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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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@xxxxxxxxxx>
> > 
> > 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.

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

Ian. 

> 
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: "Roger Pau MonnÃ" <roger.pau@xxxxxxxxxx>
> > Cc: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> > Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Cc: xen-devel@xxxxxxxxxxxxx
> > Cc: Anthony Liguori <aliguori@xxxxxxxxxx>
> > Signed-off-by: Matt Rushton <mrushton@xxxxxxxxxx>
> > Signed-off-by: Matt Wilson <msw@xxxxxxxxxx>
> > ---
> >  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);
> >  
> 
> 
> 
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