net: add alloc_skb_with_frags() helper
Extract from sock_alloc_send_pskb() code building skb with frags,
so that we can reuse this in other contexts.
Intent is to use it from tcp_send_rcvq(), tcp_collapse(), ...
We also want to replace some skb_linearize() calls to a more reliable
strategy in pathological cases where we need to reduce number of frags.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 29f7f01..06a8feb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4102,3 +4102,81 @@
return NULL;
}
EXPORT_SYMBOL(skb_vlan_untag);
+
+/**
+ * alloc_skb_with_frags - allocate skb with page frags
+ *
+ * header_len: size of linear part
+ * data_len: needed length in frags
+ * max_page_order: max page order desired.
+ * errcode: pointer to error code if any
+ * gfp_mask: allocation mask
+ *
+ * This can be used to allocate a paged skb, given a maximal order for frags.
+ */
+struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
+ unsigned long data_len,
+ int max_page_order,
+ int *errcode,
+ gfp_t gfp_mask)
+{
+ int npages = (data_len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
+ unsigned long chunk;
+ struct sk_buff *skb;
+ struct page *page;
+ gfp_t gfp_head;
+ int i;
+
+ *errcode = -EMSGSIZE;
+ /* Note this test could be relaxed, if we succeed to allocate
+ * high order pages...
+ */
+ if (npages > MAX_SKB_FRAGS)
+ return NULL;
+
+ gfp_head = gfp_mask;
+ if (gfp_head & __GFP_WAIT)
+ gfp_head |= __GFP_REPEAT;
+
+ *errcode = -ENOBUFS;
+ skb = alloc_skb(header_len, gfp_head);
+ if (!skb)
+ return NULL;
+
+ skb->truesize += npages << PAGE_SHIFT;
+
+ for (i = 0; npages > 0; i++) {
+ int order = max_page_order;
+
+ while (order) {
+ if (npages >= 1 << order) {
+ page = alloc_pages(gfp_mask |
+ __GFP_COMP |
+ __GFP_NOWARN |
+ __GFP_NORETRY,
+ order);
+ if (page)
+ goto fill_page;
+ /* Do not retry other high order allocations */
+ order = 1;
+ max_page_order = 0;
+ }
+ order--;
+ }
+ page = alloc_page(gfp_mask);
+ if (!page)
+ goto failure;
+fill_page:
+ chunk = min_t(unsigned long, data_len,
+ PAGE_SIZE << order);
+ skb_fill_page_desc(skb, i, page, 0, chunk);
+ data_len -= chunk;
+ npages -= 1 << order;
+ }
+ return skb;
+
+failure:
+ kfree_skb(skb);
+ return NULL;
+}
+EXPORT_SYMBOL(alloc_skb_with_frags);