cifs: do not poll server interfaces too regularly

We have the server interface list hanging off the tcon
structure today for reasons unknown. So each tcon which is
connected to a file server can query them separately,
which is really unnecessary. To avoid this, in the query
function, we will check the time of last update of the
interface list, and avoid querying the server if it is
within a certain range.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2ops.c

@@ -530,6 +530,14 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
 	p = buf;
 
 	spin_lock(&ses->iface_lock);
+	/* do not query too frequently, this time with lock held */
+	if (ses->iface_last_update &&
+	    time_before(jiffies, ses->iface_last_update +
+			(SMB_INTERFACE_POLL_INTERVAL * HZ))) {
+		spin_unlock(&ses->iface_lock);
+		return 0;
+	}
+
 	/*
 	 * Go through iface_list and do kref_put to remove
 	 * any unused ifaces. ifaces in use will be removed
@@ -696,6 +704,12 @@ SMB3_request_interfaces(const unsigned int xid, struct cifs_tcon *tcon, bool in_
 	struct network_interface_info_ioctl_rsp *out_buf = NULL;
 	struct cifs_ses *ses = tcon->ses;
 
+	/* do not query too frequently */
+	if (ses->iface_last_update &&
+	    time_before(jiffies, ses->iface_last_update +
+			(SMB_INTERFACE_POLL_INTERVAL * HZ)))
+		return 0;
+
 	rc = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
 			FSCTL_QUERY_NETWORK_INTERFACE_INFO,
 			NULL /* no data input */, 0 /* no data input */,