drm/amdgpu/dma_buf: fix page_link check

commit c0dd8a9253fadfb8e5357217d085f1989da4ef0a upstream.

The page_link lower bits of the first sg could contain something like
SG_END, if we are mapping a single VRAM page or contiguous blob which
fits into one sg entry. Rather pull out the struct page, and use that in
our check to know if we mapped struct pages vs VRAM.

Fixes: f44ffd6 ("drm/amdgpu: add support for exporting VRAM using DMA-buf v3")
Signed-off-by: Matthew Auld <[email protected]>
Cc: Christian König <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v5.8+
Reviewed-by: Christian König <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
(cherry picked from commit 91b646a0b2cbd1d6d1b0be49ae780b6d2ea6011c)
Signed-off-by: Jack Vogel <[email protected]>

Author: matt-auld

drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c

@@ -181,7 +181,7 @@ static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach,
 				 struct sg_table *sgt,
 				 enum dma_data_direction dir)
 {
-	if (sgt->sgl->page_link) {
+	if (sg_page(sgt->sgl)) {
 		dma_unmap_sgtable(attach->dev, sgt, dir, 0);
 		sg_free_table(sgt);
 		kfree(sgt);