lkml.org 
[lkml]   [2020]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/3] lib: Add a generic copy_oldmem_page()
On Mon, Jul 13, 2020 at 03:39:17PM +0200, Arnd Bergmann wrote:
> On Mon, Jul 13, 2020 at 3:07 PM Christoph Hellwig <hch@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?

\
 
 \ /
  Last update: 2020-07-14 13:07    [W:0.061 / U:0.164 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site