linux-kernel - Re: [PATCH v3 9/9] xen/gntdev: Implement dma-buf import functionality

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Message-ID: <cca7b9dd-a0c6-8052-c294-9e6c5d65e9eb@epam.com>
Date:   Wed, 13 Jun 2018 12:04:49 +0300
From:   Oleksandr Andrushchenko <Oleksandr_Andrushchenko@...m.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Oleksandr Andrushchenko <andr2000@...il.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        jgross@...e.com, konrad.wilk@...cle.com
Cc:     daniel.vetter@...el.com, dongwon.kim@...el.com,
        matthew.d.roper@...el.com
Subject: Re: [PATCH v3 9/9] xen/gntdev: Implement dma-buf import functionality

On 06/13/2018 06:14 AM, Boris Ostrovsky wrote:
>
>
> On 06/12/2018 09:42 AM, Oleksandr Andrushchenko wrote:
>
>>   int gntdev_dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
>>   {
>> -    return -EINVAL;
>> +    struct gntdev_dmabuf *gntdev_dmabuf;
>> +    struct dma_buf_attachment *attach;
>> +    struct dma_buf *dma_buf;
>> +
>> +    gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd);
>> +    if (IS_ERR(gntdev_dmabuf))
>> +        return PTR_ERR(gntdev_dmabuf);
>> +
>> +    pr_debug("Releasing DMA buffer with fd %d\n", fd);
>> +
>> +    attach = gntdev_dmabuf->u.imp.attach;
>> +
>> +    if (gntdev_dmabuf->u.imp.sgt)
>> +        dma_buf_unmap_attachment(attach, gntdev_dmabuf->u.imp.sgt,
>> +                     DMA_BIDIRECTIONAL);
>> +    dma_buf = attach->dmabuf;
>> +    dma_buf_detach(attach->dmabuf, attach);
>> +    dma_buf_put(dma_buf);
>> +
>> +    dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs,
>> +                      gntdev_dmabuf->nr_pages);
>
>
>
> Should you first end foreign access, before doing anything?
>
I am rolling back in reverse order here, so I think we first need
to finish local activities with the buffer and then end foreign
access.
> -boris
>
>
>> + dmabuf_imp_free_storage(gntdev_dmabuf);
>> +    return 0;
>>   }