xen-netfront: refactor making Tx requests

Eliminate all the duplicate code for making Tx requests by
consolidating them into a single xennet_make_one_txreq() function.

xennet_make_one_txreq() and xennet_make_txreqs() work with pages and
offsets so it will be easier to make netfront handle highmem frags in
the future.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 67 insertions, 114 deletions

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 803ff5356faa..01a4350eb313 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -421,99 +421,56 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue)
         xennet_maybe_wake_tx(queue);
 }
 
-static void xennet_make_frags(struct sk_buff *skb, struct netfront_queue *queue,
-                              struct xen_netif_tx_request *tx)
-{
-        char *data = skb->data;
-        unsigned long mfn;
-        RING_IDX prod = queue->tx.req_prod_pvt;
-        int frags = skb_shinfo(skb)->nr_frags;
-        unsigned int offset = offset_in_page(data);
-        unsigned int len = skb_headlen(skb);
+static struct xen_netif_tx_request *xennet_make_one_txreq(
+        struct netfront_queue *queue, struct sk_buff *skb,
+        struct page *page, unsigned int offset, unsigned int len)
+{
         unsigned int id;
+        struct xen_netif_tx_request *tx;
         grant_ref_t ref;
-        int i;
 
-        /* While the header overlaps a page boundary (including being
-           larger than a page), split it it into page-sized chunks. */
-        while (len > PAGE_SIZE - offset) {
-                tx->size = PAGE_SIZE - offset;
-                tx->flags |= XEN_NETTXF_more_data;
-                len -= tx->size;
-                data += tx->size;
-                offset = 0;
+        len = min_t(unsigned int, PAGE_SIZE - offset, len);
 
-                id = get_id_from_freelist(&queue->tx_skb_freelist, queue->tx_skbs);
-                queue->tx_skbs[id].skb = skb_get(skb);
-                tx = RING_GET_REQUEST(&queue->tx, prod++);
-                tx->id = id;
-                ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
-                BUG_ON((signed short)ref < 0);
+        id = get_id_from_freelist(&queue->tx_skb_freelist, queue->tx_skbs);
+        tx = RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);
+        ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
+        BUG_ON((signed short)ref < 0);
 
-                mfn = virt_to_mfn(data);
-                gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,
-                                                mfn, GNTMAP_readonly);
+        gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,
+                                        page_to_mfn(page), GNTMAP_readonly);
 
-                queue->grant_tx_page[id] = virt_to_page(data);
-                tx->gref = queue->grant_tx_ref[id] = ref;
-                tx->offset = offset;
-                tx->size = len;
-                tx->flags = 0;
-        }
+        queue->tx_skbs[id].skb = skb;
+        queue->grant_tx_page[id] = page;
+        queue->grant_tx_ref[id] = ref;
 
-        /* Grant backend access to each skb fragment page. */
-        for (i = 0; i < frags; i++) {
-                skb_frag_t *frag = skb_shinfo(skb)->frags + i;
-                struct page *page = skb_frag_page(frag);
+        tx->id = id;
+        tx->gref = ref;
+        tx->offset = offset;
+        tx->size = len;
+        tx->flags = 0;
 
-                len = skb_frag_size(frag);
-                offset = frag->page_offset;
+        return tx;
+}
 
-                /* Skip unused frames from start of page */
-                page += offset >> PAGE_SHIFT;
-                offset &= ~PAGE_MASK;
+static struct xen_netif_tx_request *xennet_make_txreqs(
+        struct netfront_queue *queue, struct xen_netif_tx_request *tx,
+        struct sk_buff *skb, struct page *page,
+        unsigned int offset, unsigned int len)
+{
+        /* Skip unused frames from start of page */
+        page += offset >> PAGE_SHIFT;
+        offset &= ~PAGE_MASK;
 
-                while (len > 0) {
-                        unsigned long bytes;
-
-                        bytes = PAGE_SIZE - offset;
-                        if (bytes > len)
-                                bytes = len;
-
-                        tx->flags |= XEN_NETTXF_more_data;
-
-                        id = get_id_from_freelist(&queue->tx_skb_freelist,
-                                                  queue->tx_skbs);
-                        queue->tx_skbs[id].skb = skb_get(skb);
-                        tx = RING_GET_REQUEST(&queue->tx, prod++);
-                        tx->id = id;
-                        ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
-                        BUG_ON((signed short)ref < 0);
-
-                        mfn = pfn_to_mfn(page_to_pfn(page));
-                        gnttab_grant_foreign_access_ref(ref,
-                                                        queue->info->xbdev->otherend_id,
-                                                        mfn, GNTMAP_readonly);
-
-                        queue->grant_tx_page[id] = page;
-                        tx->gref = queue->grant_tx_ref[id] = ref;
-                        tx->offset = offset;
-                        tx->size = bytes;
-                        tx->flags = 0;
-
-                        offset += bytes;
-                        len -= bytes;
-
-                        /* Next frame */
-                        if (offset == PAGE_SIZE && len) {
-                                BUG_ON(!PageCompound(page));
-                                page++;
-                                offset = 0;
-                        }
-                }
+        while (len) {
+                tx->flags |= XEN_NETTXF_more_data;
+                tx = xennet_make_one_txreq(queue, skb_get(skb),
+                                           page, offset, len);
+                page++;
+                offset = 0;
+                len -= tx->size;
         }
 
-        queue->tx.req_prod_pvt = prod;
+        return tx;
 }
 
 /*
@@ -561,18 +518,15 @@ static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb,
 
 static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
-        unsigned short id;
         struct netfront_info *np = netdev_priv(dev);
         struct netfront_stats *stats = this_cpu_ptr(np->stats);
-        struct xen_netif_tx_request *tx;
-        char *data = skb->data;
-        RING_IDX i;
-        grant_ref_t ref;
-        unsigned long mfn;
+        struct xen_netif_tx_request *tx, *first_tx;
+        unsigned int i;
         int notify;
         int slots;
-        unsigned int offset = offset_in_page(data);
-        unsigned int len = skb_headlen(skb);
+        struct page *page;
+        unsigned int offset;
+        unsigned int len;
         unsigned long flags;
         struct netfront_queue *queue = NULL;
         unsigned int num_queues = dev->real_num_tx_queues;
@@ -601,11 +555,12 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
                                     slots, skb->len);
                 if (skb_linearize(skb))
                         goto drop;
-                data = skb->data;
-                offset = offset_in_page(data);
-                len = skb_headlen(skb);
         }
 
+        page = virt_to_page(skb->data);
+        offset = offset_in_page(skb->data);
+        len = skb_headlen(skb);
+
         spin_lock_irqsave(&queue->tx_lock, flags);
 
         if (unlikely(!netif_carrier_ok(dev) ||
@@ -615,25 +570,13 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 goto drop;
         }
 
-        i = queue->tx.req_prod_pvt;
-
-        id = get_id_from_freelist(&queue->tx_skb_freelist, queue->tx_skbs);
-        queue->tx_skbs[id].skb = skb;
-
-        tx = RING_GET_REQUEST(&queue->tx, i);
+        /* First request for the linear area. */
+        first_tx = tx = xennet_make_one_txreq(queue, skb,
+                                              page, offset, len);
+        page++;
+        offset = 0;
+        len -= tx->size;
 
-        tx->id   = id;
-        ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
-        BUG_ON((signed short)ref < 0);
-        mfn = virt_to_mfn(data);
-        gnttab_grant_foreign_access_ref(
-                ref, queue->info->xbdev->otherend_id, mfn, GNTMAP_readonly);
-        queue->grant_tx_page[id] = virt_to_page(data);
-        tx->gref = queue->grant_tx_ref[id] = ref;
-        tx->offset = offset;
-        tx->size = len;
-
-        tx->flags = 0;
         if (skb->ip_summed == CHECKSUM_PARTIAL)
                 /* local packet? */
                 tx->flags |= XEN_NETTXF_csum_blank | XEN_NETTXF_data_validated;
@@ -641,11 +584,12 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 /* remote but checksummed. */
                 tx->flags |= XEN_NETTXF_data_validated;
 
+        /* Optional extra info after the first request. */
         if (skb_shinfo(skb)->gso_size) {
                 struct xen_netif_extra_info *gso;
 
                 gso = (struct xen_netif_extra_info *)
-                        RING_GET_REQUEST(&queue->tx, ++i);
+                        RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);
 
                 tx->flags |= XEN_NETTXF_extra_info;
 
@@ -660,10 +604,19 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 gso->flags = 0;
         }
 
-        queue->tx.req_prod_pvt = i + 1;
+        /* Requests for the rest of the linear area. */
+        tx = xennet_make_txreqs(queue, tx, skb, page, offset, len);
+
+        /* Requests for all the frags. */
+        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+                skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+                tx = xennet_make_txreqs(queue, tx, skb,
+                                        skb_frag_page(frag), frag->page_offset,
+                                        skb_frag_size(frag));
+        }
 
-        xennet_make_frags(skb, queue, tx);
-        tx->size = skb->len;
+        /* First request has the packet length. */
+        first_tx->size = skb->len;
 
         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
         if (notify)