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SubjectRe: [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME
Date
From: Guangming Cao <Guangming.Cao@mediatek.com>

On Tue, 2021-10-26 at 13:18 +0200, Christian König wrote:
> 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>
>

So, here is no need to check return value of 'strndup_user',
just return without error code if the almost impossible error occurs?

Guangming.

> 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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