linux-kernel - Re: [PATCH v8 1/1] f2fs: dax: implement direct access

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 26 Jul 2017 10:11:08 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...1.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        sunqiuyang <sunqiuyang@...wei.com>
Subject: Re: [PATCH v8 1/1] f2fs: dax: implement direct access

On Wed, Jul 26, 2017 at 10:01 AM, Christoph Hellwig <hch@...radead.org> wrote:
> On Wed, Jul 26, 2017 at 09:53:07AM -0700, Dan Williams wrote:
>> It allows for opt-in for applications, or administrators of those
>> applications, that know the type of access.
>
> That's BS.  We need to provide the best possible way to access the
> media to an application.  And whether that's DAX or the page cache
> is an implementation detail that should not matter to the application.
>
> Which doesn't mean there shouldn't be ways to override the default
> that the kernel chose based on hardware details, but it's certainly
> not something for the application to hardcode, but something for
> the adminstrator to decide.

Until HMAT came along we had no data in the kernel how to pick a sane
default, but we could now very easily make a "if pmem performance <
dram, disable dax by default" policy in the kernel.

The question for this patch is do we want to add yet another
filesystem that adds "-o dax" or require use of per-inode flags to
enable dax.