cifs: periodically query network interfaces from server

Currently, we only query the server for network interfaces
information at the time of mount, and never afterwards.
This can be a problem, especially for services like Azure,
where the IP address of the channel endpoints can change
over time.

With this change, we schedule a 600s polling of this info
from the server for each tree connect.

An alternative for periodic polling was to do this only at
the time of reconnect. But this could delay the reconnect
time slightly. Also, there are some challenges w.r.t how
we have cifs_reconnect implemented today.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index d8aae257649f..e666d2643ede 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -145,6 +145,25 @@ requeue_resolve:
 	return rc;
 }
 
+static void smb2_query_server_interfaces(struct work_struct *work)
+{
+	int rc;
+	struct cifs_tcon *tcon = container_of(work,
+					struct cifs_tcon,
+					query_interfaces.work);
+
+	/*
+	 * query server network interfaces, in case they change
+	 */
+	rc = SMB3_request_interfaces(0, tcon);
+	if (rc) {
+		cifs_dbg(FYI, "%s: failed to query server interfaces: %d\n",
+				__func__, rc);
+	}
+
+	queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
+			   (SMB_INTERFACE_POLL_INTERVAL * HZ));
+}
 
 static void cifs_resolve_server(struct work_struct *work)
 {
@@ -2276,6 +2295,9 @@ cifs_put_tcon(struct cifs_tcon *tcon)
 	list_del_init(&tcon->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	/* cancel polling of interfaces */
+	cancel_delayed_work_sync(&tcon->query_interfaces);
+
 	if (tcon->use_witness) {
 		int rc;
 
@@ -2513,6 +2535,12 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 	tcon->local_lease = ctx->local_lease;
 	INIT_LIST_HEAD(&tcon->pending_opens);
 
+	/* schedule query interfaces poll */
+	INIT_DELAYED_WORK(&tcon->query_interfaces,
+			  smb2_query_server_interfaces);
+	queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
+			   (SMB_INTERFACE_POLL_INTERVAL * HZ));
+
 	spin_lock(&cifs_tcp_ses_lock);
 	list_add(&tcon->tcon_list, &ses->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);