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[NET]: Clean up sk_buff walkers.

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I noticed recently that, in skb_checksum(), "offset" and "start" are
essentially the same thing and have the same value throughout the
function, despite being computed differently. Using a single variable
allows some cleanups and makes the skb_checksum() function smaller,
more readable, and presumably marginally faster.

We appear to have many other "sk_buff walker" functions built on the
exact same model, so the cleanup applies to them, too. Here is a list
of the functions I found to be affected:

net/appletalk/ddp.c:atalk_sum_skb()
net/core/datagram.c:skb_copy_datagram_iovec()
net/core/datagram.c:skb_copy_and_csum_datagram()
net/core/skbuff.c:skb_copy_bits()
net/core/skbuff.c:skb_store_bits()
net/core/skbuff.c:skb_checksum()
net/core/skbuff.c:skb_copy_and_csum_bit()
net/core/user_dma.c:dma_skb_copy_datagram_iovec()
net/xfrm/xfrm_algo.c:skb_icv_walk()
net/xfrm/xfrm_algo.c:skb_to_sgvec()

OTOH, I admit I'm a bit surprised, the cleanup is rather obvious so I'm
really wondering if I am missing something. Can anyone please comment
on this?

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jean Delvare 2007-04-26 00:44:22 -07:00 • committed by David S. Miller
parent 28d8909bc7
commit eefa390628
5 changed files with 86 additions and 158 deletions
Download patch file Download diff file Expand all files Collapse all files

25
net/core/user_dma.c
View file

@ -49,8 +49,8 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
struct sk_buff *skb, int offset, struct iovec *to,
size_t len, struct dma_pinned_list *pinned_list)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
int end = skb_headlen(skb);
int i, copy = end - offset;
dma_cookie_t cookie = 0;
/* Copy header. */
@ -69,11 +69,9 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
int end;
BUG_TRAP(len >= 0);
BUG_TRAP(start <= offset + len);
end = start + skb_shinfo(skb)->frags[i].size;
end = offset + skb_shinfo(skb)->frags[i].size;
copy = end - offset;
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@ -82,8 +80,8 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
if (copy > len)
copy = len;
cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
frag->page_offset + offset - start, copy);
cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,
page, frag->page_offset, copy);
if (cookie < 0)
goto fault;
len -= copy;
@ -91,25 +89,21 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
goto end;
offset += copy;
}
start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
int end;
BUG_TRAP(len >= 0);
BUG_TRAP(start <= offset + len);
end = start + list->len;
end = offset + list->len;
copy = end - offset;
if (copy > 0) {
if (copy > len)
copy = len;
cookie = dma_skb_copy_datagram_iovec(chan, list,
offset - start, to, copy,
pinned_list);
0, to, copy, pinned_list);
if (cookie < 0)
goto fault;
len -= copy;
@ -117,7 +111,6 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
goto end;
offset += copy;
}
start = end;
}
}