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net: add APIs for manipulating skb page fragments.

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The primary aim is to add skb_frag_(ref|unref) in order to remove the use of
bare get/put_page on SKB pages fragments and to isolate users from subsequent
changes to the skb_frag_t data structure.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ian Campbell 2011-08-19 06:25:00 +00:00 committed by David S. Miller
parent 7ae9ed8d32
commit 131ea6675c
1 changed files with 168 additions and 2 deletions
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170
include/linux/skbuff.h
View file

@ -29,6 +29,7 @@
#include <linux/rcupdate.h>
#include <linux/dmaengine.h>
#include <linux/hrtimer.h>
#include <linux/dma-mapping.h>
/* Don't change this without changing skb_csum_unnecessary! */
#define CHECKSUM_NONE 0
@ -1129,14 +1130,47 @@ static inline int skb_pagelen(const struct sk_buff *skb)
return len + skb_headlen(skb);
}
static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
struct page *page, int off, int size)
/**
* __skb_fill_page_desc - initialise a paged fragment in an skb
* @skb: buffer containing fragment to be initialised
* @i: paged fragment index to initialise
* @page: the page to use for this fragment
* @off: the offset to the data with @page
* @size: the length of the data
*
* Initialises the @i'th fragment of @skb to point to &size bytes at
* offset @off within @page.
*
* Does not take any additional reference on the fragment.
*/
static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
struct page *page, int off, int size)
{
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
frag->page = page;
frag->page_offset = off;
frag->size = size;
}
/**
* skb_fill_page_desc - initialise a paged fragment in an skb
* @skb: buffer containing fragment to be initialised
* @i: paged fragment index to initialise
* @page: the page to use for this fragment
* @off: the offset to the data with @page
* @size: the length of the data
*
* As per __skb_fill_page_desc() -- initialises the @i'th fragment of
* @skb to point to &size bytes at offset @off within @page. In
* addition updates @skb such that @i is the last fragment.
*
* Does not take any additional reference on the fragment.
*/
static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
struct page *page, int off, int size)
{
__skb_fill_page_desc(skb, i, page, off, size);
skb_shinfo(skb)->nr_frags = i + 1;
}
@ -1630,6 +1664,138 @@ static inline void netdev_free_page(struct net_device *dev, struct page *page)
__free_page(page);
}
/**
* skb_frag_page - retrieve the page refered to by a paged fragment
* @frag: the paged fragment
*
* Returns the &struct page associated with @frag.
*/
static inline struct page *skb_frag_page(const skb_frag_t *frag)
{
return frag->page;
}
/**
* __skb_frag_ref - take an addition reference on a paged fragment.
* @frag: the paged fragment
*
* Takes an additional reference on the paged fragment @frag.
*/
static inline void __skb_frag_ref(skb_frag_t *frag)
{
get_page(skb_frag_page(frag));
}
/**
* skb_frag_ref - take an addition reference on a paged fragment of an skb.
* @skb: the buffer
* @f: the fragment offset.
*
* Takes an additional reference on the @f'th paged fragment of @skb.
*/
static inline void skb_frag_ref(struct sk_buff *skb, int f)
{
__skb_frag_ref(&skb_shinfo(skb)->frags[f]);
}
/**
* __skb_frag_unref - release a reference on a paged fragment.
* @frag: the paged fragment
*
* Releases a reference on the paged fragment @frag.
*/
static inline void __skb_frag_unref(skb_frag_t *frag)
{
put_page(skb_frag_page(frag));
}
/**
* skb_frag_unref - release a reference on a paged fragment of an skb.
* @skb: the buffer
* @f: the fragment offset
*
* Releases a reference on the @f'th paged fragment of @skb.
*/
static inline void skb_frag_unref(struct sk_buff *skb, int f)
{
__skb_frag_unref(&skb_shinfo(skb)->frags[f]);
}
/**
* skb_frag_address - gets the address of the data contained in a paged fragment
* @frag: the paged fragment buffer
*
* Returns the address of the data within @frag. The page must already
* be mapped.
*/
static inline void *skb_frag_address(const skb_frag_t *frag)
{
return page_address(skb_frag_page(frag)) + frag->page_offset;
}
/**
* skb_frag_address_safe - gets the address of the data contained in a paged fragment
* @frag: the paged fragment buffer
*
* Returns the address of the data within @frag. Checks that the page
* is mapped and returns %NULL otherwise.
*/
static inline void *skb_frag_address_safe(const skb_frag_t *frag)
{
void *ptr = page_address(skb_frag_page(frag));
if (unlikely(!ptr))
return NULL;
return ptr + frag->page_offset;
}
/**
* __skb_frag_set_page - sets the page contained in a paged fragment
* @frag: the paged fragment
* @page: the page to set
*
* Sets the fragment @frag to contain @page.
*/
static inline void __skb_frag_set_page(skb_frag_t *frag, struct page *page)
{
frag->page = page;
__skb_frag_ref(frag);
}
/**
* skb_frag_set_page - sets the page contained in a paged fragment of an skb
* @skb: the buffer
* @f: the fragment offset
* @page: the page to set
*
* Sets the @f'th fragment of @skb to contain @page.
*/
static inline void skb_frag_set_page(struct sk_buff *skb, int f,
struct page *page)
{
__skb_frag_set_page(&skb_shinfo(skb)->frags[f], page);
}
/**
* skb_frag_dma_map - maps a paged fragment via the DMA API
* @device: the device to map the fragment to
* @frag: the paged fragment to map
* @offset: the offset within the fragment (starting at the
* fragment's own offset)
* @size: the number of bytes to map
* @direction: the direction of the mapping (%PCI_DMA_*)
*
* Maps the page associated with @frag to @device.
*/
static inline dma_addr_t skb_frag_dma_map(struct device *dev,
const skb_frag_t *frag,
size_t offset, size_t size,
enum dma_data_direction dir)
{
return dma_map_page(dev, skb_frag_page(frag),
frag->page_offset + offset, size, dir);
}
/**
* skb_clone_writable - is the header of a clone writable
* @skb: buffer to check