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

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Date:   Thu, 11 Aug 2022 17:02:42 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Zhang chunchao <chunchao@...china.com>
Cc:     axboe@...nel.dk, 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 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.

Thanks,
Stefano