NFS: Fix up O_DIRECT results

if we read or wrote something, we must report it
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: NJeff Layton <jlayton@poochiereds.net>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/direct.c

@@ -353,10 +353,12 @@ static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
 
 	result = wait_for_completion_killable(&dreq->completion);
 
+	if (!result) {
+		result = dreq->count;
+		WARN_ON_ONCE(dreq->count < 0);
+	}
 	if (!result)
 		result = dreq->error;
-	if (!result)
-		result = dreq->count;
 
 out:
 	return (ssize_t) result;
@@ -386,8 +388,10 @@ static void nfs_direct_complete(struct nfs_direct_req *dreq, bool write)
 
 	if (dreq->iocb) {
 		long res = (long) dreq->error;
-		if (!res)
+		if (dreq->count != 0) {
 			res = (long) dreq->count;
+			WARN_ON_ONCE(dreq->count < 0);
+		}
 		dreq->iocb->ki_complete(dreq->iocb, res, 0);
 	}