commit 73f9bfbe3d818bb52266d5c9f3ba57d97842ffe7
author Shyam Prasad N <sprasad@microsoft.com> Mon Jul 19 17:37:52 2021 +0000
committer Steve French <stfrench@microsoft.com> Fri Jan 07 20:09:22 2022 -0600
tree d2cd41b96bddfe592b5a6e9bfd1eb54223947657
parent 1913e1116a3174648cf2e6faedf29204f31cc438

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>

fs/cifs/sess.c

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 03ba308..d12490e 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -308,7 +308,6 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 
 	chan_server = cifs_get_tcp_session(&ctx, ses->server);
 
-	mutex_lock(&ses->session_mutex);
 	spin_lock(&ses->chan_lock);
 	chan = &ses->chans[ses->chan_count];
 	chan->server = chan_server;
@@ -326,6 +325,7 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 
 	spin_unlock(&ses->chan_lock);
 
+	mutex_lock(&ses->session_mutex);
 	/*
 	 * We need to allocate the server crypto now as we will need
 	 * to sign packets before we generate the channel signing key
@@ -334,6 +334,7 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 	rc = smb311_crypto_shash_allocate(chan->server);
 	if (rc) {
 		cifs_dbg(VFS, "%s: crypto alloc failed\n", __func__);
+		mutex_unlock(&ses->session_mutex);
 		goto out;
 	}
 
@@ -341,6 +342,8 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 	if (!rc)
 		rc = cifs_setup_session(xid, ses, chan->server, cifs_sb->local_nls);
 
+	mutex_unlock(&ses->session_mutex);
+
 out:
 	if (rc && chan->server) {
 		spin_lock(&ses->chan_lock);
@@ -355,8 +358,6 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 		spin_unlock(&ses->chan_lock);
 	}
 
-	mutex_unlock(&ses->session_mutex);
-
 	if (rc && chan->server)
 		cifs_put_tcp_session(chan->server, 0);
 
@@ -1053,6 +1054,7 @@ sess_establish_session(struct sess_data *sess_data)
 
 	/* Even if one channel is active, session is in good state */
 	spin_lock(&cifs_tcp_ses_lock);
+	server->tcpStatus = CifsGood;
 	ses->status = CifsGood;
 	spin_unlock(&cifs_tcp_ses_lock);