[PATCH 1/4 Trusty SRU] virtio_balloon: return the amount of freed memory from leak_balloon()

[Christopher Arges]

Does it make sense to also backport:
f68b992bbb474641881932c61c92dcfa6f5b3689

Since that patch will make this a clean cherry-pick and it fixes a ballooning
bug.  It also looks like it was queued for stable.

--chris

On Thu, Jun 23, 2016 at 07:38:37AM -0600, Tim Gardner wrote:
> From: Raushaniya Maksudova <rmaksudova at parallels.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1587089
> 
> This value would be useful in the next patch to provide the amount of
> the freed memory for OOM killer.
> 
> Signed-off-by: Raushaniya Maksudova <rmaksudova at parallels.com>
> Signed-off-by: Denis V. Lunev <den at openvz.org>
> CC: Rusty Russell <rusty at rustcorp.com.au>
> CC: Michael S. Tsirkin <mst at redhat.com>
> Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
> (back ported from commit 1fd9c67203af91977bf3b964ff3744cf74fc6f3f)
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> 
> Conflicts:
> 	drivers/virtio/virtio_balloon.c
> ---
>  drivers/virtio/virtio_balloon.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index a4531fc..54a9c033 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -169,8 +169,9 @@ static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
>  	}
>  }
>  
> -static void leak_balloon(struct virtio_balloon *vb, size_t num)
> +static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
>  {
> +	unsigned num_freed_pages;
>  	struct page *page;
>  	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
>  
> @@ -187,6 +188,7 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
>  		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
>  	}
>  
> +	num_freed_pages = vb->num_pfns;
>  	/*
>  	 * Note that if
>  	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
> @@ -196,6 +198,7 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
>  		tell_host(vb, vb->deflate_vq);
>  	release_pages_by_pfn(vb->pfns, vb->num_pfns);
>  	mutex_unlock(&vb->balloon_lock);
> +	return num_freed_pages;
>  }
>  
>  static inline void update_stat(struct virtio_balloon *vb, int idx,
> -- 
> 1.9.1
> 
> 
> -- 
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