virtio: Add ability to detach unused buffers from vrings

There's currently no way for a virtio driver to ask for unused buffers, so it has to keep a list itself to reclaim them at shutdown. This is redundant, since virtio_ring stores that information. So add a new hook to do this. Signed-off-by: Shirley Ma <xma@us.ibm.com> Signed-off-by: Amit Shah <amit.shah@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>

virtio: Add ability to detach unused buffers from vrings
There's currently no way for a virtio driver to ask for unused buffers, so it has to keep a list itself to reclaim them at shutdown. This is redundant, since virtio_ring stores that information. So add a new hook to do this. Signed-off-by: Shirley Ma <xma@us.ibm.com> Signed-off-by: Amit Shah <amit.shah@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Shirley Ma · David S. Miller
1 parent 28aecb9d77
Showing 2 changed files with 29 additions and 0 deletions Side-by-side Diff
drivers/virtio/virtio_ring.c
include/linux/virtio.h
@@ -334,6 +334,30 @@
 	return true;
 }
  
+static void *vring_detach_unused_buf(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	unsigned int i;
+	void *buf;
+
+	START_USE(vq);
+
+	for (i = 0; i < vq->vring.num; i++) {
+		if (!vq->data[i])
+			continue;
+		/* detach_buf clears data, so grab it now. */
+		buf = vq->data[i];
+		detach_buf(vq, i);
+		END_USE(vq);
+		return buf;
+	}
+	/* That should have freed everything. */
+	BUG_ON(vq->num_free != vq->vring.num);
+
+	END_USE(vq);
+	return NULL;
+}
+
 irqreturn_t vring_interrupt(int irq, void *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
@@ -360,6 +384,7 @@
 	.kick = vring_kick,
 	.disable_cb = vring_disable_cb,
 	.enable_cb = vring_enable_cb,
+	.detach_unused_buf = vring_detach_unused_buf,
 };
  
 struct virtqueue *vring_new_virtqueue(unsigned int num,
@@ -51,6 +51,9 @@
  *	This re-enables callbacks; it returns "false" if there are pending
  *	buffers in the queue, to detect a possible race between the driver
  *	checking for more work, and enabling callbacks.
+ * @detach_unused_buf: detach first unused buffer
+ * 	vq: the struct virtqueue we're talking about.
+ * 	Returns NULL or the "data" token handed to add_buf
  *
  * Locking rules are straightforward: the driver is responsible for
  * locking.  No two operations may be invoked simultaneously, with the exception
@@ -71,6 +74,7 @@
  
 	void (*disable_cb)(struct virtqueue *vq);
 	bool (*enable_cb)(struct virtqueue *vq);
+	void *(*detach_unused_buf)(struct virtqueue *vq);
 };
  
 /**
...	...	@@ -334,6 +334,30 @@
334	334	return true;
335	335	}
336	336
	337	+static void vring_detach_unused_buf(struct virtqueue _vq)
	338	+{
	339	+ struct vring_virtqueue *vq = to_vvq(_vq);
	340	+ unsigned int i;
	341	+ void *buf;
	342	+
	343	+ START_USE(vq);
	344	+
	345	+ for (i = 0; i < vq->vring.num; i++) {
	346	+ if (!vq->data[i])
	347	+ continue;
	348	+ /* detach_buf clears data, so grab it now. */
	349	+ buf = vq->data[i];
	350	+ detach_buf(vq, i);
	351	+ END_USE(vq);
	352	+ return buf;
	353	+ }
	354	+ /* That should have freed everything. */
	355	+ BUG_ON(vq->num_free != vq->vring.num);
	356	+
	357	+ END_USE(vq);
	358	+ return NULL;
	359	+}
	360	+
337	361	irqreturn_t vring_interrupt(int irq, void *_vq)
338	362	{
339	363	struct vring_virtqueue *vq = to_vvq(_vq);
...	...	@@ -360,6 +384,7 @@
360	384	.kick = vring_kick,
361	385	.disable_cb = vring_disable_cb,
362	386	.enable_cb = vring_enable_cb,
	387	+ .detach_unused_buf = vring_detach_unused_buf,
363	388	};
364	389
365	390	struct virtqueue *vring_new_virtqueue(unsigned int num,
...	...	@@ -51,6 +51,9 @@
51	51	* This re-enables callbacks; it returns "false" if there are pending
52	52	* buffers in the queue, to detect a possible race between the driver
53	53	* checking for more work, and enabling callbacks.
	54	+ * @detach_unused_buf: detach first unused buffer
	55	+ * vq: the struct virtqueue we're talking about.
	56	+ * Returns NULL or the "data" token handed to add_buf
54	57	*
55	58	* Locking rules are straightforward: the driver is responsible for
56	59	* locking. No two operations may be invoked simultaneously, with the exception
...	...	@@ -71,6 +74,7 @@
71	74
72	75	void (disable_cb)(struct virtqueue vq);
73	76	bool (enable_cb)(struct virtqueue vq);
	77	+ void (detach_unused_buf)(struct virtqueue *vq);
74	78	};
75	79
76	80	/**