[PATCH] vhost_net: Use fdget() and fdput()

[PATCH] vhost_net: Use fdget() and fdput()

[ye.xingchen]

From: Ye Xingchen <ye.xingchen@zte.com.cn>

convert the fget()/fput() uses to fdget()/fdput().

Signed-off-by: Ye Xingchen <ye.xingchen@zte.com.cn>
---
 drivers/vhost/net.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index ae2273196b0c..5b3fe4805182 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1466,17 +1466,17 @@ static struct ptr_ring *get_tap_ptr_ring(struct file *file)

 static struct socket *get_tap_socket(int fd)
 {
-	struct file *file = fget(fd);
+	struct fd f = fdget(fd);
 	struct socket *sock;

-	if (!file)
+	if (!f.file)
 		return ERR_PTR(-EBADF);
-	sock = tun_get_socket(file);
+	sock = tun_get_socket(f.file);
 	if (!IS_ERR(sock))
 		return sock;
-	sock = tap_get_socket(file);
+	sock = tap_get_socket(f.file);
 	if (IS_ERR(sock))
-		fput(file);
+		fdput(f);
 	return sock;
 }

-- 
2.25.1

Re: [PATCH] vhost_net: Use fdget() and fdput()

[Jason Wang]

On Fri, May 5, 2023 at 2:24 PM <ye.xingchen@zte.com.cn> wrote:
>
> From: Ye Xingchen <ye.xingchen@zte.com.cn>
>
> convert the fget()/fput() uses to fdget()/fdput().

What's the advantages of this?

Thanks

>
> Signed-off-by: Ye Xingchen <ye.xingchen@zte.com.cn>
> ---
>  drivers/vhost/net.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index ae2273196b0c..5b3fe4805182 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -1466,17 +1466,17 @@ static struct ptr_ring *get_tap_ptr_ring(struct file *file)
>
>  static struct socket *get_tap_socket(int fd)
>  {
> -       struct file *file = fget(fd);
> +       struct fd f = fdget(fd);
>         struct socket *sock;
>
> -       if (!file)
> +       if (!f.file)
>                 return ERR_PTR(-EBADF);
> -       sock = tun_get_socket(file);
> +       sock = tun_get_socket(f.file);
>         if (!IS_ERR(sock))
>                 return sock;
> -       sock = tap_get_socket(file);
> +       sock = tap_get_socket(f.file);
>         if (IS_ERR(sock))
> -               fput(file);
> +               fdput(f);
>         return sock;
>  }
>
> --
> 2.25.1
>

Re: [PATCH] vhost_net: Use fdget() and fdput()

[ye xingchen]

>>
>> From: Ye Xingchen <ye.xingchen@zte.com.cn>
>>
>> convert the fget()/fput() uses to fdget()/fdput().
>What's the advantages of this?
>
>Thanks
>>
>> Signed-off-by: Ye Xingchen <ye.xingchen@zte.com.cn>
>> ---
>>  drivers/vhost/net.c | 10 +++++-----
>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index ae2273196b0c..5b3fe4805182 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -1466,17 +1466,17 @@ static struct ptr_ring *get_tap_ptr_ring(struct file *file)
>>
>>  static struct socket *get_tap_socket(int fd)
>>  {
>> -       struct file *file = fget(fd);
>> +       struct fd f = fdget(fd);
>>         struct socket *sock;
>>
>> -       if (!file)
>> +       if (!f.file)
>>                 return ERR_PTR(-EBADF);
>> -       sock = tun_get_socket(file);
>> +       sock = tun_get_socket(f.file);
>>         if (!IS_ERR(sock))
>>                 return sock;
>> -       sock = tap_get_socket(file);
>> +       sock = tap_get_socket(f.file);
>>         if (IS_ERR(sock))
>> -               fput(file);
>> +               fdput(f);
>>         return sock;
>>  }
>>
>> --
>> 2.25.1
>>
fdget requires an integer type file descriptor as its parameter, 
and fget requires a pointer to the file structure as its parameter.

By using the fdget function, the socket object, can be quickly 
obtained from the process's file descriptor table without 
the need to obtain the file descriptor first before passing it 
as a parameter to the fget function. This reduces unnecessary 
operations, improves system efficiency and performance.

Best Regards
Ye

Re: [PATCH] vhost_net: Use fdget() and fdput()

[Michael S. Tsirkin]

On Fri, May 05, 2023 at 04:41:55PM +0800, ye xingchen wrote:
> >>
> >> From: Ye Xingchen <ye.xingchen@zte.com.cn>
> >>
> >> convert the fget()/fput() uses to fdget()/fdput().
> >What's the advantages of this?
> >
> >Thanks
> >>
> >> Signed-off-by: Ye Xingchen <ye.xingchen@zte.com.cn>
> >> ---
> >>  drivers/vhost/net.c | 10 +++++-----
> >>  1 file changed, 5 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> >> index ae2273196b0c..5b3fe4805182 100644
> >> --- a/drivers/vhost/net.c
> >> +++ b/drivers/vhost/net.c
> >> @@ -1466,17 +1466,17 @@ static struct ptr_ring *get_tap_ptr_ring(struct file *file)
> >>
> >>  static struct socket *get_tap_socket(int fd)
> >>  {
> >> -       struct file *file = fget(fd);
> >> +       struct fd f = fdget(fd);
> >>         struct socket *sock;
> >>
> >> -       if (!file)
> >> +       if (!f.file)
> >>                 return ERR_PTR(-EBADF);
> >> -       sock = tun_get_socket(file);
> >> +       sock = tun_get_socket(f.file);
> >>         if (!IS_ERR(sock))
> >>                 return sock;
> >> -       sock = tap_get_socket(file);
> >> +       sock = tap_get_socket(f.file);
> >>         if (IS_ERR(sock))
> >> -               fput(file);
> >> +               fdput(f);
> >>         return sock;
> >>  }
> >>
> >> --
> >> 2.25.1
> >>
> fdget requires an integer type file descriptor as its parameter, 
> and fget requires a pointer to the file structure as its parameter.

In which kernel?

include/linux/file.h:extern struct file *fget(unsigned int fd);


> By using the fdget function, the socket object, can be quickly 
> obtained from the process's file descriptor table without 
> the need to obtain the file descriptor first before passing it 
> as a parameter to the fget function. This reduces unnecessary 
> operations, improves system efficiency and performance.
> 
> Best Regards
> Ye

Re: [PATCH] vhost_net: Use fdget() and fdput()

[Al Viro]

On Fri, May 05, 2023 at 02:24:04PM +0800, ye.xingchen@zte.com.cn wrote:
> From: Ye Xingchen <ye.xingchen@zte.com.cn>
> 
> convert the fget()/fput() uses to fdget()/fdput().
> 
> Signed-off-by: Ye Xingchen <ye.xingchen@zte.com.cn>
> ---
>  drivers/vhost/net.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index ae2273196b0c..5b3fe4805182 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -1466,17 +1466,17 @@ static struct ptr_ring *get_tap_ptr_ring(struct file *file)
> 
>  static struct socket *get_tap_socket(int fd)
>  {
> -	struct file *file = fget(fd);
> +	struct fd f = fdget(fd);
>  	struct socket *sock;
> 
> -	if (!file)
> +	if (!f.file)
>  		return ERR_PTR(-EBADF);
> -	sock = tun_get_socket(file);
> +	sock = tun_get_socket(f.file);
>  	if (!IS_ERR(sock))
>  		return sock;
> -	sock = tap_get_socket(file);
> +	sock = tap_get_socket(f.file);
>  	if (IS_ERR(sock))
> -		fput(file);
> +		fdput(f);
>  	return sock;

NAK.  For the same reason why the sockfd_lookup() counterpart of that
patch is broken.  After your change there's no way for the caller
to tell whether we have bumped the refcount of file in question;
this can't possibly work.