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Date: Tue, 2 Oct 2018 07:45:47 -0700
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: Problems with VM_MIXEDMAP removal from /proc/<pid>/smaps
Message-ID: <20181002144547.GA26735@infradead.org>
References: <20181002100531.GC4135@quack2.suse.cz>
 <20181002121039.GA3274@linux-x5ow.site>
 <20181002142010.GB4963@linux-x5ow.site>
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To: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Jan Kara <jack@suse.cz>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, mhocko@suse.cz, Dan Williams <dan.j.williams@intel.com>

On Tue, Oct 02, 2018 at 04:20:10PM +0200, Johannes Thumshirn wrote:
>     Provide a F_GETDAX fcntl(2) command so an application can query
>     whether it can make use of DAX or not.

How does an application "make use of DAX"?  What actual user visible
semantics are associated with a file that has this flag set?