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SubjectRe: [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME
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Am 14.10.21 um 12:25 schrieb guangming.cao@mediatek.com:
> From: Guangming Cao <Guangming.Cao@mediatek.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.
>
> Signed-off-by: Guangming Cao <Guangming.Cao@mediatek.com>

We could now cleanup the return value from dma_buf_set_name() into a
void since that function can't fail any more as far as I can see.

But that isn't mandatory I think, patch is Reviewed-by: Christian König
<christian.koenig@amd.com>

Regards,
Christian.

> ---
> 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,

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