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Date:   Tue, 19 Nov 2019 05:29:31 -0500
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     linux-kernel@vger.kernel.org
Cc:     Wei Wang <wei.w.wang@intel.com>,
        Khazhismel Kumykov <khazhy@google.com>,
        Jason Wang <jasowang@redhat.com>,
        virtualization@lists.linux-foundation.org
Subject: [PATCH 2/2] virtio_balloon: divide/multiply instead of shifts
Message-ID: <20191119102838.39380-2-mst@redhat.com>
References: <20191119102838.39380-1-mst@redhat.com>
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We managed to get confused about the shift direction at least once.
Let's switch to division/multiplcation instead. Add a number of pages
macro for this purpose.  We still keep the order macro around too since
this is what alloc/free pages want.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/virtio/virtio_balloon.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloo=
n.c
index b6a95cd28d9f..dc1ebd638e9b 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -36,6 +36,7 @@
 /* The size of a free page block in bytes */
 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
 =09(1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
+#define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_OR=
DER)
=20
 #ifdef CONFIG_BALLOON_COMPACTION
 static struct vfsmount *balloon_mnt;
@@ -765,11 +766,11 @@ static unsigned long shrink_free_pages(struct virtio_=
balloon *vb,
 =09unsigned long blocks_to_free, blocks_freed;
=20
 =09pages_to_free =3D round_up(pages_to_free,
-=09=09=09=09 1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER);
-=09blocks_to_free =3D pages_to_free >> VIRTIO_BALLOON_HINT_BLOCK_ORDER;
+=09=09=09=09 VIRTIO_BALLOON_HINT_BLOCK_PAGES);
+=09blocks_to_free =3D pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 =09blocks_freed =3D return_free_pages_to_mm(vb, blocks_to_free);
=20
-=09return blocks_freed << VIRTIO_BALLOON_HINT_BLOCK_ORDER;
+=09return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 }
=20
 static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
@@ -825,7 +826,7 @@ static unsigned long virtio_balloon_shrinker_count(stru=
ct shrinker *shrinker,
 =09unsigned long count;
=20
 =09count =3D vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
-=09count +=3D vb->num_free_page_blocks << VIRTIO_BALLOON_HINT_BLOCK_ORDER;
+=09count +=3D vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
=20
 =09return count;
 }
--=20
MST