linux-kernel - Re: [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX

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Date:   Wed, 12 Jun 2019 05:07:49 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Larry Bassel <larry.bassel@...cle.com>
Cc:     mike.kravetz@...cle.com, willy@...radead.org,
        dan.j.williams@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX

On Fri, May 24, 2019 at 09:07:11AM -0700, Larry Bassel wrote:
> Again, I don't think this can happen in DAX. The only sharing allowed
> is for FS/DAX/2MiB pagesize.

Hm. I still don't follow. How do you guarantee that DAX actually allocated
continues space for the file on backing storage and you can map it with
PMD page? I believe you don't have such guarantee.


-- 
 Kirill A. Shutemov