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virtio: return correct capacity to users

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We can't rely on indirect buffers for capacity
calculations because they need a memory allocation
which might fail.  In particular, virtio_net can get
into this situation under stress, and it drops packets
and performs badly.

So return the number of buffers we can guarantee users.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reported-By: Krishna Kumar2 <krkumar2@in.ibm.com>
This commit is contained in:
Michael S. Tsirkin 2010-11-04 14:24:24 +02:00 committed by Rusty Russell
parent dfd62d1d84
commit 7ae4b866f8
1 changed files with 0 additions and 3 deletions
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3
drivers/virtio/virtio_ring.c
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@ -230,9 +230,6 @@ int virtqueue_add_buf_gfp(struct virtqueue *_vq,
pr_debug("Added buffer head %i to %p\n", head, vq);
END_USE(vq);
/* If we're indirect, we can fit many (assuming not OOM). */
if (vq->indirect)
return vq->num_free ? vq->vring.num : 0;
return vq->num_free;
}
EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp);