cifs: allow fsc mount option only if CONFIG_CIFS_FSCACHE is set

Currently, it is possible to specify 'fsc' mount option even if
CONFIG_CIFS_FSCACHE has not been set. The option is being ignored silently
while the user fscache functionality to work. Fix this by raising error when
the CONFIG option is not set.
Reported-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/connect.c

@@ -1352,6 +1352,11 @@ cifs_parse_mount_options(char *options, const char *devname,
 				"supported. Instead set "
 				"/proc/fs/cifs/LookupCacheEnabled to 0\n");
 		} else if (strnicmp(data, "fsc", 3) == 0) {
+#ifndef CONFIG_CIFS_FSCACHE
+			cERROR(1, "FS-Cache support needs CONFIG_CIFS_FSCACHE"
+				  "kernel config option set");
+			return 1;
+#endif
 			vol->fsc = true;
 		} else if (strnicmp(data, "mfsymlinks", 10) == 0) {
 			vol->mfsymlinks = true;