pnfs: retry after a bad stateid error from layoutget

Currently we fall through to nfs4_async_handle_error when we get
a bad stateid error back from layoutget.  nfs4_async_handle_error
with a NULL state argument will never retry the operations but return
the error to higher layer, causing an avoiable fallback to MDS I/O.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4proc.c

@@ -7577,11 +7577,16 @@ static void nfs4_layoutget_done(struct rpc_task *task, void *calldata)
 		} else {
 			LIST_HEAD(head);
 
+			/*
+			 * Mark the bad layout state as invalid, then retry
+			 * with the current stateid.
+			 */
 			pnfs_mark_matching_lsegs_invalid(lo, &head, NULL);
 			spin_unlock(&inode->i_lock);
-			/* Mark the bad layout state as invalid, then
-			 * retry using the open stateid. */
 			pnfs_free_lseg_list(&head);
+	
+			task->tk_status = 0;
+			rpc_restart_call_prepare(task);
 		}
 	}
 	if (nfs4_async_handle_error(task, server, state) == -EAGAIN)