skb: Drop bad code from pskb_expand_head

The fast-path for pskb_expand_head contains a check where the size plus the
unaligned size of skb_shared_info is compared against the size of the data
buffer.  This code path has two issues.  First is the fact that after the
recent changes by Eric Dumazet to __alloc_skb and build_skb the shared info
is always placed in the optimal spot for a buffer size making this check
unnecessary.  The second issue is the fact that the check doesn't take into
account the aligned size of shared info.  As a result the code burns cycles
doing a memcpy with nothing actually being shifted.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-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 c199aa428c6dbfc7861876e8a171e470f11458bf..4d085d4542855363aba35d0c9bd662aba51cf671 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -951,17 +951,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
                fastpath = atomic_read(&skb_shinfo(skb)->dataref) == delta;
        }
 
-       if (fastpath && !skb->head_frag &&
-           size + sizeof(struct skb_shared_info) <= ksize(skb->head)) {
-               memmove(skb->head + size, skb_shinfo(skb),
-                       offsetof(struct skb_shared_info,
-                                frags[skb_shinfo(skb)->nr_frags]));
-               memmove(skb->head + nhead, skb->head,
-                       skb_tail_pointer(skb) - skb->head);
-               off = nhead;
-               goto adjust_others;
-       }
-
        data = kmalloc(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
                       gfp_mask);
        if (!data)
@@ -997,7 +986,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 
        skb->head     = data;
        skb->head_frag = 0;
-adjust_others:
        skb->data    += off;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
        skb->end      = size;