linux-ext4 - Re: [RFC PATCH v1 00/30] fs: inode->i

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Message-ID: <20170321175129.GC17872@fieldses.org>
Date:   Tue, 21 Mar 2017 13:51:29 -0400
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-xfs@...r.kernel.org
Subject: Re: [RFC PATCH v1 00/30] fs: inode->i_version rework and optimization

On Tue, Mar 21, 2017 at 01:37:04PM -0400, J. Bruce Fields wrote:
> On Tue, Mar 21, 2017 at 01:23:24PM -0400, Jeff Layton wrote:
> > On Tue, 2017-03-21 at 12:30 -0400, J. Bruce Fields wrote:
> > > 	- NFS doesn't actually require that it increases, but I think it
> > > 	  should.  I assume 64 bits means we don't need a discussion of
> > > 	  wraparound.
> > 
> > I thought NFS spec required that you be able to recognize old change
> > attributes so that they can be discarded. I could be wrong here though.
> > I'd have to go back and look through the spec to be sure.
> 
> https://tools.ietf.org/html/rfc7862#section-10

So, I'm suggesting we implement this one:

	NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR:  The change attribute value
	  MUST monotonically increase for every atomic change to the file
	  attributes, data, or directory contents.

It may be a slight lie--after your patches we wouldn't actually increase
"for every atomic change".  I think that's OK.

--b.