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switch memcpy_to_msg() and skb_copy{,_and_csum}_datagram_msg() to primitives

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... making both non-draining.  That means that tcp_recvmsg() becomes
non-draining.  And _that_ would break iscsit_do_rx_data() unless we
	a) make sure tcp_recvmsg() is uniformly non-draining (it is)
	b) make sure it copes with arbitrary (including shifted)
iov_iter (it does, all it uses is iov_iter primitives)
	c) make iscsit_do_rx_data() initialize ->msg_iter only once.

Fortunately, (c) is doable with minimal work and we are rid of one
the two places where kernel send/recvmsg users would be unhappy with
non-draining behaviour.

Actually, that makes all but one of ->recvmsg() instances iov_iter-clean.
The exception is skcipher_recvmsg() and it also isn't hard to convert
to primitives (iov_iter_get_pages() is needed there).  That'll wait
a bit - there's some interplay with ->sendmsg() path for that one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2014-11-24 18:17:55 -05:00
parent 17836394e5
commit e5a4b0bb80
3 changed files with 28 additions and 54 deletions
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54
net/core/datagram.c
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@@ -615,27 +615,25 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
EXPORT_SYMBOL(zerocopy_sg_from_iter);
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
u8 __user *to, int len,
struct iov_iter *to, int len,
__wsum *csump)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
struct sk_buff *frag_iter;
int pos = 0;
int n;
/* Copy header. */
if (copy > 0) {
int err = 0;
if (copy > len)
copy = len;
*csump = csum_and_copy_to_user(skb->data + offset, to, copy,
*csump, &err);
if (err)
n = csum_and_copy_to_iter(skb->data + offset, copy, csump, to);
if (n != copy)
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
to += copy;
pos = copy;
}
@@ -647,26 +645,22 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
end = start + skb_frag_size(frag);
if ((copy = end - offset) > 0) {
__wsum csum2;
int err = 0;
u8 *vaddr;
__wsum csum2 = 0;
struct page *page = skb_frag_page(frag);
u8 *vaddr = kmap(page);
if (copy > len)
copy = len;
vaddr = kmap(page);
csum2 = csum_and_copy_to_user(vaddr +
frag->page_offset +
offset - start,
to, copy, 0, &err);
n = csum_and_copy_to_iter(vaddr + frag->page_offset +
offset - start, copy,
&csum2, to);
kunmap(page);
if (err)
if (n != copy)
goto fault;
*csump = csum_block_add(*csump, csum2, pos);
if (!(len -= copy))
return 0;
offset += copy;
to += copy;
pos += copy;
}
start = end;
@@ -691,7 +685,6 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
if ((len -= copy) == 0)
return 0;
offset += copy;
to += copy;
pos += copy;
}
start = end;
@@ -744,20 +737,19 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb)
EXPORT_SYMBOL(__skb_checksum_complete);
/**
* skb_copy_and_csum_datagram_iovec - Copy and checksum skb to user iovec.
* skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec.
* @skb: skbuff
* @hlen: hardware length
* @iov: io vector
* @msg: destination
*
* Caller _must_ check that skb will fit to this iovec.
*
* Returns: 0 - success.
* -EINVAL - checksum failure.
* -EFAULT - fault during copy. Beware, in this case iovec
* can be modified!
* -EFAULT - fault during copy.
*/
int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
int hlen, struct iovec *iov)
int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
int hlen, struct msghdr *msg)
{
__wsum csum;
int chunk = skb->len - hlen;
@@ -765,28 +757,20 @@ int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
if (!chunk)
return 0;
/* Skip filled elements.
* Pretty silly, look at memcpy_toiovec, though 8)
*/
while (!iov->iov_len)
iov++;
if (iov->iov_len < chunk) {
if (iov_iter_count(&msg->msg_iter) < chunk) {
if (__skb_checksum_complete(skb))
goto csum_error;
if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
if (skb_copy_datagram_msg(skb, hlen, msg, chunk))
goto fault;
} else {
csum = csum_partial(skb->data, hlen, skb->csum);
if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
if (skb_copy_and_csum_datagram(skb, hlen, &msg->msg_iter,
chunk, &csum))
goto fault;
if (csum_fold(csum))
goto csum_error;
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
netdev_rx_csum_fault(skb->dev);
iov->iov_len -= chunk;
iov->iov_base += chunk;
}
return 0;
csum_error:
@@ -794,7 +778,7 @@ csum_error:
fault:
return -EFAULT;
}
EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg);
/**
* datagram_poll - generic datagram poll