cifs: move locked sections out of DeleteMidQEntry and AllocMidQEntry

In later patches, we're going to need to have finer-grained control
over the addition and removal of these structs from the pending_mid_q
and we'll need to be able to call the destructor while holding the
spinlock. Move the locked sections out of both routines and into
the callers. Fix up current callers of DeleteMidQEntry to call a new
routine that dequeues the entry and then destroys it.

Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/transport.c

diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index b9eb0cf..801726b 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -63,9 +63,6 @@
 
 	atomic_inc(&midCount);
 	temp->midState = MID_REQUEST_ALLOCATED;
-	spin_lock(&GlobalMid_Lock);
-	list_add_tail(&temp->qhead, &server->pending_mid_q);
-	spin_unlock(&GlobalMid_Lock);
 	return temp;
 }
 
@@ -75,10 +72,7 @@
 #ifdef CONFIG_CIFS_STATS2
 	unsigned long now;
 #endif
-	spin_lock(&GlobalMid_Lock);
 	midEntry->midState = MID_FREE;
-	list_del(&midEntry->qhead);
-	spin_unlock(&GlobalMid_Lock);
 	atomic_dec(&midCount);
 	if (midEntry->largeBuf)
 		cifs_buf_release(midEntry->resp_buf);
@@ -103,6 +97,16 @@
 	mempool_free(midEntry, cifs_mid_poolp);
 }
 
+static void
+delete_mid(struct mid_q_entry *mid)
+{
+	spin_lock(&GlobalMid_Lock);
+	list_del(&mid->qhead);
+	spin_unlock(&GlobalMid_Lock);
+
+	DeleteMidQEntry(mid);
+}
+
 static int
 smb_sendv(struct TCP_Server_Info *server, struct kvec *iov, int n_vec)
 {
@@ -308,6 +312,9 @@
 	*ppmidQ = AllocMidQEntry(in_buf, ses->server);
 	if (*ppmidQ == NULL)
 		return -ENOMEM;
+	spin_lock(&GlobalMid_Lock);
+	list_add_tail(&(*ppmidQ)->qhead, &ses->server->pending_mid_q);
+	spin_unlock(&GlobalMid_Lock);
 	return 0;
 }
 
@@ -508,7 +515,7 @@
 			}
 		}
 		spin_unlock(&GlobalMid_Lock);
-		DeleteMidQEntry(midQ);
+		delete_mid(midQ);
 		/* Update # of requests on wire to server */
 		atomic_dec(&ses->server->inFlight);
 		wake_up(&ses->server->request_q);
@@ -564,14 +571,14 @@
 		if ((flags & CIFS_NO_RESP) == 0)
 			midQ->resp_buf = NULL;  /* mark it so buf will
 						   not be freed by
-						   DeleteMidQEntry */
+						   delete_mid */
 	} else {
 		rc = -EIO;
 		cFYI(1, "Bad MID state?");
 	}
 
 out:
-	DeleteMidQEntry(midQ);
+	delete_mid(midQ);
 	atomic_dec(&ses->server->inFlight);
 	wake_up(&ses->server->request_q);
 
@@ -699,7 +706,7 @@
 			}
 		}
 		spin_unlock(&GlobalMid_Lock);
-		DeleteMidQEntry(midQ);
+		delete_mid(midQ);
 		/* Update # of requests on wire to server */
 		atomic_dec(&ses->server->inFlight);
 		wake_up(&ses->server->request_q);
@@ -755,7 +762,7 @@
 	}
 
 out:
-	DeleteMidQEntry(midQ);
+	delete_mid(midQ);
 	atomic_dec(&ses->server->inFlight);
 	wake_up(&ses->server->request_q);
 
@@ -863,7 +870,7 @@
 
 	rc = cifs_sign_smb(in_buf, ses->server, &midQ->sequence_number);
 	if (rc) {
-		DeleteMidQEntry(midQ);
+		delete_mid(midQ);
 		mutex_unlock(&ses->server->srv_mutex);
 		return rc;
 	}
@@ -880,7 +887,7 @@
 	mutex_unlock(&ses->server->srv_mutex);
 
 	if (rc < 0) {
-		DeleteMidQEntry(midQ);
+		delete_mid(midQ);
 		return rc;
 	}
 
@@ -902,7 +909,7 @@
 
 			rc = send_nt_cancel(tcon, in_buf, midQ);
 			if (rc) {
-				DeleteMidQEntry(midQ);
+				delete_mid(midQ);
 				return rc;
 			}
 		} else {
@@ -914,7 +921,7 @@
 			/* If we get -ENOLCK back the lock may have
 			   already been removed. Don't exit in this case. */
 			if (rc && rc != -ENOLCK) {
-				DeleteMidQEntry(midQ);
+				delete_mid(midQ);
 				return rc;
 			}
 		}
@@ -951,7 +958,7 @@
 			}
 		}
 		spin_unlock(&GlobalMid_Lock);
-		DeleteMidQEntry(midQ);
+		delete_mid(midQ);
 		return rc;
 	}
 
@@ -1001,7 +1008,7 @@
 		BCC(out_buf) = le16_to_cpu(BCC_LE(out_buf));
 
 out:
-	DeleteMidQEntry(midQ);
+	delete_mid(midQ);
 	if (rstart && rc == -EACCES)
 		return -ERESTARTSYS;
 	return rc;