cifs: use the chans_need_reconnect bitmap for reconnect status

We use the concept of "binding" when one of the secondary channel
is in the process of connecting/reconnecting to the server. Till this
binding process completes, and the channel is bound to an existing session,
we redirect traffic from other established channels on the binding channel,
effectively blocking all traffic till individual channels get reconnected.

With my last set of commits, we can get rid of this binding serialization.
We now have a bitmap of connection states for each channel. We will use
this bitmap instead for tracking channel status.

Having a bitmap also now enables us to keep the session alive, as long
as even a single channel underneath is alive.

Unfortunately, this also meant that we need to supply the tcp connection
info for the channel during all negotiate and session setup functions.
These changes have resulted in a slightly bigger code churn.
However, I expect perf and robustness improvements in the mchan scenario
after this change.

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

1 files changed, 26 insertions, 10 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index fa80a23f9fcf..9ee5856d63cc 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -169,6 +169,7 @@ static void cifs_resolve_server(struct work_struct *work)
  */
 static void cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server)
 {
+	unsigned int num_sessions = 0;
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon;
 	struct mid_q_entry *mid, *nmid;
@@ -201,6 +202,8 @@ static void cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server
 		if (!CIFS_ALL_CHANS_NEED_RECONNECT(ses))
 			goto next_session;
 
+		num_sessions++;
+
 		list_for_each_entry(tcon, &ses->tcon_list, tcon_list)
 			tcon->need_reconnect = true;
 		if (ses->tcon_ipc)
@@ -211,6 +214,14 @@ next_session:
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	if (num_sessions == 0)
+		return;
+	/*
+	 * before reconnecting the tcp session, mark the smb session (uid)
+	 * and the tid bad so they are not used until reconnected
+	 */
+	cifs_dbg(FYI, "%s: marking sessions and tcons for reconnect\n",
+		 __func__);
 	/* do not want to be sending data on a socket we are freeing */
 	cifs_dbg(FYI, "%s: tearing down socket\n", __func__);
 	mutex_lock(&server->srv_mutex);
@@ -2005,7 +2016,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 			spin_unlock(&ses->chan_lock);
 			cifs_dbg(FYI, "Session needs reconnect\n");
 
-			rc = cifs_negotiate_protocol(xid, ses);
+			rc = cifs_negotiate_protocol(xid, ses, server);
 			if (rc) {
 				mutex_unlock(&ses->session_mutex);
 				/* problem -- put our ses reference */
@@ -2014,7 +2025,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 				return ERR_PTR(rc);
 			}
 
-			rc = cifs_setup_session(xid, ses,
+			rc = cifs_setup_session(xid, ses, server,
 						ctx->local_nls);
 			if (rc) {
 				mutex_unlock(&ses->session_mutex);
@@ -2086,9 +2097,9 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 	ses->chans_need_reconnect = 1;
 	spin_unlock(&ses->chan_lock);
 
-	rc = cifs_negotiate_protocol(xid, ses);
+	rc = cifs_negotiate_protocol(xid, ses, server);
 	if (!rc)
-		rc = cifs_setup_session(xid, ses, ctx->local_nls);
+		rc = cifs_setup_session(xid, ses, server, ctx->local_nls);
 
 	/* each channel uses a different signing key */
 	memcpy(ses->chans[0].signkey, ses->smb3signingkey,
@@ -3820,10 +3831,10 @@ cifs_umount(struct cifs_sb_info *cifs_sb)
 }
 
 int
-cifs_negotiate_protocol(const unsigned int xid, struct cifs_ses *ses)
+cifs_negotiate_protocol(const unsigned int xid, struct cifs_ses *ses,
+			struct TCP_Server_Info *server)
 {
 	int rc = 0;
-	struct TCP_Server_Info *server = cifs_ses_server(ses);
 
 	if (!server->ops->need_neg || !server->ops->negotiate)
 		return -ENOSYS;
@@ -3832,7 +3843,7 @@ cifs_negotiate_protocol(const unsigned int xid, struct cifs_ses *ses)
 	if (!server->ops->need_neg(server))
 		return 0;
 
-	rc = server->ops->negotiate(xid, ses);
+	rc = server->ops->negotiate(xid, ses, server);
 	if (rc == 0) {
 		spin_lock(&GlobalMid_Lock);
 		if (server->tcpStatus == CifsNeedNegotiate)
@@ -3847,12 +3858,17 @@ cifs_negotiate_protocol(const unsigned int xid, struct cifs_ses *ses)
 
 int
 cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
+		   struct TCP_Server_Info *server,
 		   struct nls_table *nls_info)
 {
 	int rc = -ENOSYS;
-	struct TCP_Server_Info *server = cifs_ses_server(ses);
+	bool is_binding = false;
+
+	spin_lock(&ses->chan_lock);
+	is_binding = !CIFS_ALL_CHANS_NEED_RECONNECT(ses);
+	spin_unlock(&ses->chan_lock);
 
-	if (!ses->binding) {
+	if (!is_binding) {
 		ses->capabilities = server->capabilities;
 		if (!linuxExtEnabled)
 			ses->capabilities &= (~server->vals->cap_unix);
@@ -3870,7 +3886,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		 server->sec_mode, server->capabilities, server->timeAdj);
 
 	if (server->ops->sess_setup)
-		rc = server->ops->sess_setup(xid, ses, nls_info);
+		rc = server->ops->sess_setup(xid, ses, server, nls_info);
 
 	if (rc)
 		cifs_server_dbg(VFS, "Send error in SessSetup = %d\n", rc);