[CIFS] Allow null user connections

Some servers are configured to only allow null user mounts for
guest access.  Allow nul user (anonymous) mounts e.g.
	mount -t cifs //server/share /mnt -o username=
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/CHANGES

 Version 1.46
 ------------
 Support deep tree mounts.  Better support OS/2, Win9x (DOS) time stamps.
+Allow null user to be specified on mount ("username="). Do not return
+EINVAL on readdir when filldir fails due to overwritten blocksize
+(fixes FC problem)
 
 Version 1.45
 ------------

fs/cifs/connect.c

@@ -822,10 +822,13 @@ cifs_parse_mount_options(char *options, const char *devname,struct smb_vol *vol)
 		} else if (strnicmp(data, "nouser_xattr",12) == 0) {
 			vol->no_xattr = 1;
 		} else if (strnicmp(data, "user", 4) == 0) {
-			if (!value || !*value) {
+			if (!value) {
 				printk(KERN_WARNING
 				       "CIFS: invalid or missing username\n");
 				return 1;	/* needs_arg; */
+			} else if(!*value) {
+				/* null user, ie anonymous, authentication */
+				vol->nullauth = 1;
 			}
 			if (strnlen(value, 200) < 200) {
 				vol->username = value;
@@ -1642,6 +1645,8 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 		/* BB fixme parse for domain name here */
 		cFYI(1, ("Username: %s ", volume_info.username));
 
+	} else if (volume_info.nullauth) {
+		cFYI(1,("null user"));
 	} else {
 		cifserror("No username specified");
         /* In userspace mount helper we can get user name from alternate