On Mon, 2011-05-02 at 13:53 +0300, Michael S. Tsirkin wrote:
> 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?
Yes.
> > @@ -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.
Yes, I am going through all these skbs to make sure covering all.
Thanks
Shirley
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