From: JeffleXu <jefflexu@linux.alibaba.com>
To: Theodore Ts'o <tytso@mit.edu>,
adilger.kernel@dilger.ca, "Darrick J. Wong" <djwong@kernel.org>,
ira.weiny@intel.com
Cc: 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: [Question] ext4/xfs: Default behavior changed after per-file DAX
Date: Tue, 26 Oct 2021 22:12:17 +0800 [thread overview]
Message-ID: <26ddaf6d-fea7-ed20-cafb-decd63b2652a@linux.alibaba.com> (raw)
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.
[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 reply other threads:[~2021-10-26 14:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-26 14:12 JeffleXu [this message]
2021-10-26 15:48 ` [Question] ext4/xfs: Default behavior changed after per-file DAX Darrick J. Wong
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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