linux-kernel - [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET

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Message-ID: <20211026080451.3763-1-guangming.cao@mediatek.com>
Date:   Tue, 26 Oct 2021 16:04:51 +0800
From:   <guangming.cao@...iatek.com>
To:     <christian.koenig@....com>, <sumit.semwal@...aro.org>
CC:     <dri-devel@...ts.freedesktop.org>, <guangming.cao@...iatek.com>,
        <linaro-mm-sig@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <matthias.bgg@...il.com>,
        <rdunlap@...radead.org>, <wsd_upstream@...iatek.com>,
        Guangming Cao <Guangming.Cao@...iatek.com>
Subject: [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME

From: Guangming Cao <Guangming.Cao@...iatek.com>

On Thu, 2021-10-14 at 18:25 +0800, guangming.cao@...iatek.com wrote:
> From: Guangming Cao <Guangming.Cao@...iatek.com>
> 
> In this patch(https://patchwork.freedesktop.org/patch/310349),
> it add a new IOCTL to support dma-buf user to set debug name.
> 
> But it also added a limitation of this IOCTL, it needs the
> attachments of dmabuf should be empty, otherwise it will fail.
> 
> For the original series, the idea was that allowing name change
> mid-use could confuse the users about the dma-buf.
> However, the rest of the series also makes sure each dma-buf have a
> unique
> inode(https://patchwork.freedesktop.org/patch/310387/), and any
> accounting
> should probably use that, without relying on the name as much.
> 
> So, removing this restriction will let dma-buf userspace users to use
> it
> more comfortably and without any side effect.
> 
Hi christian, sumit,

Just a gentle ping for this patch, please kindly let me know your comments about this patch.
Thanks!

Guangming

> Signed-off-by: Guangming Cao <Guangming.Cao@...iatek.com>
> ---
>  drivers/dma-buf/dma-buf.c | 17 +++--------------
>  1 file changed, 3 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 511fe0d217a0..5fbb3a2068a3 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -325,10 +325,8 @@ static __poll_t dma_buf_poll(struct file *file,
> poll_table *poll)
>  
>  /**
>   * dma_buf_set_name - Set a name to a specific dma_buf to track the
> usage.
> - * The name of the dma-buf buffer can only be set when the dma-buf
> is not
> - * attached to any devices. It could theoritically support changing
> the
> - * name of the dma-buf if the same piece of memory is used for
> multiple
> - * purpose between different devices.
> + * It could support changing the name of the dma-buf if the same
> + * piece of memory is used for multiple purpose between different
> devices.
>   *
>   * @dmabuf: [in]     dmabuf buffer that will be renamed.
>   * @buf:    [in]     A piece of userspace memory that contains the
> name of
> @@ -341,25 +339,16 @@ static __poll_t dma_buf_poll(struct file *file,
> poll_table *poll)
>  static long dma_buf_set_name(struct dma_buf *dmabuf, const char
> __user *buf)
>  {
>  	char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
> -	long ret = 0;
>  
>  	if (IS_ERR(name))
>  		return PTR_ERR(name);
>  
> -	dma_resv_lock(dmabuf->resv, NULL);
> -	if (!list_empty(&dmabuf->attachments)) {
> -		ret = -EBUSY;
> -		kfree(name);
> -		goto out_unlock;
> -	}
>  	spin_lock(&dmabuf->name_lock);
>  	kfree(dmabuf->name);
>  	dmabuf->name = name;
>  	spin_unlock(&dmabuf->name_lock);
>  
> -out_unlock:
> -	dma_resv_unlock(dmabuf->resv);
> -	return ret;
> +	return 0;
>  }
>  
>  static long dma_buf_ioctl(struct file *file,