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Commit e52c0efb authored by Juergen Gross's avatar Juergen Gross Committed by Greg Kroah-Hartman
Browse files

xen/netfront: disentangle tx_skb_freelist 



commit 21631d2d741a64a073e167c27769e73bc7844a2f upstream.

The tx_skb_freelist elements are in a single linked list with the
request id used as link reference. The per element link field is in a
union with the skb pointer of an in use request.

Move the link reference out of the union in order to enable a later
reuse of it for requests which need a populated skb pointer.

Rename add_id_to_freelist() and get_id_from_freelist() to
add_id_to_list() and get_id_from_list() in order to prepare using
those for other lists as well. Define ~0 as value to indicate the end
of a list and place that value into the link for a request not being
on the list.

When freeing a skb zero the skb pointer in the request. Use a NULL
value of the skb pointer instead of skb_entry_is_link() for deciding
whether a request has a skb linked to it.

Remove skb_entry_set_link() and open code it instead as it is really
trivial now.

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 26509bb5

drivers/net/xen-netfront.c

+25 −36
Original line number Diff line number Diff line
@@ -121,17 +121,11 @@ struct netfront_queue { 


	/*

	 * {tx,rx}_skbs store outstanding skbuffs. Free tx_skb entries

	 * are linked from tx_skb_freelist through skb_entry.link.

	 *

	 *  NB. Freelist index entries are always going to be less than

	 *  PAGE_OFFSET, whereas pointers to skbs will always be equal or

	 *  greater than PAGE_OFFSET: we use this property to distinguish

	 *  them.

	 * are linked from tx_skb_freelist through tx_link.

	 */

	union skb_entry {

		struct sk_buff *skb;

		unsigned long link;

	} tx_skbs[NET_TX_RING_SIZE];

	struct sk_buff *tx_skbs[NET_TX_RING_SIZE];

	unsigned short tx_link[NET_TX_RING_SIZE];

#define TX_LINK_NONE 0xffff

	grant_ref_t gref_tx_head;

	grant_ref_t grant_tx_ref[NET_TX_RING_SIZE];

	struct page *grant_tx_page[NET_TX_RING_SIZE];
@@ -169,33 +163,25 @@ struct netfront_rx_info { 
	struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];

};



static void skb_entry_set_link(union skb_entry *list, unsigned short id)

{

	list->link = id;

}



static int skb_entry_is_link(const union skb_entry *list)

{

	BUILD_BUG_ON(sizeof(list->skb) != sizeof(list->link));

	return (unsigned long)list->skb < PAGE_OFFSET;

}



/*

 * Access macros for acquiring freeing slots in tx_skbs[].

 */



static void add_id_to_freelist(unsigned *head, union skb_entry *list,

static void add_id_to_list(unsigned *head, unsigned short *list,

			   unsigned short id)

{

	skb_entry_set_link(&list[id], *head);

	list[id] = *head;

	*head = id;

}



static unsigned short get_id_from_freelist(unsigned *head,

					   union skb_entry *list)

static unsigned short get_id_from_list(unsigned *head, unsigned short *list)

{

	unsigned int id = *head;

	*head = list[id].link;



	if (id != TX_LINK_NONE) {

		*head = list[id];

		list[id] = TX_LINK_NONE;

	}

	return id;

}
@@ -396,7 +382,8 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue) 
				continue;



			id  = txrsp.id;

			skb = queue->tx_skbs[id].skb;

			skb = queue->tx_skbs[id];

			queue->tx_skbs[id] = NULL;

			if (unlikely(gnttab_query_foreign_access(

				queue->grant_tx_ref[id]) != 0)) {

				pr_alert("%s: warning -- grant still in use by backend domain\n",
@@ -409,7 +396,7 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue) 
				&queue->gref_tx_head, queue->grant_tx_ref[id]);

			queue->grant_tx_ref[id] = GRANT_INVALID_REF;

			queue->grant_tx_page[id] = NULL;

			add_id_to_freelist(&queue->tx_skb_freelist, queue->tx_skbs, id);

			add_id_to_list(&queue->tx_skb_freelist, queue->tx_link, id);

			dev_kfree_skb_irq(skb);

		}
@@ -442,7 +429,7 @@ static void xennet_tx_setup_grant(unsigned long gfn, unsigned int offset, 
	struct netfront_queue *queue = info->queue;

	struct sk_buff *skb = info->skb;



	id = get_id_from_freelist(&queue->tx_skb_freelist, queue->tx_skbs);

	id = get_id_from_list(&queue->tx_skb_freelist, queue->tx_link);

	tx = RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);

	ref = gnttab_claim_grant_reference(&queue->gref_tx_head);

	WARN_ON_ONCE(IS_ERR_VALUE((unsigned long)(int)ref));
@@ -450,7 +437,7 @@ static void xennet_tx_setup_grant(unsigned long gfn, unsigned int offset, 
	gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,

					gfn, GNTMAP_readonly);



	queue->tx_skbs[id].skb = skb;

	queue->tx_skbs[id] = skb;

	queue->grant_tx_page[id] = page;

	queue->grant_tx_ref[id] = ref;
@@ -1132,17 +1119,18 @@ static void xennet_release_tx_bufs(struct netfront_queue *queue) 


	for (i = 0; i < NET_TX_RING_SIZE; i++) {

		/* Skip over entries which are actually freelist references */

		if (skb_entry_is_link(&queue->tx_skbs[i]))

		if (!queue->tx_skbs[i])

			continue;



		skb = queue->tx_skbs[i].skb;

		skb = queue->tx_skbs[i];

		queue->tx_skbs[i] = NULL;

		get_page(queue->grant_tx_page[i]);

		gnttab_end_foreign_access(queue->grant_tx_ref[i],

					  GNTMAP_readonly,

					  (unsigned long)page_address(queue->grant_tx_page[i]));

		queue->grant_tx_page[i] = NULL;

		queue->grant_tx_ref[i] = GRANT_INVALID_REF;

		add_id_to_freelist(&queue->tx_skb_freelist, queue->tx_skbs, i);

		add_id_to_list(&queue->tx_skb_freelist, queue->tx_link, i);

		dev_kfree_skb_irq(skb);

	}

}
@@ -1624,13 +1612,14 @@ static int xennet_init_queue(struct netfront_queue *queue) 
	snprintf(queue->name, sizeof(queue->name), "vif%s-q%u",

		 devid, queue->id);



	/* Initialise tx_skbs as a free chain containing every entry. */

	/* Initialise tx_skb_freelist as a free chain containing every entry. */

	queue->tx_skb_freelist = 0;

	for (i = 0; i < NET_TX_RING_SIZE; i++) {

		skb_entry_set_link(&queue->tx_skbs[i], i+1);

		queue->tx_link[i] = i + 1;

		queue->grant_tx_ref[i] = GRANT_INVALID_REF;

		queue->grant_tx_page[i] = NULL;

	}

	queue->tx_link[NET_TX_RING_SIZE - 1] = TX_LINK_NONE;



	/* Clear out rx_skbs */

	for (i = 0; i < NET_RX_RING_SIZE; i++) {