nfsd: distinguish functions of NFSD_MAY_* flags

Most of the NFSD_MAY_* flags actually request permissions, but over the
years we've accreted a few that modify the behavior of the permission or
open code in other ways.

Distinguish the two cases a little more.  In particular, allow the
shortcut at the start of nfsd_permission to ignore the
non-permission-requesting bits.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/vfs.c

@@ -2027,7 +2027,7 @@ nfsd_permission(struct svc_rqst *rqstp, struct svc_export *exp,
 	struct inode	*inode = dentry->d_inode;
 	int		err;
 
-	if (acc == NFSD_MAY_NOP)
+	if ((acc & NFSD_MAY_MASK) == NFSD_MAY_NOP)
 		return 0;
 #if 0
 	dprintk("nfsd: permission 0x%x%s%s%s%s%s%s%s mode 0%o%s%s%s\n",

fs/nfsd/vfs.h

@@ -17,6 +17,9 @@
 #define NFSD_MAY_SATTR		8
 #define NFSD_MAY_TRUNC		16
 #define NFSD_MAY_LOCK		32
+#define NFSD_MAY_MASK		63
+
+/* extra hints to permission and open routines: */
 #define NFSD_MAY_OWNER_OVERRIDE	64
 #define NFSD_MAY_LOCAL_ACCESS	128 /* IRIX doing local access check on device special file*/
 #define NFSD_MAY_BYPASS_GSS_ON_ROOT 256