[CRIU] combining pre-copy and post-copy doesn't work anymore

[Mike Rapoport]

Hello Adrian,

On Mon, Jan 16, 2017 at 06:37:21PM +0100, Adrian Reber wrote:
> Hello Mike,
> 
> I just tried lazy migration in combination with pre-dumping. In my tests
> it fails and I wanted to ask if you tested it recently?

Not really. I've done most of the recent testing with
zdtm.py --remote-lazy-pages
 
> (46.566404) polling timeout
> (46.566415) lazy-pages: Start handling remaining pages
> (46.566417) pr2 Read b0e000 1 pages
> (46.580431) lazy-pages: 1119: uffd_copy: 0xb0e000/4096
> (46.580447) Error (criu/uffd.c:529): lazy-pages: 1119: UFFDIO_COPY failed: rc:-1 copy:-17
> (46.580452) polling timeout
> (46.580454) pr2 Read dba000 1 pages
> 
> Or is this works as designed as the page is already in the parent
> image? The error message just sounds a bit scary.
>
> The restore does not work, so something seems wrong. The lazy-pages
> daemon ends with 0 and:

If you are trying to migrate multithreaded application, you probably hit
the race between completion of page faults for different threads at the
same address.
If you see "no iovs found, zero pages" in the dump log, then something went
wrong.
 
> lazy-pages: Process 1119: with UFFD transferred pages: (1777/1777)
> 
> 		Adrian

--
Sincerely yours,
Mike.