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Commit e19d6763 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by David S. Miller
Browse files

skb: report completion status for zero copy skbs 



Even if skb is marked for zero copy, net core might still decide
to copy it later which is somewhat slower than a copy in user context:
besides copying the data we need to pin/unpin the pages.

Add a parameter reporting such cases through zero copy callback:
if this happens a lot, device can take this into account
and switch to copying in user context.

This patch updates all users but ignores the passed value for now:
it will be used by follow-up patches.

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 202975b4

drivers/vhost/vhost.c

+1 −1
Original line number Diff line number Diff line
@@ -1600,7 +1600,7 @@ void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs) 
	kfree(ubufs);

}



void vhost_zerocopy_callback(struct ubuf_info *ubuf)

void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool status)

{

	struct vhost_ubuf_ref *ubufs = ubuf->ctx;

	struct vhost_virtqueue *vq = ubufs->vq;

drivers/vhost/vhost.h

+1 −1
Original line number Diff line number Diff line
@@ -191,7 +191,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *); 


int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,

		    unsigned int log_num, u64 len);

void vhost_zerocopy_callback(struct ubuf_info *);

void vhost_zerocopy_callback(struct ubuf_info *, bool);

int vhost_zerocopy_signal_used(struct vhost_virtqueue *vq);



#define vq_err(vq, fmt, ...) do {                                  \

include/linux/skbuff.h

+3 −1
Original line number Diff line number Diff line
@@ -235,11 +235,13 @@ enum { 
/*

 * The callback notifies userspace to release buffers when skb DMA is done in

 * lower device, the skb last reference should be 0 when calling this.

 * The zerocopy_success argument is true if zero copy transmit occurred,

 * false on data copy or out of memory error caused by data copy attempt.

 * The ctx field is used to track device context.

 * The desc field is used to track userspace buffer index.

 */

struct ubuf_info {

	void (*callback)(struct ubuf_info *);

	void (*callback)(struct ubuf_info *, bool zerocopy_success);

	void *ctx;

	unsigned long desc;

};

net/core/skbuff.c

+2 −2
Original line number Diff line number Diff line
@@ -519,7 +519,7 @@ static void skb_release_data(struct sk_buff *skb) 


			uarg = skb_shinfo(skb)->destructor_arg;

			if (uarg->callback)

				uarg->callback(uarg);

				uarg->callback(uarg, true);

		}



		if (skb_has_frag_list(skb))
@@ -797,7 +797,7 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) 
	for (i = 0; i < num_frags; i++)

		skb_frag_unref(skb, i);



	uarg->callback(uarg);

	uarg->callback(uarg, false);



	/* skb frags point to kernel buffers */

	for (i = num_frags - 1; i >= 0; i--) {