Re: [PATCH net-next v1 01/11] net: Get skb fragment addresses through netmem

[saeed bishara]

On Tue, Nov 10, 2026 at 12:27 PM Björn Töpel <bjorn@xxxxxxxxxx> wrote:
>
> skb_frag_address() goes through struct page, so a net_iov never has an
> address. Only unreadable memory should lack one: XDP and BPF read
> fragments through this helper, and AF_XDP UMEM will back readable
> net_iovs. netmem_address() also returns NULL, not a bogus pointer, for
> an unmapped highmem page.
Does this mean that skb_frag_address_safe() is practically identical
to skb_frag_address()? I assume highmem page is the only case where
non niov page isn't mapped.
>

>   *
> - * Returns: the address of the data within @frag. The page must already
> - * be mapped.
> + * Returns: the address of the data within @frag, or %NULL if the CPU cannot
> + * read it.
"CPU cannot read" isn't accurate, I assume that in iouring case the
buffer is mapped to userspace.
>   */