Re: [PATCH 2/2] nfsd: implement chage_attr_type attribute

[Dave Chinner <david@fromorbit.com>]

On Thu, Nov 13, 2014 at 08:02:43AM -0500, Trond Myklebust wrote:
> On Wed, Nov 12, 2014 at 7:28 PM, Dave Chinner <david@fromorbit.com> wrote:
> > On Wed, Nov 12, 2014 at 09:26:16AM -0500, Trond Myklebust wrote:
> >> On Wed, Nov 12, 2014 at 5:24 AM, Christoph Hellwig <hch@lst.de> wrote:
> >> > On Wed, Nov 12, 2014 at 09:27:10AM +1100, Dave Chinner wrote:
> >> >> To clarify what Christoph wrote, XFS updates i_version is updated
> >> >> once per transaction that modifies the inode. So if a VFS level
> >> >> operation results in multiple transactions then each transaction
> >> >> will but the version.
> >> >>
> >> >> It was implemented that way because nobody could tell me what the
> >> >> actual granularity requirement for change detection was.  Hence what
> >> >> I implemented was "be able to detect any persistent change that is
> >> >> made" to cover all bases.

FWIW, ext4 takes the same approach.  See Ted's post today:

http://www.spinics.net/lists/linux-ext4/msg46194.html

"The inode_inc_iversion() in mark4_ext4_iloc_dirty() is probably not
necessary, since we already should be incrementing i_version whenever
ctime and mtime gets updated.  The inode_inc_iversion() there is more
of a "belt and suspenders" safety thing, on the theory that the extra
bump in i_version won't hurt anything."

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com