Re: [PATCH] Do not set page's count_info directly

[Gianluca Guida <gianluca.guida@eu.citrix.com>]

Jiang, Yunhong wrote:
> Keir Fraser <mailto:keir.fraser@eu.citrix.com> wrote:
>> On 05/03/2009 12:45, "Gianluca Guida" <glguida@gmail.com> wrote:
>>
>>> On Thu, Mar 5, 2009 at 1:38 PM, Tim Deegan
>> <Tim.Deegan@citrix.com> wrote:
>>>> The check doesn't tell you it's a shadow page -- it just tells you it's
>>>> *not* allocated in another way.  Checking with the mask is OK here,
>>>> perhaps with a comment change.
>>> Yes, but this is what the code (in the shadow code) intends to check.
>>> My complete plan is to have this macro and restore the idea of having
>>> a flag for shadow pages because, as for now, the fact that we can't
>>> distinguish clearly a shadow page should be considered a sort of bug,
>>> given the code assumptions. Or at least a good basis for future bugs.
>> I'm happy for shadow code to have another bit in count_info
>> for its own use.
>> I don't think it's good to have other code (e.g., generic page offlining
>> code) peeking at it, is all. The particular case for a new
>> flag described
>> above sounds fine.
> 
> The new code is not using that flag anymore, it is use the page_get_owner_and_reference() to get the owner.

Yes, I was actually thinking about adding it. Turns out that I realized 
that it's not the best way to do stuff, but I think that I'll do the 
following:

- add a sh_page_is_a_shadow_page() in shadow code to make the code less 
confusing (with a small caveat comment about not being perfectly precise).
- exercise my English skills by writing a comment in page_info that 
summarizes this thread findings about current use if count_info and 
shadow pages.

Thanks,
Gianluca