[PATCH 10/11] cifs: handle when server stops supporting multichannel

[Shyam Prasad N <nspmangalore@gmail.com>]

When a server stops supporting multichannel, we will
keep attempting reconnects to the secondary channels today.
Avoid this by freeing extra channels when negotiate
returns no multichannel support.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
---
 fs/cifs/cifsproto.h |  2 ++
 fs/cifs/connect.c   |  6 ++++++
 fs/cifs/sess.c      | 35 +++++++++++++++++++++++++++++++++++
 fs/cifs/smb2ops.c   |  8 ++++++++
 4 files changed, 51 insertions(+)

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 30fd81268eb7..343e582672b9 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -638,6 +638,8 @@ cifs_chan_needs_reconnect(struct cifs_ses *ses,
 bool
 cifs_chan_is_iface_active(struct cifs_ses *ses,
 			  struct TCP_Server_Info *server);
+void
+cifs_disable_extra_channels(struct cifs_ses *ses);
 int
 cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server);
 int
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index b9af60417194..6375b08b9bcb 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -130,6 +130,12 @@ static void smb2_query_server_interfaces(struct work_struct *work)
 	if (rc) {
 		cifs_dbg(FYI, "%s: failed to query server interfaces: %d\n",
 				__func__, rc);
+
+		if (rc == -EOPNOTSUPP) {
+			/* cancel polling of interfaces and do not resched */
+			cancel_delayed_work_sync(&tcon->query_interfaces);
+			return;
+		}
 	}
 
 	queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 9b51b2309e9c..34ae292bdff2 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -274,6 +274,41 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 	return new_chan_count - old_chan_count;
 }
 
+/*
+ * called when multichannel is disabled by the server
+ */
+void
+cifs_disable_extra_channels(struct cifs_ses *ses)
+{
+	int i, chan_count;
+	struct cifs_server_iface *iface = NULL;
+	struct TCP_Server_Info *server = NULL;
+
+	spin_lock(&ses->chan_lock);
+	chan_count = ses->chan_count;
+	ses->chan_count = 1;
+	for (i = 1; i < chan_count; i++) {
+		iface = ses->chans[i].iface;
+		server = ses->chans[i].server;
+		spin_unlock(&ses->chan_lock);
+
+		if (iface) {
+			spin_lock(&ses->iface_lock);
+			kref_put(&iface->refcount, release_iface);
+			iface->num_channels--;
+			if (--iface->weight_fulfilled < 0)
+				iface->weight_fulfilled = 0;
+			spin_unlock(&ses->iface_lock);
+		}
+		cifs_put_tcp_session(server, 0);
+
+		spin_lock(&ses->chan_lock);
+		ses->chans[i].iface = NULL;
+		ses->chans[i].server = NULL;
+	}
+	spin_unlock(&ses->chan_lock);
+}
+
 /*
  * update the iface for the channel if necessary.
  * will return 0 when iface is updated, 1 if removed, 2 otherwise
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index a5e53cb1ac49..c7a8a6049291 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -411,6 +411,14 @@ smb2_negotiate(const unsigned int xid,
 	/* BB we probably don't need to retry with modern servers */
 	if (rc == -EAGAIN)
 		rc = -EHOSTDOWN;
+
+	if (!rc &&
+	    ses->chan_count > 1 &&
+	    !(server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL)) {
+		cifs_dbg(VFS, "server %s does not support multichannel anymore\n", ses->server->hostname);
+		cifs_disable_extra_channels(ses);
+	}
+
 	return rc;
 }
 
-- 
2.34.1