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

[KOSAKI Motohiro]

On Tue, May 7, 2013 at 8:51 PM, Jerome Glisse <j.glisse@xxxxxxxxx> wrote:
> 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.

Why? The following bug_on inhibit both case.

>>     VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/