From: Shyam Prasad N <sprasad@microsoft.com>
Date: Mon, 3 Jan 2022 08:47:30 +0000
Subject: [PATCH] cifs: during reconnect, update interface if necessary
Git-commit: b54034a73baf9fe31fb3f218c17bd5308a27a1ca
References: bsc#1193629
Patch-mainline: v5.19-rc4

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>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/cifsproto.h |  5 +++
 fs/cifs/connect.c   |  4 +++
 fs/cifs/sess.c      | 79 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)

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)
 {
@@ -244,6 +254,75 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 	return new_chan_count - old_chan_count;
 }
 
+/*
+ * 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.
-- 
2.37.3