[PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs()

From: Leandro Dorileo
Date: Sat Jan 25 2014 - 15:24:01 EST


Cchange init_vqs() to avoid calling twice the virtio_has_feature()
- attempting to find out if VIRTIO_BALLOON_F_STATS_VQ feature was negotiated -
consequently we prevent unnecessarily running the drivers' feature_table more
than needed.

Signed-off-by: Leandro Dorileo <l@xxxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 34bdaba..41771c1 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -320,19 +320,21 @@ static int init_vqs(struct virtio_balloon *vb)
vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
const char *names[] = { "inflate", "deflate", "stats" };
int err, nvqs;
+ bool stats;

/*
* We expect two virtqueues: inflate and deflate, and
* optionally stat.
*/
- nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
+ stats = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ);
+ nvqs = stats ? 3 : 2;
err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
if (err)
return err;

vb->inflate_vq = vqs[0];
vb->deflate_vq = vqs[1];
- if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
+ if (stats) {
struct scatterlist sg;
vb->stats_vq = vqs[2];

--
1.8.5.3

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