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net: add callback for setting a ubuf_info to skb

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At the moment an skb can only have one ubuf_info associated with it,
which might be a performance problem for zerocopy sends in cases like
TCP via io_uring. Add a callback for assigning ubuf_info to skb, this
way we will implement smarter assignment later like linking ubuf_info
together.

Note, it's an optional callback, which should be compatible with
skb_zcopy_set(), that's because the net stack might potentially decide
to clone an skb and take another reference to ubuf_info whenever it
wishes. Also, a correct implementation should always be able to bind to
an skb without prior ubuf_info, otherwise we could end up in a situation
when the send would not be able to progress.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/all/b7918aadffeb787c84c9e72e34c729dc04f3a45d.1713369317.git.asml.silence@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Pavel Begunkov 2024-04-19 12:08:40 +01:00 committed by Jakub Kicinski
parent 7ab4f16f9e
commit 65bada80de
2 changed files with 16 additions and 6 deletions
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2
include/linux/skbuff.h
View File

@ -530,6 +530,8 @@ enum {
struct ubuf_info_ops {
void (*complete)(struct sk_buff *, struct ubuf_info *,
bool zerocopy_success);
/* has to be compatible with skb_zcopy_set() */
int (*link_skb)(struct sk_buff *skb, struct ubuf_info *uarg);
};
/*

20
net/core/skbuff.c
View File

@ -1880,11 +1880,18 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
struct ubuf_info *orig_uarg = skb_zcopy(skb);
int err, orig_len = skb->len;
/* An skb can only point to one uarg. This edge case happens when
* TCP appends to an skb, but zerocopy_realloc triggered a new alloc.
*/
if (orig_uarg && uarg != orig_uarg)
return -EEXIST;
if (uarg->ops->link_skb) {
err = uarg->ops->link_skb(skb, uarg);
if (err)
return err;
} else {
/* An skb can only point to one uarg. This edge case happens
* when TCP appends to an skb, but zerocopy_realloc triggered
* a new alloc.
*/
if (orig_uarg && uarg != orig_uarg)
return -EEXIST;
}
err = __zerocopy_sg_from_iter(msg, sk, skb, &msg->msg_iter, len);
if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) {
@ -1898,7 +1905,8 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
return err;
}
skb_zcopy_set(skb, uarg, NULL);
if (!uarg->ops->link_skb)
skb_zcopy_set(skb, uarg, NULL);
return skb->len - orig_len;
}
EXPORT_SYMBOL_GPL(skb_zerocopy_iter_stream);