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Date:   Mon, 14 Feb 2022 14:27:03 +0900
From:   Sergey Senozhatsky <senozhatsky@chromium.org>
To:     Miguel Ojeda <ojeda@kernel.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        Boqun Feng <boqun.feng@gmail.com>,
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        =?iso-8859-1?B?TOlv?= Lanteri Thauvin 
        <leseulartichaut@gmail.com>, Niklas Mohrin <dev@niklasmohrin.de>,
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        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        John Ogness <john.ogness@linutronix.de>
Subject: Re: [PATCH v4 10/20] rust: add `kernel` crate
Message-ID: <YgnoJ97y3I2hE8UJ@google.com>
References: <20220212130410.6901-1-ojeda@kernel.org>
 <20220212130410.6901-11-ojeda@kernel.org>
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On (22/02/12 14:03), Miguel Ojeda wrote:
[..]
> +unsafe impl GlobalAlloc for KernelAllocator {
> +    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
> +        // `krealloc()` is used instead of `kmalloc()` because the latter is
> +        // an inline function and cannot be bound to as a result.
> +        unsafe { bindings::krealloc(ptr::null(), layout.size(), bindings::GFP_KERNEL) as *mut u8 }

[..]

> +impl<const ORDER: u32> Pages<ORDER> {
> +    /// Allocates a new set of contiguous pages.
> +    pub fn new() -> Result<Self> {
> +        // TODO: Consider whether we want to allow callers to specify flags.
> +        // SAFETY: This only allocates pages. We check that it succeeds in the next statement.
> +        let pages = unsafe {
> +            bindings::alloc_pages(
> +                bindings::GFP_KERNEL | bindings::__GFP_ZERO | bindings::__GFP_HIGHMEM,
> +                ORDER,
> +            )
> +        };

[..]

Is this flexible enough? Why not let user pass bindings::GFP_* bitmask,
just like what the underlying kernel API does.