Re: [PATCH] rust: file: use to_result for error handling

[Elle Rhumsaa <elle@weathered-steel.dev>]

On Thu, Aug 21, 2025 at 12:10:01PM +0300, Onur Özkan wrote:
> Simplifies error handling by replacing the manual check
> of the return value with the `to_result` helper.
> 
> Signed-off-by: Onur Özkan <work@onurozkan.dev>
> ---
>  rust/kernel/fs/file.rs | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
> index 35fd5db35c46..924f01bd64c2 100644
> --- a/rust/kernel/fs/file.rs
> +++ b/rust/kernel/fs/file.rs
> @@ -10,7 +10,7 @@
>  use crate::{
>      bindings,
>      cred::Credential,
> -    error::{code::*, Error, Result},
> +    error::{code::*, to_result, Error, Result},
>      types::{ARef, AlwaysRefCounted, NotThreadSafe, Opaque},
>  };
>  use core::ptr;
> @@ -398,9 +398,8 @@ impl FileDescriptorReservation {
>      pub fn get_unused_fd_flags(flags: u32) -> Result<Self> {
>          // SAFETY: FFI call, there are no safety requirements on `flags`.
>          let fd: i32 = unsafe { bindings::get_unused_fd_flags(flags) };
> -        if fd < 0 {
> -            return Err(Error::from_errno(fd));
> -        }
> +        to_result(fd)?;
> +
>          Ok(Self {
>              fd: fd as u32,
>              _not_send: NotThreadSafe,

Can be further simplified with:

```rust
to_result(fd).map(|_| Self { fd: fd as u32, // rest... })
```

> --
> 2.50.0

Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>