From: "Christian König" <christian.koenig@amd.com>
To: guangming.cao@mediatek.com
Cc: 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, sumit.semwal@linaro.org,
wsd_upstream@mediatek.com
Subject: Re: [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME
Date: Thu, 28 Oct 2021 13:35:20 +0200 [thread overview]
Message-ID: <1d681a88-5c3e-f2b1-2865-c380599a4f71@amd.com> (raw)
In-Reply-To: <20211026115248.9564-1-guangming.cao@mediatek.com>
Am 26.10.21 um 13:52 schrieb guangming.cao@mediatek.com:
> 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://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.freedesktop.org%2Fpatch%2F310349&data=04%7C01%7Cchristian.koenig%40amd.com%7C6652f423b96547b8321308d998772121%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637708459727236977%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=4EFg60sCxQzNuMKB0VjhbpvoeGlcAbofErMtcjPtIfw%3D&reserved=0),
>>> 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://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.freedesktop.org%2Fpatch%2F310387%2F&data=04%7C01%7Cchristian.koenig%40amd.com%7C6652f423b96547b8321308d998772121%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637708459727236977%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=c%2Bbso%2BSxiPjwlv%2B9tAzA4x0gf5UktREhSiAsODFkihk%3D&reserved=0), 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?
Good point, totally missed that one.
In that case I'm going to push the patch to drm-misc-next as is.
Regards,
Christian.
>
> 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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prev parent reply other threads:[~2021-10-28 11:38 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
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 [this message]
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