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 02:57:42 +0100 [thread overview]
Message-ID: <20110111015742.GL9506@random.random> (raw)
In-Reply-To: <alpine.LSU.2.00.1101101652200.11559@sister.anvils>
Hi Hugh,
On Mon, Jan 10, 2011 at 04:55:53PM -0800, Hugh Dickins wrote:
> If you configure THP in addition to HUGETLB_PAGE on x86_32 without PAE,
> the p?d-folding works out that munlock_vma_pages_range() can crash to
> follow_page()'s pud_huge() BUG_ON(flags & FOLL_GET): it needs the same
> VM_HUGETLB check already there on the pmd_huge() line. Conveniently,
> openSUSE provides a "blogd" which tests this out at startup!
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> ---
> This massive rework belongs just after thp-transparent-hugepage-core.patch
>
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- mmotm.orig/mm/memory.c 2011-01-10 16:31:29.000000000 -0800
> +++ mmotm/mm/memory.c 2011-01-10 16:33:16.000000000 -0800
> @@ -1288,7 +1288,7 @@ struct page *follow_page(struct vm_area_
> pud = pud_offset(pgd, address);
> if (pud_none(*pud))
> goto no_page_table;
> - if (pud_huge(*pud)) {
> + if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
> BUG_ON(flags & FOLL_GET);
> page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
> goto out;
How is THP related to this? pud_trans_huge doesn't exist, if pud_huge
is true, vma is already guaranteed to belong to hugetlbfs without
requiring the additional check.
I added the check to pmd_huge already, there it is needed, but for
pud_huge it isn't as far as I can tell.
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next prev parent reply other threads:[~2011-01-11 1:57 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 [this message]
2011-01-11 2:29 ` Hugh Dickins
2011-01-11 14:04 ` Andrea Arcangeli
2011-01-11 16:31 ` Andrea Arcangeli
2011-01-11 22:59 ` Hugh Dickins
2011-01-12 2:02 ` Andrea Arcangeli
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