[PATCH 1/2] dma-buf: add dma_resv_for_each_fence v3

[Tvrtko Ursulin]

On 06/10/2021 13:36, Christian König wrote:
> A simpler version of the iterator to be used when the dma_resv object is
> locked.
> 
> v2: fix index check here as well
> v3: minor coding improvement, some documentation cleanup
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>   drivers/dma-buf/dma-resv.c | 51 ++++++++++++++++++++++++++++++++++++++
>   include/linux/dma-resv.h   | 20 +++++++++++++++
>   2 files changed, 71 insertions(+)
> 
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index a480af9581bd..2f98caa68ae5 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -423,6 +423,57 @@ struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
>   }
>   EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
>   
> +/**
> + * dma_resv_iter_first - first fence from a locked dma_resv object
> + * @cursor: cursor to record the current position
> + *
> + * Return the first fence in the dma_resv object while holding the
> + * &dma_resv.lock.
> + */
> +struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor)
> +{
> +	struct dma_fence *fence;
> +
> +	dma_resv_assert_held(cursor->obj);
> +
> +	cursor->index = 0;
> +	if (cursor->all_fences)
> +		cursor->fences = dma_resv_shared_list(cursor->obj);
> +	else
> +		cursor->fences = NULL;
> +
> +	fence = dma_resv_excl_fence(cursor->obj);
> +	if (!fence)
> +		fence = dma_resv_iter_next(cursor);
> +
> +	cursor->is_restarted = true;
> +	return fence;
> +}
> +EXPORT_SYMBOL_GPL(dma_resv_iter_first);
> +
> +/**
> + * dma_resv_iter_next - next fence from a locked dma_resv object
> + * @cursor: cursor to record the current position
> + *
> + * Return the next fences from the dma_resv object while holding the
> + * &dma_resv.lock.
> + */
> +struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor)
> +{
> +	unsigned int idx;
> +
> +	dma_resv_assert_held(cursor->obj);
> +
> +	cursor->is_restarted = false;
> +	if (!cursor->fences || cursor->index >= cursor->fences->shared_count)
> +		return NULL;
> +
> +	idx = cursor->index++;
> +	return rcu_dereference_protected(cursor->fences->shared[idx],
> +					 dma_resv_held(cursor->obj));
> +}
> +EXPORT_SYMBOL_GPL(dma_resv_iter_next);
> +
>   /**
>    * dma_resv_copy_fences - Copy all fences from src to dst.
>    * @dst: the destination reservation object
> diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> index 764138ad8583..491359cea54c 100644
> --- a/include/linux/dma-resv.h
> +++ b/include/linux/dma-resv.h
> @@ -179,6 +179,8 @@ struct dma_resv_iter {
>   
>   struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor);
>   struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor);
> +struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
> +struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor);
>   
>   /**
>    * dma_resv_iter_begin - initialize a dma_resv_iter object
> @@ -244,6 +246,24 @@ static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
>   	for (fence = dma_resv_iter_first_unlocked(cursor);		\
>   	     fence; fence = dma_resv_iter_next_unlocked(cursor))
>   
> +/**
> + * dma_resv_for_each_fence - fence iterator
> + * @cursor: a struct dma_resv_iter pointer
> + * @obj: a dma_resv object pointer
> + * @all_fences: true if all fences should be returned
> + * @fence: the current fence
> + *
> + * Iterate over the fences in a struct dma_resv object while holding the
> + * &dma_resv.lock. @all_fences controls if the shared fences are returned as
> + * well. The cursor initialisation is part of the iterator and the fence stays
> + * valid as long as the lock is held and so no extra reference to the fence is
> + * taken.
> + */
> +#define dma_resv_for_each_fence(cursor, obj, all_fences, fence)	\
> +	for (dma_resv_iter_begin(cursor, obj, all_fences),	\
> +	     fence = dma_resv_iter_first(cursor); fence;	\
> +	     fence = dma_resv_iter_next(cursor))
> +
>   #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
>   #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
>   
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko