linux-kernel - Re: [PATCH v4 08/15] rust: init/sync: add `InPlaceInit` trait to pin-initialize smart pointers

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Date:   Sat, 01 Apr 2023 07:44:32 +0000
From:   Benno Lossin <y86-dev@...tonmail.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Alice Ryhl <alice@...l.io>, rust-for-linux@...r.kernel.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        Andreas Hindborg <a.hindborg@...sung.com>,
        Alice Ryhl <aliceryhl@...gle.com>
Subject: Re: [PATCH v4 08/15] rust: init/sync: add `InPlaceInit` trait to pin-initialize smart pointers

On 01.04.23 00:42, Boqun Feng wrote:
> On Fri, Mar 31, 2023 at 09:53:25PM +0000, y86-dev@...tonmail.com wrote:
> [...]
>> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
>> index eee7008e5e3e..24dc96603090 100644
>> --- a/rust/kernel/sync/arc.rs
>> +++ b/rust/kernel/sync/arc.rs
>> @@ -17,6 +17,7 @@
>>
>>   use crate::{
>>       bindings,
>> +    init::{InPlaceInit, Init, PinInit},
>>       types::{ForeignOwnable, Opaque},
>>   };
>>   use alloc::boxed::Box;
>> @@ -163,6 +164,28 @@ impl<T> Arc<T> {
>>           // `Arc` object.
>>           Ok(unsafe { Self::from_inner(Box::leak(inner).into()) })
>>       }
>> +
>> +    /// Use the given initializer to in-place initialize a `T`.
>> +    ///
>> +    /// If `T: !Unpin` it will not be able to move afterwards.
>> +    #[inline]
>> +    pub fn pin_init<E>(init: impl PinInit<T, E>) -> Result<Self>
>
> `Result` became `core::result::Result` after patch #3, so you will need
> to refer to `crate::error::Result` here. Alternatively you can change
> patch #3 to use the full path i.e. `core::result::Result`.
>
>> +    where
>> +        Error: From<E>,
>
> In my env, looks like the compiler doesn't know which `Error` it
> is after removing use of `crate::error::Result` in patch #3, you
> probably need to deal with this as well.
>
> Regards,
> Boqun
>
>> +    {
>> +        UniqueArc::pin_init(init).map(|u| u.into())
>> +    }
>> +
>> +    /// Use the given initializer to in-place initialize a `T`.
>> +    ///
>> +    /// This is equivalent to [`pin_init`], since an [`Arc`] is always pinned.
>> +    #[inline]
>> +    pub fn init<E>(init: impl Init<T, E>) -> Result<Self>
>> +    where
>> +        Error: From<E>,
>> +    {
>> +        UniqueArc::init(init).map(|u| u.into())
>> +    }
>>   }
>>
>>   impl<T: ?Sized> Arc<T> {
>> --
>> 2.39.2
>>
>>

Sorry, forgot to compile check that.
--
Cheers,
Benno