[Devel] [PATCH vz7.39] scsi: virtio: Reduce BUG if total_sg > virtqueue size to WARN.

[Roman Kagan]

From: "Richard W.M. Jones" <rjones at redhat.com>

If using indirect descriptors, you can make the total_sg as large as you
want.  If not, BUG is too serious because the function later returns
-ENOSPC.

Signed-off-by: Richard W.M. Jones <rjones at redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
(cherry picked from commit 44ed8089e991a60d614abe0ee4b9057a28b364e4)
Signed-off-by: Roman Kagan <rkagan at virtuozzo.com>
VZ-Bug: PSBM-79523
---
 drivers/virtio/virtio_ring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d77a91f39d55..5903139aede2 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -275,7 +275,6 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	}
 #endif
 
-	BUG_ON(total_sg > vq->vring.num);
 	BUG_ON(total_sg == 0);
 
 	head = vq->free_head;
@@ -284,8 +283,10 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	 * buffers, then go indirect. FIXME: tune this threshold */
 	if (vq->indirect && total_sg > 1 && vq->vq.num_free)
 		desc = alloc_indirect(_vq, total_sg, gfp);
-	else
+	else {
 		desc = NULL;
+		WARN_ON_ONCE(total_sg > vq->vring.num && !vq->indirect);
+	}
 
 	if (desc) {
 		/* Use a single buffer which doesn't continue */
-- 
2.14.3