On Wed, Oct 20, 2021 at 10:19:46AM +0800, Xuan Zhuo wrote:
> On Tue, 19 Oct 2021 09:21:51 -0400, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> > On Tue, Oct 19, 2021 at 07:52:35PM +0800, Xuan Zhuo wrote:
> > > When using indirect with packed, we don't check for allocation failures.
> > > This patch checks that and fall back on direct.
> > >
> > > Fixes: 1ce9e6055fa ("virtio_ring: introduce packed ring support")
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > > ---
> > > drivers/virtio/virtio_ring.c | 13 ++++++++++---
> > > 1 file changed, 10 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > index 91a46c4da87d..44a03b6e4dc4 100644
> > > --- a/drivers/virtio/virtio_ring.c
> > > +++ b/drivers/virtio/virtio_ring.c
> > > @@ -1065,6 +1065,9 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> > >
> > > head = vq->packed.next_avail_idx;
> > > desc = alloc_indirect_packed(total_sg, gfp);
> > > + if (!desc)
> > > + /* fall back on direct */
> >
> > this comment belongs in virtqueue_add_packed right after
> > return.
> >
> > > + return -EAGAIN;
> > >
> >
> > -ENOMEM surely?
>
> virtqueue_add_indirect_packed() will return -ENOMEM when dma mmap fails, so we
> have to choose a different error code.
>
> Thanks.
That's exactly the point. Why would we want to recover from allocation
failure but not DMA map failure?
> >
> > > if (unlikely(vq->vq.num_free < 1)) {
> > > pr_debug("Can't add buf len 1 - avail = 0\n");
> > > @@ -1176,6 +1179,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> > > unsigned int i, n, c, descs_used, err_idx;
> > > __le16 head_flags, flags;
> > > u16 head, id, prev, curr, avail_used_flags;
> > > + int err;
> > >
> > > START_USE(vq);
> > >
> > > @@ -1191,9 +1195,12 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> > >
> > > BUG_ON(total_sg == 0);
> > >
> > > - if (virtqueue_use_indirect(_vq, total_sg))
> > > - return virtqueue_add_indirect_packed(vq, sgs, total_sg,
> > > - out_sgs, in_sgs, data, gfp);
> > > + if (virtqueue_use_indirect(_vq, total_sg)) {
> > > + err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
> > > + in_sgs, data, gfp);
> > > + if (err != -EAGAIN)
> > > + return err;
> > > + }
> > >
> > > head = vq->packed.next_avail_idx;
> > > avail_used_flags = vq->packed.avail_used_flags;
> > > --
> > > 2.31.0
> >
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