From patchwork Wed Jul 6 22:22:12 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shirley Ma X-Patchwork-Id: 951432 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.4) with ESMTP id p66MMLKQ020703 for ; Wed, 6 Jul 2011 22:22:21 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751754Ab1GFWWS (ORCPT ); Wed, 6 Jul 2011 18:22:18 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:40599 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751552Ab1GFWWS (ORCPT ); Wed, 6 Jul 2011 18:22:18 -0400 Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by e35.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p66M3iik022283; Wed, 6 Jul 2011 16:03:44 -0600 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p66MMENZ159660; Wed, 6 Jul 2011 16:22:14 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p66GLkSR015694; Wed, 6 Jul 2011 10:21:47 -0600 Received: from [9.49.135.143] (sig-9-49-135-143.mts.ibm.com [9.49.135.143]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id p66GLjdO015658; Wed, 6 Jul 2011 10:21:45 -0600 Subject: [PATCH V8 2/4 net-next] skbuff: skb supports zero-copy buffers From: Shirley Ma To: David Miller , mst@redhat.com Cc: netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 06 Jul 2011 15:22:12 -0700 Message-ID: <1309990932.10209.19.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Wed, 06 Jul 2011 22:22:21 +0000 (UTC) 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). If there is any userspace apps to reference these userspace buffers, then these userspaces buffers will be copied into kernel. This way we can prevent userspace apps from holding these userspace buffers too long. Use destructor_arg to point to the userspace buffer info; a new tx flags SKBTX_DEV_ZEROCOPY is added for zero-copy buffer check. Signed-off-by: Shirley Ma --- include/linux/skbuff.h | 16 ++++++++++ net/core/skbuff.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 94 insertions(+), 1 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 3e54337..08d4507 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -187,6 +187,20 @@ enum { /* ensure the originating sk reference is available on driver level */ SKBTX_DRV_NEEDS_SK_REF = 1 << 3, + + /* device driver supports TX zero-copy buffers */ + SKBTX_DEV_ZEROCOPY = 1 << 4, +}; + +/* + * 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 ubuf_info { + void (*callback)(void *); + void *arg; + unsigned long desc; }; /* This data is invariant across clones and lives at @@ -211,6 +225,7 @@ struct skb_shared_info { /* Intermediate layers must ensure that destructor_arg * remains valid until skb destructor */ void * destructor_arg; + /* must be last field, see pskb_expand_head() */ skb_frag_t frags[MAX_SKB_FRAGS]; }; @@ -2265,5 +2280,6 @@ static inline void skb_checksum_none_assert(struct sk_buff *skb) } bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off); + #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 46cbd28..42462f5 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -329,6 +329,18 @@ 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)->tx_flags & SKBTX_DEV_ZEROCOPY) { + struct ubuf_info *uarg; + + uarg = skb_shinfo(skb)->destructor_arg; + if (uarg->callback) + uarg->callback(uarg); + } + if (skb_has_frag_list(skb)) skb_drop_fraglist(skb); @@ -481,6 +493,9 @@ bool skb_recycle_check(struct sk_buff *skb, int skb_size) if (irqs_disabled()) return false; + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) + return false; + if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE) return false; @@ -596,6 +611,50 @@ struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src) } EXPORT_SYMBOL_GPL(skb_morph); +/* skb frags copy userspace buffers to kernel */ +static int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) +{ + int i; + int num_frags = skb_shinfo(skb)->nr_frags; + struct page *page, *head = NULL; + struct ubuf_info *uarg = skb_shinfo(skb)->destructor_arg; + + for (i = 0; i < num_frags; i++) { + u8 *vaddr; + skb_frag_t *f = &skb_shinfo(skb)->frags[i]; + + page = alloc_page(GFP_ATOMIC); + if (!page) { + while (head) { + put_page(head); + head = (struct page *)head->private; + } + return -ENOMEM; + } + vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]); + memcpy(page_address(page), + vaddr + f->page_offset, f->size); + kunmap_skb_frag(vaddr); + page->private = (unsigned long)head; + head = page; + } + + /* skb frags release userspace buffers */ + for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) + put_page(skb_shinfo(skb)->frags[i].page); + + uarg->callback(uarg); + + /* skb frags point to kernel buffers */ + for (i = skb_shinfo(skb)->nr_frags; i > 0; i--) { + skb_shinfo(skb)->frags[i - 1].page_offset = 0; + skb_shinfo(skb)->frags[i - 1].page = head; + head = (struct page *)head->private; + } + return 0; +} + + /** * skb_clone - duplicate an sk_buff * @skb: buffer to clone @@ -614,6 +673,11 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask) { struct sk_buff *n; + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) { + if (skb_copy_ubufs(skb, gfp_mask)) + return NULL; + } + n = skb + 1; if (skb->fclone == SKB_FCLONE_ORIG && n->fclone == SKB_FCLONE_UNAVAILABLE) { @@ -731,6 +795,12 @@ struct sk_buff *pskb_copy(struct sk_buff *skb, gfp_t gfp_mask) if (skb_shinfo(skb)->nr_frags) { int i; + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) { + if (skb_copy_ubufs(skb, gfp_mask)) { + kfree(n); + goto out; + } + } for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { skb_shinfo(n)->frags[i] = skb_shinfo(skb)->frags[i]; get_page(skb_shinfo(n)->frags[i].page); @@ -788,7 +858,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, fastpath = true; else { int delta = skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1; - fastpath = atomic_read(&skb_shinfo(skb)->dataref) == delta; } @@ -819,6 +888,11 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, if (fastpath) { kfree(skb->head); } else { + /* copy this zero copy skb frags */ + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) { + if (skb_copy_ubufs(skb, gfp_mask)) + goto nofrags; + } for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) get_page(skb_shinfo(skb)->frags[i].page); @@ -853,6 +927,8 @@ adjust_others: atomic_set(&skb_shinfo(skb)->dataref, 1); return 0; +nofrags: + kfree(data); nodata: return -ENOMEM; } @@ -1354,6 +1430,7 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) } start = end; } + if (!len) return 0;