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Re: [PATCH 3/3] Add timeout feature

To: Pavel Machek <pavel@xxxxxxx>
Subject: Re: [PATCH 3/3] Add timeout feature
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 9 Jul 2008 09:10:27 +1000
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Takashi Sato <t-sato@xxxxxxxxxxxxx>, akpm@xxxxxxxxxxxxxxxxxxxx, viro@xxxxxxxxxxxxxxxxxx, "linux-ext4@xxxxxxxxxxxxxxx" <linux-ext4@xxxxxxxxxxxxxxx>, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, "dm-devel@xxxxxxxxxx" <dm-devel@xxxxxxxxxx>, "linux-fsdevel@xxxxxxxxxxxxxxx" <linux-fsdevel@xxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, axboe@xxxxxxxxx, mtk.manpages@xxxxxxxxxxxxxx
In-reply-to: <20080707110730.GG5643@xxxxxx>
Mail-followup-to: Pavel Machek <pavel@xxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Takashi Sato <t-sato@xxxxxxxxxxxxx>, akpm@xxxxxxxxxxxxxxxxxxxx, viro@xxxxxxxxxxxxxxxxxx, "linux-ext4@xxxxxxxxxxxxxxx" <linux-ext4@xxxxxxxxxxxxxxx>, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, "dm-devel@xxxxxxxxxx" <dm-devel@xxxxxxxxxx>, "linux-fsdevel@xxxxxxxxxxxxxxx" <linux-fsdevel@xxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, axboe@xxxxxxxxx, mtk.manpages@xxxxxxxxxxxxxx
References: <20080630212450t-sato@xxxxxxxxxxxxxxx> <20080701081026.GB16691@xxxxxxxxxxxxx> <20080707110730.GG5643@xxxxxx>
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User-agent: Mutt/1.5.17+20080114 (2008-01-14)
On Mon, Jul 07, 2008 at 01:07:31PM +0200, Pavel Machek wrote:
> Hi!
> 
> > I still disagree with this whole patch.  There is not reason to let
> > the freeze request timeout - an auto-unfreezing will only confuse the
> > hell out of the caller.  The only reason where the current XFS freeze
> > call can hang and this would be theoretically useful is when the
> 
> What happens when someone dirties so much data that vm swaps out
> whatever process that frozen the filesystem?

a) you can't dirty a frozen filesystem - by definition a frozen
   filesystem is a *clean filesystem* and *cannot be dirtied*.
b) Swap doesn't write through the filesystem
c) you can still read from a frozen filesystem to page your
   executableѕ in.
d) if dirtying another unfrozen filesystem swaps out your
   application so it can't run, then there's a major VM bug.
   Regardless, until the app completes it is relying on the
   filesystem being frozen, so it better remain frozen....

> I though that was why the timeout was there...

Not that I know of. 

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx


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