dma-buf: fix check in dma_resv_add_fence

It's valid to add the same fence multiple times to a dma-resv object and
we shouldn't need one extra slot for each.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Fixes: a3f7c10a269d5 ("dma-buf/dma-resv: check if the new fence is really later")
Cc: stable@vger.kernel.org # v5.19+
Link: https://patchwork.freedesktop.org/patch/msgid/20231115093035.1889-1-christian.koenig@amd.com

1 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index ebe78bd3d121..b3772edca2e6 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -499,6 +499,21 @@ static inline bool dma_fence_is_later(struct dma_fence *f1,
 }
 
 /**
+ * dma_fence_is_later_or_same - return true if f1 is later or same as f2
+ * @f1: the first fence from the same context
+ * @f2: the second fence from the same context
+ *
+ * Returns true if f1 is chronologically later than f2 or the same fence. Both
+ * fences must be from the same context, since a seqno is not re-used across
+ * contexts.
+ */
+static inline bool dma_fence_is_later_or_same(struct dma_fence *f1,
+					      struct dma_fence *f2)
+{
+	return f1 == f2 || dma_fence_is_later(f1, f2);
+}
+
+/**
  * dma_fence_later - return the chronologically later fence
  * @f1:	the first fence from the same context
  * @f2:	the second fence from the same context