linux-kernel - Re: [PATCH v1] mm: thp: check pmd_trans_unstable() after split_huge

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Message-ID: <20160601093957.GA8493@node.shutemov.name>
Date:	Wed, 1 Jun 2016 12:39:57 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v1] mm: thp: check pmd_trans_unstable() after
 split_huge_pmd()

On Wed, Jun 01, 2016 at 09:36:40AM +0900, Naoya Horiguchi wrote:
> split_huge_pmd() doesn't guarantee that the pmd is normal pmd pointing to
> pte entries, which can be checked with pmd_trans_unstable().

Could you be more specific on when we don't have normal ptes after
split_huge_pmd? Race with other thread? DAX?

I guess we can modify split_huge_pmd() to return if the pmd was split or
not.

-- 
 Kirill A. Shutemov