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Howlett" , Andrew Morton , Danilo Krummrich , Matthew Wilcox , Tamir Duberstein , Andreas Hindborg , Miguel Ojeda Cc: Boqun Feng , Gary Guo , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Benno Lossin , Trevor Gross , linux-mm@kvack.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Alice Ryhl Content-Type: text/plain; charset="utf-8" X-Rspamd-Queue-Id: A505AA000A X-Stat-Signature: geyqtf959iwkc5r5no9gbhmf8s7xgbju X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1754915527-947060 X-HE-Meta: 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 h/7fw7dv 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The kernel's allocators sometimes provide a higher alignment than the end-user requested, so add a new constant on the Allocator trait to let the allocator specify what its minimum guaranteed alignment is. This allows the ForeignOwnable trait to provide a more accurate value of FOREIGN_ALIGN when using a pointer type such as Box, which will be useful with certain collections such as XArray that store its own data in the low bits of pointers. Reviewed-by: Benno Lossin Signed-off-by: Alice Ryhl --- rust/kernel/alloc.rs | 8 ++++++++ rust/kernel/alloc/allocator.rs | 8 ++++++++ 2 files changed, 16 insertions(+) diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs index a2c49e5494d334bfde67328464dafcdb31052947..907301334d8c111eb26719ad89700a289e03f037 100644 --- a/rust/kernel/alloc.rs +++ b/rust/kernel/alloc.rs @@ -137,6 +137,14 @@ pub mod flags { /// - Implementers must ensure that all trait functions abide by the guarantees documented in the /// `# Guarantees` sections. pub unsafe trait Allocator { + /// The minimum alignment satisfied by all allocations from this allocator. + /// + /// # Guarantees + /// + /// Any pointer allocated by this allocator is guaranteed to be aligned to `MIN_ALIGN` even if + /// the requested layout has a smaller alignment. + const MIN_ALIGN: usize; + /// Allocate memory based on `layout` and `flags`. /// /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index aa2dfa9dca4c309e5a9eafc7da6a8a9bd7b54b11..25fc9f9ae3b4e471a08d77130b374bd1397f7384 100644 --- a/rust/kernel/alloc/allocator.rs +++ b/rust/kernel/alloc/allocator.rs @@ -17,6 +17,8 @@ use crate::bindings; use crate::pr_warn; +const ARCH_KMALLOC_MINALIGN: usize = bindings::ARCH_KMALLOC_MINALIGN as usize; + /// The contiguous kernel allocator. /// /// `Kmalloc` is typically used for physically contiguous allocations up to page size, but also @@ -128,6 +130,8 @@ unsafe fn call( // - passing a pointer to a valid memory allocation is OK, // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same. unsafe impl Allocator for Kmalloc { + const MIN_ALIGN: usize = ARCH_KMALLOC_MINALIGN; + #[inline] unsafe fn realloc( ptr: Option>, @@ -145,6 +149,8 @@ unsafe fn realloc( // - passing a pointer to a valid memory allocation is OK, // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same. unsafe impl Allocator for Vmalloc { + const MIN_ALIGN: usize = kernel::page::PAGE_SIZE; + #[inline] unsafe fn realloc( ptr: Option>, @@ -169,6 +175,8 @@ unsafe fn realloc( // - passing a pointer to a valid memory allocation is OK, // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same. unsafe impl Allocator for KVmalloc { + const MIN_ALIGN: usize = ARCH_KMALLOC_MINALIGN; + #[inline] unsafe fn realloc( ptr: Option>, -- 2.50.1.703.g449372360f-goog