[PATCH 03/26] dma-buf: use new iterator in dma_resv_copy_fences

From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org,
	linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org
Cc: daniel@ffwll.ch, tvrtko.ursulin@linux.intel.com
Subject: [PATCH 03/26] dma-buf: use new iterator in dma_resv_copy_fences
Date: Thu, 16 Sep 2021 13:30:19 +0200	[thread overview]
Message-ID: <20210916113042.3631-4-christian.koenig@amd.com> (raw)
In-Reply-To: <20210916113042.3631-1-christian.koenig@amd.com>

This makes the function much simpler since the complex
retry logic is now handled else where.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-resv.c | 81 +++++++++++++++-----------------------
 1 file changed, 32 insertions(+), 49 deletions(-)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index bbf36a08ced0..91c040cb7d63 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -431,74 +431,57 @@ EXPORT_SYMBOL_GPL(dma_resv_walk_unlocked);
  */
 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 {
-	struct dma_resv_list *src_list, *dst_list;
-	struct dma_fence *old, *new;
-	unsigned int i;
+	struct dma_resv_iter cursor;
+	struct dma_resv_list *list;
+	struct dma_fence *f, *excl;
 
 	dma_resv_assert_held(dst);
 
-	rcu_read_lock();
-	src_list = dma_resv_shared_list(src);
+	list = NULL;
+	excl = NULL;
 
-retry:
-	if (src_list) {
-		unsigned int shared_count = src_list->shared_count;
+	rcu_read_lock();
+	dma_resv_for_each_fence_unlocked(dst, &cursor, true, f) {
 
-		rcu_read_unlock();
+		if (cursor.is_first) {
+			dma_resv_list_free(list);
+			dma_fence_put(excl);
 
-		dst_list = dma_resv_list_alloc(shared_count);
-		if (!dst_list)
-			return -ENOMEM;
+			if (cursor.fences) {
+				unsigned int cnt = cursor.fences->shared_count;
 
-		rcu_read_lock();
-		src_list = dma_resv_shared_list(src);
-		if (!src_list || src_list->shared_count > shared_count) {
-			kfree(dst_list);
-			goto retry;
-		}
+				rcu_read_unlock();
+				list = dma_resv_list_alloc(cnt);
+				if (!list)
+					return -ENOMEM;
 
-		dst_list->shared_count = 0;
-		for (i = 0; i < src_list->shared_count; ++i) {
-			struct dma_fence __rcu **dst;
-			struct dma_fence *fence;
+				list->shared_count = 0;
+				rcu_read_lock();
 
-			fence = rcu_dereference(src_list->shared[i]);
-			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
-				     &fence->flags))
-				continue;
-
-			if (!dma_fence_get_rcu(fence)) {
-				dma_resv_list_free(dst_list);
-				src_list = dma_resv_shared_list(src);
-				goto retry;
+			} else {
+				list = NULL;
 			}
+			excl = NULL;
+		}
 
-			if (dma_fence_is_signaled(fence)) {
-				dma_fence_put(fence);
-				continue;
-			}
+		if (dma_resv_iter_is_exclusive(&cursor))
+			excl = f;
+		else
+			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
 
-			dst = &dst_list->shared[dst_list->shared_count++];
-			rcu_assign_pointer(*dst, fence);
-		}
-	} else {
-		dst_list = NULL;
+		/* Don't drop the reference */
+		f = NULL;
 	}
 
-	new = dma_fence_get_rcu_safe(&src->fence_excl);
 	rcu_read_unlock();
 
-	src_list = dma_resv_shared_list(dst);
-	old = dma_resv_excl_fence(dst);
-
 	write_seqcount_begin(&dst->seq);
-	/* write_seqcount_begin provides the necessary memory barrier */
-	RCU_INIT_POINTER(dst->fence_excl, new);
-	RCU_INIT_POINTER(dst->fence, dst_list);
+	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
+	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
 	write_seqcount_end(&dst->seq);
 
-	dma_resv_list_free(src_list);
-	dma_fence_put(old);
+	dma_resv_list_free(list);
+	dma_fence_put(excl);
 
 	return 0;
 }
-- 
2.25.1

