1 files changed, 63 insertions, 23 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 1844a47636b6..c65b636bcab9 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1030,14 +1030,21 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
 {
         struct gnttab_map_grant_ref *gop_map = *gopp_map;
         u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
+        /* This always points to the shinfo of the skb being checked, which
+         * could be either the first or the one on the frag_list
+         */
         struct skb_shared_info *shinfo = skb_shinfo(skb);
+        /* If this is non-NULL, we are currently checking the frag_list skb, and
+         * this points to the shinfo of the first one
+         */
+        struct skb_shared_info *first_shinfo = NULL;
         int nr_frags = shinfo->nr_frags;
+        const bool sharedslot = nr_frags &&
+                                frag_get_pending_idx(&shinfo->frags[0]) == pending_idx;
         int i, err;
-        struct sk_buff *first_skb = NULL;
 
         /* Check status of header. */
         err = (*gopp_copy)->status;
-        (*gopp_copy)++;
         if (unlikely(err)) {
                 if (net_ratelimit())
                         netdev_dbg(queue->vif->dev,
@@ -1045,8 +1052,12 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
                                    (*gopp_copy)->status,
                                    pending_idx,
                                    (*gopp_copy)->source.u.ref);
-                xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_ERROR);
+                /* The first frag might still have this slot mapped */
+                if (!sharedslot)
+                        xenvif_idx_release(queue, pending_idx,
+                                           XEN_NETIF_RSP_ERROR);
         }
+        (*gopp_copy)++;
 
 check_frags:
         for (i = 0; i < nr_frags; i++, gop_map++) {
@@ -1062,8 +1073,19 @@ check_frags:
                                                 pending_idx,
                                                 gop_map->handle);
                         /* Had a previous error? Invalidate this fragment. */
-                        if (unlikely(err))
+                        if (unlikely(err)) {
                                 xenvif_idx_unmap(queue, pending_idx);
+                                /* If the mapping of the first frag was OK, but
+                                 * the header's copy failed, and they are
+                                 * sharing a slot, send an error
+                                 */
+                                if (i == 0 && sharedslot)
+                                        xenvif_idx_release(queue, pending_idx,
+                                                           XEN_NETIF_RSP_ERROR);
+                                else
+                                        xenvif_idx_release(queue, pending_idx,
+                                                           XEN_NETIF_RSP_OKAY);
+                        }
                         continue;
                 }
 
@@ -1075,42 +1097,53 @@ check_frags:
                                    gop_map->status,
                                    pending_idx,
                                    gop_map->ref);
+
                 xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_ERROR);
 
                 /* Not the first error? Preceding frags already invalidated. */
                 if (err)
                         continue;
-                /* First error: invalidate preceding fragments. */
+
+                /* First error: if the header haven't shared a slot with the
+                 * first frag, release it as well.
+                 */
+                if (!sharedslot)
+                        xenvif_idx_release(queue,
+                                           XENVIF_TX_CB(skb)->pending_idx,
+                                           XEN_NETIF_RSP_OKAY);
+
+                /* Invalidate preceding fragments of this skb. */
                 for (j = 0; j < i; j++) {
                         pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
                         xenvif_idx_unmap(queue, pending_idx);
+                        xenvif_idx_release(queue, pending_idx,
+                                           XEN_NETIF_RSP_OKAY);
+                }
+
+                /* And if we found the error while checking the frag_list, unmap
+                 * the first skb's frags
+                 */
+                if (first_shinfo) {
+                        for (j = 0; j < first_shinfo->nr_frags; j++) {
+                                pending_idx = frag_get_pending_idx(&first_shinfo->frags[j]);
+                                xenvif_idx_unmap(queue, pending_idx);
+                                xenvif_idx_release(queue, pending_idx,
+                                                   XEN_NETIF_RSP_OKAY);
+                        }
                 }
 
                 /* Remember the error: invalidate all subsequent fragments. */
                 err = newerr;
         }
 
-        if (skb_has_frag_list(skb)) {
-                first_skb = skb;
-                skb = shinfo->frag_list;
-                shinfo = skb_shinfo(skb);
+        if (skb_has_frag_list(skb) && !first_shinfo) {
+                first_shinfo = skb_shinfo(skb);
+                shinfo = skb_shinfo(skb_shinfo(skb)->frag_list);
                 nr_frags = shinfo->nr_frags;
 
                 goto check_frags;
         }
 
-        /* There was a mapping error in the frag_list skb. We have to unmap
-         * the first skb's frags
-         */
-        if (first_skb && err) {
-                int j;
-                shinfo = skb_shinfo(first_skb);
-                for (j = 0; j < shinfo->nr_frags; j++) {
-                        pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
-                        xenvif_idx_unmap(queue, pending_idx);
-                }
-        }
-
         *gopp_map = gop_map;
         return err;
 }
@@ -1518,7 +1551,16 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
 
                 /* Check the remap error code. */
                 if (unlikely(xenvif_tx_check_gop(queue, skb, &gop_map, &gop_copy))) {
+                        /* If there was an error, xenvif_tx_check_gop is
+                         * expected to release all the frags which were mapped,
+                         * so kfree_skb shouldn't do it again
+                         */
                         skb_shinfo(skb)->nr_frags = 0;
+                        if (skb_has_frag_list(skb)) {
+                                struct sk_buff *nskb =
+                                                skb_shinfo(skb)->frag_list;
+                                skb_shinfo(nskb)->nr_frags = 0;
+                        }
                         kfree_skb(skb);
                         continue;
                 }
@@ -1822,8 +1864,6 @@ void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx)
                            tx_unmap_op.status);
                 BUG();
         }
-
-        xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_OKAY);
 }
 
 static inline int rx_work_todo(struct xenvif_queue *queue)