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: Thu, 02 Mar 2006 23:00:54 +0000 [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
WARNING: multiple messages have this Message-ID (diff)
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 23:00 UTC|newest]
Thread overview: 20+ 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 4:52 ` 'David Gibson'
2006-03-02 18:53 ` Hugh Dickins
2006-03-02 18:53 ` Hugh Dickins
2006-03-02 19:42 ` Chen, Kenneth W
2006-03-02 19:42 ` Chen, Kenneth W
2006-03-02 20:27 ` Hugh Dickins
2006-03-02 20:27 ` Hugh Dickins
2006-03-02 23:14 ` 'David Gibson'
2006-03-02 23:14 ` 'David Gibson'
2006-03-02 21:29 ` Chen, Kenneth W
2006-03-02 21:29 ` Chen, Kenneth W
2006-03-02 23:00 ` 'David Gibson' [this message]
2006-03-02 23:00 ` 'David Gibson'
2006-03-03 1:04 ` hugepage: Fix hugepage logic in free_pgtables() harder 'David Gibson'
2006-03-03 1:04 ` 'David Gibson'
2006-03-03 5:18 ` Hugh Dickins
2006-03-03 5:18 ` Hugh Dickins
2006-03-03 5:26 ` 'David Gibson'
2006-03-03 5:26 ` 'David Gibson'
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20060302230054.GA23766@localhost.localdomain \
--to=david@gibson.dropbear.id.au \
--cc=akpm@osdl.org \
--cc=hugh@veritas.com \
--cc=kenneth.w.chen@intel.com \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=wli@holomorphy.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.