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net: xdp: add xdp_update_skb_shared_info utility routine

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Introduce xdp_update_skb_shared_info routine to update frags array
metadata in skb_shared_info data structure converting to a skb from
a xdp_buff or xdp_frame.
According to the current skb_shared_info architecture in
xdp_frame/xdp_buff and to the xdp frags support, there is
no need to run skb_add_rx_frag() and reset frags array converting the buffer
to a skb since the frag array will be in the same position for xdp_buff/xdp_frame
and for the skb, we just need to update memory metadata.
Introduce XDP_FLAGS_PF_MEMALLOC flag in xdp_buff_flags in order to mark
the xdp_buff or xdp_frame as under memory-pressure if pages of the frags array
are under memory pressure. Doing so we can avoid looping over all fragments in
xdp_update_skb_shared_info routine. The driver is expected to set the
flag constructing the xdp_buffer using xdp_buff_set_frag_pfmemalloc
utility routine.
Rely on xdp_update_skb_shared_info in __xdp_build_skb_from_frame routine
converting the non-linear xdp_frame to a skb after performing a XDP_REDIRECT.

Acked-by: Toke Hoiland-Jorgensen <toke@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/bfd23fb8a8d7438724f7819c567cdf99ffd6226f.1642758637.git.lorenzo@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Lorenzo Bianconi
2022-01-21 11:09:48 +01:00
committed by Alexei Starovoitov
parent d094c9851a
commit d65a1906b3
2 changed files with 44 additions and 1 deletions
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12
net/core/xdp.c
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@@ -561,8 +561,14 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
struct sk_buff *skb,
struct net_device *dev)
{
struct skb_shared_info *sinfo = xdp_get_shared_info_from_frame(xdpf);
unsigned int headroom, frame_size;
void *hard_start;
u8 nr_frags;
/* xdp frags frame */
if (unlikely(xdp_frame_has_frags(xdpf)))
nr_frags = sinfo->nr_frags;
/* Part of headroom was reserved to xdpf */
headroom = sizeof(*xdpf) + xdpf->headroom;
@@ -582,6 +588,12 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
if (xdpf->metasize)
skb_metadata_set(skb, xdpf->metasize);
if (unlikely(xdp_frame_has_frags(xdpf)))
xdp_update_skb_shared_info(skb, nr_frags,
sinfo->xdp_frags_size,
nr_frags * xdpf->frame_sz,
xdp_frame_is_frag_pfmemalloc(xdpf));
/* Essential SKB info: protocol and skb->dev */
skb->protocol = eth_type_trans(skb, dev);