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Date: Thu, 18 Jan 2018 06:07:39 -0800
From: Matthew Wilcox <willy@infradead.org>
To: Jan =?iso-8859-1?Q?H=2E_Sch=F6nherr?= <jschoenh@amazon.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>,
        Ross Zwisler <ross.zwisler@linux.intel.com>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] dax: Release PMD lock even when there is no PMD support
 in DAX
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On Thu, Jan 18, 2018 at 02:38:39PM +0100, Jan H. Sch�nherr wrote:
> The function follow_pte_pmd() can theoretically return after having
> acquired a PMD lock, even when DAX was not compiled with
> CONFIG_FS_DAX_PMD.

I don't think it can.  How would a PMD entry get into a DAX VMA if we
compiled the kernel without CONFIG_FS_DAX_PMD?