From: "Darrick J. Wong" <djwong@kernel.org>
To: JeffleXu <jefflexu@linux.alibaba.com>
Cc: Theodore Ts'o <tytso@mit.edu>,
adilger.kernel@dilger.ca, ira.weiny@intel.com,
linux-xfs@vger.kernel.org,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, dan.j.williams@intel.com,
Vivek Goyal <vgoyal@redhat.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [Question] ext4/xfs: Default behavior changed after per-file DAX
Date: Tue, 26 Oct 2021 08:48:34 -0700 [thread overview]
Message-ID: <20211026154834.GB24307@magnolia> (raw)
In-Reply-To: <26ddaf6d-fea7-ed20-cafb-decd63b2652a@linux.alibaba.com>
On Tue, Oct 26, 2021 at 10:12:17PM +0800, JeffleXu wrote:
> Hi,
>
> Recently I'm working on supporting per-file DAX for virtiofs [1]. Vivek
> Goyal and I are interested [2] why the default behavior has changed
> since introduction of per-file DAX on ext4 and xfs [3][4].
>
> That is, before the introduction of per-file DAX, when user doesn't
> specify '-o dax', DAX is disabled for all files. After supporting
> per-file DAX, when neither '-o dax' nor '-o dax=always|inode|never' is
> specified, it actually works in a '-o dax=inode' way if the underlying
> blkdev is DAX capable, i.e. depending on the persistent inode flag. That
> is, the default behavior has changed from user's perspective.
>
> We are not sure if this is intentional or not. Appreciate if anyone
> could offer some hint.
Yes, that was an intentional change to all three filesystems to make the
steps we expose to sysadmins/users consistent and documented officially:
https://lore.kernel.org/linux-fsdevel/20200429043328.411431-1-ira.weiny@intel.com/
(This was the first step; ext* were converted as separate series around
the same time.)
--D
>
>
> [1] https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@redhat.com/T/
> [2]
> https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@redhat.com/T/#mf067498887ca2023c64c8b8f6aec879557eb28f8
> [3] 9cb20f94afcd2964944f9468e38da736ee855b19 ("fs/ext4: Make DAX mount
> option a tri-state")
> [4] 02beb2686ff964884756c581d513e103542dcc6a ("fs/xfs: Make DAX mount
> option a tri-state")
>
>
> --
> Thanks,
> Jeffle
next prev parent reply other threads:[~2021-10-26 15:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-26 14:12 [Question] ext4/xfs: Default behavior changed after per-file DAX JeffleXu
2021-10-26 15:48 ` Darrick J. Wong [this message]
2021-10-26 19:25 ` Vivek Goyal
2021-10-26 20:57 ` Ira Weiny
2021-10-27 14:36 ` Vivek Goyal
2021-10-28 5:52 ` JeffleXu
2021-10-28 13:01 ` Vivek Goyal
2021-10-28 18:24 ` Ira Weiny
2021-10-28 19:19 ` Vivek Goyal
2021-10-26 22:33 ` Dave Chinner
2021-10-27 13:14 ` Vivek Goyal
2021-10-28 16:29 ` Eric Sandeen
2021-10-28 16:42 ` Darrick J. Wong
2021-10-27 2:52 ` JeffleXu
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