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virtio_balloon: fix towards_target when deflating balloon

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Both v and vb->num_pages are u32 and unsigned int respectively.  If v is less
than vb->num_pages (and it is, when deflating the balloon), the result is a
very large 32-bit number.  Since we're returning a s64, instead of getting the
same negative number we desire, we get a very large positive number.

This handles the case where v < vb->num_pages and ensures we get a small,
negative, s64 as the result.

Rusty: please push this for 2.6.27-rc4.  It's probably appropriate for the
stable tree too as it will cause an unexpected OOM when ballooning.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (simplified)
This commit is contained in:
Anthony Liguori 2008-08-18 17:15:31 -05:00 committed by Rusty Russell
parent 83097aca85
commit 532a6086e3
1 changed files with 1 additions and 1 deletions
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2
drivers/virtio/virtio_balloon.c
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@ -158,7 +158,7 @@ static inline s64 towards_target(struct virtio_balloon *vb)
vb->vdev->config->get(vb->vdev, vb->vdev->config->get(vb->vdev,
offsetof(struct virtio_balloon_config, num_pages), offsetof(struct virtio_balloon_config, num_pages),
&v, sizeof(v)); &v, sizeof(v));
return v - vb->num_pages; return (s64)v - vb->num_pages;
} }
static void update_balloon_size(struct virtio_balloon *vb) static void update_balloon_size(struct virtio_balloon *vb)