[PATCH 1/2] dma-buf: Expand reservation_list to fill allocation

[Michel Dänzer]

On 2019-07-12 10:03 a.m., Chris Wilson wrote:
> Since kmalloc() will round up the allocation to the next slab size or
> page, it will normally return a pointer to a memory block bigger than we
> asked for. We can query for the actual size of the allocated block using
> ksize() and expand our variable size reservation_list to take advantage
> of that extra space.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Michel Dänzer <michel.daenzer at amd.com>
> ---
>  drivers/dma-buf/reservation.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index a6ac2b3a0185..80ecc1283d15 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -153,7 +153,9 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
>  			RCU_INIT_POINTER(new->shared[j++], fence);
>  	}
>  	new->shared_count = j;
> -	new->shared_max = max;
> +	new->shared_max =
> +		(ksize(new) - offsetof(typeof(*new), shared)) /
> +		sizeof(*new->shared);
>  
>  	preempt_disable();
>  	write_seqcount_begin(&obj->seq);
> @@ -169,7 +171,7 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
>  		return 0;
>  
>  	/* Drop the references to the signaled fences */
> -	for (i = k; i < new->shared_max; ++i) {
> +	for (i = k; i < max; ++i) {
>  		struct dma_fence *fence;
>  
>  		fence = rcu_dereference_protected(new->shared[i],
> 

Nice, TIL about ksize(), wonder where else that could be used.

Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>


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-- 
Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer