Re: [PATCH v3 9/9] xen/gntdev: Implement dma-buf import functionality

[Oleksandr Andrushchenko]

On 06/14/2018 01:03 AM, Boris Ostrovsky wrote:
> On 06/13/2018 05:04 AM, Oleksandr Andrushchenko wrote:
> > On 06/13/2018 06:14 AM, Boris Ostrovsky wrote:
> > > On 06/12/2018 09:42 AM, Oleksandr Andrushchenko wrote:
> > >
> > > >  Â int gntdev_dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32
> > > > fd)
> > > >  Â {
> > > > -ÂÂÂ return -EINVAL;
> > > > +ÂÂÂ struct gntdev_dmabuf *gntdev_dmabuf;
> > > > +ÂÂÂ struct dma_buf_attachment *attach;
> > > > +ÂÂÂ struct dma_buf *dma_buf;
> > > > +
> > > > +ÂÂÂ gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd);
> > > > +ÂÂÂ if (IS_ERR(gntdev_dmabuf))
> > > > +ÂÂÂÂÂÂÂ return PTR_ERR(gntdev_dmabuf);
> > > > +
> > > > +ÂÂÂ pr_debug("Releasing DMA buffer with fd %d\n", fd);
> > > > +
> > > > +ÂÂÂ attach = gntdev_dmabuf->u.imp.attach;
> > > > +
> > > > +ÂÂÂ if (gntdev_dmabuf->u.imp.sgt)
> > > > +ÂÂÂÂÂÂÂ dma_buf_unmap_attachment(attach, gntdev_dmabuf->u.imp.sgt,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ DMA_BIDIRECTIONAL);
> > > > +ÂÂÂ dma_buf = attach->dmabuf;
> > > > +ÂÂÂ dma_buf_detach(attach->dmabuf, attach);
> > > > +ÂÂÂ dma_buf_put(dma_buf);
> > > > +
> > > > +ÂÂÂ dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ gntdev_dmabuf->nr_pages);
> > >
> > >
> > > Should you first end foreign access, before doing anything?
> > I am rolling back in reverse order here, so I think we first need
> > to finish local activities with the buffer and then end foreign
> > access.
> Looking at gntdev_dmabuf_imp_to_refs(), the order is
>  ÂÂÂ dmabuf_imp_alloc_storage()
>  ÂÂÂ dma_buf_attach()
>  ÂÂÂ dma_buf_map_attachment()
>  ÂÂÂ dmabuf_imp_grant_foreign_access()
>
> Or was I looking at wrong place?
Agree, will move as you suggest
> -boris