From: David Gibson <david@gibson.dropbear.id.au>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>, Andrew Barry <abarry@cray.com>,
linux-mm <linux-mm@kvack.org>, Rik van Riel <riel@redhat.com>,
Minchan Kim <minchan.kim@gmail.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Hastings <abh@cray.com>
Subject: Re: [PATCH v2 1/1] hugepages: Fix race between hugetlbfs umount and quota update.
Date: Mon, 17 Oct 2011 16:14:45 +1100 [thread overview]
Message-ID: <20111017051445.GI4580@truffala.fritz.box> (raw)
In-Reply-To: <20111014135948.a45a8ac1.akpm@linux-foundation.org>
On Fri, Oct 14, 2011 at 01:59:48PM -0700, Andrew Morton wrote:
> On Wed, 12 Oct 2011 15:43:17 +1100
> Paul Mackerras <paulus@samba.org> wrote:
>
> > In the meantime we have a user-triggerable kernel crash. As far as I
> > can see, if we did what you suggest, we would end up with a situation
> > where we could run out of huge pages even though everyone was within
> > quota. Which is arguably better than a kernel crash, but still less
> > than ideal. What do you suggest?
>
> My issue with the patch is that it's rather horrible. We have a layer
> of separation between core hugetlb pages and hugetlbfs. That layering
> has already been mucked up in various places and this patch mucks it up
> further, and quite severely.
>
> So I believe we should rethink the patch. Either a) get the layering
> correct by not poking into hugetlbfs internals from within hugetlb core
> via one of the usual techniques or
Which usual techniques did you have in mind?
> b) make a deliberate decision to
> just give up on that layering: state that hugetlb and hugetlbfs are now
> part of the same subsystem. Make the necessaary Kconfig changes,
> remove ifdefs, move code around, etc.
Well, that might have something to be said for it, the distinction has
always been tenuous at best.
> If we go ahead with the proposed patch-n-run bugfix, the bad code will
> be there permanently - nobody will go in and clean this mess up and the
> kernel is permanently worsened.
Hrm, as opposed to leaving the crash bug there until someone has time
to do the requested cleanup.
--
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: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>, Andrew Barry <abarry@cray.com>,
linux-mm <linux-mm@kvack.org>, Rik van Riel <riel@redhat.com>,
Minchan Kim <minchan.kim@gmail.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Hastings <abh@cray.com>
Subject: Re: [PATCH v2 1/1] hugepages: Fix race between hugetlbfs umount and quota update.
Date: Mon, 17 Oct 2011 16:14:45 +1100 [thread overview]
Message-ID: <20111017051445.GI4580@truffala.fritz.box> (raw)
In-Reply-To: <20111014135948.a45a8ac1.akpm@linux-foundation.org>
On Fri, Oct 14, 2011 at 01:59:48PM -0700, Andrew Morton wrote:
> On Wed, 12 Oct 2011 15:43:17 +1100
> Paul Mackerras <paulus@samba.org> wrote:
>
> > In the meantime we have a user-triggerable kernel crash. As far as I
> > can see, if we did what you suggest, we would end up with a situation
> > where we could run out of huge pages even though everyone was within
> > quota. Which is arguably better than a kernel crash, but still less
> > than ideal. What do you suggest?
>
> My issue with the patch is that it's rather horrible. We have a layer
> of separation between core hugetlb pages and hugetlbfs. That layering
> has already been mucked up in various places and this patch mucks it up
> further, and quite severely.
>
> So I believe we should rethink the patch. Either a) get the layering
> correct by not poking into hugetlbfs internals from within hugetlb core
> via one of the usual techniques or
Which usual techniques did you have in mind?
> b) make a deliberate decision to
> just give up on that layering: state that hugetlb and hugetlbfs are now
> part of the same subsystem. Make the necessaary Kconfig changes,
> remove ifdefs, move code around, etc.
Well, that might have something to be said for it, the distinction has
always been tenuous at best.
> If we go ahead with the proposed patch-n-run bugfix, the bad code will
> be there permanently - nobody will go in and clean this mess up and the
> kernel is permanently worsened.
Hrm, as opposed to leaving the crash bug there until someone has time
to do the requested cleanup.
--
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
--
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next prev parent reply other threads:[~2011-10-17 5:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-19 19:14 [PATCH v2 1/1] hugepages: Fix race between hugetlbfs umount and quota update Andrew Barry
2011-08-19 19:14 ` Andrew Barry
2011-08-19 21:51 ` Andrew Morton
2011-08-19 21:51 ` Andrew Morton
2011-08-22 20:07 ` Andrew Barry
2011-08-23 4:10 ` David Gibson
2011-09-01 5:28 ` David Gibson
2011-09-01 5:28 ` David Gibson
2011-10-12 4:43 ` Paul Mackerras
2011-10-12 4:43 ` Paul Mackerras
2011-10-14 20:59 ` Andrew Morton
2011-10-14 20:59 ` Andrew Morton
2011-10-17 5:14 ` David Gibson [this message]
2011-10-17 5:14 ` David Gibson
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