[PATCH net-next v2 3/3] net: add netmem_t to skb_frag_t
From: Mina Almasry
Date: Sun Dec 17 2023 - 03:11:01 EST
Use netmem_t instead of page directly in skb_frag_t. Currently netmem_t
is always a struct page underneath, but the abstraction allows efforts
to add support for skb frags not backed by pages.
There is unfortunately 1 instance where the skb_frag_t is assumed to be
a bio_vec in kcm. For this case, add a debug assert that the skb frag is
indeed backed by a page, and do a cast.
Add skb[_frag]_fill_netmem_*() and skb_add_rx_frag_netmem() helpers so
that the API can be used to create netmem skbs.
Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
---
v2:
- Add skb frag filling helpers.
---
include/linux/skbuff.h | 70 ++++++++++++++++++++++++++++++++----------
net/core/skbuff.c | 22 +++++++++----
net/kcm/kcmsock.c | 10 ++++--
3 files changed, 78 insertions(+), 24 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 7ce38874dbd1..03ab13072962 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -37,6 +37,7 @@
#endif
#include <net/net_debug.h>
#include <net/dropreason-core.h>
+#include <net/netmem.h>
/**
* DOC: skb checksums
@@ -359,7 +360,11 @@ extern int sysctl_max_skb_frags;
*/
#define GSO_BY_FRAGS 0xFFFF
-typedef struct bio_vec skb_frag_t;
+typedef struct skb_frag {
+ struct netmem *bv_page;
+ unsigned int bv_len;
+ unsigned int bv_offset;
+} skb_frag_t;
/**
* skb_frag_size() - Returns the size of a skb fragment
@@ -2431,22 +2436,37 @@ static inline unsigned int skb_pagelen(const struct sk_buff *skb)
return skb_headlen(skb) + __skb_pagelen(skb);
}
+static inline void skb_frag_fill_netmem_desc(skb_frag_t *frag,
+ struct netmem *netmem, int off,
+ int size)
+{
+ frag->bv_page = netmem;
+ frag->bv_offset = off;
+ skb_frag_size_set(frag, size);
+}
+
static inline void skb_frag_fill_page_desc(skb_frag_t *frag,
struct page *page,
int off, int size)
{
- frag->bv_page = page;
- frag->bv_offset = off;
- skb_frag_size_set(frag, size);
+ skb_frag_fill_netmem_desc(frag, page_to_netmem(page), off, size);
+}
+
+static inline void __skb_fill_netmem_desc_noacc(struct skb_shared_info *shinfo,
+ int i, struct netmem *netmem,
+ int off, int size)
+{
+ skb_frag_t *frag = &shinfo->frags[i];
+
+ skb_frag_fill_netmem_desc(frag, netmem, off, size);
}
static inline void __skb_fill_page_desc_noacc(struct skb_shared_info *shinfo,
int i, struct page *page,
int off, int size)
{
- skb_frag_t *frag = &shinfo->frags[i];
-
- skb_frag_fill_page_desc(frag, page, off, size);
+ __skb_fill_netmem_desc_noacc(shinfo, i, page_to_netmem(page), off,
+ size);
}
/**
@@ -2462,10 +2482,10 @@ static inline void skb_len_add(struct sk_buff *skb, int delta)
}
/**
- * __skb_fill_page_desc - initialise a paged fragment in an skb
+ * __skb_fill_netmem_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
+ * @netmem: the netmem to use for this fragment
* @off: the offset to the data with @page
* @size: the length of the data
*
@@ -2474,10 +2494,13 @@ static inline void skb_len_add(struct sk_buff *skb, int delta)
*
* 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)
+static inline void __skb_fill_netmem_desc(struct sk_buff *skb, int i,
+ struct netmem *netmem, int off,
+ int size)
{
- __skb_fill_page_desc_noacc(skb_shinfo(skb), i, page, off, size);
+ struct page *page = netmem_to_page(netmem);
+
+ __skb_fill_netmem_desc_noacc(skb_shinfo(skb), i, netmem, off, size);
/* Propagate page pfmemalloc to the skb if we can. The problem is
* that not all callers have unique ownership of the page but rely
@@ -2485,7 +2508,21 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
*/
page = compound_head(page);
if (page_is_pfmemalloc(page))
- skb->pfmemalloc = true;
+ skb->pfmemalloc = true;
+}
+
+static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
+ struct page *page, int off, int size)
+{
+ __skb_fill_netmem_desc(skb, i, page_to_netmem(page), off, size);
+}
+
+static inline void skb_fill_netmem_desc(struct sk_buff *skb, int i,
+ struct netmem *netmem, int off,
+ int size)
+{
+ __skb_fill_netmem_desc(skb, i, netmem, off, size);
+ skb_shinfo(skb)->nr_frags = i + 1;
}
/**
@@ -2505,8 +2542,7 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
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;
+ skb_fill_netmem_desc(skb, i, page_to_netmem(page), off, size);
}
/**
@@ -2532,6 +2568,8 @@ static inline void skb_fill_page_desc_noacc(struct sk_buff *skb, int i,
void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
int size, unsigned int truesize);
+void skb_add_rx_frag_netmem(struct sk_buff *skb, int i, struct netmem *netmem,
+ int off, int size, unsigned int truesize);
void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
unsigned int truesize);
@@ -3422,7 +3460,7 @@ static inline void skb_frag_off_copy(skb_frag_t *fragto,
*/
static inline struct page *skb_frag_page(const skb_frag_t *frag)
{
- return frag->bv_page;
+ return netmem_to_page(frag->bv_page);
}
/**
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 83af8aaeb893..053d220aa2f2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -845,16 +845,24 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
}
EXPORT_SYMBOL(__napi_alloc_skb);
-void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
- int size, unsigned int truesize)
+void skb_add_rx_frag_netmem(struct sk_buff *skb, int i, struct netmem *netmem,
+ int off, int size, unsigned int truesize)
{
DEBUG_NET_WARN_ON_ONCE(size > truesize);
- skb_fill_page_desc(skb, i, page, off, size);
+ skb_fill_netmem_desc(skb, i, netmem, off, size);
skb->len += size;
skb->data_len += size;
skb->truesize += truesize;
}
+EXPORT_SYMBOL(skb_add_rx_frag_netmem);
+
+void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
+ int size, unsigned int truesize)
+{
+ skb_add_rx_frag_netmem(skb, i, page_to_netmem(page), off, size,
+ truesize);
+}
EXPORT_SYMBOL(skb_add_rx_frag);
void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
@@ -1868,10 +1876,11 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
/* skb frags point to kernel buffers */
for (i = 0; i < new_frags - 1; i++) {
- __skb_fill_page_desc(skb, i, head, 0, psize);
+ __skb_fill_netmem_desc(skb, i, page_to_netmem(head), 0, psize);
head = (struct page *)page_private(head);
}
- __skb_fill_page_desc(skb, new_frags - 1, head, 0, d_off);
+ __skb_fill_netmem_desc(skb, new_frags - 1, page_to_netmem(head), 0,
+ d_off);
skb_shinfo(skb)->nr_frags = new_frags;
release:
@@ -3609,7 +3618,8 @@ skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
if (plen) {
page = virt_to_head_page(from->head);
offset = from->data - (unsigned char *)page_address(page);
- __skb_fill_page_desc(to, 0, page, offset, plen);
+ __skb_fill_netmem_desc(to, 0, page_to_netmem(page),
+ offset, plen);
get_page(page);
j = 1;
len -= plen;
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 65d1f6755f98..5c46db045f4c 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -636,9 +636,15 @@ static int kcm_write_msgs(struct kcm_sock *kcm)
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
msize += skb_shinfo(skb)->frags[i].bv_len;
+ /* The cast to struct bio_vec* here assumes the frags are
+ * struct page based.
+ */
+ DEBUG_NET_WARN_ON_ONCE(
+ !skb_frag_page(&skb_shinfo(skb)->frags[0]));
+
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE,
- skb_shinfo(skb)->frags, skb_shinfo(skb)->nr_frags,
- msize);
+ (const struct bio_vec *)skb_shinfo(skb)->frags,
+ skb_shinfo(skb)->nr_frags, msize);
iov_iter_advance(&msg.msg_iter, txm->frag_offset);
do {
--
2.43.0.472.g3155946c3a-goog