On Mon, Jul 13, 2020 at 03:39:17PM +0200, Arnd Bergmann wrote: > On Mon, Jul 13, 2020 at 3:07 PM Christoph Hellwig <h...@infradead.org> wrote: > > On Fri, Jul 10, 2020 at 08:55:42PM -0700, Palmer Dabbelt wrote: > > > +ssize_t copy_oldmem_page(unsigned long pfn, char *buf, > > > + size_t csize, unsigned long offset, > > > + int userbuf) > > > +{ > > > + void *vaddr; > > > + > > > + if (!csize) > > > + return 0; > > > + > > > + vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB); > > > + if (!vaddr) > > > + return -ENOMEM; > > > > Doing a memremap for every page is very inefficient. Also I don't see > > why you'd want to even do that. All memory is in the direct mapping > > for RISC-V. For other architecture that support highmem kmap_atomic_pfn > > would do the job, which is what I'd use in a generic version. > > I would expect the 'oldmem' data to not have a 'struct page', which would > be a problem at least for the generic implementation of kmap_atomic_pfn()
Why do you expect it to not have a struct page?