From: Dave Chinner <david@fromorbit.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>,
Eric Sandeen <sandeen@sandeen.net>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Christoph Hellwig <hch@infradead.org>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-xfs <linux-xfs@vger.kernel.org>,
jlayton@redhat.com
Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts
Date: Sat, 20 Jun 2020 08:10:44 +1000 [thread overview]
Message-ID: <20200619221044.GO2005@dread.disaster.area> (raw)
In-Reply-To: <20200619204033.GB1564@fieldses.org>
On Fri, Jun 19, 2020 at 04:40:33PM -0400, J. Bruce Fields wrote:
> On Fri, Jun 19, 2020 at 12:44:55PM +1000, Dave Chinner wrote:
> > On Thu, Jun 18, 2020 at 10:20:05PM -0400, J. Bruce Fields wrote:
> > > My memory was that after Jeff Layton's i_version patches, there wasn't
> > > really a significant performance hit any more, so the ability to turn it
> > > off is no longer useful.
> >
> > Yes, I completely agree with you here. However, with some
> > filesystems allowing it to be turned off, we can't just wave our
> > hands and force enable the option. Those filesystems - if the
> > maintainers chose to always enable iversion - will have to go
> > through a mount option deprecation period before permanently
> > enabling it.
>
> I don't understand why.
>
> The filesystem can continue to let people set iversion or noiversion as
> they like, while under the covers behaving as if iversion is always set.
> I can't see how that would break any application. (Or even how an
> application would be able to detect that the filesystem was doing this.)
It doesn't break functionality, but it affects performance. IOWs, it
can make certain workloads go a lot slower in some circumstances.
And that can result in unexectedly breaking SLAs or slow down a
complex, finely tuned data center wide workload to the point it no
longer meets requirements. Such changes in behaviour are considered
a regression, especially if they result from a change that just
ignores the mount option that turned off that specific feature.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2020-06-19 22:11 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 20:21 [PATCH] fs: i_version mntopt gets visible through /proc/mounts Masayoshi Mizuma
2020-06-17 8:03 ` Christoph Hellwig
2020-06-17 13:33 ` Masayoshi Mizuma
2020-06-17 15:58 ` J. Bruce Fields
2020-06-17 17:14 ` Eric Sandeen
2020-06-17 17:24 ` Darrick J. Wong
2020-06-17 17:55 ` Eric Sandeen
2020-06-17 18:18 ` J. Bruce Fields
2020-06-17 18:28 ` Eric Sandeen
2020-06-17 18:45 ` J. Bruce Fields
2020-06-18 1:30 ` Masayoshi Mizuma
2020-06-18 1:44 ` Darrick J. Wong
2020-06-18 3:33 ` Masayoshi Mizuma
2020-06-18 3:05 ` Dave Chinner
2020-06-18 3:45 ` Masayoshi Mizuma
2020-06-18 22:39 ` Dave Chinner
2020-06-19 2:20 ` J. Bruce Fields
2020-06-19 2:44 ` Dave Chinner
2020-06-19 12:04 ` Jeff Layton
2020-06-19 20:40 ` J. Bruce Fields
2020-06-19 22:10 ` Dave Chinner [this message]
2020-06-19 22:28 ` J. Bruce Fields
2020-06-20 1:49 ` Dave Chinner
2020-06-20 1:56 ` J. Bruce Fields
2020-06-20 17:00 ` Eric Sandeen
2020-06-20 17:09 ` J. Bruce Fields
2020-06-20 23:54 ` Dave Chinner
2020-06-22 21:26 ` J. Bruce Fields
2020-06-22 22:03 ` Dave Chinner
2020-06-19 13:17 ` Christoph Hellwig
2020-07-13 23:45 ` Eric Sandeen
2020-07-14 8:30 ` Christoph Hellwig
2020-07-14 20:26 ` Eric Sandeen
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