nfsd: allow nfsd to advertise multiple layout types

If the underlying filesystem supports multiple layout types, then there
is little reason not to advertise that fact to clients and let them
choose what type to use.

Turn the ex_layout_type field into a bitfield. For each supported
layout type, we set a bit in that field. When the client requests a
layout, ensure that the bit for that layout type is set. When the
client requests attributes, send back a list of supported types.

Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
Reviewed-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 89fad8a..e0c15f8 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1219,12 +1219,12 @@
 static const struct nfsd4_layout_ops *
 nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type)
 {
-	if (!exp->ex_layout_type) {
+	if (!exp->ex_layout_types) {
 		dprintk("%s: export does not support pNFS\n", __func__);
 		return NULL;
 	}
 
-	if (exp->ex_layout_type != layout_type) {
+	if (!(exp->ex_layout_types & (1 << layout_type))) {
 		dprintk("%s: layout type %d not supported\n",
 			__func__, layout_type);
 		return NULL;