This patch adds userspace buffers support in skb. A new struct
skb_ubuf_info is needed to maintain the userspace buffers argument
and index, a callback is used to notify userspace to release the
buffers once lower device has done DMA (Last reference to that skb
has gone).
Signed-off-by: Shirley Ma <xma@xxxxxxxxxx>
---
include/linux/skbuff.h | 14 ++++++++++++++
net/core/skbuff.c | 15 ++++++++++++++-
2 files changed, 28 insertions(+), 1 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index d0ae90a..47a187b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -189,6 +189,16 @@ enum {
SKBTX_DRV_NEEDS_SK_REF = 1 << 3,
};
+/* The callback notifies userspace to release buffers when skb DMA is done in
+ * lower device, the desc is used to track userspace buffer index.
+ */
+struct skb_ubuf_info {
+ /* support buffers allocation from userspace */
+ void (*callback)(struct sk_buff *);
+ void *arg;
+ size_t desc;
+};
+
/* This data is invariant across clones and lives at
* the end of the header data, ie. at skb->end.
*/
@@ -211,6 +221,10 @@ struct skb_shared_info {
/* Intermediate layers must ensure that destructor_arg
* remains valid until skb destructor */
void * destructor_arg;
+
+ /* DMA mapping from/to userspace buffers */
+ struct skb_ubuf_info ubuf;
+
/* must be last field, see pskb_expand_head() */
skb_frag_t frags[MAX_SKB_FRAGS];
};
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7ebeed0..822c07d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -210,6 +210,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
shinfo = skb_shinfo(skb);
memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
atomic_set(&shinfo->dataref, 1);
+ shinfo->ubuf.callback = NULL;
+ shinfo->ubuf.arg = NULL;
kmemcheck_annotate_variable(shinfo->destructor_arg);
if (fclone) {
@@ -327,7 +329,15 @@ static void skb_release_data(struct sk_buff *skb)
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
put_page(skb_shinfo(skb)->frags[i].page);
}
-
+ /*
+ * if skb buf is from userspace, we need to notify the caller
+ * the lower device DMA has done;
+ */
+ if (skb_shinfo(skb)->ubuf.callback) {
+ skb_shinfo(skb)->ubuf.callback(skb);
+ skb_shinfo(skb)->ubuf.callback = NULL;
+ skb_shinfo(skb)->ubuf.arg = NULL;
+ }
if (skb_has_frag_list(skb))
skb_drop_fraglist(skb);
@@ -480,6 +490,9 @@ bool skb_recycle_check(struct sk_buff *skb, int skb_size)
if (irqs_disabled())
return false;
+ if (shinfo->ubuf.callback)
+ return false;
+
if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE)
return false;
--
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