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Date: Tue, 13 Jan 2015 14:43:39 +0000
From: David Vrabel <david.vrabel@...rix.com>
To: David Vrabel <david.vrabel@...rix.com>,
<xen-devel@...ts.xenproject.org>,
"David S. Miller" <davem@...emloft.net>
CC: Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Jenny Herbert <jennifer.herbert@...rix.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 08/14] xen-netback: use foreign page information
from the pages themselves
On 12/01/15 15:43, David Vrabel wrote:
> From: Jenny Herbert <jenny.herbert@...rix.com>
>
> Use the foreign page flag in netback to get the domid and grant ref
> needed for the grant copy. This signficiantly simplifies the netback
> code and makes netback work with foreign pages from other backends
> (e.g., blkback).
>
> This allows blkback to use iSCSI disks provided by domUs running on
> the same host.
Dave,
This depends on several xen changes. It's been Acked-by: Ian Campbell
<ian.campbell@...rix.com>
Are you happy for me to merge this via the xen tree in 3.20?
David
> Signed-off-by: Jenny Herbert <jennifer.herbert@...rix.com>
> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
> ---
> drivers/net/xen-netback/netback.c | 100 ++++---------------------------------
> 1 file changed, 9 insertions(+), 91 deletions(-)
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 6441318..ae3ab37 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -314,9 +314,7 @@ static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif_queue *queue,
> static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb,
> struct netrx_pending_operations *npo,
> struct page *page, unsigned long size,
> - unsigned long offset, int *head,
> - struct xenvif_queue *foreign_queue,
> - grant_ref_t foreign_gref)
> + unsigned long offset, int *head)
> {
> struct gnttab_copy *copy_gop;
> struct xenvif_rx_meta *meta;
> @@ -333,6 +331,8 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
> offset &= ~PAGE_MASK;
>
> while (size > 0) {
> + struct xen_page_foreign *foreign;
> +
> BUG_ON(offset >= PAGE_SIZE);
> BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);
>
> @@ -361,9 +361,10 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
> copy_gop->flags = GNTCOPY_dest_gref;
> copy_gop->len = bytes;
>
> - if (foreign_queue) {
> - copy_gop->source.domid = foreign_queue->vif->domid;
> - copy_gop->source.u.ref = foreign_gref;
> + foreign = xen_page_foreign(page);
> + if (foreign) {
> + copy_gop->source.domid = foreign->domid;
> + copy_gop->source.u.ref = foreign->gref;
> copy_gop->flags |= GNTCOPY_source_gref;
> } else {
> copy_gop->source.domid = DOMID_SELF;
> @@ -406,35 +407,6 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
> }
>
> /*
> - * Find the grant ref for a given frag in a chain of struct ubuf_info's
> - * skb: the skb itself
> - * i: the frag's number
> - * ubuf: a pointer to an element in the chain. It should not be NULL
> - *
> - * Returns a pointer to the element in the chain where the page were found. If
> - * not found, returns NULL.
> - * See the definition of callback_struct in common.h for more details about
> - * the chain.
> - */
> -static const struct ubuf_info *xenvif_find_gref(const struct sk_buff *const skb,
> - const int i,
> - const struct ubuf_info *ubuf)
> -{
> - struct xenvif_queue *foreign_queue = ubuf_to_queue(ubuf);
> -
> - do {
> - u16 pending_idx = ubuf->desc;
> -
> - if (skb_shinfo(skb)->frags[i].page.p ==
> - foreign_queue->mmap_pages[pending_idx])
> - break;
> - ubuf = (struct ubuf_info *) ubuf->ctx;
> - } while (ubuf);
> -
> - return ubuf;
> -}
> -
> -/*
> * Prepare an SKB to be transmitted to the frontend.
> *
> * This function is responsible for allocating grant operations, meta
> @@ -459,8 +431,6 @@ static int xenvif_gop_skb(struct sk_buff *skb,
> int head = 1;
> int old_meta_prod;
> int gso_type;
> - const struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg;
> - const struct ubuf_info *const head_ubuf = ubuf;
>
> old_meta_prod = npo->meta_prod;
>
> @@ -507,68 +477,16 @@ static int xenvif_gop_skb(struct sk_buff *skb,
> len = skb_tail_pointer(skb) - data;
>
> xenvif_gop_frag_copy(queue, skb, npo,
> - virt_to_page(data), len, offset, &head,
> - NULL,
> - 0);
> + virt_to_page(data), len, offset, &head);
> data += len;
> }
>
> for (i = 0; i < nr_frags; i++) {
> - /* This variable also signals whether foreign_gref has a real
> - * value or not.
> - */
> - struct xenvif_queue *foreign_queue = NULL;
> - grant_ref_t foreign_gref;
> -
> - if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
> - (ubuf->callback == &xenvif_zerocopy_callback)) {
> - const struct ubuf_info *const startpoint = ubuf;
> -
> - /* Ideally ubuf points to the chain element which
> - * belongs to this frag. Or if frags were removed from
> - * the beginning, then shortly before it.
> - */
> - ubuf = xenvif_find_gref(skb, i, ubuf);
> -
> - /* Try again from the beginning of the list, if we
> - * haven't tried from there. This only makes sense in
> - * the unlikely event of reordering the original frags.
> - * For injected local pages it's an unnecessary second
> - * run.
> - */
> - if (unlikely(!ubuf) && startpoint != head_ubuf)
> - ubuf = xenvif_find_gref(skb, i, head_ubuf);
> -
> - if (likely(ubuf)) {
> - u16 pending_idx = ubuf->desc;
> -
> - foreign_queue = ubuf_to_queue(ubuf);
> - foreign_gref =
> - foreign_queue->pending_tx_info[pending_idx].req.gref;
> - /* Just a safety measure. If this was the last
> - * element on the list, the for loop will
> - * iterate again if a local page were added to
> - * the end. Using head_ubuf here prevents the
> - * second search on the chain. Or the original
> - * frags changed order, but that's less likely.
> - * In any way, ubuf shouldn't be NULL.
> - */
> - ubuf = ubuf->ctx ?
> - (struct ubuf_info *) ubuf->ctx :
> - head_ubuf;
> - } else
> - /* This frag was a local page, added to the
> - * array after the skb left netback.
> - */
> - ubuf = head_ubuf;
> - }
> xenvif_gop_frag_copy(queue, skb, npo,
> skb_frag_page(&skb_shinfo(skb)->frags[i]),
> skb_frag_size(&skb_shinfo(skb)->frags[i]),
> skb_shinfo(skb)->frags[i].page_offset,
> - &head,
> - foreign_queue,
> - foreign_queue ? foreign_gref : UINT_MAX);
> + &head);
> }
>
> return npo->meta_prod - old_meta_prod;
>
--
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