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

From: Jens Axboe
Date: Thu Aug 11 2022 - 11:49:49 EST


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@xxxxxxxxxxxx>
>> ---
>> 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