linux-kernel - Re: [PATCH] Modify the return value ret to EOPNOTSUPP when initialized to reduce repeated assignment of errno

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Message-ID: <8f3d1bf5-48f6-411d-674e-1568e3841d75@kernel.dk>
Date:   Thu, 11 Aug 2022 09:41:38 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Stefano Garzarella <sgarzare@...hat.com>,
        Zhang chunchao <chunchao@...china.com>
Cc:     asml.silence@...il.com, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...china.com
Subject: Re: [PATCH] Modify the return value ret to EOPNOTSUPP when
 initialized to reduce repeated assignment of errno

On 8/11/22 9:02 AM, Stefano Garzarella wrote:
> On Thu, Aug 11, 2022 at 03:56:38PM +0800, Zhang chunchao wrote:
>> Remove unnecessary initialization assignments.
>>
>> Signed-off-by: Zhang chunchao <chunchao@...china.com>
>> ---
>> io_uring/io_uring.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
>> index b54218da075c..8c267af06401 100644
>> --- a/io_uring/io_uring.c
>> +++ b/io_uring/io_uring.c
>> @@ -3859,14 +3859,13 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
>>         void __user *, arg, unsigned int, nr_args)
>> {
>>     struct io_ring_ctx *ctx;
>> -    long ret = -EBADF;
>> +    long ret = -EOPNOTSUPP;
>>     struct fd f;
>>
>>     f = fdget(fd);
>>     if (!f.file)
>>         return -EBADF;
>>
>> -    ret = -EOPNOTSUPP;
>>     if (!io_is_uring_fops(f.file))
>>         goto out_fput;
>>
> 
> What about remove the initialization and assign it in the if branch?
> I find it a bit easier to read.
> 
> I mean something like this:
> 
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -3859,16 +3859,17 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
>                 void __user *, arg, unsigned int, nr_args)
>  {
>         struct io_ring_ctx *ctx;
> -       long ret = -EBADF;
> +       long ret;
>         struct fd f;
> 
>         f = fdget(fd);
>         if (!f.file)
>                 return -EBADF;
> 
> -       ret = -EOPNOTSUPP;
> -       if (!io_is_uring_fops(f.file))
> +       if (!io_is_uring_fops(f.file)) {
> +               ret = -EOPNOTSUPP;
>                 goto out_fput;
> +       }
> 
>         ctx = f.file->private_data;
> 
> 
> Otherwise remove the initialization, but leave the assignment as it is now.

Generally the kernel likes to do:

err = -EFOO;
if (something)
	goto err_out;

rather than put it inside the if clause. I guess the rationale is it
makes it harder to forget to init the error value. I don't feel too
strongly, I'm fine with your patch too. Can you send it as a real patch?

-- 
Jens Axboe