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Re: [PATCH-v2 0/5] add support for a lazytime mount option

To: Theodore Ts'o <tytso@xxxxxxx>
Subject: Re: [PATCH-v2 0/5] add support for a lazytime mount option
From: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Date: Mon, 24 Nov 2014 17:11:45 -0500
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20141124115727.GA19918@xxxxxxxxx>
References: <1416675267-2191-1-git-send-email-tytso@xxxxxxx> <20141124090755.GA28534@xxxxxxxxxxxxx> <20141124115727.GA19918@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Nov 24, 2014 at 06:57:27AM -0500, Theodore Ts'o wrote:
> If we want to be paranoid, we handle i_version updates non-lazily; I
> can see arguments in favor of that.
> 
> Ext4 only enables MS_I_VERSION if the user asks for it explicitly, so
> it wouldn't cause me any problems.  However, xfs and btrfs enables it
> by default, so that means xfs and btrfs wouldn't see the benefits of
> lazytime (if you're going to have to push I_VERSION to disk, you might
> as well update the [acm]time while you're at it).  I've always thought
> that we *should* do is to only enable it if nfsv4 is serving the file
> system, and not otherwise, though, which would also give us
> consistency across all the file systems.

I guess you need to worry about the case where you shutdown nfsd, modify
a file, then restart nfsd--you don't want a client to miss the
modification in that case.

--b.

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