[PATCH 05/12] dma-buf: add dma_buf_(un)map_attachment_locked variants v4

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Add function variants which can be called with the reservation lock
already held.

v2: reordered, add lockdep asserts, fix kerneldoc
v3: rebased on sgt caching
v4: reorder once more

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-buf.c | 83 +++++++++++++++++++++++++++++++++------
 include/linux/dma-buf.h   |  5 +++
 2 files changed, 76 insertions(+), 12 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 0aa97bb05636..95bcd2ed795b 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -660,6 +660,48 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
 }
 EXPORT_SYMBOL_GPL(dma_buf_detach);
 
+/**
+ * dma_buf_map_attachment_locked - Maps the buffer into _device_ address space
+ * with the reservation lock held. Is a wrapper for map_dma_buf() of the
+ *
+ * Returns the scatterlist table of the attachment;
+ * dma_buf_ops.
+ * @attach:	[in]	attachment whose scatterlist is to be returned
+ * @direction:	[in]	direction of DMA transfer
+ *
+ * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
+ * on error. May return -EINTR if it is interrupted by a signal.
+ *
+ * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
+ * the underlying backing storage is pinned for as long as a mapping exists,
+ * therefore users/importers should not hold onto a mapping for undue amounts of
+ * time.
+ */
+struct sg_table *
+dma_buf_map_attachment_locked(struct dma_buf_attachment *attach,
+			      enum dma_data_direction direction)
+{
+	struct sg_table *sg_table;
+	int r;
+
+	might_sleep();
+	reservation_object_assert_held(attach->dmabuf->resv);
+
+	if (attach->sgt)
+		return attach->sgt;
+
+	r = dma_buf_pin(attach->dmabuf);
+	if (r)
+		return ERR_PTR(r);
+
+	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	if (!sg_table)
+		return ERR_PTR(-ENOMEM);
+
+	return sg_table;
+}
+EXPORT_SYMBOL_GPL(dma_buf_map_attachment_locked);
+
 /**
  * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
  * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
@@ -679,7 +721,6 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 					enum dma_data_direction direction)
 {
 	struct sg_table *sg_table;
-	int r;
 
 	might_sleep();
 
@@ -690,21 +731,40 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 		return attach->sgt;
 
 	reservation_object_lock(attach->dmabuf->resv, NULL);
-	r = dma_buf_pin(attach->dmabuf);
-	if (r) {
-		reservation_object_unlock(attach->dmabuf->resv);
-		return ERR_PTR(r);
-	}
-
-	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
-	if (!sg_table)
-		sg_table = ERR_PTR(-ENOMEM);
+	sg_table = dma_buf_map_attachment(attach, direction);
 	reservation_object_unlock(attach->dmabuf->resv);
 
 	return sg_table;
 }
 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
 
+/**
+ * dma_buf_unmap_attachment_locked - unmaps the buffer with reservation lock
+ * held, should deallocate the associated scatterlist. Is a wrapper for
+ * unmap_dma_buf() of dma_buf_ops.
+ * @attach:	[in]	attachment to unmap buffer from
+ * @sg_table:	[in]	scatterlist info of the buffer to unmap
+ * @direction:  [in]    direction of DMA transfer
+ *
+ * This unmaps a DMA mapping for @attached obtained by
+ * dma_buf_map_attachment_locked().
+ */
+void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *attach,
+				     struct sg_table *sg_table,
+				     enum dma_data_direction direction)
+{
+	might_sleep();
+	reservation_object_assert_held(attach->dmabuf->resv);
+
+	if (attach->sgt == sg_table)
+		return;
+
+	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
+						direction);
+	dma_buf_unpin(attach->dmabuf);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment_locked);
+
 /**
  * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
  * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
@@ -728,8 +788,7 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
 		return;
 
 	reservation_object_lock(attach->dmabuf->resv, NULL);
-	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
-	dma_buf_unpin(attach->dmabuf);
+	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 425a771d229c..f7d6fc049b39 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -427,8 +427,13 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags);
 struct dma_buf *dma_buf_get(int fd);
 void dma_buf_put(struct dma_buf *dmabuf);
 
+struct sg_table *dma_buf_map_attachment_locked(struct dma_buf_attachment *,
+					       enum dma_data_direction);
 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
 					enum dma_data_direction);
+void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *,
+				     struct sg_table *,
+				     enum dma_data_direction);
 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
 				enum dma_data_direction);
 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
-- 
2.17.1

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