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Re: Cleancache support in XFS

To: James Dingwall <james.dingwall@xxxxxxxxxxx>
Subject: Re: Cleancache support in XFS
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Mon, 22 Jul 2013 11:48:12 -0400
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, Ben Myers <bpm@xxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <51E8E834.6080509@xxxxxxxxxxx>
References: <51810CED.4080003@xxxxxxxxxxx> <20130501162044.GN29359@xxxxxxx> <20130501223022.GQ10481@dastard> <518222D3.3080109@xxxxxxxxxxx> <20130522192834.GD10617@xxxxxxxxxxxxxxxxxxx> <519F1708.10603@xxxxxxxxxxx> <20130607170826.GA6925@xxxxxxxxxxxxxxxxxxx> <51E8E834.6080509@xxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri, Jul 19, 2013 at 08:18:12AM +0100, James Dingwall wrote:
> Konrad Rzeszutek Wilk wrote:
> >On Fri, May 24, 2013 at 08:30:16AM +0100, James Dingwall wrote:
> >>Konrad Rzeszutek Wilk wrote:
> >>>On Thu, May 02, 2013 at 09:24:51AM +0100, James Dingwall wrote:
> >>>>Dave Chinner wrote:
> >>>>>On Wed, May 01, 2013 at 11:20:44AM -0500, Ben Myers wrote:
> >>>>>>Hi James,
> >>>Hey folks,
> >>>I am walking through my vacation-emails-mbox.
> >>>
> >>>>>>On Wed, May 01, 2013 at 01:39:09PM +0100, James Dingwall wrote:
> >>>>>>>In reference to: http://oss.sgi.com/archives/xfs/2012-05/msg00046.html
> >>>>>>>
> >>>>>>>$ grep -r cleancache fs/xfs
> >>>>>>>on the 3.9 kernel source suggests that no patch was submitted to
> >>>>>>>enable cleancache for the XFS filesystem.  Since it was suggested
> >>>>>>>that this could be a one liner I've had a go and my first effort is
> >>>>>>>inline below.  While this seems to compile OK I have no experience
> >>>>>>>in filesystems so I would appreciate it if anyone can point out that
> >>>>>>>it is obviously wrong and likely to eat my data before I try booting
> >>>>>>>the kernel.
> >>>>>>>
> >>>>>>>If it seems a reasonable attempt what would be the best way to check
> >>>>>>>that it isn't doing nasty things?
> >>>>>>Hrm.. Looks like there is a doc in Documentation/vm/cleancache.txt which
> >>>>>>includes a list of attributes the filesystem needs to have to work 
> >>>>>>properly
> >>>>>>with cleancache.
> >>>>>So, those points are:
> >>>>I had started to look at these too but I feel very out of my depth!
> >>>>I had similar conclusions to what Dave wrote but I don't think my
> >>>>thoughts should carry very much (any) weight.  Anyway I gambled and
> >>>>booted my xen domU with this patch and so far so good...  xen top
> >>>>shows that tmem is now being used where previously it wasn't.  I'll
> >>>>try running the xfstests at the weekend after a couple more days up
> >>>>time to see what happens.
> >>>And how did it go?
> >>I am running the patch I created on 3.9.3 on half of my xen guests
> >>now and have not noticed any stability or filesystem problems.  xl
> >>top with 'T' shows that the guests running with it are using
> >>ephemeral pages were those without do not.  I did do some runs with
> >>xfstests which had some failures but they were present with and
> >>without the patch.  The best I can really offer is that it works for
> >>me, ymmv.  The patch is available as commit
> >>c725011c4fc5d47e12d131f61bd91a58a40036b5 in
> >>https://github.com/JKDingwall/linux.git xfs-enable-cleancache or in
> >>the first message of this thread.
> >Hey James,
> >
> >I've run this patch on my local tree and it looks to work right. I am
> >saying "looks" as I am hitting some other issue that I believe are
> >unralted to the patch - but I need to figure them out before I can
> >comfortably say: "Yes, this looks right and works for me as well."
> >
> >Stay tuned.
> Just to add that I have also had no observable problems running this
> patch on 3.10.0 or 3.10.1.

Yup. And I tested it as well. In other words if you would like to add
Acked-by from me that would be super. Thanks!
> 
> Regards,
> James

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