[net-next v1 11/16] net: support non paged skb frags

Mina Almasry
2023-12-08T00:53:18Z

Make skb_frag_page() fail in the case where the frag is not backed
by a page, and fix its relevant callers to handle this case.

Correctly handle skb_frag refcounting in the page_pool_iovs case.

Signed-off-by: Mina Almasry <almasrymina@google.com>

---

Changes in v1:
- Fix illegal_highdma() (Yunsheng).
- Rework napi_pp_put_page() slightly to reduce code churn (Willem).

---
include/linux/skbuff.h | 42 +++++++++++++++++++++++++++++++++++-------
net/core/dev.c | 3 ++-
net/core/gro.c | 2 +-
net/core/skbuff.c | 3 +++
net/ipv4/tcp.c | 3 +++
5 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b370eb8d70f7..851f448d2181 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -37,6 +37,8 @@
#endif
#include <net/net_debug.h>
#include <net/dropreason-core.h>
+#include <net/page_pool/types.h>
+#include <net/page_pool/helpers.h>

/**
* DOC: skb checksums
@@ -3414,15 +3416,38 @@ static inline void skb_frag_off_copy(skb_frag_t *fragto,
fragto->bv_offset = fragfrom->bv_offset;
}

+/* Returns true if the skb_frag contains a page_pool_iov. */
+static inline bool skb_frag_is_page_pool_iov(const skb_frag_t *frag)
+{
+ return page_is_page_pool_iov(frag->bv_page);
+}
+
/**
* skb_frag_page - retrieve the page referred to by a paged fragment
* @frag: the paged fragment
*
- * Returns the &struct page associated with @frag.
+ * Returns the &struct page associated with @frag. Returns NULL if this frag
+ * has no associated page.
*/
static inline struct page *skb_frag_page(const skb_frag_t *frag)
{
- return frag->bv_page;
+ if (!page_is_page_pool_iov(frag->bv_page))
+ return frag->bv_page;
+
+ return NULL;
+}
+
+/**
+ * skb_frag_page_pool_iov - retrieve the page_pool_iov referred to by fragment
+ * @frag: the fragment
+ *
+ * Returns the &struct page_pool_iov associated with @frag. Returns NULL if this
+ * frag has no associated page_pool_iov.
+ */
+static inline struct page_pool_iov *
+skb_frag_page_pool_iov(const skb_frag_t *frag)
+{
+ return page_to_page_pool_iov(frag->bv_page);
}

/**
@@ -3433,7 +3458,7 @@ static inline struct page *skb_frag_page(const skb_frag_t *frag)
*/
static inline void __skb_frag_ref(skb_frag_t *frag)
{
- get_page(skb_frag_page(frag));
+ page_pool_page_get_many(frag->bv_page, 1);
}

/**
@@ -3453,13 +3478,13 @@ bool napi_pp_put_page(struct page *page, bool napi_safe);
static inline void
napi_frag_unref(skb_frag_t *frag, bool recycle, bool napi_safe)
{
- struct page *page = skb_frag_page(frag);
-
#ifdef CONFIG_PAGE_POOL
- if (recycle && napi_pp_put_page(page, napi_safe))
+ if (recycle && napi_pp_put_page(frag->bv_page, napi_safe))
return;
+ page_pool_page_put_many(frag->bv_page, 1);
+#else
+ put_page(skb_frag_page(frag));
#endif
- put_page(page);
}

/**
@@ -3499,6 +3524,9 @@ static inline void skb_frag_unref(struct sk_buff *skb, int f)
*/
static inline void *skb_frag_address(const skb_frag_t *frag)
{
+ if (!skb_frag_page(frag))
+ return NULL;
+
return page_address(skb_frag_page(frag)) + skb_frag_off(frag);
}

diff --git a/net/core/dev.c b/net/core/dev.c
index 30667e4c3b95..1ae9257df441 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3709,8 +3709,9 @@ static int illegal_highdma(struct net_device *dev, struct sk_buff *skb)
if (!(dev->features & NETIF_F_HIGHDMA)) {
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ struct page *page = skb_frag_page(frag);

- if (PageHighMem(skb_frag_page(frag)))
+ if (page && PageHighMem(page))
return 1;
}
}
diff --git a/net/core/gro.c b/net/core/gro.c
index 0759277dc14e..42d7f6755f32 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -376,7 +376,7 @@ static inline void skb_gro_reset_offset(struct sk_buff *skb, u32 nhoff)
NAPI_GRO_CB(skb)->frag0 = NULL;
NAPI_GRO_CB(skb)->frag0_len = 0;

- if (!skb_headlen(skb) && pinfo->nr_frags &&
+ if (!skb_headlen(skb) && pinfo->nr_frags && skb_frag_page(frag0) &&
!PageHighMem(skb_frag_page(frag0)) &&
(!NET_IP_ALIGN || !((skb_frag_off(frag0) + nhoff) & 3))) {
NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 07f802f1adf1..2ce64f57a0f6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2999,6 +2999,9 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];

+ if (WARN_ON_ONCE(!skb_frag_page(f)))
+ return false;
+
if (__splice_segment(skb_frag_page(f),
skb_frag_off(f), skb_frag_size(f),
offset, len, spd, false, sk, pipe))
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 70a1bafbefba..e22681c4bfac 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2157,6 +2157,9 @@ static int tcp_zerocopy_receive(struct sock *sk,
break;
}
page = skb_frag_page(frags);
+ if (WARN_ON_ONCE(!page))
+ break;
+
prefetchw(page);
pages[pages_to_map++] = page;
length += PAGE_SIZE;
--
2.43.0.472.g3155946c3a-goog