Hello,
I'm submitting this patch for inclusion in the Linux kernel if deemed
generally useful.
The purpose of this patch is to add a new function called alloc_skb_custom()
(or whatever) that allows the data portion of an sk_buff to reside in any
memory region, not just a region returned by kmalloc(). For example, if a
networking device has a restriction on where receive buffers may reside,
then the device driver can avoid copying every incoming packet if it is
able to create an sk_buff that points to the receive buffer memory.
Basically this amounts to adding a 'free_data' function pointer to the
sk_buff structure. By default this points to kfree() but in general could
point to anywhere.
FYI FreeBSD has had equivalent functionality in its 'struct mbuf' for
many years (I'm also a FreeBSD developer).
Thanks for your review.
Cheers,
-Archie
__________________________________________________________________________
Archie Cobbs * Precision I/O * http://www.precisionio.com
Index: include/linux/skbuff.h
===================================================================
RCS file: /home/cvs/linux-2.4.20/include/linux/skbuff.h,v
retrieving revision 1.1.1.1
retrieving revision 1.2
diff -u -r1.1.1.1 -r1.2
--- include/linux/skbuff.h 3 Jan 2003 22:31:40 -0000 1.1.1.1
+++ include/linux/skbuff.h 15 Mar 2003 01:13:35 -0000 1.2
@@ -193,6 +193,7 @@
unsigned char *tail; /* Tail pointer
*/
unsigned char *end; /* End pointer
*/
+ void (*free_data)(const void *); /* Free data
buffer function */
void (*destructor)(struct sk_buff *); /* Destruct
function */
#ifdef CONFIG_NETFILTER
/* Can be used for communication between hooks. */
@@ -230,6 +231,8 @@
extern void __kfree_skb(struct sk_buff *skb);
extern struct sk_buff * alloc_skb(unsigned int size, int
priority);
+extern struct sk_buff * alloc_skb_custom(unsigned int size, int
priority,
+ void (*free_data)(const void *), u8
*data);
extern void kfree_skbmem(struct sk_buff *skb);
extern struct sk_buff * skb_clone(struct sk_buff *skb, int
priority);
extern struct sk_buff * skb_copy(const struct sk_buff *skb, int
priority);
Index: net/netsyms.c
===================================================================
RCS file: /home/cvs/linux-2.4.20/net/netsyms.c,v
retrieving revision 1.1.1.1
retrieving revision 1.2
diff -u -r1.1.1.1 -r1.2
--- net/netsyms.c 3 Jan 2003 22:31:42 -0000 1.1.1.1
+++ net/netsyms.c 15 Mar 2003 01:13:35 -0000 1.2
@@ -489,6 +489,7 @@
EXPORT_SYMBOL(eth_copy_and_sum);
#endif
EXPORT_SYMBOL(alloc_skb);
+EXPORT_SYMBOL(alloc_skb_custom);
EXPORT_SYMBOL(__kfree_skb);
EXPORT_SYMBOL(skb_clone);
EXPORT_SYMBOL(skb_copy);
Index: net/core/skbuff.c
===================================================================
RCS file: /home/cvs/linux-2.4.20/net/core/skbuff.c,v
retrieving revision 1.1
retrieving revision 1.3
diff -u -r1.1 -r1.3
--- net/core/skbuff.c 7 Jan 2003 00:35:25 -0000 1.1
+++ net/core/skbuff.c 18 Mar 2003 23:14:54 -0000 1.3
@@ -149,7 +149,7 @@
*/
/**
- * alloc_skb - allocate a network buffer
+ * alloc_skb - allocate a network buffer using kmalloc
* @size: size to allocate
* @gfp_mask: allocation mask
*
@@ -169,8 +169,46 @@
if (in_interrupt() && (gfp_mask & __GFP_WAIT)) {
static int count = 0;
if (++count < 5) {
- printk(KERN_ERR "alloc_skb called nonatomically "
- "from interrupt %p\n", NET_CALLER(size));
+ printk(KERN_ERR "%s called nonatomically from "
+ "interrupt %p\n", "alloc_skb", NET_CALLER(size));
+ BUG();
+ }
+ gfp_mask &= ~__GFP_WAIT;
+ }
+
+ /* Get the DATA. Size must match skb_add_mtu(). */
+ size = SKB_DATA_ALIGN(size);
+ data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask);
+ if (data == NULL)
+ return NULL;
+
+ /* Allocate the rest of the skb */
+ if ((skb = alloc_skb_custom(size, gfp_mask, kfree, data)) == NULL)
+ kfree(data);
+
+ /* Done */
+ return skb;
+}
+
+/**
+ * alloc_skb_custom - allocate a network buffer
+ * using the supplied data area
+ *
+ * This assumes that size is aligned via SKB_DATA_ALIGN(), and
+ * that 'data' points to size + sizeof(struct skb_shared_info)
+ * bytes.
+ */
+
+struct sk_buff *alloc_skb_custom(unsigned int size, int gfp_mask,
+ void (*free_data)(const void *), u8 *data)
+{
+ struct sk_buff *skb;
+
+ if (in_interrupt() && (gfp_mask & __GFP_WAIT)) {
+ static int count = 0;
+ if (++count < 5) {
+ printk(KERN_ERR "%s called nonatomically from "
+ "interrupt %p\n", "alloc_skb_custom",
NET_CALLER(size));
BUG();
}
gfp_mask &= ~__GFP_WAIT;
@@ -184,11 +222,9 @@
goto nohead;
}
- /* Get the DATA. Size must match skb_add_mtu(). */
- size = SKB_DATA_ALIGN(size);
- data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask);
- if (data == NULL)
- goto nodata;
+ /* Size must match skb_add_mtu(). */
+ if (size != SKB_DATA_ALIGN(size))
+ BUG();
/* XXX: does not include slab overhead */
skb->truesize = size + sizeof(struct sk_buff);
@@ -198,6 +234,7 @@
skb->data = data;
skb->tail = data;
skb->end = data + size;
+ skb->free_data = free_data;
/* Set up other state */
skb->len = 0;
@@ -210,8 +247,6 @@
skb_shinfo(skb)->frag_list = NULL;
return skb;
-nodata:
- skb_head_to_pool(skb);
nohead:
return NULL;
}
@@ -285,7 +320,10 @@
if (skb_shinfo(skb)->frag_list)
skb_drop_fraglist(skb);
- kfree(skb->head);
+ if (skb->free_data == NULL)
+ BUG();
+ (*skb->free_data)(skb->head);
+ skb->free_data = NULL;
}
}
@@ -384,6 +422,7 @@
C(tail);
C(end);
n->destructor = NULL;
+ C(free_data);
#ifdef CONFIG_NETFILTER
C(nfmark);
C(nfcache);
@@ -520,6 +559,7 @@
skb->head = data;
skb->end = data + size;
+ skb->free_data = kfree;
/* Set up new pointers */
skb->h.raw += offset;
@@ -647,6 +687,7 @@
skb->head = data;
skb->end = data+size;
+ skb->free_data = kfree;
skb->data += off;
skb->tail += off;
|