Hi

Am 11.05.20 um 11:35 schrieb Daniel Vetter:
> There's no direct harm, because for the shmem helpers these are noops
> on imported buffers. The trouble is in the locks these take - I want
> to change dma_buf_vmap locking, and so need to make sure that we only
> ever take certain locks on one side of the dma-buf interface: Either
> for exporters, or for importers.
> 
> Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
> Cc: Dave Airlie <airl...@redhat.com>
> Cc: Sean Paul <s...@poorly.run>
> Cc: Gerd Hoffmann <kra...@redhat.com>
> Cc: Thomas Zimmermann <tzimmerm...@suse.de>
> Cc: Alex Deucher <alexander.deuc...@amd.com>
> Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Sam Ravnborg <s...@ravnborg.org>
> ---
>  drivers/gpu/drm/udl/udl_gem.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/udl/udl_gem.c b/drivers/gpu/drm/udl/udl_gem.c
> index b6e26f98aa0a..c68d3e265329 100644
> --- a/drivers/gpu/drm/udl/udl_gem.c
> +++ b/drivers/gpu/drm/udl/udl_gem.c
> @@ -46,29 +46,31 @@ static void *udl_gem_object_vmap(struct drm_gem_object 
> *obj)

It's still not clear to me why this function exists in the first place.
It's the same code as the default implementation, except that it doesn't
support cached mappings.

I don't see why udl is special. I'd suggest to try to use the original
shmem function and remove this one. Same for the mmap code.

Best regards
Thomas

>       if (shmem->vmap_use_count++ > 0)
>               goto out;
>  
> -     ret = drm_gem_shmem_get_pages(shmem);
> -     if (ret)
> -             goto err_zero_use;
> -
> -     if (obj->import_attach)
> +     if (obj->import_attach) {
>               shmem->vaddr = dma_buf_vmap(obj->import_attach->dmabuf);
> -     else
> +     } else {
> +             ret = drm_gem_shmem_get_pages(shmem);
> +             if (ret)
> +                     goto err;
> +
>               shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
>                                   VM_MAP, PAGE_KERNEL);
>  
> +             if (!shmem->vaddr)
> +                     drm_gem_shmem_put_pages(shmem);
> +     }
> +
>       if (!shmem->vaddr) {
>               DRM_DEBUG_KMS("Failed to vmap pages\n");
>               ret = -ENOMEM;
> -             goto err_put_pages;
> +             goto err;
>       }
>  
>  out:
>       mutex_unlock(&shmem->vmap_lock);
>       return shmem->vaddr;
>  
> -err_put_pages:
> -     drm_gem_shmem_put_pages(shmem);
> -err_zero_use:
> +err:
>       shmem->vmap_use_count = 0;
>       mutex_unlock(&shmem->vmap_lock);
>       return ERR_PTR(ret);
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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