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

From: Oleksandr Andrushchenko
Date: Thu Jun 14 2018 - 02:39:50 EST

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:

 int gntdev_dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32
-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,
+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
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