kernel: rework postqueue

Keeping its old name for now to make things easier for myself.

This might just be replaced by sys/queue.h soon.

2 files changed, 71 insertions, 0 deletions

diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index d4ea16c..8f44afb 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -242,3 +242,62 @@ vfsback_provdown(VfsBackend *b)
 	}
 	vfsback_checkfree(b);
 }
+
+void
+postqueue_init(ReqQueue *q)
+{
+	q->head = NULL;
+}
+
+void
+postqueue_join(ReqQueue *q, VfsReq *req)
+{
+	if (req->postqueue_next)
+		panic_invalid_state();
+
+	VfsReq **it = &q->head;
+	while (*it != NULL) {
+		it = &(*it)->postqueue_next;
+	}
+	*it = req;
+}
+
+VfsReq *
+postqueue_pop(ReqQueue *q)
+{
+	VfsReq *req = q->head;
+	if (req) {
+		q->head = req->postqueue_next;
+		req->postqueue_next = NULL;
+	}
+	return req;
+}
+
+void
+postqueue_ringreadall(ReqQueue *q, ring_t *r)
+{
+	VfsReq **queue = &q->head; /* whatever */
+	VfsReq *req;
+	char tmp[64];
+	size_t mlen = 0;
+	if (ring_used(r) == 0) return;
+
+	/* read as much as the biggest request wants */
+	for (req = *queue; req; req = req->postqueue_next)
+		mlen = max(mlen, req->output.len);
+	mlen = min(mlen, sizeof tmp);
+	mlen = ring_get(r, tmp, mlen);
+
+	while (*queue) {
+		req = *queue;
+		*queue = req->postqueue_next;
+		req->postqueue_next = NULL;
+
+		size_t ret = min(mlen, req->output.len);
+		assert(req->type == VFSOP_READ);
+		if (req->caller) {
+			pcpy_to(req->caller, req->output.buf, tmp, ret);
+		}
+		vfsreq_finish_short(req, ret);
+	}
+}
diff --git a/src/kernel/vfs/request.h b/src/kernel/vfs/request.h
index 06c46e7..616c044 100644
--- a/src/kernel/vfs/request.h
+++ b/src/kernel/vfs/request.h
@@ -1,5 +1,6 @@
 #pragma once
 #include <kernel/types.h>
+#include <shared/ring.h>
 #include <stdbool.h>
 #include <stddef.h>
 
@@ -77,3 +78,14 @@ void vfsback_userdown(VfsBackend *);
 
 /** Decrements the "provider" reference count. */
 void vfsback_provdown(VfsBackend *);
+
+struct ReqQueue {
+	VfsReq *head;
+};
+void postqueue_init(ReqQueue *q);
+void postqueue_join(ReqQueue *q, VfsReq *req);
+VfsReq *postqueue_pop(ReqQueue *q);
+
+/** If there are any pending read requests, and the ring buffer isn't empty, fulfill them
+ * all with a single read. */
+void postqueue_ringreadall(ReqQueue *q, ring_t *r);