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.
> 
> Cc: Gerd Hoffmann <kra...@redhat.com>
> Cc: Rob Herring <r...@kernel.org>
> Cc: Noralf Trønnes <nor...@tronnes.org>
> Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c 
> b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 2a70159d50ef..b9cba5cc61c3 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -252,32 +252,33 @@ static void *drm_gem_shmem_vmap_locked(struct 
> drm_gem_shmem_object *shmem)
>       if (shmem->vmap_use_count++ > 0)
>               return shmem->vaddr;
>  
> -     ret = drm_gem_shmem_get_pages(shmem);
> -     if (ret)
> -             goto err_zero_use;
> -
>       if (obj->import_attach) {
>               shmem->vaddr = dma_buf_vmap(obj->import_attach->dmabuf);
>       } else {
>               pgprot_t prot = PAGE_KERNEL;
>  
> +             ret = drm_gem_shmem_get_pages(shmem);
> +             if (ret)
> +                     goto err;
> +
>               if (!shmem->map_cached)
>                       prot = pgprot_writecombine(prot);
>               shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
>                                   VM_MAP, prot);
> +
> +             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;
>       }
>  
>       return shmem->vaddr;
>  
> -err_put_pages:
> -     drm_gem_shmem_put_pages(shmem);

I found the new code to be less readable. Maybe keep the error rollback
as-is and protect _put_pages() with if (!import_attach).

In any case

Acked-by: Thomas Zimmermann <tzimmerm...@suse.de>

> -err_zero_use:
> +err:
>       shmem->vmap_use_count = 0;
>  
>       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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