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From:   ye xingchen <yexingchen116@gmail.com>
To:     jasowang@redhat.com
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com,
        netdev@vger.kernel.org, virtualization@lists.linux-foundation.org,
        ye.xingchen@zte.com.cn
Subject: Re: [PATCH] vhost_net: Use fdget() and fdput()
Date:   Fri,  5 May 2023 16:41:55 +0800
Message-Id: <20230505084155.63839-1-ye.xingchen@zte.com.cn>
In-Reply-To: <CACGkMEsmf3PgxmhgRCsPZe7fRWHDXQ=TtYu5Tgx1=_Ymyvi-pA@mail.gmail.com>
References: <CACGkMEsmf3PgxmhgRCsPZe7fRWHDXQ=TtYu5Tgx1=_Ymyvi-pA@mail.gmail.com>
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>>
>> 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