drm/i915: use the new iterator in i915_sw_fence_await_reservation v3

Simplifying the code a bit.

v2: use dma_resv_for_each_fence instead, according to Tvrtko the lock is
    held here anyway.
v3: back to using dma_resv_for_each_fence_unlocked.
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211116102431.198905-4-christian.koenig@amd.com

drivers/gpu/drm/i915/i915_sw_fence.c

@@ -572,56 +572,25 @@ int i915_sw_fence_await_reservation(struct i915_sw_fence *fence,
 				    unsigned long timeout,
 				    gfp_t gfp)
 {
-	struct dma_fence *excl;
+	struct dma_resv_iter cursor;
+	struct dma_fence *f;
 	int ret = 0, pending;
 
 	debug_fence_assert(fence);
 	might_sleep_if(gfpflags_allow_blocking(gfp));
 
-	if (write) {
-		struct dma_fence **shared;
-		unsigned int count, i;
-
-		ret = dma_resv_get_fences(resv, &excl, &count, &shared);
-		if (ret)
-			return ret;
-
-		for (i = 0; i < count; i++) {
-			if (shared[i]->ops == exclude)
-				continue;
-
-			pending = i915_sw_fence_await_dma_fence(fence,
-								shared[i],
-								timeout,
-								gfp);
-			if (pending < 0) {
-				ret = pending;
-				break;
-			}
-
-			ret |= pending;
-		}
-
-		for (i = 0; i < count; i++)
-			dma_fence_put(shared[i]);
-		kfree(shared);
-	} else {
-		excl = dma_resv_get_excl_unlocked(resv);
-	}
-
-	if (ret >= 0 && excl && excl->ops != exclude) {
-		pending = i915_sw_fence_await_dma_fence(fence,
-							excl,
-							timeout,
+	dma_resv_iter_begin(&cursor, resv, write);
+	dma_resv_for_each_fence_unlocked(&cursor, f) {
+		pending = i915_sw_fence_await_dma_fence(fence, f, timeout,
 							gfp);
-		if (pending < 0)
+		if (pending < 0) {
 			ret = pending;
-		else
-			ret |= pending;
-	}
-
-	dma_fence_put(excl);
+			break;
+		}
 
+		ret |= pending;
+	}
+	dma_resv_iter_end(&cursor);
 	return ret;
 }