On Mon, Jan 15, 2024 at 03:23:33PM -0800, Mina Almasry wrote:

quoted

quoted

You did not answer my question that I asked here, and ignoring this
question is preventing us from making any forward progress on this
discussion. What do you expect or want skb_frag_page() to do when
there is no page in the frag?

I would expect it to do nothing.

I don't understand. skb_frag_page() with an empty implementation just
results in a compiler error as the function needs to return a page
pointer. Do you actually expect skb_frag_page() to unconditionally
cast frag->netmem to a page pointer? That was explained as
unacceptable over and over again by Jason and Christian as it risks
casting devmem to page; completely unacceptable and will get nacked.
Do you have a suggestion of what skb_frag_page() should do that will
not get nacked by mm?

WARN_ON and return NULL seems reasonable?

Jason