[PATCH 1/2] virtio_balloon: fix pages_to_free calculation

From: Khazhismel Kumykov <khazhy@google.com>
To: mst@redhat.com, jasowang@redhat.com, wei.w.wang@intel.com
Cc: linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Khazhismel Kumykov <khazhy@google.com>
Subject: [PATCH 1/2] virtio_balloon: fix pages_to_free calculation
Date: Mon, 18 Nov 2019 13:38:10 -0800	[thread overview]
Message-ID: <20191118213811.22017-1-khazhy@google.com> (raw)
In-Reply-To: <CACGdZYJoHSN3vkj_QBz6Txmec9mJMmkH66j2XtqzpUWpfpw4Tg@mail.gmail.com>

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.

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(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.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 virtio_balloon *vb,
 	 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
 	 * multiple times to deflate pages till reaching pages_to_free.
 	 */
-	while (vb->num_pages && pages_to_free) {
-		pages_freed += leak_balloon(vb, pages_to_free) /
-					VIRTIO_BALLOON_PAGES_PER_PAGE;
-		pages_to_free -= pages_freed;
-	}
+	while (vb->num_pages && pages_to_free > pages_freed)
+		pages_freed += leak_balloon(vb, pages_to_free - pages_freed);
 	update_balloon_size(vb);
 
 	return pages_freed;
-- 
2.24.0.432.g9d3f5f5b63-goog

