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, 16 insertions, 8 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 3ef2796e2f24..071e2f21a7db 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -73,6 +73,16 @@ cifs_mark_open_files_invalid(struct cifs_tcon *tcon)
 	struct list_head *tmp;
 	struct list_head *tmp1;
 
+	/* only send once per connect */
+	spin_lock(&cifs_tcp_ses_lock);
+	if (tcon->ses->status != CifsGood ||
+	    tcon->tidStatus != CifsNeedReconnect) {
+		spin_unlock(&cifs_tcp_ses_lock);
+		return;
+	}
+	tcon->tidStatus = CifsInFilesInvalidate;
+	spin_unlock(&cifs_tcp_ses_lock);
+
 	/* list all files open on tree connection and mark them invalid */
 	spin_lock(&tcon->open_file_lock);
 	list_for_each_safe(tmp, tmp1, &tcon->openFileList) {
@@ -89,6 +99,11 @@ cifs_mark_open_files_invalid(struct cifs_tcon *tcon)
 	memset(tcon->crfid.fid, 0, sizeof(struct cifs_fid));
 	mutex_unlock(&tcon->crfid.fid_mutex);
 
+	spin_lock(&cifs_tcp_ses_lock);
+	if (tcon->tidStatus == CifsInFilesInvalidate)
+		tcon->tidStatus = CifsNeedTcon;
+	spin_unlock(&cifs_tcp_ses_lock);
+
 	/*
 	 * BB Add call to invalidate_inodes(sb) for all superblocks mounted
 	 * to this tcon.
@@ -183,12 +198,6 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
 	nls_codepage = load_nls_default();
 
 	/*
-	 * need to prevent multiple threads trying to simultaneously
-	 * reconnect the same SMB session
-	 */
-	mutex_lock(&ses->session_mutex);
-
-	/*
 	 * Recheck after acquire mutex. If another thread is negotiating
 	 * and the server never sends an answer the socket will be closed
 	 * and tcpStatus set to reconnect.
@@ -197,7 +206,6 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
 	if (server->tcpStatus == CifsNeedReconnect) {
 		spin_unlock(&cifs_tcp_ses_lock);
 		rc = -EHOSTDOWN;
-		mutex_unlock(&ses->session_mutex);
 		goto out;
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
@@ -215,11 +223,11 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
 			goto skip_sess_setup;
 
 		rc = -EHOSTDOWN;
-		mutex_unlock(&ses->session_mutex);
 		goto out;
 	}
 	spin_unlock(&ses->chan_lock);
 
+	mutex_lock(&ses->session_mutex);
 	rc = cifs_negotiate_protocol(0, ses, server);
 	if (!rc)
 		rc = cifs_setup_session(0, ses, server, nls_codepage);