Re: [PATCH v3] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME

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Am 26.10.21 um 13:52 schrieb guangming.cao@xxxxxxxxxxxx:
From: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>

On Tue, 2021-10-26 at 13:18 +0200, Christian König wrote:
Am 14.10.21 um 12:25 schrieb guangming.cao@xxxxxxxxxxxx:
From: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>

In this patch(https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.freedesktop.org%2Fpatch%2F310349&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C6652f423b96547b8321308d998772121%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637708459727236977%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=4EFg60sCxQzNuMKB0VjhbpvoeGlcAbofErMtcjPtIfw%3D&amp;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&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C6652f423b96547b8321308d998772121%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637708459727236977%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=c%2Bbso%2BSxiPjwlv%2B9tAzA4x0gf5UktREhSiAsODFkihk%3D&amp;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@xxxxxxxxxxxx>
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@xxxxxxx>

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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