This patch adds userspace buffers support in skb shared info. 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 <[email protected]> --- include/linux/skbuff.h | 26 ++++++++++++++++++++++++++ net/core/skbuff.c | 13 +++++++++++++ 2 files changed, 39 insertions(+), 0 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 79aafbb..40faffe 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -189,6 +189,18 @@ enum { SKBTX_DRV_NEEDS_SK_REF = 1 << 3, }; +/* + * The callback notifies userspace to release buffers when skb DMA is done in + * lower device, the skb last reference should be 0 when calling this. + * 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 +223,10 @@ 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]; }; @@ -2261,5 +2277,15 @@ static inline void skb_checksum_none_assert(struct sk_buff *skb) } bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off); + +/* + * skb_ubuf - is the buffer from userspace + * @skb: buffer to check + */ +static inline int skb_ubuf(const struct sk_buff *skb) +{ + return (skb_shinfo(skb)->ubuf.callback != NULL); +} + #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 7ebeed0..9cbd3fc 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) { @@ -328,6 +330,14 @@ static void skb_release_data(struct sk_buff *skb) 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; + } 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 (skb_ubuf(skb)) + return false; + if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE) return false; -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
