From: "'David Gibson'" <david@gibson.dropbear.id.au>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: "'Hugh Dickins'" <hugh@veritas.com>,
Andrew Morton <akpm@osdl.org>, William Irwin <wli@holomorphy.com>,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: hugepage: Fix hugepage logic in free_pgtables()
Date: Fri, 3 Mar 2006 10:00:54 +1100 [thread overview]
Message-ID: <20060302230054.GA23766@localhost.localdomain> (raw)
In-Reply-To: <200603022129.k22LTog14318@unix-os.sc.intel.com>
On Thu, Mar 02, 2006 at 01:29:50PM -0800, Chen, Kenneth W wrote:
> Hugh Dickins wrote on Thursday, March 02, 2006 12:27 PM
> > But the first part, || instead of && in is_hugepage_only_range, looks
> > insufficient: the start and end of the range might each fall in a
> > non-huge region, but the range still cross a huge region.
> >
> > Ah, does RGN_HPAGE nestle up against the TASK_SIZE roof, so any range
> > already tested against TASK_SIZE (as get_unmapped_area has) cannot
> > cross RGN_HPAGE? If so, perhaps it deserves a comment there. And
> > if that is so, and can be relied upon, is_hugepage_only_range need
> > only be testing REGION_NUMBER(addr+len-1) - but it does seem fragile.
>
> There are many address range check before we hit get_unmapped area.
> ia64 can never have a vma range that crosses region boundary. David
> pointed out earlier that shmat and mremap can still slip through the
> crack and he has a patch that fixed it. But yes, this patch is making
> that assumption (or relying on checks being done properly beforehand).
In fact with that other patch, which ensures that no region-crossing
ranges get through, simply (REGION_NUMBER(addr) == RGN_HPAGE) would be
sufficient; either both start and end are in the hugepage region, or
they're both in the same different region.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
next prev parent reply other threads:[~2006-03-02 23:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-02 4:52 hugepage: Fix hugepage logic in free_pgtables() 'David Gibson'
2006-03-02 18:53 ` Hugh Dickins
2006-03-02 19:42 ` Chen, Kenneth W
2006-03-02 20:27 ` Hugh Dickins
2006-03-02 21:29 ` Chen, Kenneth W
2006-03-02 23:00 ` 'David Gibson' [this message]
2006-03-02 23:14 ` 'David Gibson'
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