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Re: Cleancache support in XFS

To: James Dingwall <james.dingwall@xxxxxxxxxxx>
Subject: Re: Cleancache support in XFS
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 23 Jul 2013 18:27:00 +1000
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Ben Myers <bpm@xxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <51EE2F54.80701@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> <20130722154812.GC30300@xxxxxxxxxxxxxxxxxxx> <51EE2F54.80701@xxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Jul 23, 2013 at 08:23:00AM +0100, James Dingwall wrote:
> Konrad Rzeszutek Wilk wrote:
> >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!
> My patch is now available in https://github.com/JKDingwall/linux.git
> xfs-enable-cleancache as commit id
> 6d50663e4ec88b7e1fd872b12ac310b1f4bb38c6.  I have rebased it on 3.10
> with KRW's Acked-by and my Signed-off-by in the commit message.  Is
> it reasonable for this to be considered for 3.12 or would further
> testing be required?

I think that's sufficient. Send it to the list ;)

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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