netdev - Re: [PATCH v2 09/18] drm/via: set FOLL_PIN via pin_user_pages

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Message-ID: <20191104174445.GF5134@redhat.com>
Date:   Mon, 4 Nov 2019 12:44:45 -0500
From:   Jerome Glisse <jglisse@...hat.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Jonathan Corbet <corbet@....net>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Paul Mackerras <paulus@...ba.org>,
        Shuah Khan <shuah@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, bpf@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, kvm@...r.kernel.org,
        linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-media@...r.kernel.org, linux-rdma@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 09/18] drm/via: set FOLL_PIN via pin_user_pages_fast()

On Sun, Nov 03, 2019 at 01:18:04PM -0800, John Hubbard wrote:
> Convert drm/via to use the new pin_user_pages_fast() call, which sets
> FOLL_PIN. Setting FOLL_PIN is now required for code that requires
> tracking of pinned pages, and therefore for any code that calls
> put_user_page().
> 
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>

Please be more explicit that via_dmablit.c is already using put_user_page()
as i am expecting that any conversion to pin_user_pages*() must be pair with
a put_user_page(). I find above commit message bit unclear from that POV.

Reviewed-by: Jérôme Glisse <jglisse@...hat.com>


> ---
>  drivers/gpu/drm/via/via_dmablit.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/via/via_dmablit.c b/drivers/gpu/drm/via/via_dmablit.c
> index 3db000aacd26..37c5e572993a 100644
> --- a/drivers/gpu/drm/via/via_dmablit.c
> +++ b/drivers/gpu/drm/via/via_dmablit.c
> @@ -239,7 +239,7 @@ via_lock_all_dma_pages(drm_via_sg_info_t *vsg,  drm_via_dmablit_t *xfer)
>  	vsg->pages = vzalloc(array_size(sizeof(struct page *), vsg->num_pages));
>  	if (NULL == vsg->pages)
>  		return -ENOMEM;
> -	ret = get_user_pages_fast((unsigned long)xfer->mem_addr,
> +	ret = pin_user_pages_fast((unsigned long)xfer->mem_addr,
>  			vsg->num_pages,
>  			vsg->direction == DMA_FROM_DEVICE ? FOLL_WRITE : 0,
>  			vsg->pages);
> -- 
> 2.23.0
>