[Intel-gfx] [PATCH 4/4] dma-buf: lock the reservation object during (un)map_dma_buf v3

Christian König ckoenig.leichtzumerken at gmail.com
Wed Jul 18 10:47:41 UTC 2018


First step towards unpinned DMA buf operation.

I've checked the DRM drivers to potential locking of the reservation
object, but essentially we need to audit all implementations of the
dma_buf _ops for this to work.

v2: reordered
v3: rebased on sgt caching

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/dma-buf/dma-buf.c | 15 ++++++---------
 include/linux/dma-buf.h   |  6 ++++++
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index e68322c953a9..21608306349d 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -686,10 +686,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 	if (WARN_ON(!attach || !attach->dmabuf))
 		return ERR_PTR(-EINVAL);
 
-	if (attach->sgt)
-		return attach->sgt;
-
-	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	reservation_object_lock(attach->dmabuf->resv, NULL);
+	sg_table = dma_buf_map_attachment_locked(attach, direction);
+	reservation_object_unlock(attach->dmabuf->resv);
 	if (!sg_table)
 		sg_table = ERR_PTR(-ENOMEM);
 
@@ -742,11 +741,9 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
 	if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
 		return;
 
-	if (attach->sgt == sg_table)
-		return;
-
-	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
-						direction);
+	reservation_object_lock(attach->dmabuf->resv, NULL);
+	dma_buf_unmap_attachment_locked(attach, sg_table, direction);
+	reservation_object_unlock(attach->dmabuf->resv);
 }
 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
 
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index a40f8f586a95..e964077a7e7e 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -128,6 +128,9 @@ struct dma_buf_ops {
 	 * any other kind of sharing that the exporter might wish to make
 	 * available to buffer-users.
 	 *
+	 * This is always called with the dmabuf->resv object locked when
+	 * no_sgt_cache is true.
+	 *
 	 * Returns:
 	 *
 	 * A &sg_table scatter list of or the backing storage of the DMA buffer,
@@ -148,6 +151,9 @@ struct dma_buf_ops {
 	 * It should also unpin the backing storage if this is the last mapping
 	 * of the DMA buffer, it the exporter supports backing storage
 	 * migration.
+	 *
+	 * This is always called with the dmabuf->resv object locked when
+	 * no_sgt_cache is true.
 	 */
 	void (*unmap_dma_buf)(struct dma_buf_attachment *,
 			      struct sg_table *,
-- 
2.14.1



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