2017-12-01 09:50:54

by Jan Stancek

[permalink] [raw]
Subject: [PATCH] virtio_balloon: fix increment of vb->num_pfns in fill_balloon()

commit c7cdff0e8647 ("virtio_balloon: fix deadlock on OOM")
changed code to increment vb->num_pfns before call to
set_page_pfns(), which used to happen only after.

This patch fixes boot hang for me on ppc64le KVM guests.

Fixes: c7cdff0e8647 ("virtio_balloon: fix deadlock on OOM")
Cc: Michael S. Tsirkin <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Wei Wang <[email protected]>
Signed-off-by: Jan Stancek <[email protected]>
---
drivers/virtio/virtio_balloon.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 7960746f7597..a1fb52cb3f0a 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -174,13 +174,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
while ((page = balloon_page_pop(&pages))) {
balloon_page_enqueue(&vb->vb_dev_info, page);

- vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
-
set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
if (!virtio_has_feature(vb->vdev,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
adjust_managed_page_count(page, -1);
+ vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
}

num_allocated_pages = vb->num_pfns;
--
1.8.3.1