[CRIU] [PATCH v4 07/12] criu: page-xfer: add ability to skip writing lazy pages

[Pavel Emelyanov]

On 06/09/2016 04:42 PM, Mike Rapoport wrote:
> On Thu, Jun 9, 2016 at 4:39 PM, Pavel Emelyanov <xemul at virtuozzo.com> wrote:
>> On 06/09/2016 04:24 PM, Mike Rapoport wrote:
>>> On Thu, Jun 9, 2016 at 4:22 PM, Pavel Emelyanov <xemul at virtuozzo.com> wrote:
>>>> On 06/09/2016 04:12 PM, Mike Rapoport wrote:
>>>>> On Thu, Jun 9, 2016 at 4:12 PM, Mike Rapoport <mike.rapoport at gmail.com> wrote:
>>>>>>>
>>>>>>> I have a question here -- if page_xfer_dump_pages sends a pagemap the receiver
>>>>>>> would expect the subsequent pages on the socket, but instead, it _may_ receive
>>>>>>> next pagemap if the previous one was lazy. How it this handled?
>>>>>>
>>>>>> Hmmm. It is not... I think that page-server and, most probably,
>>>>>> incremental dumps are not compatible with lazy-pages...
>>>>>
>>>>> As of now :(
>>>>
>>>> OK... And when in the lazy-pages code-flow would this page_xfer_dump_pages()
>>>> get called?
>>>
>>> At the "usual place", dump_pages will have yet another boolean
>>> parameter 'lazy' that will be passed to page_xfer_dump_pages()
>>
>> OK, so we do "regular" dump that doesn't write lazy pages into pages.img, right?
> 
> Yes

OK, this creates ... broken pagemap/pages image set, as pagemap is present,
but the respective page-set is not :( Can we add optional bool lazy bit
for this? AFAIU the restore side reads the pagemap and understands that
it's lazy by looking at VMA, does it?

-- Pavel