2 files changed, 41 insertions, 16 deletions

diff --git a/src/kernel/queue.h b/src/kernel/queue.h
new file mode 100644
index 0000000..896824f
--- /dev/null
+++ b/src/kernel/queue.h
@@ -0,0 +1,37 @@
+/* documented in queue(9) */
+#include <kernel/panic.h>
+
+/* struct QueueNode {
+ *   ...
+ *   struct QueueNode *name_next;
+ *   ...
+ * }
+ * struct QueueHead {
+ *   struct QueueNode *head, **slot;
+ * }
+ */
+
+#define QUEUE_INIT(q) do { \
+	(q)->head = NULL; \
+	(q)->slot = &(q)->head; \
+} while(0)
+
+#define QUEUE_APPEND(q, name, el) do { \
+	assert((el)->name##_next == NULL); \
+	assert((q)->slot != NULL); \
+	assert(*(q)->slot == NULL); \
+	*(q)->slot = (el); \
+	(q)->slot = &(el)->name##_next; \
+} while(0)
+
+#define QUEUE_POP(q, name) ({ \
+	typeof((q)->head) __q_el = (q)->head; \
+	if (__q_el) { \
+		(q)->head = __q_el->name##_next; \
+		__q_el->name##_next = NULL; \
+		if ((q)->slot == &__q_el->name##_next) { \
+			(q)->slot = &(q)->head; \
+		} \
+	} \
+	__q_el; \
+})
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index 8a80f04..8e6f14a 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -3,6 +3,7 @@
 #include <kernel/malloc.h>
 #include <kernel/panic.h>
 #include <kernel/proc.h>
+#include <kernel/queue.h>
 #include <kernel/vfs/request.h>
 #include <shared/mem.h>
 
@@ -236,32 +237,19 @@ vfsback_provdown(VfsBackend *b)
 void
 reqqueue_init(ReqQueue *q)
 {
-	q->head = NULL;
-	q->slot = &q->head;
+	QUEUE_INIT(q);
 }
 
 void
 reqqueue_join(ReqQueue *q, VfsReq *req)
 {
-	assert(req->reqqueue_next == NULL);
-	assert(q->slot != NULL);
-	assert(*q->slot == NULL);
-	*q->slot = req;
-	q->slot = &req->reqqueue_next;
+	QUEUE_APPEND(q, reqqueue, req);
 }
 
 VfsReq *
 reqqueue_pop(ReqQueue *q)
 {
-	VfsReq *req = q->head;
-	if (req) {
-		q->head = req->reqqueue_next;
-		req->reqqueue_next = NULL;
-		if (q->slot == &req->reqqueue_next) {
-			q->slot = &q->head;
-		}
-	}
-	return req;
+	return QUEUE_POP(q, reqqueue);
 }
 
 void