[CRIU] Combining pre-copy and post-copy

[Mike Rapoport]

Hello Adrian,

Sorry for the delay, I was on vacation last week.

On Mon, Feb 13, 2017 at 11:02:59AM +0100, Adrian Reber wrote:
> Hello Mike,
> 
> I have to come back to an old topic from September:
> 
> https://lists.openvz.org/pipermail/criu/2016-September/031672.html
> 
> I am currently trying to restore a process with pre-copy and post-copy
> and it fails. The reason it fails is that the kernel claims that a page
> is already there:
> 
> (03.614379) polling timeout
> (03.614389) uffd: Start handling remaining pages
> (03.614393) pr15740-2 Read b0e000 1 pages
> (03.618349) uffd: 15740-6: uffd_copy: 0xb0e000/4096
> (03.618368) Error (criu/uffd.c:682): uffd: 15740-6: UFFDIO_COPY failed: rc:-1 copy:-17

Can you please share the entire restore.log + lazy-pages.log?
 
> According to the pagemap it is a lazy page:
> 
>         {
>             "vaddr": "0xb0e000", 
>             "nr_pages": 1, 
>             "flags": "PE_LAZY"
>         }, 
> 
> But the kernel thinks it is already there. If I manually do an madvise MADV_DONTNEED
> the uffd_copy works. So it seems somehow that the kernel thinks that the page
> has already been written.
> 
> Any idea what is going on here?
> 
> 		Adrian
>