cifs: during reconnect, update interface if necessary

Going forward, the plan is to periodically query the server
for it's interfaces (when multichannel is enabled).

This change allows checking for inactive interfaces during
reconnect, and reconnect to a new interface if necessary.

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

3 files changed, 88 insertions, 0 deletions

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 3b7366ec03c7..00c4a8aa2649 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -636,6 +636,11 @@ cifs_chan_clear_need_reconnect(struct cifs_ses *ses,
 bool
 cifs_chan_needs_reconnect(struct cifs_ses *ses,
 			  struct TCP_Server_Info *server);
+bool
+cifs_chan_is_iface_active(struct cifs_ses *ses,
+			  struct TCP_Server_Info *server);
+int
+cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server);
 
 void extract_unc_hostname(const char *unc, const char **h, size_t *len);
 int copy_path_name(char *dst, const char *src);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 248fe1805c17..d8aae257649f 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -232,6 +232,10 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
 
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+		/* check if iface is still active */
+		if (!cifs_chan_is_iface_active(ses, server))
+			cifs_chan_update_iface(ses, server);
+
 		spin_lock(&ses->chan_lock);
 		if (!mark_smb_session && cifs_chan_needs_reconnect(ses, server))
 			goto next_session;
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index d7b6e5687df2..7c26ee70c8b0 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -146,6 +146,16 @@ cifs_chan_needs_reconnect(struct cifs_ses *ses,
 	return CIFS_CHAN_NEEDS_RECONNECT(ses, chan_index);
 }
 
+bool
+cifs_chan_is_iface_active(struct cifs_ses *ses,
+			  struct TCP_Server_Info *server)
+{
+	unsigned int chan_index = cifs_ses_get_chan_index(ses, server);
+
+	return ses->chans[chan_index].iface &&
+		ses->chans[chan_index].iface->is_active;
+}
+
 /* returns number of channels added */
 int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 {
@@ -245,6 +255,75 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 }
 
 /*
+ * update the iface for the channel if necessary.
+ * will return 0 when iface is updated. 1 otherwise
+ * Must be called with chan_lock held.
+ */
+int
+cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server)
+{
+	unsigned int chan_index = cifs_ses_get_chan_index(ses, server);
+	struct cifs_server_iface *iface = NULL;
+	struct cifs_server_iface *old_iface = NULL;
+	int rc = 0;
+
+	/* primary channel. This can never go away */
+	if (!chan_index)
+		return 0;
+
+	if (ses->chans[chan_index].iface) {
+		old_iface = ses->chans[chan_index].iface;
+		if (old_iface->is_active)
+			return 1;
+	}
+
+	spin_lock(&ses->iface_lock);
+
+	/* then look for a new one */
+	list_for_each_entry(iface, &ses->iface_list, iface_head) {
+		if (!iface->is_active ||
+		    (is_ses_using_iface(ses, iface) &&
+		     !iface->rss_capable)) {
+			continue;
+		}
+		kref_get(&iface->refcount);
+	}
+
+	if (!list_entry_is_head(iface, &ses->iface_list, iface_head)) {
+		rc = 1;
+		iface = NULL;
+		cifs_dbg(FYI, "unable to find a suitable iface\n");
+	}
+
+	ses->chans[chan_index].iface = iface;
+
+	/* now drop the ref to the current iface */
+	if (old_iface && iface) {
+		kref_put(&old_iface->refcount, release_iface);
+		cifs_dbg(FYI, "replacing iface: %pIS with %pIS\n",
+			 &old_iface->sockaddr,
+			 &iface->sockaddr);
+	} else if (old_iface) {
+		kref_put(&old_iface->refcount, release_iface);
+		cifs_dbg(FYI, "releasing ref to iface: %pIS\n",
+			 &old_iface->sockaddr);
+	} else {
+		WARN_ON(!iface);
+		cifs_dbg(FYI, "adding new iface: %pIS\n", &iface->sockaddr);
+	}
+
+	spin_unlock(&ses->iface_lock);
+
+	/* No iface is found. if secondary chan, drop connection */
+	if (!iface && CIFS_SERVER_IS_CHAN(server)) {
+		cifs_put_tcp_session(server, false);
+		ses->chans[chan_index].server = NULL;
+	}
+
+	return rc;
+}
+
+/*
  * If server is a channel of ses, return the corresponding enclosing
  * cifs_chan otherwise return NULL.
  */