Hi,
I noticed that skb_copy_datagram_iovec calls itself recursively to copy a
fragment list. This isn't actually wrong or even inefficient, it is just
somehow disturbing. Oh, and it uses an extra stack frame, and is hard to
read. Once I got started straightening that out, I couldn't resist cleaning
it up the rest of the way.
* Recursion changed to nested loop
* Three copy cases folded into one
* Miscellaneous funky stuff simplified
* Efficiency should be about the same
* Comments gone, it's all perfectly obvious now ;-)
I booted it, my nics still work, that's as far as I've tested it. Please try
it.
There are a couple of cosmetic things to do, like BUG on impossible offset. Why
does the current code just kprint this and not BUG?
datagram.c | 78 +++++++++++++++++--------------------------------------------
1 files changed, 22 insertions(+), 56 deletions(-)
diff -up --recursive 2.6.12.3.clean/net/core/datagram.c
2.6.12.3/net/core/datagram.c
--- 2.6.12.3.clean/net/core/datagram.c 2005-07-15 17:18:57.000000000 -0400
+++ 2.6.12.3/net/core/datagram.c 2005-08-25 01:39:56.000000000 -0400
@@ -211,74 +211,40 @@ void skb_free_datagram(struct sock *sk,
int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
struct iovec *to, int len)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
-
- /* Copy header. */
- if (copy > 0) {
- if (copy > len)
- copy = len;
- if (memcpy_toiovec(to, skb->data + offset, copy))
- goto fault;
- if ((len -= copy) == 0)
- return 0;
- offset += copy;
- }
+ int i, err, fraglen, end = 0;
+next_skb:
+ fraglen = skb_headlen(skb);
+ i = -1;
- /* Copy paged appendix. Hmm... why does this look so complicated? */
- for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ while (1) {
+ int start = end;
- end = start + skb_shinfo(skb)->frags[i].size;
- if ((copy = end - offset) > 0) {
- int err;
- u8 *vaddr;
- skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
- struct page *page = frag->page;
+ if ((end += fraglen) > offset) {
+ int copy = end - offset, o = offset - start;
if (copy > len)
copy = len;
- vaddr = kmap(page);
- err = memcpy_toiovec(to, vaddr + frag->page_offset +
- offset - start, copy);
- kunmap(page);
+ if (i == -1)
+ err = memcpy_toiovec(to, skb->data + o, copy);
+ else {
+ skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ struct page *page = frag->page;
+ void *p = kmap(page) + frag->page_offset + o;
+ err = memcpy_toiovec(to, p, copy);
+ kunmap(page);
+ }
if (err)
goto fault;
if (!(len -= copy))
return 0;
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(start <= offset + len);
-
- end = start + list->len;
- if ((copy = end - offset) > 0) {
- if (copy > len)
- copy = len;
- if (skb_copy_datagram_iovec(list,
- offset - start,
- to, copy))
- goto fault;
- if ((len -= copy) == 0)
- return 0;
- offset += copy;
- }
- start = end;
- }
+ if (++i >= skb_shinfo(skb)->nr_frags)
+ break;
+ fraglen = skb_shinfo(skb)->frags[i].size;
}
- if (!len)
- return 0;
-
+ if ((skb = skb->next))
+ goto next_skb;
fault:
return -EFAULT;
}
-
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