diff options
| -rw-r--r-- | drivers/net/xen-netback/netback.c | 98 |
1 files changed, 80 insertions, 18 deletions
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 76665405c5aa..64ab1d141f1c 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -104,7 +104,7 @@ static inline unsigned long idx_to_kaddr(struct xenvif *vif, /* Find the containing VIF's structure from a pointer in pending_tx_info array */ -static inline struct xenvif* ubuf_to_vif(struct ubuf_info *ubuf) +static inline struct xenvif *ubuf_to_vif(const struct ubuf_info *ubuf) { u16 pending_idx = ubuf->desc; struct pending_tx_info *temp = @@ -323,6 +323,35 @@ static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, } /* + * Find the grant ref for a given frag in a chain of struct ubuf_info's + * skb: the skb itself + * i: the frag's number + * ubuf: a pointer to an element in the chain. It should not be NULL + * + * Returns a pointer to the element in the chain where the page were found. If + * not found, returns NULL. + * See the definition of callback_struct in common.h for more details about + * the chain. + */ +static const struct ubuf_info *xenvif_find_gref(const struct sk_buff *const skb, + const int i, + const struct ubuf_info *ubuf) +{ + struct xenvif *foreign_vif = ubuf_to_vif(ubuf); + + do { + u16 pending_idx = ubuf->desc; + + if (skb_shinfo(skb)->frags[i].page.p == + foreign_vif->mmap_pages[pending_idx]) + break; + ubuf = (struct ubuf_info *) ubuf->ctx; + } while (ubuf); + + return ubuf; +} + +/* * Prepare an SKB to be transmitted to the frontend. * * This function is responsible for allocating grant operations, meta @@ -346,9 +375,8 @@ static int xenvif_gop_skb(struct sk_buff *skb, int head = 1; int old_meta_prod; int gso_type; - struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg; - grant_ref_t foreign_grefs[MAX_SKB_FRAGS]; - struct xenvif *foreign_vif = NULL; + const struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg; + const struct ubuf_info *const head_ubuf = ubuf; old_meta_prod = npo->meta_prod; @@ -386,19 +414,6 @@ static int xenvif_gop_skb(struct sk_buff *skb, npo->copy_off = 0; npo->copy_gref = req->gref; - if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) && - (ubuf->callback == &xenvif_zerocopy_callback)) { - int i = 0; - foreign_vif = ubuf_to_vif(ubuf); - - do { - u16 pending_idx = ubuf->desc; - foreign_grefs[i++] = - foreign_vif->pending_tx_info[pending_idx].req.gref; - ubuf = (struct ubuf_info *) ubuf->ctx; - } while (ubuf); - } - data = skb->data; while (data < skb_tail_pointer(skb)) { unsigned int offset = offset_in_page(data); @@ -415,13 +430,60 @@ static int xenvif_gop_skb(struct sk_buff *skb, } for (i = 0; i < nr_frags; i++) { + /* This variable also signals whether foreign_gref has a real + * value or not. + */ + struct xenvif *foreign_vif = NULL; + grant_ref_t foreign_gref; + + if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) && + (ubuf->callback == &xenvif_zerocopy_callback)) { + const struct ubuf_info *const startpoint = ubuf; + + /* Ideally ubuf points to the chain element which + * belongs to this frag. Or if frags were removed from + * the beginning, then shortly before it. + */ + ubuf = xenvif_find_gref(skb, i, ubuf); + + /* Try again from the beginning of the list, if we + * haven't tried from there. This only makes sense in + * the unlikely event of reordering the original frags. + * For injected local pages it's an unnecessary second + * run. + */ + if (unlikely(!ubuf) && startpoint != head_ubuf) + ubuf = xenvif_find_gref(skb, i, head_ubuf); + + if (likely(ubuf)) { + u16 pending_idx = ubuf->desc; + + foreign_vif = ubuf_to_vif(ubuf); + foreign_gref = foreign_vif->pending_tx_info[pending_idx].req.gref; + /* Just a safety measure. If this was the last + * element on the list, the for loop will + * iterate again if a local page were added to + * the end. Using head_ubuf here prevents the + * second search on the chain. Or the original + * frags changed order, but that's less likely. + * In any way, ubuf shouldn't be NULL. + */ + ubuf = ubuf->ctx ? + (struct ubuf_info *) ubuf->ctx : + head_ubuf; + } else + /* This frag was a local page, added to the + * array after the skb left netback. + */ + ubuf = head_ubuf; + } xenvif_gop_frag_copy(vif, skb, npo, skb_frag_page(&skb_shinfo(skb)->frags[i]), skb_frag_size(&skb_shinfo(skb)->frags[i]), skb_shinfo(skb)->frags[i].page_offset, &head, foreign_vif, - foreign_grefs[i]); + foreign_vif ? foreign_gref : UINT_MAX); } return npo->meta_prod - old_meta_prod; |