From: Jeff Layton <jlayton@redhat.com>
To: Dave Chinner <david@fromorbit.com>,
"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>
Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts
Date: Fri, 19 Jun 2020 08:04:53 -0400 [thread overview]
Message-ID: <a25ec32fd836fafeb2d4dd2f41e9255d02182a84.camel@redhat.com> (raw)
In-Reply-To: <20200619024455.GN2005@dread.disaster.area>
On Fri, 2020-06-19 at 12:44 +1000, Dave Chinner wrote:
> On Thu, Jun 18, 2020 at 10:20:05PM -0400, J. Bruce Fields wrote:
> > On Fri, Jun 19, 2020 at 08:39:48AM +1000, Dave Chinner wrote:
> > > On Wed, Jun 17, 2020 at 11:45:35PM -0400, Masayoshi Mizuma wrote:
> > > > Thank you for pointed it out.
> > > > How about following change? I believe it works both xfs and btrfs...
> > > >
> > > > diff --git a/fs/super.c b/fs/super.c
> > > > index b0a511bef4a0..42fc6334d384 100644
> > > > --- a/fs/super.c
> > > > +++ b/fs/super.c
> > > > @@ -973,6 +973,9 @@ int reconfigure_super(struct fs_context *fc)
> > > > }
> > > > }
> > > >
> > > > + if (sb->s_flags & SB_I_VERSION)
> > > > + fc->sb_flags |= MS_I_VERSION;
> > > > +
> > > > WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
> > > > (fc->sb_flags & fc->sb_flags_mask)));
> > > > /* Needs to be ordered wrt mnt_is_readonly() */
> > >
> > > This will prevent SB_I_VERSION from being turned off at all. That
> > > will break existing filesystems that allow SB_I_VERSION to be turned
> > > off on remount, such as ext4.
> > >
> > > The manipulations here need to be in the filesystem specific code;
> > > we screwed this one up so badly there is no "one size fits all"
> > > behaviour that we can implement in the generic code...
> >
> > 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.
>
> > But looking back through Jeff's postings, I don't see him claiming that;
> > e.g. in:
> >
> > https://lore.kernel.org/lkml/20171222120556.7435-1-jlayton@kernel.org/
> > https://lore.kernel.org/linux-nfs/20180109141059.25929-1-jlayton@kernel.org/
> > https://lore.kernel.org/linux-nfs/1517228795.5965.24.camel@redhat.com/
> >
> > he reports comparing old iversion behavior to new iversion behavior, but
> > not new iversion behavior to new noiversion behavior.
>
> Yeah, it's had to compare noiversion behaviour on filesystems where
> it was understood that it couldn't actually be turned off. And,
> realistically, the comaprison to noiversion wasn't really relevant
> to the problem Jeff's patchset was addressing...
>
I actually did do some comparison with that patchset vs. noiversion
mounted ext4, and found that there was a small performance delta. It
wasn't much but it was measurable enough that I didn't want to propose
removing the option from ext4 altogether at the time. It may be worth it
to do that now though.
--
Jeff Layton <jlayton@redhat.com>
next prev parent reply other threads:[~2020-06-19 12:05 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 [this message]
2020-06-19 20:40 ` J. Bruce Fields
2020-06-19 22:10 ` Dave Chinner
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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