From: <guangming.cao@mediatek.com>
To: <christian.koenig@amd.com>
Cc: <dri-devel@lists.freedesktop.org>, <guangming.cao@mediatek.com>,
<linaro-mm-sig@lists.linaro.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <linux-media@vger.kernel.org>,
<linux-mediatek@lists.infradead.org>, <matthias.bgg@gmail.com>,
<rdunlap@infradead.org>, <sumit.semwal@linaro.org>,
<wsd_upstream@mediatek.com>,
Guangming Cao <Guangming.Cao@mediatek.com>
Subject: Re: [PATCH v2] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME
Date: Tue, 12 Oct 2021 16:41:09 +0800 [thread overview]
Message-ID: <20211012084109.176542-1-guangming.cao@mediatek.com> (raw)
In-Reply-To: <eba79a76-413b-570c-aec0-899a5f918d38@amd.com>
From: Guangming Cao <Guangming.Cao@mediatek.com>
> Am 09.10.21 um 07:55 schrieb guangming.cao@mediatek.com:
> From: Guangming Cao <Guangming.Cao@mediatek.com>
> >
> > If dma-buf don't want userspace users to touch the dmabuf buffer,
> > it seems we should add this restriction into dma_buf_ops.mmap,
> > not in this IOCTL:DMA_BUF_SET_NAME.
> >
> > With this restriction, we can only know the kernel users of the dmabuf
> > by attachments.
> > However, for many userspace users, such as userpsace users of dma_heap,
> > they also need to mark the usage of dma-buf, and they don't care about
> > who attached to this dmabuf, and seems it's no meaning to be waiting for
> > IOCTL:DMA_BUF_SET_NAME rather than mmap.
>
> Sounds valid to me, but I have no idea why this restriction was added in
> the first place.
>
> Can you double check the git history and maybe identify when that was
> added? Mentioning this change in the commit message then might make
> things a bit easier to understand.
>
> Thanks,
> Christian.
It was add in this patch: https://patchwork.freedesktop.org/patch/310349/.
However, there is no illustration about it.
I guess it wants users to set_name when no attachments on the dmabuf,
for case with attachments, we can find owner by device in attachments.
But just I said in commit message, this is might not a good idea.
Do you have any idea?
>
> >
> > Signed-off-by: Guangming Cao <Guangming.Cao@mediatek.com>
> > ---
> > drivers/dma-buf/dma-buf.c | 14 ++------------
> > 1 file changed, 2 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > index 511fe0d217a0..db2f4efdec32 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 theoretically 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
> > @@ -346,19 +344,11 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
> > 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;
> > }
> >
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next prev parent reply other threads:[~2021-10-12 8:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 2:47 [PATCH] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME guangming.cao
2021-10-09 4:41 ` Randy Dunlap
2021-10-09 5:55 ` [PATCH v2] " guangming.cao
2021-10-11 8:20 ` Christian König
2021-10-12 8:41 ` guangming.cao [this message]
2021-10-14 10:25 ` [PATCH v3] " guangming.cao
2021-10-14 10:35 ` guangming.cao
2021-10-26 8:04 ` guangming.cao
2021-10-26 11:18 ` Christian König
2021-10-26 11:52 ` guangming.cao
2021-10-28 11:35 ` Christian König
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