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b=eKDJA8ZsepSStAinu05nkqg9IxmoQzqO19goRvSM9tAkpt6BivEWMEcIHZc7TSd3Y V0PTL13PuYuNRxYy6eV2HMJmXV/ygh0lB9aGOKyT4iZhIBA+m7nHJHbJa3aM7LSWjK ZKMJLJmA7zZ7H4QisuM1oY5rgLzDIcM741TlsZDDBnte5RewhCDPAhCv3ouwdjP38k GRJkAmn1aVi/MFUpxjuIidFvQ9kw4M9bSTsq5rXFw+h7iYrDcDjYenUMqbxM2CYMw0 ghn2MRllwCSHH2d3DmV4lDgBn/iteg9XaZDhQ7K0FkoQeJzTLMv+hNre58R3IphviK 3i/8ItehQCiYA== Date: Thu, 26 Sep 2024 14:00:50 +0000 To: Danilo Krummrich From: Benno Lossin Cc: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, a.hindborg@samsung.com, aliceryhl@google.com, akpm@linux-foundation.org, daniel.almeida@collabora.com, faith.ekstrand@collabora.com, boris.brezillon@collabora.com, lina@asahilina.net, mcanal@igalia.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, airlied@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v7 04/26] rust: alloc: implement `Allocator` for `Kmalloc` Message-ID: In-Reply-To: References: <20240911225449.152928-1-dakr@kernel.org> <20240911225449.152928-5-dakr@kernel.org> <15f42ddd-b011-4136-b2e4-bc266fab25b6@proton.me> Feedback-ID: 71780778:user:proton X-Pm-Message-ID: a662ef8837cfaa33d2d32dd6e8dc52cc57197097 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 7CE7EA0012 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: tn18zqbecr4ku56au5xf3uoyjrobtwsa X-HE-Tag: 1727359257-761995 X-HE-Meta: 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 TVC3QTgV bnpEXXAKcOsBv3QlDDpHBuFjkhW2VQMrYKR46y/ukATE8w0/be06Ja5UbyDFdrZTIDY3mfkwHIdrEJy848f2zZw7mOZ3koQpLO7//D6O8I1v7lW52ZpiJGUyWbnHKzEFlRMVx2qcs8cDl1ZhX950K8Bo12D26CJA8gamwUvM6b20MFs8KJGO4nLx9O3ARkEDecmYAHw+W011ULb+YZS2rKPXowfASJEGutVWZsUM0OPDUmNjXkv/egdYEI6xaZQ/+ZDTJNGAu5JR0GPpnXWFGT6JGptIKvUOGsA1MJoyDnIAAmkfqNqecT8iMhhZI2dICwlIU6E95FbTia1MmYtHhCHwhgz3RdvA4KEbFlfkd1iehZOnR30OK6Cjnte/UCp9Xckn8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000496, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 26.09.24 15:24, Danilo Krummrich wrote: > On Thu, Sep 26, 2024 at 01:00:58PM +0000, Benno Lossin wrote: >> On 12.09.24 00:52, Danilo Krummrich wrote: >>> +/// # Invariants >>> +/// >>> +/// One of the following `krealloc`, `vrealloc`, `kvrealloc`. >>> +struct ReallocFunc( >>> + unsafe extern "C" fn(*const core::ffi::c_void, usize, u32) -> *mut= core::ffi::c_void, >>> +); >>> + >>> +impl ReallocFunc { >>> + // INVARIANT: `krealloc` satisfies the type invariants. >>> + const KREALLOC: Self =3D Self(bindings::krealloc); >>> + >>> + /// # Safety >>> + /// >>> + /// This method has the same safety requirements as [`Allocator::r= ealloc`]. >>> + /// >>> + /// # Guarantees >>> + /// >>> + /// This method has the same guarantees as `Allocator::realloc`. A= dditionally >>> + /// - it accepts any pointer to a valid memory allocation allocate= d by this function. >>> + /// - memory allocated by this function remains valid until it is = passed to this function. >>> + unsafe fn call( >>> + &self, >>> + ptr: Option>, >>> + layout: Layout, >>> + flags: Flags, >>> + ) -> Result, AllocError> { >>> + let size =3D aligned_size(layout); >>> + let ptr =3D match ptr { >>> + Some(ptr) =3D> ptr.as_ptr(), >>> + None =3D> ptr::null(), >>> + }; >>> + >>> + // SAFETY: >>> + // - `self.0` is one of `krealloc`, `vrealloc`, `kvrealloc` an= d thus only requires that >>> + // `ptr` is NULL or valid. >>> + // - `ptr` is either NULL or valid by the safety requirements = of this function. >>> + // >>> + // GUARANTEE: >>> + // - `self.0` is one of `krealloc`, `vrealloc`, `kvrealloc`. >>> + // - Those functions provide the guarantees of this function. >>> + let raw_ptr =3D unsafe { >>> + // If `size =3D=3D 0` and `ptr !=3D NULL` the memory behin= d the pointer is freed. >>> + self.0(ptr.cast(), size, flags.0).cast() >>> + }; >>> + >>> + let ptr =3D if size =3D=3D 0 { >>> + NonNull::dangling() >>> + } else { >>> + NonNull::new(raw_ptr).ok_or(AllocError)? >>> + }; >>> + >>> + Ok(NonNull::slice_from_raw_parts(ptr, size)) >>> + } >>> +} >> >> I remember asking you to split this into a different commit. I think you >> argued that it would be better to keep it in the same commit when >> bisecting. I don't think that applies in this case, are there any other >> disadvantages? >=20 > I don't really like the intermediate `#[expect(dead_code)]`, plus it's > additional work you didn't really give me a motivation for, i.e. you did = not > mention what would be the advantage. The advantage would be that it's easier to review (granted it probably is a bit late for that). I got confused a couple of times (but that's probably on me). > But sure, I will change it for the next version. Thanks --- Cheers, Benno