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Date:   Mon, 18 Nov 2019 17:52:56 -0500
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Khazhismel Kumykov <khazhy@google.com>
Cc:     jasowang@redhat.com, wei.w.wang@intel.com,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 1/2] virtio_balloon: fix pages_to_free calculation
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On Mon, Nov 18, 2019 at 01:38:10PM -0800, Khazhismel Kumykov wrote:
> freed_pages was accumulating total freed pages, but was also subtracted
> on each iteration from pages_to_free, which could potentially result in
> attempting to free fewer pages than asked for. This change also makes
> both freed_pages and pages_to_free in terms of "balloon pages", where
> they were mismatched before.

And then patch 2/2 changes it back to both be regular pages.
Which is good, but why do we have to go back and forth
breaking then fixing it back?


>=20
> Fixes: 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"=
)
> Cc: Wei Wang <wei.w.wang@intel.com>
> Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
> ---
>  drivers/virtio/virtio_balloon.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>=20
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_ball=
oon.c
> index 226fbb995fb0..7cf9540a40b8 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -782,11 +782,8 @@ static unsigned long shrink_balloon_pages(struct vir=
tio_balloon *vb,
>  =09 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
>  =09 * multiple times to deflate pages till reaching pages_to_free.
>  =09 */
> -=09while (vb->num_pages && pages_to_free) {
> -=09=09pages_freed +=3D leak_balloon(vb, pages_to_free) /
> -=09=09=09=09=09VIRTIO_BALLOON_PAGES_PER_PAGE;
> -=09=09pages_to_free -=3D pages_freed;
> -=09}
> +=09while (vb->num_pages && pages_to_free > pages_freed)
> +=09=09pages_freed +=3D leak_balloon(vb, pages_to_free - pages_freed);
>  =09update_balloon_size(vb);
> =20
>  =09return pages_freed;
> --=20
> 2.24.0.432.g9d3f5f5b63-goog