From: Herbert Xu <herbert.xu@redhat.com> Date: Thu, 4 Jun 2009 21:15:56 +1000 Subject: [net] skb_copy_datagram_from_iovec Message-id: 20090604111556.GA28526@gondor.apana.org.au O-Subject: [RHEL5.4 PATCH 1/2] net: skb_copy_datagram_from_iovec() Bugzilla: 503309 RH-Acked-by: Thomas Graf <tgraf@redhat.com> RHEL5 bugzilla 503309 On Mon, Jun 01, 2009 at 10:23:05PM +1000, Herbert Xu wrote: > > tun: Use non-linear packets where possible > > The tun backport always used linear packets which causes problems > when memory becomes fragmented as we can no longer allocate enough > contiguous pages for linear packets longer than a page. This patch > backports the current upstream code where we use non-linear packets > to avoid this. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> This back was incomplete, here's the corrected version. First we need this patch: net: skb_copy_datagram_from_iovec() There's an skb_copy_datagram_iovec() to copy out of a paged skb, but nothing the other way around (because we don't do that). We want to allocate big skbs in tun.c, so let's add the function. It's a carbon copy of skb_copy_datagram_iovec() with enough changes to be annoying. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index a0d942d..8c0b6d3 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1455,6 +1455,10 @@ extern int skb_copy_datagram_iovec(const struct sk_buff *from, extern int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb, int hlen, struct iovec *iov); +extern int skb_copy_datagram_from_iovec(struct sk_buff *skb, + int offset, + struct iovec *from, + int len); extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb); extern void skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags); diff --git a/net/core/datagram.c b/net/core/datagram.c index e968f9f..fa1e8ad 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -339,6 +339,93 @@ fault: return -EFAULT; } +/** + * skb_copy_datagram_from_iovec - Copy a datagram from an iovec. + * @skb: buffer to copy + * @offset: offset in the buffer to start copying to + * @from: io vector to copy to + * @len: amount of data to copy to buffer from iovec + * + * Returns 0 or -EFAULT. + * Note: the iovec is modified during the copy. + */ +int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset, + struct iovec *from, int len) +{ + int start = skb_headlen(skb); + int i, copy = start - offset; + + /* Copy header. */ + if (copy > 0) { + if (copy > len) + copy = len; + if (memcpy_fromiovec(skb->data + offset, from, copy)) + goto fault; + if ((len -= copy) == 0) + return 0; + offset += copy; + } + + /* Copy paged appendix. Hmm... why does this look so complicated? */ + for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { + int end; + + WARN_ON(start > offset + len); + + 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 (copy > len) + copy = len; + vaddr = kmap(page); + err = memcpy_fromiovec(vaddr + frag->page_offset + + offset - start, from, 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; + + WARN_ON(start > offset + len); + + end = start + list->len; + if ((copy = end - offset) > 0) { + if (copy > len) + copy = len; + if (skb_copy_datagram_from_iovec(list, + offset - start, + from, copy)) + goto fault; + if ((len -= copy) == 0) + return 0; + offset += copy; + } + start = end; + } + } + if (!len) + return 0; + +fault: + return -EFAULT; +} +EXPORT_SYMBOL(skb_copy_datagram_from_iovec); + static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, u8 __user *to, int len, unsigned int *csump)