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From: Dan Williams <dan.j.williams@intel.com>
Date: Mon, 10 Sep 2018 07:26:55 -0700
Message-ID: <CAPcyv4jr9353bgUjzKaVsu4ZqFkwkwEKMpETLSqeyJQgYcg_tQ@mail.gmail.com>
Subject: Re: open sets ext4_da_aops for DAX existing files
To: "Kani, Toshi" <toshi.kani@hpe.com>
Cc: "jmoyer@redhat.com" <jmoyer@redhat.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
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On Mon, Sep 10, 2018 at 7:21 AM, Kani, Toshi <toshi.kani@hpe.com> wrote:
> On Mon, 2018-09-10 at 08:54 -0400, Jeff Moyer wrote:
>> "Kani, Toshi" <toshi.kani@hpe.com> writes:
>>
>> > I noticed that both ext4_da_aops and ext4_dax_aops are used on DAX
>> > mounted ext4 files.  Looking at open() path:
>>
>> Eek.  How did you notice this?
>
> I tested sync path on DAX files to see if it flushes processor cache
> properly. Then I noticed that it sometimes does, but sometimes doesn't.
> Looking into function traces, I realized that ext4_dax_writepages() and
> ext4_writepages() are called depending on their file status.

Yikes, and nice find!