From: Andrew Morton <akpm@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Mel Gorman <mgorman@techsingularity.net>,
Hugh Dickins <hughd@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Dave Hansen <dave.hansen@intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [BUG/REGRESSION] THP: broken page count after commit aa88b68c
Date: Thu, 2 Jun 2016 11:40:31 -0700 [thread overview]
Message-ID: <20160602114031.64b178c823901c171ec82745@linux-foundation.org> (raw)
In-Reply-To: <20160602155149.GB8493@node.shutemov.name>
On Thu, 2 Jun 2016 18:51:50 +0300 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> On Thu, Jun 02, 2016 at 05:21:41PM +0200, Gerald Schaefer wrote:
> > Christian Borntraeger reported a kernel panic after corrupt page counts,
> > and it turned out to be a regression introduced with commit aa88b68c
> > "thp: keep huge zero page pinned until tlb flush", at least on s390.
> >
> > put_huge_zero_page() was moved over from zap_huge_pmd() to release_pages(),
> > and it was replaced by tlb_remove_page(). However, release_pages() might
> > not always be triggered by (the arch-specific) tlb_remove_page().
> >
> > On s390 we call free_page_and_swap_cache() from tlb_remove_page(), and not
> > tlb_flush_mmu() -> free_pages_and_swap_cache() like the generic version,
> > because we don't use the MMU-gather logic. Although both functions have very
> > similar names, they are doing very unsimilar things, in particular
> > free_page_xxx is just doing a put_page(), while free_pages_xxx calls
> > release_pages().
> >
> > This of course results in very harmful put_page()s on the huge zero page,
> > on architectures where tlb_remove_page() is implemented in this way. It
> > seems to affect only s390 and sh, but sh doesn't have THP support, so
> > the problem (currently) probably only exists on s390.
> >
> > The following quick hack fixed the issue:
> >
> > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > index 0d457e7..c99463a 100644
> > --- a/mm/swap_state.c
> > +++ b/mm/swap_state.c
> > @@ -252,7 +252,10 @@ static inline void free_swap_cache(struct page *page)
> > void free_page_and_swap_cache(struct page *page)
> > {
> > free_swap_cache(page);
> > - put_page(page);
> > + if (is_huge_zero_page(page))
> > + put_huge_zero_page();
> > + else
> > + put_page(page);
> > }
> >
> > /*
>
> The fix looks good to me.
Yes. A bit regrettable, but that's what release_pages() does.
Can we have a signed-off-by please?
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next prev parent reply other threads:[~2016-06-02 18:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-02 15:21 [BUG/REGRESSION] THP: broken page count after commit aa88b68c Gerald Schaefer
2016-06-02 15:51 ` Kirill A. Shutemov
2016-06-02 18:40 ` Andrew Morton [this message]
2016-06-02 18:56 ` Christian Borntraeger
2016-06-02 18:56 ` Christian Borntraeger
[not found] ` <201606021856.u52ImC6o037023@mx0a-001b2d01.pphosted.com>
2016-06-02 19:03 ` Andrew Morton
2016-06-02 19:10 ` Christian Borntraeger
2016-06-02 19:10 ` Christian Borntraeger
2016-06-02 19:47 ` Hugh Dickins
2016-06-03 10:36 ` Kirill A. Shutemov
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