Re: [PATCH v19 14/30] drm/shmem-helper: Add drm_gem_shmem_put_pages()

[Boris Brezillon <boris.brezillon@collabora.com>]

On Fri,  5 Jan 2024 21:46:08 +0300
Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote:

> We're going to move away from having implicit get_pages() done by
> get_pages_sgt() to ease simplify refcnt handling. Drivers will manage
> get/put_pages() by themselves. Add drm_gem_shmem_put_pages().
> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 20 ++++++++++++++++++++
>  include/drm/drm_gem_shmem_helper.h     |  1 +
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index dc416a4bce1b..f5ed64f78648 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -218,6 +218,7 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>   * @shmem: shmem GEM object
>   *
>   * This function decreases the use count and puts the backing pages when use drops to zero.
> + * Caller must hold GEM's reservation lock.
>   */
>  void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>  {
> @@ -228,6 +229,25 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
>  
> +/*
> + * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
> + * @shmem: shmem GEM object
> + *
> + * This function decreases the use count and puts the backing pages when use drops to zero.
> + * It's unlocked version of drm_gem_shmem_put_pages_locked(), caller must not hold
> + * GEM's reservation lock.
> + */
> +void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
> +{
> +	if (refcount_dec_not_one(&shmem->pages_use_count))
> +		return;
> +
> +	dma_resv_lock(shmem->base.resv, NULL);
> +	drm_gem_shmem_put_pages_locked(shmem);
> +	dma_resv_unlock(shmem->base.resv);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages);
> +
>  /*
>   * drm_gem_shmem_get_pages - Increase use count on the backing pages for a shmem GEM object
>   * @shmem: shmem GEM object
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 6dedc0739fbc..525480488451 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -111,6 +111,7 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
>  void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem);
>  
>  int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem);
> +void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem);
>  void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem);
>  int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem);
>  void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem);