eefa390628
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>
126 lines
3.2 KiB
C
126 lines
3.2 KiB
C
/*
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* Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
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* Portions based on net/core/datagram.c and copyrighted by their authors.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 59
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* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* The full GNU General Public License is included in this distribution in the
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* file called COPYING.
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*/
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/*
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* This code allows the net stack to make use of a DMA engine for
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* skb to iovec copies.
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*/
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#include <linux/dmaengine.h>
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#include <linux/socket.h>
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#include <linux/rtnetlink.h> /* for BUG_TRAP */
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#include <net/tcp.h>
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#include <net/netdma.h>
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#define NET_DMA_DEFAULT_COPYBREAK 4096
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int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
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/**
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* dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
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* @skb - buffer to copy
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* @offset - offset in the buffer to start copying from
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* @iovec - io vector to copy to
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* @len - amount of data to copy from buffer to iovec
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* @pinned_list - locked iovec buffer data
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*
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* Note: the iovec is modified during the copy.
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*/
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int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
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struct sk_buff *skb, int offset, struct iovec *to,
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size_t len, struct dma_pinned_list *pinned_list)
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{
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int end = skb_headlen(skb);
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int i, copy = end - offset;
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dma_cookie_t cookie = 0;
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/* Copy header. */
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if (copy > 0) {
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if (copy > len)
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copy = len;
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cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
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skb->data + offset, copy);
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if (cookie < 0)
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goto fault;
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len -= copy;
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if (len == 0)
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goto end;
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offset += copy;
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}
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/* Copy paged appendix. Hmm... why does this look so complicated? */
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for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
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BUG_TRAP(len >= 0);
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end = offset + skb_shinfo(skb)->frags[i].size;
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copy = end - offset;
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if ((copy = end - offset) > 0) {
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skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
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struct page *page = frag->page;
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if (copy > len)
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copy = len;
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cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,
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page, frag->page_offset, copy);
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if (cookie < 0)
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goto fault;
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len -= copy;
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if (len == 0)
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goto end;
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offset += copy;
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}
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}
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if (skb_shinfo(skb)->frag_list) {
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struct sk_buff *list = skb_shinfo(skb)->frag_list;
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for (; list; list = list->next) {
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BUG_TRAP(len >= 0);
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end = offset + list->len;
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copy = end - offset;
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if (copy > 0) {
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if (copy > len)
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copy = len;
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cookie = dma_skb_copy_datagram_iovec(chan, list,
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0, to, copy, pinned_list);
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if (cookie < 0)
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goto fault;
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len -= copy;
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if (len == 0)
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goto end;
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offset += copy;
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}
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}
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}
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end:
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if (!len) {
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skb->dma_cookie = cookie;
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return cookie;
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}
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fault:
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return -EFAULT;
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}
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