linux-kernel - Re: [PATCH mm-unstable v1 17/20] drm/exynos: remove FOLL

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Message-ID: <Y3TAkWy/xXfX1cIv@phenom.ffwll.local>
Date:   Wed, 16 Nov 2022 11:50:57 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-alpha@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-ia64@...r.kernel.org, linux-mips@...r.kernel.org,
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        linux-um@...ts.infradead.org, etnaviv@...ts.freedesktop.org,
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        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
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        linux-security-module@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Peter Xu <peterx@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>, Nadav Amit <namit@...are.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Shuah Khan <shuah@...nel.org>,
        Lucas Stach <l.stach@...gutronix.de>,
        David Airlie <airlied@...il.com>,
        Oded Gabbay <ogabbay@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christoph Hellwig <hch@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Inki Dae <inki.dae@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH mm-unstable v1 17/20] drm/exynos: remove FOLL_FORCE usage

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@...sung.com>
> Cc: Seung-Woo Kim <sw0312.kim@...sung.com>
> Cc: Kyungmin Park <kyungmin.park@...sung.com>
> Cc: David Airlie <airlied@...il.com>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.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