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datagram: consolidate datagram copy to iter helpers
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skb_copy_datagram_iter and skb_copy_and_csum_datagram are essentialy
the same but with a couple of differences: The first is the copy
operation used which either a simple copy or a csum_and_copy, and the
second are the behavior on the "short copy" path where simply copy
needs to return the number of bytes successfully copied while csum_and_copy
needs to fault immediately as the checksum is partial.

Introduce __skb_datagram_iter that additionally accepts:
1. copy operation function pointer
2. private data that goes with the copy operation
3. fault_short flag to indicate the action on short copy

Suggested-by: David S. Miller <[email protected]>
Acked-by: David S. Miller <[email protected]>
Signed-off-by: Sagi Grimberg <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
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Sagi Grimberg authored and Christoph Hellwig committed Dec 13, 2018
1 parent cb002d0 commit 950fcae
Showing 1 changed file with 42 additions and 94 deletions.
136 changes: 42 additions & 94 deletions net/core/datagram.c
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Original file line number Diff line number Diff line change
Expand Up @@ -408,27 +408,20 @@ int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
}
EXPORT_SYMBOL(skb_kill_datagram);

/**
* skb_copy_datagram_iter - Copy a datagram to an iovec iterator.
* @skb: buffer to copy
* @offset: offset in the buffer to start copying from
* @to: iovec iterator to copy to
* @len: amount of data to copy from buffer to iovec
*/
int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
struct iov_iter *to, int len)
int __skb_datagram_iter(const struct sk_buff *skb, int offset,
struct iov_iter *to, int len, bool fault_short,
size_t (*cb)(const void *, size_t, void *, struct iov_iter *),
void *data)
{
int start = skb_headlen(skb);
int i, copy = start - offset, start_off = offset, n;
struct sk_buff *frag_iter;

trace_skb_copy_datagram_iovec(skb, len);

/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
n = copy_to_iter(skb->data + offset, copy, to);
n = cb(skb->data + offset, copy, data, to);
offset += n;
if (n != copy)
goto short_copy;
Expand All @@ -450,8 +443,8 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,

if (copy > len)
copy = len;
n = copy_to_iter(vaddr + frag->page_offset +
offset - start, copy, to);
n = cb(vaddr + frag->page_offset +
offset - start, copy, data, to);
kunmap(page);
offset += n;
if (n != copy)
Expand All @@ -471,8 +464,8 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
if (skb_copy_datagram_iter(frag_iter, offset - start,
to, copy))
if (__skb_datagram_iter(frag_iter, offset - start,
to, copy, short_copy, cb, data))
goto fault;
if ((len -= copy) == 0)
return 0;
Expand All @@ -493,11 +486,32 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
return -EFAULT;

short_copy:
if (iov_iter_count(to))
if (fault_short || iov_iter_count(to))
goto fault;

return 0;
}

static size_t simple_copy_to_iter(const void *addr, size_t bytes,
void *data __always_unused, struct iov_iter *i)
{
return copy_to_iter(addr, bytes, i);
}

/**
* skb_copy_datagram_iter - Copy a datagram to an iovec iterator.
* @skb: buffer to copy
* @offset: offset in the buffer to start copying from
* @to: iovec iterator to copy to
* @len: amount of data to copy from buffer to iovec
*/
int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
struct iov_iter *to, int len)
{
trace_skb_copy_datagram_iovec(skb, len);
return __skb_datagram_iter(skb, offset, to, len, false,
simple_copy_to_iter, NULL);
}
EXPORT_SYMBOL(skb_copy_datagram_iter);

/**
Expand Down Expand Up @@ -648,87 +662,21 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
}
EXPORT_SYMBOL(zerocopy_sg_from_iter);

/**
* skb_copy_and_csum_datagram_iter - Copy datagram to an iovec iterator
* and update a checksum.
* @skb: buffer to copy
* @offset: offset in the buffer to start copying from
* @to: iovec iterator to copy to
* @len: amount of data to copy from buffer to iovec
* @csump: checksum pointer
*/
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
struct iov_iter *to, int len,
__wsum *csump)
{
int start = skb_headlen(skb);
int i, copy = start - offset, start_off = offset;
struct sk_buff *frag_iter;
int pos = 0;
int n;

/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
n = csum_and_copy_to_iter(skb->data + offset, copy, csump, to);
offset += n;
if (n != copy)
goto fault;
if ((len -= copy) == 0)
return 0;
pos = copy;
}

for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
int end;
const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

WARN_ON(start > offset + len);

end = start + skb_frag_size(frag);
if ((copy = end - offset) > 0) {
__wsum csum2 = 0;
struct page *page = skb_frag_page(frag);
u8 *vaddr = kmap(page);

if (copy > len)
copy = len;
n = csum_and_copy_to_iter(vaddr + frag->page_offset +
offset - start, copy,
&csum2, to);
kunmap(page);
offset += n;
if (n != copy)
goto fault;
*csump = csum_block_add(*csump, csum2, pos);
if (!(len -= copy))
return 0;
pos += copy;
}
start = end;
}

skb_walk_frags(skb, frag_iter) {
int end;

WARN_ON(start > offset + len);

end = start + frag_iter->len;
if ((copy = end - offset) > 0) {
__wsum csum2 = 0;
if (copy > len)
copy = len;
if (skb_copy_and_csum_datagram(frag_iter,
offset - start,
to, copy,
&csum2))
goto fault;
*csump = csum_block_add(*csump, csum2, pos);
if ((len -= copy) == 0)
return 0;
offset += copy;
pos += copy;
}
start = end;
}
if (!len)
return 0;

fault:
iov_iter_revert(to, offset - start_off);
return -EFAULT;
return __skb_datagram_iter(skb, offset, to, len, true,
csum_and_copy_to_iter, csump);
}

__sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
Expand Down

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