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;