From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Vineet Gupta <vgupta@synopsys.com>,
Russell King <linux@armlinux.org.uk>,
Will Deacon <will.deacon@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Ralf Baechle <ralf@linux-mips.org>,
"David S. Miller" <davem@davemloft.net>,
Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [HELP-NEEDED, PATCH 0/3] Do not loose dirty bit on THP pages
Date: Wed, 14 Jun 2017 16:51:40 +0300 [thread overview]
Message-ID: <20170614135143.25068-1-kirill.shutemov@linux.intel.com> (raw)
Hi,
Vlastimil noted that pmdp_invalidate() is not atomic and we can loose
dirty and access bits if CPU sets them after pmdp dereference, but
before set_pmd_at().
The bug doesn't lead to user-visible misbehaviour in current kernel, but
fixing this would be critical for future work on THP: both huge-ext4 and THP
swap out rely on proper dirty tracking.
Unfortunately, there's no way to address the issue in a generic way. We need to
fix all architectures that support THP one-by-one.
All architectures that have THP supported have to provide atomic
pmdp_invalidate(). If generic implementation of pmdp_invalidate() is used,
architecture needs to provide atomic pmdp_mknonpresent().
I've fixed the issue for x86, but I need help with the rest.
So far THP is supported on 8 architectures. Power and S390 already provides
atomic pmdp_invalidate(). x86 is fixed by this patches, so 5 architectures
left:
- arc;
- arm;
- arm64;
- mips;
- sparc -- it has custom pmdp_invalidate(), but it's racy too;
Please, help me with them.
Kirill A. Shutemov (3):
x86/mm: Provide pmdp_mknotpresent() helper
mm: Do not loose dirty and access bits in pmdp_invalidate()
mm, thp: Do not loose dirty bit in __split_huge_pmd_locked()
arch/x86/include/asm/pgtable-3level.h | 17 +++++++++++++++++
arch/x86/include/asm/pgtable.h | 13 +++++++++++++
mm/huge_memory.c | 13 +++++++++----
mm/pgtable-generic.c | 3 +--
4 files changed, 40 insertions(+), 6 deletions(-)
--
2.11.0
next reply other threads:[~2017-06-14 13:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-14 13:51 Kirill A. Shutemov [this message]
2017-06-14 13:51 ` [PATCH 1/3] x86/mm: Provide pmdp_mknotpresent() helper Kirill A. Shutemov
2017-06-14 16:09 ` Andrea Arcangeli
2017-06-15 4:43 ` kbuild test robot
2017-06-14 13:51 ` [PATCH 2/3] mm: Do not loose dirty and access bits in pmdp_invalidate() Kirill A. Shutemov
2017-06-15 8:48 ` kbuild test robot
2017-06-14 13:51 ` [PATCH 3/3] mm, thp: Do not loose dirty bit in __split_huge_pmd_locked() Kirill A. Shutemov
2017-06-14 14:18 ` Martin Schwidefsky
2017-06-14 15:31 ` Andrea Arcangeli
2017-06-15 8:46 ` Kirill A. Shutemov
2017-06-14 15:28 ` Aneesh Kumar K.V
2017-06-14 14:06 ` [HELP-NEEDED, PATCH 0/3] Do not loose dirty bit on THP pages Martin Schwidefsky
2017-06-14 15:25 ` Aneesh Kumar K.V
2017-06-14 16:55 ` Will Deacon
2017-06-14 17:00 ` Vlastimil Babka
2017-06-15 1:36 ` Aneesh Kumar K.V
2017-06-15 1:05 ` Aneesh Kumar K.V
2017-06-15 2:50 ` Aneesh Kumar K.V
2017-06-15 8:48 ` Kirill A. Shutemov
2017-06-15 9:36 ` Aneesh Kumar K.V
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