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net: introduce netdev_alloc_frag()

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Fix two issues introduced in commit a1c7fff7e1
( net: netdev_alloc_skb() use build_skb() )

- Must be IRQ safe (non NAPI drivers can use it)
- Must not leak the frag if build_skb() fails to allocate sk_buff

This patch introduces netdev_alloc_frag() for drivers willing to
use build_skb() instead of __netdev_alloc_skb() variants.

Factorize code so that :
__dev_alloc_skb() is a wrapper around __netdev_alloc_skb(), and
dev_alloc_skb() a wrapper around netdev_alloc_skb()

Use __GFP_COLD flag.

Almost all network drivers now benefit from skb->head_frag
infrastructure.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-05-18 05:12:12 +00:00 committed by David S. Miller
parent 56138f50d1
commit 6f532612cc
2 changed files with 59 additions and 65 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
include/linux/skbuff.h
View File

@ -1680,31 +1680,11 @@ static inline void __skb_queue_purge(struct sk_buff_head *list)
kfree_skb(skb);
}
/**
* __dev_alloc_skb - allocate an skbuff for receiving
* @length: length to allocate
* @gfp_mask: get_free_pages mask, passed to alloc_skb
*
* Allocate a new &sk_buff and assign it a usage count of one. The
* buffer has unspecified headroom built in. Users should allocate
* the headroom they think they need without accounting for the
* built in space. The built in space is used for optimisations.
*
* %NULL is returned if there is no free memory.
*/
static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
gfp_t gfp_mask)
{
struct sk_buff *skb = alloc_skb(length + NET_SKB_PAD, gfp_mask);
if (likely(skb))
skb_reserve(skb, NET_SKB_PAD);
return skb;
}
extern struct sk_buff *dev_alloc_skb(unsigned int length);
extern void *netdev_alloc_frag(unsigned int fragsz);
extern struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
unsigned int length, gfp_t gfp_mask);
unsigned int length,
gfp_t gfp_mask);
/**
* netdev_alloc_skb - allocate an skbuff for rx on a specific device
@ -1725,6 +1705,20 @@ static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
}
/* legacy helper around __netdev_alloc_skb() */
static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
gfp_t gfp_mask)
{
return __netdev_alloc_skb(NULL, length, gfp_mask);
}
/* legacy helper around netdev_alloc_skb() */
static inline struct sk_buff *dev_alloc_skb(unsigned int length)
{
return netdev_alloc_skb(NULL, length);
}
static inline struct sk_buff *__netdev_alloc_skb_ip_align(struct net_device *dev,
unsigned int length, gfp_t gfp)
{

80
net/core/skbuff.c
View File

@ -299,6 +299,40 @@ struct netdev_alloc_cache {
};
static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);
/**
* netdev_alloc_frag - allocate a page fragment
* @fragsz: fragment size
*
* Allocates a frag from a page for receive buffer.
* Uses GFP_ATOMIC allocations.
*/
void *netdev_alloc_frag(unsigned int fragsz)
{
struct netdev_alloc_cache *nc;
void *data = NULL;
unsigned long flags;
local_irq_save(flags);
nc = &__get_cpu_var(netdev_alloc_cache);
if (unlikely(!nc->page)) {
refill:
nc->page = alloc_page(GFP_ATOMIC | __GFP_COLD);
nc->offset = 0;
}
if (likely(nc->page)) {
if (nc->offset + fragsz > PAGE_SIZE) {
put_page(nc->page);
goto refill;
}
data = page_address(nc->page) + nc->offset;
nc->offset += fragsz;
get_page(nc->page);
}
local_irq_restore(flags);
return data;
}
EXPORT_SYMBOL(netdev_alloc_frag);
/**
* __netdev_alloc_skb - allocate an skbuff for rx on a specific device
* @dev: network device to receive on
@ -315,30 +349,18 @@ static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);
struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
unsigned int length, gfp_t gfp_mask)
{
struct sk_buff *skb;
struct sk_buff *skb = NULL;
unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
if (fragsz <= PAGE_SIZE && !(gfp_mask & __GFP_WAIT)) {
struct netdev_alloc_cache *nc;
void *data = NULL;
void *data = netdev_alloc_frag(fragsz);
nc = &get_cpu_var(netdev_alloc_cache);
if (!nc->page) {
refill: nc->page = alloc_page(gfp_mask);
nc->offset = 0;
if (likely(data)) {
skb = build_skb(data, fragsz);
if (unlikely(!skb))
put_page(virt_to_head_page(data));
}
if (likely(nc->page)) {
if (nc->offset + fragsz > PAGE_SIZE) {
put_page(nc->page);
goto refill;
}
data = page_address(nc->page) + nc->offset;
nc->offset += fragsz;
get_page(nc->page);
}
put_cpu_var(netdev_alloc_cache);
skb = data ? build_skb(data, fragsz) : NULL;
} else {
skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, 0, NUMA_NO_NODE);
}
@ -360,28 +382,6 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
}
EXPORT_SYMBOL(skb_add_rx_frag);
/**
* dev_alloc_skb - allocate an skbuff for receiving
* @length: length to allocate
*
* Allocate a new &sk_buff and assign it a usage count of one. The
* buffer has unspecified headroom built in. Users should allocate
* the headroom they think they need without accounting for the
* built in space. The built in space is used for optimisations.
*
* %NULL is returned if there is no free memory. Although this function
* allocates memory it can be called from an interrupt.
*/
struct sk_buff *dev_alloc_skb(unsigned int length)
{
/*
* There is more code here than it seems:
* __dev_alloc_skb is an inline
*/
return __dev_alloc_skb(length, GFP_ATOMIC);
}
EXPORT_SYMBOL(dev_alloc_skb);
static void skb_drop_list(struct sk_buff **listp)
{
struct sk_buff *list = *listp;