2023-05-05 06:37:52

by ye.xingchen

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

From: Ye Xingchen <[email protected]>

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

Signed-off-by: Ye Xingchen <[email protected]>
---
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

2023-05-05 07:02:12

by Jason Wang

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

On Fri, May 5, 2023 at 2:24 PM <[email protected]> wrote:
>
> From: Ye Xingchen <[email protected]>
>
> convert the fget()/fput() uses to fdget()/fdput().

What's the advantages of this?

Thanks

>
> Signed-off-by: Ye Xingchen <[email protected]>
> ---
> 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
>

2023-05-05 08:56:49

by ye xingchen

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

>>
>> From: Ye Xingchen <[email protected]>
>>
>> convert the fget()/fput() uses to fdget()/fdput().
>What's the advantages of this?
>
>Thanks
>>
>> Signed-off-by: Ye Xingchen <[email protected]>
>> ---
>> 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

2023-05-05 15:12:07

by Michael S. Tsirkin

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

On Fri, May 05, 2023 at 04:41:55PM +0800, ye xingchen wrote:
> >>
> >> From: Ye Xingchen <[email protected]>
> >>
> >> convert the fget()/fput() uses to fdget()/fdput().
> >What's the advantages of this?
> >
> >Thanks
> >>
> >> Signed-off-by: Ye Xingchen <[email protected]>
> >> ---
> >> 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

2023-05-11 05:43:52

by Al Viro

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

On Fri, May 05, 2023 at 02:24:04PM +0800, [email protected] wrote:
> From: Ye Xingchen <[email protected]>
>
> convert the fget()/fput() uses to fdget()/fdput().
>
> Signed-off-by: Ye Xingchen <[email protected]>
> ---
> 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.