linux-kernel - Re: [Xen-devel] [PATCH] xen-blkback: fix memory leak when persistent grants are used

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Date:	Sat, 25 Jan 2014 13:07:00 -0800
From:	Matt Wilson <msw@...ux.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	Matt Wilson <msw@...zon.com>, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xen.org, Matt Rushton <mrushton@...zon.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Anthony Liguori <aliguori@...zon.com>,
	Roger Pau Monné <roger.pau@...rix.com>
Subject: Re: [Xen-devel] [PATCH] xen-blkback: fix memory leak when persistent
 grants are used

On Fri, Jan 24, 2014 at 03:36:22PM +0000, Ian Campbell wrote:
> On Fri, 2014-01-24 at 09:21 +0000, Ian Campbell wrote:
> > On Thu, 2014-01-23 at 11:28 -0800, Matt Wilson wrote:
> > > From: Matt Rushton <mrushton@...zon.com>
> > > 
> > > Currently shrink_free_pagepool() is called before the pages used for
> > > persistent grants are released via free_persistent_gnts(). This
> > > results in a memory leak when a VBD that uses persistent grants is
> > > torn down.
> > 
> > This may well be the explanation for the memory leak I was observing on
> > ARM last night. I'll give it a go and let you know.
> 
> Results are a bit inconclusive unfortunately, it seems like I am seeing
> some other leak too (or instead).
> 
> Totally unscientifically it does seem to be leaking more slowly than
> before, so perhaps this patch has helped, but nothing conclusive I'm
> afraid.

Testing here looks good. I don't know if perhaps something else is
going on with ARM...

> I don't think that quite qualifies for a Tested-by though, sorry.

How about an Acked-by? ;-)

--msw

> Ian. 
> 
> > 
> > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > > Cc: "Roger Pau Monné" <roger.pau@...rix.com>
> > > Cc: Ian Campbell <Ian.Campbell@...rix.com>
> > > Cc: David Vrabel <david.vrabel@...rix.com>
> > > Cc: linux-kernel@...r.kernel.org
> > > Cc: xen-devel@...ts.xen.org
> > > Cc: Anthony Liguori <aliguori@...zon.com>
> > > Signed-off-by: Matt Rushton <mrushton@...zon.com>
> > > Signed-off-by: Matt Wilson <msw@...zon.com>
> > > ---
> > >  drivers/block/xen-blkback/blkback.c |    6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> > > index 6620b73..30ef7b3 100644
> > > --- a/drivers/block/xen-blkback/blkback.c
> > > +++ b/drivers/block/xen-blkback/blkback.c
> > > @@ -625,9 +625,6 @@ purge_gnt_list:
> > >  			print_stats(blkif);
> > >  	}
> > >  
> > > -	/* Since we are shutting down remove all pages from the buffer */
> > > -	shrink_free_pagepool(blkif, 0 /* All */);
> > > -
> > >  	/* Free all persistent grant pages */
> > >  	if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
> > >  		free_persistent_gnts(blkif, &blkif->persistent_gnts,
> > > @@ -636,6 +633,9 @@ purge_gnt_list:
> > >  	BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
> > >  	blkif->persistent_gnt_c = 0;
> > >  
> > > +	/* Since we are shutting down remove all pages from the buffer */
> > > +	shrink_free_pagepool(blkif, 0 /* All */);
> > > +
> > >  	if (log_stats)
> > >  		print_stats(blkif);
> > >  
> > 
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@...ts.xen.org
> > http://lists.xen.org/xen-devel
> 
> 
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