From: Dan Williams <dan.j.williams@intel.com>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Eric Sandeen <sandeen@redhat.com>,
Lukas Czerner <lczerner@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Christoph Hellwig <hch@lst.de>,
Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.cz>,
linux-ext4 <linux-ext4@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH 0/9] add ext4 per-inode DAX flag
Date: Thu, 7 Sep 2017 13:54:45 -0700 [thread overview]
Message-ID: <CAPcyv4hfhDT9NFRXL+MT5epiqWHJ0RLraV4P3CZ4EJM6L-s0Nw@mail.gmail.com> (raw)
In-Reply-To: <20170906170754.GB17663@linux.intel.com>
On Wed, Sep 6, 2017 at 10:07 AM, Ross Zwisler
<ross.zwisler@linux.intel.com> wrote:
> On Tue, Sep 05, 2017 at 09:12:35PM -0500, Eric Sandeen wrote:
>> On 9/5/17 5:35 PM, Ross Zwisler wrote:
>> > The original intent of this series was to add a per-inode DAX flag to ext4
>> > so that it would be consistent with XFS. In my travels I found and fixed
>> > several related issues in both ext4 and XFS.
>>
>> Hi Ross -
>>
>> hch had a lot of reasons to nuke the dax flag from orbit, and we just
>> /disabled/ it in xfs due to its habit of crashing the kernel...
>
> Ah, sorry, I wasn't CC'd on those threads and missed them. For any interested
> bystanders:
>
> https://www.spinics.net/lists/linux-ext4/msg57840.html
> https://www.spinics.net/lists/linux-xfs/msg09831.html
> https://www.spinics.net/lists/linux-xfs/msg10124.html
>
>> so a couple questions:
>>
>> 1) does this series pass hch's "test the per-inode DAX flag" fstest?
>
> Nope, it has the exact same problems as the XFS per-inode DAX flag.
>
>> 2) do we have an agreement that we need this flag at all, or is this
>> just a parity item because xfs has^whad a per-inode flag?
>
> It was for parity, and because it allows admins finer grained control over
> their system. Basically all things discussed in response to Lukas's original
> patch in the first link above.
I think it's more than parity. When pmem is slower than page cache it
is actively harmful to have DAX enabled globally for a filesystem. So,
not only should we push for per-inode DAX control, we should also push
to deprecate the mount option. I agree with Christoph that we should
try to automatically and transparently enable DAX where it makes
sense, but we also need a finer-grained mechanism than a mount flag to
force the behavior one way or the other.
next prev parent reply other threads:[~2017-09-07 20:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-05 22:35 [PATCH 0/9] add ext4 per-inode DAX flag Ross Zwisler
2017-09-05 22:35 ` [PATCH 1/9] ext4: remove duplicate extended attributes defs Ross Zwisler
2017-09-06 7:29 ` Jan Kara
2017-09-05 22:35 ` [PATCH 2/9] xfs: always use DAX if mount option is used Ross Zwisler
2017-09-05 22:35 ` [PATCH 3/9] xfs: validate bdev support for DAX inode flag Ross Zwisler
2017-09-05 22:35 ` [PATCH 4/9] ext4: add ext4_should_use_dax() Ross Zwisler
2017-09-05 22:35 ` [PATCH 5/9] ext4: ext4_change_inode_journal_flag error handling Ross Zwisler
2017-09-05 22:35 ` [PATCH 6/9] ext4: safely transition S_DAX on journaling changes Ross Zwisler
2017-09-06 9:47 ` Jan Kara
2017-09-06 17:09 ` Ross Zwisler
2017-09-05 22:35 ` [PATCH 7/9] ext4: prevent data corruption with inline data + DAX Ross Zwisler
2017-09-06 20:55 ` Andreas Dilger
2017-09-06 23:11 ` Ross Zwisler
2017-09-05 22:35 ` [PATCH 8/9] ext4: add sanity check for encryption " Ross Zwisler
2017-09-05 22:35 ` [PATCH 9/9] ext4: add per-inode DAX flag Ross Zwisler
2017-09-06 2:12 ` [PATCH 0/9] add ext4 " Eric Sandeen
2017-09-06 17:07 ` Ross Zwisler
2017-09-07 20:54 ` Dan Williams [this message]
2017-09-07 21:13 ` Ross Zwisler
2017-09-07 21:26 ` Andreas Dilger
2017-09-07 21:51 ` Ross Zwisler
2017-09-07 22:12 ` Dave Chinner
2017-09-07 22:19 ` Ross Zwisler
2017-09-07 23:25 ` Dave Chinner
2017-09-08 9:48 ` Jan Kara
2017-09-08 15:39 ` Theodore Ts'o
2017-09-11 8:47 ` Jan Kara
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