linux-kernel - Re: [PATCH v4 7/7] rust: alloc: add Vec::insert_within

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Message-ID: <2025042925-kindly-squash-fa6f@gregkh>
Date: Tue, 29 Apr 2025 17:30:06 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Danilo Krummrich <dakr@...nel.org>, Matthew Maurer <mmaurer@...gle.com>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/7] rust: alloc: add Vec::insert_within_capacity

On Tue, Apr 29, 2025 at 02:44:27PM +0000, Alice Ryhl wrote:
> This adds a variant of Vec::insert that does not allocate memory. This
> makes it safe to use this function while holding a spinlock. Rust Binder
> uses it for the range allocator fast path.
> 
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
>  rust/kernel/alloc/kvec.rs | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
> index 0682108951675cbee05faa130e5a9ce72fc343ba..998afdcde47bec94b2c9d990ba3afbb3488ea99e 100644
> --- a/rust/kernel/alloc/kvec.rs
> +++ b/rust/kernel/alloc/kvec.rs
> @@ -355,6 +355,45 @@ pub unsafe fn push_within_capacity_unchecked(&mut self, v: T) {
>          unsafe { self.inc_len(1) };
>      }
>  
> +    /// Inserts an element at the given index in the [`Vec`] instance.
> +    ///
> +    /// Fails if the vector does not have capacity for the new element. Panics if the index is out
> +    /// of bounds.

Why panic and why not just return an error instead?

thanks,

greg k-h