linux/net/core/user_dma.c
Jean Delvare eefa390628 [NET]: Clean up sk_buff walkers.
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>
2007-04-26 00:44:22 -07:00

126 lines
3.2 KiB
C

/*
* Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
* Portions based on net/core/datagram.c and copyrighted by their authors.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 59
* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* The full GNU General Public License is included in this distribution in the
* file called COPYING.
*/
/*
* This code allows the net stack to make use of a DMA engine for
* skb to iovec copies.
*/
#include <linux/dmaengine.h>
#include <linux/socket.h>
#include <linux/rtnetlink.h> /* for BUG_TRAP */
#include <net/tcp.h>
#include <net/netdma.h>
#define NET_DMA_DEFAULT_COPYBREAK 4096
int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
/**
* dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
* @skb - buffer to copy
* @offset - offset in the buffer to start copying from
* @iovec - io vector to copy to
* @len - amount of data to copy from buffer to iovec
* @pinned_list - locked iovec buffer data
*
* Note: the iovec is modified during the copy.
*/
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 end = skb_headlen(skb);
int i, copy = end - offset;
dma_cookie_t cookie = 0;
/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
skb->data + offset, copy);
if (cookie < 0)
goto fault;
len -= copy;
if (len == 0)
goto end;
offset += copy;
}
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
BUG_TRAP(len >= 0);
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];
struct page *page = frag->page;
if (copy > len)
copy = len;
cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,
page, frag->page_offset, copy);
if (cookie < 0)
goto fault;
len -= copy;
if (len == 0)
goto end;
offset += copy;
}
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
BUG_TRAP(len >= 0);
end = offset + list->len;
copy = end - offset;
if (copy > 0) {
if (copy > len)
copy = len;
cookie = dma_skb_copy_datagram_iovec(chan, list,
0, to, copy, pinned_list);
if (cookie < 0)
goto fault;
len -= copy;
if (len == 0)
goto end;
offset += copy;
}
}
}
end:
if (!len) {
skb->dma_cookie = cookie;
return cookie;
}
fault:
return -EFAULT;
}