From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Andrey Ryabinin <a.ryabinin@samsung.com>,
Stable <stable@vger.kernel.org>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Peter Feiner <pfeiner@google.com>
Subject: Re: [PATCH] proc/pagemap: walk page tables under pte lock
Date: Tue, 27 Jan 2015 03:34:41 +0200 [thread overview]
Message-ID: <20150127013441.GB3007@node.dhcp.inet.fi> (raw)
In-Reply-To: <20150126145214.11053.5670.stgit@buzz>
On Mon, Jan 26, 2015 at 05:52:14PM +0300, Konstantin Khlebnikov wrote:
> Lockless access to pte in pagemap_pte_range() might race with page migration
> and trigger BUG_ON(!PageLocked()) in migration_entry_to_page():
>
> CPU A (pagemap) CPU B (migration)
> lock_page()
> try_to_unmap(page, TTU_MIGRATION...)
> make_migration_entry()
> set_pte_at()
> <read *pte>
> pte_to_pagemap_entry()
> remove_migration_ptes()
> unlock_page()
> if(is_migration_entry())
> migration_entry_to_page()
> BUG_ON(!PageLocked(page))
>
> Also lockless read might be non-atomic if pte is larger than wordsize.
> Other pte walkers (smaps, numa_maps, clear_refs) already lock ptes.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> Reported-by: Andrey Ryabinin <a.ryabinin@samsung.com>
> Fixes: 052fb0d635df ("proc: report file/anon bit in /proc/pid/pagemap")
> Cc: Stable <stable@vger.kernel.org> (v3.5+)
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2015-01-27 1:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-26 14:52 Konstantin Khlebnikov
2015-01-26 15:14 ` Cyrill Gorcunov
2015-01-27 1:34 ` Kirill A. Shutemov [this message]
2015-01-27 1:51 ` Naoya Horiguchi
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