From: Andrea Arcangeli <aarcange@redhat.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
Subject: Re: [PATCH mmotm] thp: transparent hugepage core fixlet
Date: Tue, 11 Jan 2011 17:31:20 +0100 [thread overview]
Message-ID: <20110111163120.GR9506@random.random> (raw)
In-Reply-To: <20110111140421.GM9506@random.random>
On Tue, Jan 11, 2011 at 03:04:21PM +0100, Andrea Arcangeli wrote:
> architectural bug to me. Why can't pud_huge simply return 0 for
> x86_32? Any other place dealing with hugepages and calling pud_huge on
> x86 noPAE would be at risk, otherwise, no?
Isn't this better solution?
======
Subject: avoid confusing hugetlbfs code when pmd_trans_huge is set
From: Andrea Arcangeli <aarcange@redhat.com>
If pmd is set huge by THP, pud_huge shouldn't return 1 when pud doesn't exist
and it's just a 1:1 bypass over the pmd (like it happens on 32bit x86 because
there are at most 2 or 3 level of pagetables). Only pmd_huge can return 1.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -227,7 +227,15 @@ int pmd_huge(pmd_t pmd)
int pud_huge(pud_t pud)
{
+#ifdef CONFIG_X86_64
return !!(pud_val(pud) & _PAGE_PSE);
+#else
+ /*
+ * pud is a bypass with 2 or 3 level pagetables, only pmd_huge
+ * can return 1.
+ */
+ return 0;
+#endif
}
struct page *
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next prev parent reply other threads:[~2011-01-11 16:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-11 0:55 [PATCH mmotm] thp: transparent hugepage core fixlet Hugh Dickins
2011-01-11 1:57 ` Andrea Arcangeli
2011-01-11 2:29 ` Hugh Dickins
2011-01-11 14:04 ` Andrea Arcangeli
2011-01-11 16:31 ` Andrea Arcangeli [this message]
2011-01-11 22:59 ` Hugh Dickins
2011-01-12 2:02 ` Andrea Arcangeli
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