Re: [PATCH 10 of 20] ipath - support for userspace apps using coredriver

From: Bryan O'Sullivan
Date: Thu Mar 16 2006 - 14:50:09 EST

On Thu, 2006-03-16 at 17:23 +0000, Hugh Dickins wrote:

> But your backport driver will
> have to be using PageReserved still, not relying on __GFP_COMP: although
> __GFP_COMP was defined in 2.6.9 and a few earlier, it used to take effect
> only when #ifdef CONFIG_HUGETLB_PAGE - only in 2.6.15 did we make it
> available to all configurations. You'll have irritating accounting
> differences between the two drivers: it used to be the case that put_page
> on a PageReserved page did nothing, so you had to avoid get_page on it to
> get the page accounting right; we straightened that out in 2.6.15.

OK. Would it be correct to say that this is what we should do, then?

* On 2.6.15 and later kernels, use __GFP_COMP at allocation time,
and get_page in ->nopage. This is what we're doing as of this
morning, and it works.
* For backports to 2.6.14 and earlier, avoid __GFP_COMP, mark each
page with SetPageReserved at allocation time, and do nothing
special in ->nopage. Do we need to ClearPageReserved before



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