STATS_INC(ip->i_mount, vn_remove);
 
-	if (xfs_is_reflink_inode(ip)) {
-		error = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, true);
-		if (error && !XFS_FORCED_SHUTDOWN(ip->i_mount))
-			xfs_warn(ip->i_mount,
-"Error %d while evicting CoW blocks for inode %llu.",
-					error, ip->i_ino);
-	}
-
 	xfs_inactive(ip);
 
 	ASSERT(XFS_FORCED_SHUTDOWN(ip->i_mount) || ip->i_delayed_blks == 0);