On Tue, Jun 04, 2024 at 07:42:24AM -0700, Jakub Kicinski wrote:

I'd guess the thinking was that if we push back the callers would
switch the relevant allocations to be page-backed. But we can add
a comment above the helper that says "you'd be better off using
page frags and calling sendmsg(MSG_SPLICE_PAGES) directly".

That's just not how network block devices or file systems work, they
don't control the allocations and need to take what gets fed to them.