Re: [PATCH] mm: honor FOLL_GET flag in follow_hugetlb_page v2

[Jerome Glisse]

On Tue, May 7, 2013 at 8:47 PM, KOSAKI Motohiro
<kosaki.motohiro@xxxxxxxxx> wrote:
> On Tue, May 7, 2013 at 6:58 PM,  <j.glisse@xxxxxxxxx> wrote:
>> From: Jerome Glisse <jglisse@xxxxxxxxxx>
>>
>> Do not increase page count if FOLL_GET is not set. None of the
>> current user can trigger the issue because none of the current
>> user call __get_user_pages with both the pages array ptr non
>> NULL and the FOLL_GET flags non set in other word all caller
>> of __get_user_pages that don't set the FOLL_GET flags also call
>> with pages == NULL.
>
> Because, __get_user_pages() doesn't allow pages==NULL and FOLL_GET is on.

Yes but this allow pages != NULL and FOLL_GET not set and as i said
there is no such user of that yet and this is exactly what i was
trying to use.

Cheers,
Jerome

>
> long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> {
> (snip)
>     VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
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