[Xen-devel] [RFC PATCH 10/13] xen-netfront: refactor claim/release grant

[Joao Martins <joao.martins@xxxxxxxxx>]

Refactors how grants are claimed/released/revoked by moving that code
into claim_grant and release_grant helpers routines that can be shared
in both TX/RX path.

Signed-off-by: Joao Martins <joao.martins@xxxxxxxxx>
---
 drivers/net/xen-netfront.c | 87 ++++++++++++++++++++++++++++++----------------
 1 file changed, 58 insertions(+), 29 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 8f49ed4..99c17c9 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -256,6 +256,43 @@ static void xennet_maybe_wake_tx(struct netfront_queue 
*queue)
                netif_tx_wake_queue(netdev_get_tx_queue(dev, queue->id));
 }
 
+static grant_ref_t claim_grant(struct page *page,
+                              grant_ref_t *gref_head,
+                              int otherend_id,
+                              int flags)
+{
+       grant_ref_t ref;
+       unsigned long mfn;
+
+       ref = gnttab_claim_grant_reference(gref_head);
+       BUG_ON(ref < 0);
+
+       mfn = pfn_to_mfn(page_to_pfn(page));
+       gnttab_grant_foreign_access_ref(
+               ref, otherend_id, mfn, flags);
+
+       return ref;
+}
+
+static void release_grant(grant_ref_t ref,
+                         grant_ref_t *gref_head,
+                         int otherend_id,
+                         int flags)
+{
+       int ret;
+
+       if (unlikely(gnttab_query_foreign_access(
+               ref) != 0)) {
+               pr_alert("%s: warning -- grant still in use by backend 
domain\n",
+                        __func__);
+               BUG();
+       }
+
+       ret = gnttab_end_foreign_access_ref(ref, flags);
+       BUG_ON(!ret);
+
+       gnttab_release_grant_reference(gref_head, ref);
+}
 
 static struct sk_buff *xennet_alloc_one_rx_buffer(struct netfront_queue *queue)
 {
@@ -297,7 +334,7 @@ static void xennet_alloc_rx_buffers(struct netfront_queue 
*queue)
                struct sk_buff *skb;
                unsigned short id;
                grant_ref_t ref;
-               unsigned long pfn;
+               struct page *page;
                struct xen_netif_rx_request *req;
 
                skb = xennet_alloc_one_rx_buffer(queue);
@@ -309,17 +346,15 @@ static void xennet_alloc_rx_buffers(struct netfront_queue 
*queue)
                BUG_ON(queue->rx_skbs[id]);
                queue->rx_skbs[id] = skb;
 
-               ref = gnttab_claim_grant_reference(&queue->gref_rx_head);
-               BUG_ON((signed short)ref < 0);
-               queue->grant_rx[id].ref = ref;
+               page = skb_frag_page(&skb_shinfo(skb)->frags[0]);
+               ref = claim_grant(page,
+                                 &queue->gref_rx_head,
+                                 queue->info->xbdev->otherend_id,
+                                 0);
 
-               pfn = page_to_pfn(skb_frag_page(&skb_shinfo(skb)->frags[0]));
+               queue->grant_rx[id].ref = ref;
 
                req = RING_GET_REQUEST(&queue->rx, req_prod);
-               gnttab_grant_foreign_access_ref(ref,
-                                               queue->info->xbdev->otherend_id,
-                                               pfn_to_mfn(pfn),
-                                               0);
 
                req->id = id;
                req->gref = ref;
@@ -387,16 +422,12 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue)
 
                        id  = txrsp->id;
                        skb = queue->tx_skbs[id].skb;
-                       if (unlikely(gnttab_query_foreign_access(
-                               queue->grant_tx[id].ref) != 0)) {
-                               pr_alert("%s: warning -- grant still in use by 
backend domain\n",
-                                        __func__);
-                               BUG();
-                       }
-                       gnttab_end_foreign_access_ref(
-                               queue->grant_tx[id].ref, GNTMAP_readonly);
-                       gnttab_release_grant_reference(
-                               &queue->gref_tx_head, queue->grant_tx[id].ref);
+
+                       release_grant(queue->grant_tx[id].ref,
+                                     &queue->gref_tx_head,
+                                     queue->info->xbdev->otherend_id,
+                                     GNTMAP_readonly);
+
                        queue->grant_tx[id].ref = GRANT_INVALID_REF;
                        queue->grant_tx[id].page = NULL;
                        add_id_to_freelist(&queue->tx_skb_freelist, 
queue->tx_skbs, id);
@@ -433,11 +464,10 @@ static struct xen_netif_tx_request *xennet_make_one_txreq(
 
        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);
-
-       gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,
-                                       page_to_mfn(page), GNTMAP_readonly);
+       ref = claim_grant(page,
+                         &queue->gref_tx_head,
+                         queue->info->xbdev->otherend_id,
+                         GNTMAP_readonly);
 
        queue->tx_skbs[id].skb = skb;
        queue->grant_tx[id].page = page;
@@ -727,7 +757,6 @@ static int xennet_get_responses(struct netfront_queue 
*queue,
        int max = MAX_SKB_FRAGS + (rx->status <= RX_COPY_THRESHOLD);
        int slots = 1;
        int err = 0;
-       unsigned long ret;
 
        if (rx->flags & XEN_NETRXF_extra_info) {
                err = xennet_get_extras(queue, extras, rp);
@@ -758,10 +787,10 @@ static int xennet_get_responses(struct netfront_queue 
*queue,
                        goto next;
                }
 
-               ret = gnttab_end_foreign_access_ref(ref, 0);
-               BUG_ON(!ret);
-
-               gnttab_release_grant_reference(&queue->gref_rx_head, ref);
+               release_grant(ref,
+                             &queue->gref_rx_head,
+                             queue->info->xbdev->otherend_id,
+                             0);
 
                __skb_queue_tail(list, skb);
 
-- 
2.1.3


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