[PATCH 1/5] drm/panfrost: Stop using drm_gem_shmem_put_pages()

[Boris Brezillon]

On Mon, 26 Jun 2023 16:20:53 +0300
Dmitry Osipenko <dmitry.osipenko at collabora.com> wrote:

> On 6/26/23 15:02, Boris Brezillon wrote:
> > -err_pages:
> > -	drm_gem_shmem_put_pages(&bo->base);
> >  err_unlock:
> >  	dma_resv_unlock(obj->resv);
> > +
> > +	if (ret && pinned)
> > +		drm_gem_shmem_unpin(&bo->base);  
> 
> The drm_gem_shmem_unpin() was supposed to be used only in conjunction
> with drm_gem_shmem_pin(). I've a pending patch to enable the pin/unpin
> refcounting needed by drm-shmem shrinker, it will prohibit invocation of
> unpin without a previous pin.
> 
> I'm wondering whether it will be okay to simply remove
> drm_gem_shmem_put_pages() from the Panfrost code, letting pages to be
> kept allocated in a error case. They will be freed once BO is destroyed.
> 

Okay, so after looking at your shmem-shrinker series, I confirm we need
to take a pin ref here (hard-pin), otherwise the buffer might be
evicted before the GPU is done, especially after you drop gpu_usecount
and use only pin_count to check whether a GEM object can be evicted or
not.