On Wed, Jan 19, 2022 at 01:28:14PM +0000, Robin Murphy wrote: > Is it page_to_pfn() guaranteed to work without blowing up if page is invalid > in the first place? Looking at the CONFIG_SPARSEMEM case I'm not sure that's > true... Something that all the ARM people weighing in on this don't understand is that basically nobody uses SPARSEMEM without SPARSEMEM_VMEMMAP. So all this complicated code to do page_to_pfn() is never tested. Real users all do a simple subtraction and so the simple pfn_valid() works fine.
