linux-ext4 - Re: [PATCH] ext4: turn on i_version updates by default

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Message-ID: <20120514235432.GA3199@fieldses.org>
Date:	Mon, 14 May 2012 19:54:32 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	"Myklebust, Trond" <Trond.Myklebust@...app.com>,
	Theodore Ts'o <tytso@....edu>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] ext4: turn on i_version updates by default

On Mon, May 14, 2012 at 05:33:04PM -0600, Andreas Dilger wrote:
> I said as much in another reply - that once i_version is used on
> a filesystem, it should be made "sticky" (i.e. permanently enabled
> for that filesystem).  However, until that time it shouldn't be
> enabled just because it might one day be used.
> 
> Even better than just blindly bumping the i_version on every change,
> it would be better to have users of i_version (i.e. knfsd) flag the
> inode with "needs i_version update" then read the version.  When the
> filesystem/VFS bumps i_version the next time it can clear this flag
> and not update i_version again until after the next time i_version
> is actually used.

I really don't want to do anything more complicated than necessary.

What would be the worst-case test for the extra inode dirtying, so we
can see what the numbers actually are?

--b.
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