Re: [PATCH] xen-blkback: fix memory leak when persistent grants areused

From: Ian Campbell
Date: Fri Jan 24 2014 - 04:21:45 EST


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.

> 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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