From: <guangming.cao@mediatek.com>
To: <christian.koenig@amd.com>, <sumit.semwal@linaro.org>
Cc: <guangming.cao@mediatek.com>, <dri-devel@lists.freedesktop.org>,
<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>, <wsd_upstream@mediatek.com>,
Guangming Cao <Guangming.Cao@mediatek.com>
Subject: [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME
Date: Thu, 14 Oct 2021 18:35:24 +0800 [thread overview]
Message-ID: <20211014103524.55368-1-guangming.cao@mediatek.com> (raw)
In-Reply-To: <20211014102551.54983-1-guangming.cao@mediatek.com>
From: Guangming Cao <Guangming.Cao@mediatek.com>
On Wed, 2021-10-13 at 14:20 +0200, Christian König wrote:
> Am 13.10.21 um 01:56 schrieb Sumit Semwal:
> > Hello Guangming, Christian,
> >
> >
> >
> > On Tue, 12 Oct 2021, 14:09 , <guangming.cao@mediatek.com> wrote:
> > > 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?
> > >
> >
> > 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, and any accounting should probably use that, without relying
> > on the name as much.
> > So I don't have an objection to this change.
>
> I suggest to add that explanation and the original commit id into the
> commit message.
>
> With that changed the patch has my rb as well.
>
> Regards,
> Christian.
>
updated, thanks!
Guangming.
> > Best,
> > Sumit.
> > > >
> > > > >
> > > > > 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:[~2021-10-14 10:38 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
2021-10-14 10:25 ` [PATCH v3] " guangming.cao
2021-10-14 10:35 ` guangming.cao [this message]
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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