[RFC PATCH 4/4] virtio_balloon: skip inflation if guest is under pressure

From: Luiz Capitulino
Date: Thu Jan 16 2014 - 11:25:48 EST

From: Luiz capitulino <lcapitulino@xxxxxxxxxx>

This is necessary for automatic ballooning. If the guest gets
under pressure while there's an on-going inflation operation,
we want the guest to do the following:

1. Stop on-going inflation
2. Notify the host we're under pressure
3. Wait for host's acknowledge

While the guest is waiting the host has the opportunity to
reset num_pages to a value before the guest got into pressure.
This will cancel current inflation.

Signed-off-by: Luiz capitulino <lcapitulino@xxxxxxxxxx>
drivers/virtio/virtio_balloon.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1c3ee71..7f5b7d2 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -188,8 +188,13 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
for (vb->num_pfns = 0; vb->num_pfns < num;
- struct page *page = balloon_page_enqueue(vb_dev_info);
+ struct page *page;

+ if (guest_under_pressure(vb)) {
+ break;
+ }
+ page = balloon_page_enqueue(vb_dev_info);
if (!page) {
"Out of puff! Can't get %u pages\n",

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/