On Mon, 12 Nov 2012 21:50:40 +0800 Wei Yongjun <weiyj.lk@xxxxxxxxx> wrote: > From: Wei Yongjun <yongjun_wei@xxxxxxxxxxxxxxxxx> > > Add the missing unlock before return from function fill_balloon() > in the error handling case. > > Introduced by 9864a8(virtio_balloon: introduce migration primitives > to balloon pages) > > dpatch engine is used to auto generate this patch. > (https://github.com/weiyj/dpatch) > > Signed-off-by: Wei Yongjun <yongjun_wei@xxxxxxxxxxxxxxxxx> > --- > drivers/virtio/virtio_balloon.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index f70151b..72e8dcb 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -152,8 +152,10 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num) > } > > /* Didn't get any? Oh well. */ > - if (vb->num_pfns == 0) > + if (vb->num_pfns == 0) { > + mutex_unlock(&vb->balloon_lock); > return; > + } > > tell_host(vb, vb->inflate_vq); > mutex_unlock(&vb->balloon_lock); Well. Why did this bug occur in the first place? Because fill_balloon() has multiple return points and one of those was overlooked when adding new locking. This (and the addition of memory leaks) is quite common. It is part of the reason why so much kernel code uses goto's to avoid multiple return points. A maintainability thing. And we can fix this shortcoming in fill_balloon() without even needing a goto: --- a/drivers/virtio/virtio_balloon.c~virtio_balloon-introduce-migration-primitives-to-balloon-pages-fix-fix +++ a/drivers/virtio/virtio_balloon.c @@ -151,13 +151,9 @@ static void fill_balloon(struct virtio_b totalram_pages--; } - /* Didn't get any? Oh well. */ - if (vb->num_pfns == 0) { - mutex_unlock(&vb->balloon_lock); - return; - } - - tell_host(vb, vb->inflate_vq); + /* Did we get any? */ + if (vb->num_pfns != 0) + tell_host(vb, vb->inflate_vq); mutex_unlock(&vb->balloon_lock); } _ _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
