pnfs: Prepare for flexfiles by pulling out common code

The flexfilelayout driver will share some common code
with the filelayout driver. This set of changes refactors
that common code out to avoid any module depenencies.

Signed-off-by: Tom Haynes <loghyr@primarydata.com>

fs/nfs/filelayout/filelayoutdev.c

@@ -708,7 +708,7 @@ nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx)
 	if (ds == NULL) {
 		printk(KERN_ERR "NFS: %s: No data server for offset index %d\n",
 			__func__, ds_idx);
-		filelayout_mark_devid_invalid(devid);
+		pnfs_generic_mark_devid_invalid(devid);
 		goto out;
 	}
 	smp_rmb();