[Xen-devel] xen 2.6.8.1 sparse diff

[Adam Heath <doogie@xxxxxxxxxxxxx>]

So, I'm begining to look more closely at xen.  Trying to get it all to
compile, and work with our hardware.

After overlaying the 2.6.8.1 sparse tree, I looked at the diff of the source.
In net/core/skbuff.c, I see a function alloc_skb_from_cache.  This function
uses goto, when it's not needed.

+struct sk_buff *alloc_skb_from_cache(kmem_cache_t *cp,
+                                    unsigned int size, int gfp_mask)
+{
+       struct sk_buff *skb;
+       u8 *data;
+
+       /* Get the HEAD */
+       skb = kmem_cache_alloc(skbuff_head_cache,
+                              gfp_mask & ~__GFP_DMA);
+       if (!skb)
+               goto out;

Replace the above 2 lines with:

if (!skb)
        return NULL;

+
+       /* Get the DATA. */
+       size = SKB_DATA_ALIGN(size);
+       data = kmem_cache_alloc(cp, gfp_mask);
+       if (!data)
+               goto nodata;

Replace the above 2 lines with:

if (!data) {
        kmem_cache_free(skbuff_head_cache, skb);
        return NULL;
}

+
+       memset(skb, 0, offsetof(struct sk_buff, truesize));
+       skb->truesize = size + sizeof(struct sk_buff);
+       atomic_set(&skb->users, 1);
+       skb->head = data;
+       skb->data = data;
+       skb->tail = data;
+       skb->end  = data + size;
+
+       atomic_set(&(skb_shinfo(skb)->dataref), 1);
+       skb_shinfo(skb)->nr_frags  = 0;
+       skb_shinfo(skb)->tso_size = 0;
+       skb_shinfo(skb)->tso_segs = 0;
+       skb_shinfo(skb)->frag_list = NULL;
+out:

Remove this line.

+       return skb;
+nodata:
+       kmem_cache_free(skbuff_head_cache, skb);
+       skb = NULL;
+       goto out;

Remove these 4 lines.

Also, why use atomic_set here?  Wouldn't this newly allocated skb only have
one reference?


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