[PATCH 5/6] RFC: dma-buf: Add an extra fence to dma_resv_get_singleton_unlocked

[Jason Ekstrand]

For dma-buf sync_file import, we want to get all the fences on a
dma_resv plus one more.  We could wrap the fence we get back in an array
fence or we could make dma_resv_get_singleton_unlocked take "one more"
to make this case easier.

Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
---
 drivers/dma-buf/dma-buf.c  |  2 +-
 drivers/dma-buf/dma-resv.c | 23 +++++++++++++++++++++--
 include/linux/dma-resv.h   |  3 ++-
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 86efe71c0db96..f23d939e0e833 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -386,7 +386,7 @@ static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
 		return fd;
 
 	if (arg.flags & DMA_BUF_SYNC_WRITE) {
-		fence = dma_resv_get_singleton_unlocked(dmabuf->resv);
+		fence = dma_resv_get_singleton_unlocked(dmabuf->resv, NULL);
 		if (IS_ERR(fence)) {
 			ret = PTR_ERR(fence);
 			goto err_put_fd;
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 312a3a59dac6a..3c0ef8d0f599b 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -527,6 +527,7 @@ EXPORT_SYMBOL_GPL(dma_resv_get_fences_unlocked);
 /**
  * dma_resv_get_singleton_unlocked - get a single fence for the dma_resv object
  * @obj: the reservation object
+ * @extra: extra fence to add to the resulting array
  * @result: resulting dma_fence
  *
  * Get a single fence representing all unsignaled fences in the dma_resv object
@@ -536,7 +537,8 @@ EXPORT_SYMBOL_GPL(dma_resv_get_fences_unlocked);
  * RETURNS
  * Returns -NOMEM if allocations fail, zero otherwise.
  */
-struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
+struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj,
+						  struct dma_fence *extra)
 {
 	struct dma_fence *result, **resv_fences, *fence, *chain, **fences;
 	struct dma_fence_array *array;
@@ -547,7 +549,7 @@ struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
 	if (err)
 		return ERR_PTR(err);
 
-	if (num_resv_fences == 0)
+	if (num_resv_fences == 0 && !extra)
 		return NULL;
 
 	num_fences = 0;
@@ -563,6 +565,16 @@ struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
 		}
 	}
 
+	if (extra) {
+		dma_fence_deep_dive_for_each(fence, chain, j, extra) {
+			if (dma_fence_is_signaled(fence))
+				continue;
+
+			result = fence;
+			++num_fences;
+		}
+	}
+
 	if (num_fences <= 1) {
 		result = dma_fence_get(result);
 		goto put_resv_fences;
@@ -583,6 +595,13 @@ struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
 		}
 	}
 
+	if (extra) {
+		dma_fence_deep_dive_for_each(fence, chain, j, extra) {
+			if (dma_fence_is_signaled(fence))
+				fences[num_fences++] = dma_fence_get(fence);
+		}
+	}
+
 	if (num_fences <= 1) {
 		result = num_fences ? fences[0] : NULL;
 		kfree(fences);
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index c529ccee94bc5..156d989e95ab4 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -285,7 +285,8 @@ int dma_resv_get_fences_unlocked(struct dma_resv *obj,
 
 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
 
-struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj);
+struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj,
+						  struct dma_fence *extra);
 
 long dma_resv_wait_timeout_unlocked(struct dma_resv *obj, bool wait_all, bool intr,
 				    unsigned long timeout);
-- 
2.31.1