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Message-ID: <20231223025554.2316836-13-aleksander.lobakin@intel.com>
Date: Sat, 23 Dec 2023 03:55:32 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Michal Kubiak <michal.kubiak@...el.com>,
Larysa Zaremba <larysa.zaremba@...el.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
intel-wired-lan@...ts.osuosl.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH RFC net-next 12/34] xdp: add generic xdp_buff_add_frag()
The code piece which would attach a frag to &xdp_buff is almost
identical across the drivers supporting XDP multi-buffer on Rx.
Make it a generic elegant onelner.
Also, I see lots of drivers calculating frags_truesize as
`xdp->frame_sz * nr_frags`. I can't say this is fully correct, since
frags might be backed by chunks of different sizes, especially with
stuff like the header split. Even page_pool_alloc() can give you two
different truesizes on two subsequent requests to allocate the same
buffer size. Add a field to &skb_shared_info (unionized as there's no
free slot currently on x6_64) to track the "true" truesize. It can be
used later when updating an skb.
Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
include/linux/skbuff.h | 14 ++++++++++----
include/net/xdp.h | 36 +++++++++++++++++++++++++++++++++++-
2 files changed, 45 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ea5c8ab3ed00..e350efa04070 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -598,11 +598,17 @@ struct skb_shared_info {
* Warning : all fields before dataref are cleared in __alloc_skb()
*/
atomic_t dataref;
- unsigned int xdp_frags_size;
- /* Intermediate layers must ensure that destructor_arg
- * remains valid until skb destructor */
- void * destructor_arg;
+ union {
+ struct {
+ unsigned int xdp_frags_size;
+ u32 xdp_frags_truesize;
+ };
+
+ /* 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];
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 909c0bc50517..a3dc0f39b437 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -165,6 +165,34 @@ xdp_get_buff_len(const struct xdp_buff *xdp)
return len;
}
+static inline bool xdp_buff_add_frag(struct xdp_buff *xdp, struct page *page,
+ u32 offset, u32 size, u32 truesize)
+{
+ struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
+
+ if (!xdp_buff_has_frags(xdp)) {
+ sinfo->nr_frags = 0;
+
+ sinfo->xdp_frags_size = 0;
+ sinfo->xdp_frags_truesize = 0;
+
+ xdp_buff_set_frags_flag(xdp);
+ }
+
+ if (unlikely(sinfo->nr_frags == MAX_SKB_FRAGS))
+ return false;
+
+ __skb_fill_page_desc_noacc(sinfo, sinfo->nr_frags++, page, offset,
+ size);
+ sinfo->xdp_frags_size += size;
+ sinfo->xdp_frags_truesize += truesize;
+
+ if (unlikely(page_is_pfmemalloc(page)))
+ xdp_buff_set_frag_pfmemalloc(xdp);
+
+ return true;
+}
+
struct xdp_frame {
void *data;
u16 len;
@@ -230,7 +258,13 @@ xdp_update_skb_shared_info(struct sk_buff *skb, u8 nr_frags,
unsigned int size, unsigned int truesize,
bool pfmemalloc)
{
- skb_shinfo(skb)->nr_frags = nr_frags;
+ struct skb_shared_info *sinfo = skb_shinfo(skb);
+
+ sinfo->nr_frags = nr_frags;
+ /* ``destructor_arg`` is unionized with ``xdp_frags_{,true}size``,
+ * reset it after that these fields aren't used anymore.
+ */
+ sinfo->destructor_arg = NULL;
skb->len += size;
skb->data_len += size;
--
2.43.0
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