Re: [PATCH mm-unstable v1 17/20] drm/exynos: remove FOLL_FORCE usage

From: Daniel Vetter <daniel@ffwll.ch>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
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	Matthew Wilcox <willy@infradead.org>,
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	Muchun Song <songmuchun@bytedance.com>,
	Shuah Khan <shuah@kernel.org>,
	Lucas Stach <l.stach@pengutronix.de>,
	David Airlie <airlied@gmail.com>,
	Oded Gabbay <ogabbay@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Christoph Hellwig <hch@infradead.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Inki Dae <inki.dae@samsung.com>,
	Seung-Woo Kim <sw0312.kim@samsung.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Subject: Re: [PATCH mm-unstable v1 17/20] drm/exynos: remove FOLL_FORCE usage
Date: Wed, 16 Nov 2022 11:50:57 +0100	[thread overview]
Message-ID: <Y3TAkWy/xXfX1cIv@phenom.ffwll.local> (raw)
In-Reply-To: <20221116102659.70287-18-david@redhat.com>

On Wed, Nov 16, 2022 at 11:26:56AM +0100, David Hildenbrand wrote:
> FOLL_FORCE is really only for ptrace access. As we unpin the pinned pages
> using unpin_user_pages_dirty_lock(true), the assumption is that all these
> pages are writable.
> 
> FOLL_FORCE in this case seems to be a legacy leftover. Let's just remove
> it.
> 
> Cc: Inki Dae <inki.dae@samsung.com>
> Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Plus ack for merging through the appropriate non-drm tree.
-Daniel

> ---
>  drivers/gpu/drm/exynos/exynos_drm_g2d.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> index 471fd6c8135f..e19c2ceb3759 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> @@ -477,7 +477,7 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2d_data *g2d,
>  	}
>  
>  	ret = pin_user_pages_fast(start, npages,
> -				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
> +				  FOLL_WRITE | FOLL_LONGTERM,
>  				  g2d_userptr->pages);
>  	if (ret != npages) {
>  		DRM_DEV_ERROR(g2d->dev,
> -- 
> 2.38.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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