From: Andrea Arcangeli <aarcange@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, Mel Gorman <mel@csn.ul.ie>,
Johannes Weiner <jweiner@redhat.com>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH 3 of 3] thp: mremap support and TLB optimization
Date: Wed, 24 Aug 2011 00:13:21 +0200 [thread overview]
Message-ID: <20110823221321.GD23870@redhat.com> (raw)
In-Reply-To: <20110823141445.35864dc8.akpm@linux-foundation.org>
Hi Andrew,
On Tue, Aug 23, 2011 at 02:14:45PM -0700, Andrew Morton wrote:
> > + if ((old_addr & ~HPAGE_PMD_MASK) ||
> > + (new_addr & ~HPAGE_PMD_MASK) ||
> > + (old_addr + HPAGE_PMD_SIZE) > old_end ||
>
> Can (old_addr + HPAGE_PMD_SIZE) wrap past zero?
Good question. old_addr is hpage aligned so to overflow it'd need to
be exactly at address 0-HPAGE_PMD_SIZE. Can any userland map an
address there? I doubt and surely not x86* or sparc (currently THP is
only enabled on x86 anyway so answer is it can't wrap past zero). But
probably we should add a wrap check for other archs in the future
unless we have a real guarantee from all archs to avoid the check. I
only can guarantee about x86*.
> - if (!pmd_none(*new_pmd)) {
> - WARN_ON(1);
> + if (!WARN_ON(pmd_none(*new_pmd))) {
WARN_ON(!pmd_none
Thanks for the cleanups!
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next prev parent reply other threads:[~2011-08-23 22:13 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-06 16:58 [PATCH 0 of 3] THP: mremap support and TLB optimization #3 aarcange
2011-08-06 16:58 ` [PATCH 1 of 3] mremap: check for overflow using deltas aarcange
2011-08-08 8:20 ` Johannes Weiner
2011-08-10 10:48 ` Mel Gorman
2011-08-11 0:14 ` Rik van Riel
2011-08-06 16:58 ` [PATCH 2 of 3] mremap: avoid sending one IPI per page aarcange
2011-08-08 8:23 ` Johannes Weiner
2011-08-10 10:55 ` Mel Gorman
2011-08-11 0:16 ` Rik van Riel
2011-08-06 16:58 ` [PATCH 3 of 3] thp: mremap support and TLB optimization aarcange
2011-08-08 8:25 ` Johannes Weiner
2011-08-10 11:01 ` Mel Gorman
2011-08-11 0:26 ` Rik van Riel
2011-08-23 21:14 ` Andrew Morton
2011-08-23 22:13 ` Andrea Arcangeli [this message]
2011-08-23 22:25 ` Andrea Arcangeli
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