fs: dlm: simplify writequeue handling

This patch cleans up the current dlm sending allocator handling by using
some named macros, list functionality and removes some goto statements.
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

@@ -102,6 +102,9 @@ struct listen_connection {
 	struct work_struct rwork;
 };
 
+#define DLM_WQ_REMAIN_BYTES(e) (PAGE_SIZE - e->end)
+#define DLM_WQ_LENGTH_BYTES(e) (e->end - e->offset)
+
 /* An entry waiting to be sent */
 struct writequeue_entry {
 	struct list_head list;
@@ -1351,7 +1354,7 @@ static struct writequeue_entry *new_writequeue_entry(struct connection *con,
 {
 	struct writequeue_entry *entry;
 
-	entry = kmalloc(sizeof(struct writequeue_entry), allocation);
+	entry = kzalloc(sizeof(*entry), allocation);
 	if (!entry)
 		return NULL;
 
@@ -1361,62 +1364,62 @@ static struct writequeue_entry *new_writequeue_entry(struct connection *con,
 		return NULL;
 	}
 
-	entry->offset = 0;
-	entry->len = 0;
-	entry->end = 0;
-	entry->users = 0;
 	entry->con = con;
+	entry->users = 1;
 
 	return entry;
 }
 
-void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
+static struct writequeue_entry *new_wq_entry(struct connection *con, int len,
+					     gfp_t allocation, char **ppc)
 {
-	struct connection *con;
 	struct writequeue_entry *e;
-	int offset = 0;
-
-	if (len > DEFAULT_BUFFER_SIZE ||
-	    len < sizeof(struct dlm_header)) {
-		BUILD_BUG_ON(PAGE_SIZE < DEFAULT_BUFFER_SIZE);
-		log_print("failed to allocate a buffer of size %d", len);
-		WARN_ON(1);
-		return NULL;
-	}
-
-	con = nodeid2con(nodeid, allocation);
-	if (!con)
-		return NULL;
 
 	spin_lock(&con->writequeue_lock);
-	e = list_entry(con->writequeue.prev, struct writequeue_entry, list);
-	if ((&e->list == &con->writequeue) ||
-	    (PAGE_SIZE - e->end < len)) {
-		e = NULL;
-	} else {
-		offset = e->end;
+	if (!list_empty(&con->writequeue)) {
+		e = list_last_entry(&con->writequeue, struct writequeue_entry, list);
+		if (DLM_WQ_REMAIN_BYTES(e) >= len) {
+			*ppc = page_address(e->page) + e->end;
 			e->end += len;
 			e->users++;
-	}
 			spin_unlock(&con->writequeue_lock);
 
-	if (e) {
-	got_one:
-		*ppc = page_address(e->page) + offset;
 			return e;
 		}
+	}
+	spin_unlock(&con->writequeue_lock);
 
 	e = new_writequeue_entry(con, allocation);
-	if (e) {
-		spin_lock(&con->writequeue_lock);
-		offset = e->end;
+	if (!e)
+		return NULL;
+
+	*ppc = page_address(e->page);
 	e->end += len;
-		e->users++;
+
+	spin_lock(&con->writequeue_lock);
 	list_add_tail(&e->list, &con->writequeue);
 	spin_unlock(&con->writequeue_lock);
-		goto got_one;
+
+	return e;
+};
+
+void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
+{
+	struct connection *con;
+
+	if (len > DEFAULT_BUFFER_SIZE ||
+	    len < sizeof(struct dlm_header)) {
+		BUILD_BUG_ON(PAGE_SIZE < DEFAULT_BUFFER_SIZE);
+		log_print("failed to allocate a buffer of size %d", len);
+		WARN_ON(1);
+		return NULL;
 	}
+
+	con = nodeid2con(nodeid, allocation);
+	if (!con)
 		return NULL;
+
+	return new_wq_entry(con, len, allocation, ppc);
 }
 
 void dlm_lowcomms_commit_buffer(void *mh)
@@ -1429,7 +1432,8 @@ void dlm_lowcomms_commit_buffer(void *mh)
 	users = --e->users;
 	if (users)
 		goto out;
-	e->len = e->end - e->offset;
+
+	e->len = DLM_WQ_LENGTH_BYTES(e);
 	spin_unlock(&con->writequeue_lock);
 
 	queue_work(send_workqueue, &con->swork);
@@ -1455,11 +1459,10 @@ static void send_to_sock(struct connection *con)
 
 	spin_lock(&con->writequeue_lock);
 	for (;;) {
-		e = list_entry(con->writequeue.next, struct writequeue_entry,
-			       list);
-		if ((struct list_head *) e == &con->writequeue)
+		if (list_empty(&con->writequeue))
 			break;
 
+		e = list_first_entry(&con->writequeue, struct writequeue_entry, list);
 		len = e->len;
 		offset = e->offset;
 		BUG_ON(len == 0 && e->users == 0);