On Sun, Mar 8, 2015 at 11:35 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>> As a second hack (not to be applied), could we change:
>>
>> #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL
>>
>> to:
>>
>> #define _PAGE_BIT_PROTNONE (_PAGE_BIT_GLOBAL+1)
>>
>> to double check that the position of the bit does not matter?
>
> Agreed. We should definitely try that.
There's a second reason to do that, actually: the __supported_pte_mask
thing, _and_ the pageattr stuff in __split_large_page() etc play games
with _PAGE_GLOBAL. As does drivers/lguest for some reason.
So looking at this all, there's a lot of room for confusion with _PAGE_GLOBAL.
That kind of confusion would certainly explain the whole "the changes
_look_ like they do the same thing, but don't" - because of silly
semantic conflicts with PROTNONE vs GLOBAL.
Linus
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>