Re: [PATCH net-next 2/8] skb: api to report errors for zero copy skbs

Vlad Yasevich
2012-10-30T15:44:26Z

On 10/29/2012 11:49 AM, Michael S. Tsirkin wrote:
> Orphaning frags for zero copy skbs needs to allocate data in atomic
> context so is has a chance to fail. If it does we currently discard
> the skb which is safe, but we don't report anything to the caller,
> so it can not recover by e.g. disabling zero copy.
>
> Add an API to free skb reporting such errors: this is used
> by tun in case orphaning frags fails.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> include/linux/skbuff.h | 1 +
> net/core/skbuff.c | 19 +++++++++++++++++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 8bac11b..0644432 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -568,6 +568,7 @@ static inline struct rtable *skb_rtable(const struct sk_buff *skb)
> }
>
> extern void kfree_skb(struct sk_buff *skb);
> +extern void skb_tx_error(struct sk_buff *skb, int err);
> extern void consume_skb(struct sk_buff *skb);
> extern void __kfree_skb(struct sk_buff *skb);
> extern struct kmem_cache *skbuff_head_cache;
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index eb31f6e..ad99c64 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -635,6 +635,25 @@ void kfree_skb(struct sk_buff *skb)
> EXPORT_SYMBOL(kfree_skb);
>
> /**
> + * kfree_skb_on_error - report an sk_buff xmit error
> + * @skb: buffer that triggered an error
> + *
> + * Report xmit error if a device callback is tracking this skb.
> + */

Nit: Comment doesn't match new function.

-vlad

> +void skb_tx_error(struct sk_buff *skb, int err)
> +{
> + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) {
> + struct ubuf_info *uarg;
> +
> + uarg = skb_shinfo(skb)->destructor_arg;
> + if (uarg->callback)
> + uarg->callback(uarg, err);
> + skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> + }
> +}
> +EXPORT_SYMBOL(skb_tx_error);
> +
> +/**
> * consume_skb - free an skbuff
> * @skb: buffer to free
> *
>