cifs: maintain a state machine for tcp/smb/tcon sessions

If functions like cifs_negotiate_protocol, cifs_setup_session,
cifs_tree_connect are called in parallel on different channels,
each of these will be execute the requests. This maybe unnecessary
in some cases, and only the first caller may need to do the work.

This is achieved by having more states for the tcp/smb/tcon session
status fields. And tracking the state of reconnection based on the
state machine.

For example:
for tcp connections:
CifsNew/CifsNeedReconnect ->
  CifsNeedNegotiate ->
    CifsInNegotiate ->
      CifsNeedSessSetup ->
        CifsInSessSetup ->
          CifsGood

for smb sessions:
CifsNew/CifsNeedReconnect ->
  CifsGood

for tcon:
CifsNew/CifsNeedReconnect ->
  CifsInFilesInvalidate ->
    CifsNeedTcon ->
      CifsInTcon ->
        CifsGood

If any channel reconnect sees that it's in the middle of
transition to CifsGood, then they can skip the function.

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

1 files changed, 49 insertions, 12 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 815f629933de..a408187c7002 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -208,10 +208,13 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
 		if (!mark_smb_session && !CIFS_ALL_CHANS_NEED_RECONNECT(ses))
 			goto next_session;
 
+		ses->status = CifsNeedReconnect;
 		num_sessions++;
 
-		list_for_each_entry(tcon, &ses->tcon_list, tcon_list)
+		list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 			tcon->need_reconnect = true;
+			tcon->tidStatus = CifsNeedReconnect;
+		}
 		if (ses->tcon_ipc)
 			ses->tcon_ipc->need_reconnect = true;
 
@@ -2035,12 +2038,12 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 		cifs_dbg(FYI, "Existing smb sess found (status=%d)\n",
 			 ses->status);
 
-		mutex_lock(&ses->session_mutex);
 		spin_lock(&ses->chan_lock);
 		if (cifs_chan_needs_reconnect(ses, server)) {
 			spin_unlock(&ses->chan_lock);
 			cifs_dbg(FYI, "Session needs reconnect\n");
 
+			mutex_lock(&ses->session_mutex);
 			rc = cifs_negotiate_protocol(xid, ses, server);
 			if (rc) {
 				mutex_unlock(&ses->session_mutex);
@@ -2059,10 +2062,11 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 				free_xid(xid);
 				return ERR_PTR(rc);
 			}
+			mutex_unlock(&ses->session_mutex);
+
 			spin_lock(&ses->chan_lock);
 		}
 		spin_unlock(&ses->chan_lock);
-		mutex_unlock(&ses->session_mutex);
 
 		/* existing SMB ses has a server reference already */
 		cifs_put_tcp_session(server, 0);
@@ -2112,7 +2116,6 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 
 	ses->sectype = ctx->sectype;
 	ses->sign = ctx->sign;
-	mutex_lock(&ses->session_mutex);
 
 	/* add server as first channel */
 	spin_lock(&ses->chan_lock);
@@ -2122,15 +2125,16 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 	ses->chans_need_reconnect = 1;
 	spin_unlock(&ses->chan_lock);
 
+	mutex_lock(&ses->session_mutex);
 	rc = cifs_negotiate_protocol(xid, ses, server);
 	if (!rc)
 		rc = cifs_setup_session(xid, ses, server, ctx->local_nls);
+	mutex_unlock(&ses->session_mutex);
 
 	/* each channel uses a different signing key */
 	memcpy(ses->chans[0].signkey, ses->smb3signingkey,
 	       sizeof(ses->smb3signingkey));
 
-	mutex_unlock(&ses->session_mutex);
 	if (rc)
 		goto get_ses_fail;
 
@@ -2347,10 +2351,6 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 		}
 	}
 
-	/*
-	 * BB Do we need to wrap session_mutex around this TCon call and Unix
-	 * SetFS as we do on SessSetup and reconnect?
-	 */
 	xid = get_xid();
 	rc = ses->server->ops->tree_connect(xid, ses, ctx->UNC, tcon,
 					    ctx->local_nls);
@@ -3870,14 +3870,20 @@ cifs_negotiate_protocol(const unsigned int xid, struct cifs_ses *ses,
 		return -ENOSYS;
 
 	/* only send once per connect */
-	if (!server->ops->need_neg(server))
+	spin_lock(&cifs_tcp_ses_lock);
+	if (!server->ops->need_neg(server) ||
+	    server->tcpStatus != CifsNeedNegotiate) {
+		spin_unlock(&cifs_tcp_ses_lock);
 		return 0;
+	}
+	server->tcpStatus = CifsInNegotiate;
+	spin_unlock(&cifs_tcp_ses_lock);
 
 	rc = server->ops->negotiate(xid, ses, server);
 	if (rc == 0) {
 		spin_lock(&cifs_tcp_ses_lock);
-		if (server->tcpStatus == CifsNeedNegotiate)
-			server->tcpStatus = CifsGood;
+		if (server->tcpStatus == CifsInNegotiate)
+			server->tcpStatus = CifsNeedSessSetup;
 		else
 			rc = -EHOSTDOWN;
 		spin_unlock(&cifs_tcp_ses_lock);
@@ -3894,6 +3900,15 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 	int rc = -ENOSYS;
 	bool is_binding = false;
 
+	/* only send once per connect */
+	spin_lock(&cifs_tcp_ses_lock);
+	if (server->tcpStatus != CifsNeedSessSetup) {
+		spin_unlock(&cifs_tcp_ses_lock);
+		return 0;
+	}
+	ses->status = CifsInSessSetup;
+	spin_unlock(&cifs_tcp_ses_lock);
+
 	spin_lock(&ses->chan_lock);
 	is_binding = !CIFS_ALL_CHANS_NEED_RECONNECT(ses);
 	spin_unlock(&ses->chan_lock);
@@ -4264,6 +4279,17 @@ static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *t
 	struct dfs_cache_tgt_iterator *tit;
 	bool target_match;
 
+	/* only send once per connect */
+	spin_lock(&cifs_tcp_ses_lock);
+	if (tcon->ses->status != CifsGood ||
+	    (tcon->tidStatus != CifsNew &&
+	    tcon->tidStatus != CifsNeedTcon)) {
+		spin_unlock(&cifs_tcp_ses_lock);
+		return 0;
+	}
+	tcon->tidStatus = CifsInTcon;
+	spin_unlock(&cifs_tcp_ses_lock);
+
 	extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
 
 	tit = dfs_cache_get_tgt_iterator(tl);
@@ -4422,6 +4448,17 @@ int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const stru
 {
 	const struct smb_version_operations *ops = tcon->ses->server->ops;
 
+	/* only send once per connect */
+	spin_lock(&cifs_tcp_ses_lock);
+	if (tcon->ses->status != CifsGood ||
+	    (tcon->tidStatus != CifsNew &&
+	    tcon->tidStatus != CifsNeedTcon)) {
+		spin_unlock(&cifs_tcp_ses_lock);
+		return 0;
+	}
+	tcon->tidStatus = CifsInTcon;
+	spin_unlock(&cifs_tcp_ses_lock);
+
 	return ops->tree_connect(xid, tcon->ses, tcon->treeName, tcon, nlsc);
 }
 #endif