[CRIU] Preserve the "dumpable" flag on criu dump/restore.

[Filipe Brandenburger]

Hi,

On Mon, May 12, 2014 at 5:01 PM, Filipe Brandenburger
<filbranden at google.com> wrote:
> Setting paddr = decode_pointer(p->premmaped_addr); instead seems to help...
>
> After doing that I get many pages COWed:
>
> (00.013729)  17521: nr_restored_pages: 182
> (00.013731)  17521: nr_compared_pages: 370
> (00.013733)  17521: nr_shared_pages:   188
> (00.013735)  17521: nr_droped_pages:   35
>
> However, that introduces many fails like the one below:
>
> 16:59:15.995: 17521: FAIL: cow01.c:151: 1: 0x2b35fff8f000 data mismatch
>
> Will keep looking.

So after using paddr = decode_pointer(p->premapped_addr); the (first)
problem seems to be in case where the parent and child share a vma in
the same address space but it's not really COWed. With that patch in
place, it will try to COW it at first, which should be fine. The
problem then is that restore_priv_vma_content() will jump the zero
pages and those pages will not be reset from the parent...

It seems the fix for that is not that simple and requires some deeper
changes to that function to detect whether zero pages were added in
the COWed case, in which case it should zero them out (or mmap them
again?)

That doesn't seem to be the only problem though, I seem to also be
having problem on the other runs when bit with value 8 is set
(a_f_write_parent?), all other bits unset, except for bit with value 2
(b_f_read?) which can be both set and unset... Not sure if I'm reading
the bits right though.

Cheers,
Filipe