cifs: reinstate sharing of tree connections

Use a similar approach to the SMB session sharing. Add a list of tcons
attached to each SMB session. Move the refcount to non-atomic. Protect
all of the above with the cifs_tcp_ses_lock. Add functions to
properly find and put references to the tcons.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 12 insertions, 31 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 9c95617baa4d..e6bb2d9d5b09 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -742,50 +742,31 @@ CIFSSMBTDis(const int xid, struct cifsTconInfo *tcon)
 	int rc = 0;
 
 	cFYI(1, ("In tree disconnect"));
-	/*
-	 *  If last user of the connection and
-	 *  connection alive - disconnect it
-	 *  If this is the last connection on the server session disconnect it
-	 *  (and inside session disconnect we should check if tcp socket needs
-	 *  to be freed and kernel thread woken up).
-	 */
-	if (tcon)
-		down(&tcon->tconSem);
-	else
-		return -EIO;
 
-	atomic_dec(&tcon->useCount);
-	if (atomic_read(&tcon->useCount) > 0) {
-		up(&tcon->tconSem);
-		return -EBUSY;
-	}
+	/* BB: do we need to check this? These should never be NULL. */
+	if ((tcon->ses == NULL) || (tcon->ses->server == NULL))
+		return -EIO;
 
-	/* No need to return error on this operation if tid invalidated and
-	closed on server already e.g. due to tcp session crashing */
-	if (tcon->need_reconnect) {
-		up(&tcon->tconSem);
+	/*
+	 * No need to return error on this operation if tid invalidated and
+	 * closed on server already e.g. due to tcp session crashing. Also,
+	 * the tcon is no longer on the list, so no need to take lock before
+	 * checking this.
+	 */
+	if (tcon->need_reconnect)
 		return 0;
-	}
 
-	if ((tcon->ses == NULL) || (tcon->ses->server == NULL)) {
-		up(&tcon->tconSem);
-		return -EIO;
-	}
 	rc = small_smb_init(SMB_COM_TREE_DISCONNECT, 0, tcon,
 			    (void **)&smb_buffer);
-	if (rc) {
-		up(&tcon->tconSem);
+	if (rc)
 		return rc;
-	}
 
 	rc = SendReceiveNoRsp(xid, tcon->ses, smb_buffer, 0);
 	if (rc)
 		cFYI(1, ("Tree disconnect failed %d", rc));
 
-	up(&tcon->tconSem);
-
 	/* No need to return error on this operation if tid invalidated and
-	closed on server already e.g. due to tcp session crashing */
+	   closed on server already e.g. due to tcp session crashing */
 	if (rc == -EAGAIN)
 		rc = 0;