[PATCH] dma-buf: fix check in dma_resv_add_fence

[Christian König]

Ping? Can I get an rb or acked-by for that?

Thanks,
Christian.

Am 15.11.23 um 10:30 schrieb Christian König:
> 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 at amd.com>
> Fixes: a3f7c10a269d5 ("dma-buf/dma-resv: check if the new fence is really later")
> Cc: stable at vger.kernel.org # v5.19+
> ---
>   drivers/dma-buf/dma-resv.c |  2 +-
>   include/linux/dma-fence.h  | 15 +++++++++++++++
>   2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index 38b4110378de..eb8b733065b2 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -301,7 +301,7 @@ void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
>   
>   		dma_resv_list_entry(fobj, i, obj, &old, &old_usage);
>   		if ((old->context == fence->context && old_usage >= usage &&
> -		     dma_fence_is_later(fence, old)) ||
> +		     dma_fence_is_later_or_same(fence, old)) ||
>   		    dma_fence_is_signaled(old)) {
>   			dma_resv_list_set(fobj, i, fence, usage);
>   			dma_fence_put(old);
> 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
> @@ -498,6 +498,21 @@ static inline bool dma_fence_is_later(struct dma_fence *f1,
>   	return __dma_fence_is_later(f1->seqno, f2->seqno, f1->ops);
>   }
>   
> +/**
> + * 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