From: Benno Lossin <benno.lossin@proton.me>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
"Miguel Ojeda" <ojeda@kernel.org>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Martin Rodriguez Reboredo" <yakoyoku@gmail.com>
Subject: Re: [PATCH v2] rust: alloc: Add realloc and alloc_zeroed to the GlobalAlloc impl
Date: Wed, 28 Jun 2023 10:07:18 +0000 [thread overview]
Message-ID: <ffYDfWJfSkQZnT-rW-AJ2S8KyMvWqSzuqHVEFiMEJAz0EzRbuwllUKKOV-evQpo6XA8aoeCpuF6Wjh5cLRJQyz1CyO9LeT0olkZhcH5y5P4=@proton.me> (raw)
In-Reply-To: <20230625232528.89306-1-boqun.feng@gmail.com>
On 26.06.23 01:25, Boqun Feng wrote:
> While there are default impls for these methods, using the respective C
> api's is faster. Currently neither the existing nor these new
> GlobalAlloc method implementations are actually called. Instead the
> __rust_* function defined below the GlobalAlloc impl are used. With
> rustc 1.71 these functions will be gone and all allocation calls will go
> through the GlobalAlloc implementation.
>
> Link: https://github.com/Rust-for-Linux/linux/issues/68
> Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
> [boqun: add size adjustment for alignment requirement]
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> ---
> Miguel, I fold my diff into Björn's original patch and make a v2, it
> relies on the other patch:
>
> https://lore.kernel.org/rust-for-linux/6e61f06f-2411-0bcb-926b-0a6927096f20@gmail.com/
>
> So this v2 (if all goes well) is targeted for v6.6, JFYI.
>
> v1 -> v2:
>
> * Add size adjustment for align requirement.
>
> rust/kernel/allocator.rs | 59 ++++++++++++++++++++++++++++++++++++----
> 1 file changed, 54 insertions(+), 5 deletions(-)
>
> diff --git a/rust/kernel/allocator.rs b/rust/kernel/allocator.rs
> index 66575cf87ce2..af723c2924dc 100644
> --- a/rust/kernel/allocator.rs
> +++ b/rust/kernel/allocator.rs
> @@ -9,8 +9,17 @@
>
> struct KernelAllocator;
>
> -unsafe impl GlobalAlloc for KernelAllocator {
> - unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
> +impl KernelAllocator {
> + /// # Safety
> + ///
> + /// * `ptr` can be either null or a pointer which has been allocated by this allocator.
> + /// * `layout` must have a non-zero size.
> + unsafe fn krealloc_with_flags(
> + &self,
> + ptr: *mut u8,
> + layout: Layout,
> + flags: bindings::gfp_t,
> + ) -> *mut u8 {
> // Customized layouts from `Layout::from_size_align()` can have size < align, so pads first.
> let layout = layout.pad_to_align();
>
> @@ -26,9 +35,22 @@ unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
> size = size.next_power_of_two();
> }
>
> - // `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(), size, bindings::GFP_KERNEL) as *mut u8 }
> + // SAFETY:
> + //
> + // * `ptr` is either null or a pointer returned from a previous k{re}alloc() by the function
> + // safety requirement.
> + //
> + // * `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero
> + // according to the function safety requirement) or a result from `next_power_of_two()`.
> + unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags) as *mut u8 }
> + }
> +}
> +
> +unsafe impl GlobalAlloc for KernelAllocator {
> + unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
> + // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
> + // requirement.
> + unsafe { self.krealloc_with_flags(ptr::null_mut(), layout, bindings::GFP_KERNEL) }
> }
>
> unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
> @@ -36,6 +58,33 @@ unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
> bindings::kfree(ptr as *const core::ffi::c_void);
> }
> }
> +
> + unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
> + // SAFETY:
> + // * `new_size` when rounded up to the nearest multiple of `layout.align()`, will not
> + // overflow `isize` by the function safety requirement.
> + // * `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).
> + let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
> +
> + // SAFETY:
> + // * `ptr` is either null or a pointer allocated by this allocator by function safety
> + // requirement.
> + // * the size of `layout` is not zero because `new_size` is not zero by function safety
> + // requirement.
> + unsafe { self.krealloc_with_flags(ptr, layout, bindings::GFP_KERNEL) }
> + }
> +
> + unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
> + // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
> + // requirement.
> + unsafe {
> + self.krealloc_with_flags(
> + ptr::null_mut(),
> + layout,
> + bindings::GFP_KERNEL | bindings::__GFP_ZERO,
> + )
> + }
> + }
> }
>
> #[global_allocator]
> --
> 2.39.2
>
next prev parent reply other threads:[~2023-06-28 10:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-25 23:25 [PATCH v2] rust: alloc: Add realloc and alloc_zeroed to the GlobalAlloc impl Boqun Feng
2023-06-26 3:34 ` Martin Rodriguez Reboredo
2023-06-26 9:40 ` Miguel Ojeda
2023-06-26 13:11 ` Martin Rodriguez Reboredo
2023-06-28 10:07 ` Benno Lossin [this message]
2023-06-28 16:43 ` Gary Guo
2023-07-29 14:01 ` Miguel Ojeda
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='ffYDfWJfSkQZnT-rW-AJ2S8KyMvWqSzuqHVEFiMEJAz0EzRbuwllUKKOV-evQpo6XA8aoeCpuF6Wjh5cLRJQyz1CyO9LeT0olkZhcH5y5P4=@proton.me' \
--to=benno.lossin@proton.me \
--cc=alex.gaynor@gmail.com \
--cc=bjorn3_gh@protonmail.com \
--cc=boqun.feng@gmail.com \
--cc=gary@garyguo.net \
--cc=linux-kernel@vger.kernel.org \
--cc=ojeda@kernel.org \
--cc=rust-for-linux@vger.kernel.org \
--cc=wedsonaf@gmail.com \
--cc=yakoyoku@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).