linux-kernel - Re: [PATCH v2] drm/etnaviv: convert get_user_pages() --> pin_user

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Date:   Thu, 18 Jun 2020 17:51:34 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     David Airlie <airlied@...ux.ie>, etnaviv@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Russell King <linux+etnaviv@...linux.org.uk>
Subject: Re: [PATCH v2] drm/etnaviv: convert get_user_pages() -->
 pin_user_pages()

Am Montag, den 25.05.2020, 16:49 -0700 schrieb John Hubbard:
> This code was using get_user_pages*(), in a "Case 2" scenario
> (DMA/RDMA), using the categorization from [1]. That means that it's
> time to convert the get_user_pages*() + put_page() calls to
> pin_user_pages*() + unpin_user_pages() calls.
> 
> There is some helpful background in [2]: basically, this is a small
> part of fixing a long-standing disconnect between pinning pages, and
> file systems' use of those pages.
> 
> [1] Documentation/core-api/pin_user_pages.rst
> 
> [2] "Explicit pinning of user-space pages":
>     https://lwn.net/Articles/807108/
> 
> Signed-off-by: John Hubbard <jhubbard@...dia.com>

Thanks, I've applied this to etnaviv/next.

Regards,
Lucas

> ---
> 
> Hi,
> 
> Changes since v1:
> 
> * Rebased onto Linux 5.7-rc7
> 
> * Added: Lucas Stach
> 
> thanks
> John Hubbard
> NVIDIA
> 
> 
>  drivers/gpu/drm/etnaviv/etnaviv_gem.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> index dc9ef302f517..0f4578dc169d 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> @@ -675,10 +675,10 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj)
>  		uint64_t ptr = userptr->ptr + pinned * PAGE_SIZE;
>  		struct page **pages = pvec + pinned;
>  
> -		ret = get_user_pages_fast(ptr, num_pages,
> +		ret = pin_user_pages_fast(ptr, num_pages,
>  					  !userptr->ro ? FOLL_WRITE : 0, pages);
>  		if (ret < 0) {
> -			release_pages(pvec, pinned);
> +			unpin_user_pages(pvec, pinned);
>  			kvfree(pvec);
>  			return ret;
>  		}
> @@ -702,7 +702,7 @@ static void etnaviv_gem_userptr_release(struct etnaviv_gem_object *etnaviv_obj)
>  	if (etnaviv_obj->pages) {
>  		int npages = etnaviv_obj->base.size >> PAGE_SHIFT;
>  
> -		release_pages(etnaviv_obj->pages, npages);
> +		unpin_user_pages(etnaviv_obj->pages, npages);
>  		kvfree(etnaviv_obj->pages);
>  	}
>  }