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Commit c021eac4 authored by Shirley Ma's avatar Shirley Ma Committed by Rusty Russell
Browse files

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: default avatarShirley Ma <xma@us.ibm.com>
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 69740c8b

drivers/virtio/virtio_ring.c

+25 −0
Original line number Original line Diff line number Diff line
@@ -351,6 +351,30 @@ static bool vring_enable_cb(struct virtqueue *_vq) 
	return true;

	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)

irqreturn_t vring_interrupt(int irq, void *_vq)

{

{

	struct vring_virtqueue *vq = to_vvq(_vq);

	struct vring_virtqueue *vq = to_vvq(_vq);
@@ -377,6 +401,7 @@ static struct virtqueue_ops vring_vq_ops = { 
	.kick = vring_kick,

	.kick = vring_kick,

	.disable_cb = vring_disable_cb,

	.disable_cb = vring_disable_cb,

	.enable_cb = vring_enable_cb,

	.enable_cb = vring_enable_cb,

	.detach_unused_buf = vring_detach_unused_buf,

};

};





struct virtqueue *vring_new_virtqueue(unsigned int num,

struct virtqueue *vring_new_virtqueue(unsigned int num,

include/linux/virtio.h

+4 −0
Original line number Original line Diff line number Diff line
@@ -51,6 +51,9 @@ struct virtqueue { 
 *	This re-enables callbacks; it returns "false" if there are pending

 *	This re-enables callbacks; it returns "false" if there are pending

 *	buffers in the queue, to detect a possible race between the driver

 *	buffers in the queue, to detect a possible race between the driver

 *	checking for more work, and enabling callbacks.

 *	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 rules are straightforward: the driver is responsible for

 * locking.  No two operations may be invoked simultaneously, with the exception

 * locking.  No two operations may be invoked simultaneously, with the exception
@@ -71,6 +74,7 @@ struct virtqueue_ops { 




	void (*disable_cb)(struct virtqueue *vq);

	void (*disable_cb)(struct virtqueue *vq);

	bool (*enable_cb)(struct virtqueue *vq);

	bool (*enable_cb)(struct virtqueue *vq);

	void *(*detach_unused_buf)(struct virtqueue *vq);

};

};





/**

/**