NFS: Clean up find_nfs_version()

It's good practice to check the return value of request_module() to see
if the module has been found. It's also a little easier to follow the
code if __find_nfs_version() doesn't attempt to convert NULL pointers
into -EPROTONOSUPPORT.

Signed-off-by: Anna Schumaker <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/client.c

···
 	read_lock(&nfs_version_lock);
 	nfs = nfs_version_mods[version];
 	read_unlock(&nfs_version_lock);
-
-	if (nfs == NULL)
-		return ERR_PTR(-EPROTONOSUPPORT);
 	return nfs;
 }
 
···
 {
 	struct nfs_subversion *nfs = __find_nfs_version(version);
 
-	if (IS_ERR(nfs)) {
-		request_module("nfsv%d", version);
+	if (!nfs && request_module("nfsv%d", version) == 0)
 		nfs = __find_nfs_version(version);
-	}
 
-	if (!IS_ERR(nfs) && !try_module_get(nfs->owner))
+	if (!nfs)
+		return ERR_PTR(-EPROTONOSUPPORT);
+
+	if (!try_module_get(nfs->owner))
 		return ERR_PTR(-EAGAIN);
+
 	return nfs;
 }