On Wed, Apr 20, 2011 at 12:47:57PM -0700, Shirley Ma wrote:
> 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);
>
We probably don't need to touch arg if callback is NULL?
> @@ -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;
This is not the only API unsupported for these skbs, is it?
Probably need to check and fail there as well.
>
> --
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