cifs: add server conn_id to fscache client cookie

The fscache client cookie uses the server address
(and port) as the cookie key. This is a problem when
nosharesock is used. Two different connections will
use duplicate cookies. Avoid this by adding
server->conn_id to the key, so that it's guaranteed
that cookie will not be duplicated.

Also, for secondary channels of a session, copy the
fscache pointer from the primary channel. The primary
channel is guaranteed not to go away as long as secondary
channels are in use.  Also addresses minor problem found
by kernel test robot.
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NShyam Prasad N <sprasad@microsoft.com>
Reviewed-by: NPaulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: NSteve French <stfrench@microsoft.com>

fs/cifs/connect.c

@@ -1562,6 +1562,10 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 	/* fscache server cookies are based on primary channel only */
 	if (!CIFS_SERVER_IS_CHAN(tcp_ses))
 		cifs_fscache_get_client_cookie(tcp_ses);
+#ifdef CONFIG_CIFS_FSCACHE
+	else
+		tcp_ses->fscache = tcp_ses->primary_server->fscache;
+#endif /* CONFIG_CIFS_FSCACHE */
 
 	/* queue echo request delayed work */
 	queue_delayed_work(cifsiod_wq, &tcp_ses->echo, tcp_ses->echo_interval);

fs/cifs/fscache.c

@@ -24,6 +24,7 @@ struct cifs_server_key {
 		struct in_addr	ipv4_addr;
 		struct in6_addr	ipv6_addr;
 	};
+	__u64 conn_id;
 } __packed;
 
 /*
@@ -37,6 +38,14 @@ void cifs_fscache_get_client_cookie(struct TCP_Server_Info *server)
 	struct cifs_server_key key;
 	uint16_t key_len = sizeof(key.hdr);
 
+	/*
+	 * Check if cookie was already initialized so don't reinitialize it.
+	 * In the future, as we integrate with newer fscache features,
+	 * we may want to instead add a check if cookie has changed
+	 */
+	if (server->fscache)
+		return;
+
 	memset(&key, 0, sizeof(key));
 
 	/*
@@ -62,6 +71,7 @@ void cifs_fscache_get_client_cookie(struct TCP_Server_Info *server)
 		server->fscache = NULL;
 		return;
 	}
+	key.conn_id = server->conn_id;
 
 	server->fscache =
 		fscache_acquire_cookie(cifs_fscache_netfs.primary_index,