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@xxxxxxxxxx/ > > https://lore.kernel.org/linux-nfs/20180109141059.25929-1-jlayton@xxxxxxxxxx/ > > https://lore.kernel.org/linux-nfs/1517228795.5965.24.camel@xxxxxxxxxx/ > > > > 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@xxxxxxxxxx>
