Re: [PATCH net-next v3 3/3] net: add netmem_ref to skb_frag_t
From: Simon Horman <horms@kernel.org>
Date: 2023-12-21 17:16:58
Also in:
kvm, lkml, virtualization
On Wed, Dec 20, 2023 at 01:45:02PM -0800, Mina Almasry wrote:
Use netmem_ref instead of page in skb_frag_t. Currently netmem_ref is always a struct page underneath, but the abstraction allows efforts to add support for skb frags not backed by pages. There is unfortunately 1 instance where the skb_frag_t is assumed to be a bio_vec in kcm. For this case, add a debug assert that the skb frag is indeed backed by a page, and do a cast. Add skb[_frag]_fill_netmem_*() and skb_add_rx_frag_netmem() helpers so that the API can be used to create netmem skbs. Signed-off-by: Mina Almasry <redacted>
...
quoted hunk ↗ jump to hunk
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c index 65d1f6755f98..3180a54b2c68 100644 --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c@@ -636,9 +636,15 @@ static int kcm_write_msgs(struct kcm_sock *kcm) for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) msize += skb_shinfo(skb)->frags[i].bv_len; + /* The cast to struct bio_vec* here assumes the frags are + * struct page based. WARN if there is no page in this skb. + */ + DEBUG_NET_WARN_ON_ONCE( + !skb_frag_page(&skb_shinfo(skb)->frags[0])); + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, - skb_shinfo(skb)->frags, skb_shinfo(skb)->nr_frags, - msize); + (const struct bio_vec *)skb_shinfo(skb)->frags, + skb_shinfo(skb)->nr_frags, msize); iov_iter_advance(&msg.msg_iter, txm->frag_offset); do {
Hi Mina,
something isn't quite right here.
...//kcmsock.c:637:39: error: no member named 'bv_len' in 'struct skb_frag'
637 | msize += skb_shinfo(skb)->frags[i].bv_len;
| ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
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pw-bot: changes-requested