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, 7 insertions, 1 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 4ba35faff79c..f88d2b10045a 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -113,7 +113,13 @@ enum statusEnum {
 	CifsGood,
 	CifsExiting,
 	CifsNeedReconnect,
-	CifsNeedNegotiate
+	CifsNeedNegotiate,
+	CifsInNegotiate,
+	CifsNeedSessSetup,
+	CifsInSessSetup,
+	CifsNeedTcon,
+	CifsInTcon,
+	CifsInFilesInvalidate
 };
 
 enum securityEnum {