Commit 4fb66994 authored by Jarek Poplawski's avatar Jarek Poplawski Committed by David S. Miller

net: Optimize memory usage when splicing from sockets.

The recent fix of data corruption when splicing from sockets uses
memory very inefficiently allocating a new page to copy each chunk of
linear part of skb. This patch uses the same page until it's full
(almost) by caching the page in sk_sndmsg_page field.

With changes from David S. Miller <>
Signed-off-by: default avatarJarek Poplawski <>
Signed-off-by: default avatarDavid S. Miller <>
parent 31f45747
......@@ -1333,14 +1333,39 @@ static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)
static inline struct page *linear_to_page(struct page *page, unsigned int len,
unsigned int offset)
struct page *p = alloc_pages(GFP_KERNEL, 0);
static inline struct page *linear_to_page(struct page *page, unsigned int *len,
unsigned int *offset,
struct sk_buff *skb)
struct sock *sk = skb->sk;
struct page *p = sk->sk_sndmsg_page;
unsigned int off;
if (!p) {
p = sk->sk_sndmsg_page = alloc_pages(sk->sk_allocation, 0);
if (!p)
return NULL;
if (!p)
return NULL;
memcpy(page_address(p) + offset, page_address(page) + offset, len);
off = sk->sk_sndmsg_off = 0;
/* hold one ref to this page until it's full */
} else {
unsigned int mlen;
off = sk->sk_sndmsg_off;
mlen = PAGE_SIZE - off;
if (mlen < 64 && mlen < *len) {
goto new_page;
*len = min_t(unsigned int, *len, mlen);
memcpy(page_address(p) + off, page_address(page) + *offset, *len);
sk->sk_sndmsg_off += *len;
*offset = off;
return p;
......@@ -1349,21 +1374,21 @@ static inline struct page *linear_to_page(struct page *page, unsigned int len,
* Fill page/offset/length into spd, if it can hold more pages.
static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page,
unsigned int len, unsigned int offset,
unsigned int *len, unsigned int offset,
struct sk_buff *skb, int linear)
if (unlikely(spd->nr_pages == PIPE_BUFFERS))
return 1;
if (linear) {
page = linear_to_page(page, len, offset);
page = linear_to_page(page, len, &offset, skb);
if (!page)
return 1;
} else
spd->pages[spd->nr_pages] = page;
spd->partial[spd->nr_pages].len = len;
spd->partial[spd->nr_pages].len = *len;
spd->partial[spd->nr_pages].offset = offset;
......@@ -1405,7 +1430,7 @@ static inline int __splice_segment(struct page *page, unsigned int poff,
/* the linear region may spread across several pages */
flen = min_t(unsigned int, flen, PAGE_SIZE - poff);
if (spd_fill_page(spd, page, flen, poff, skb, linear))
if (spd_fill_page(spd, page, &flen, poff, skb, linear))
return 1;
__segment_seek(&page, &poff, &plen, flen);
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