From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1363832144B; Tue, 26 Aug 2025 11:32:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756207959; cv=none; b=B918ZgBWyQH/kxsDCAOVjA+/EVztJerfCVRWAY/4DA49RMYdvBLAziA6BfyLpYV2rKMJt1bd5GSIqIgJ9fJ4kdch6hmGFxkJhTdpcZ9HOENa1E3AYE8Ci63cc6un0qdfTs8OFcUyDYOZhB2JSnicw0jn9pwt7XwLk905rlJRXwU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756207959; c=relaxed/simple; bh=hINt2RYz1hVIanxuI5wet5r9iqwDzvv59AaIMHlnR54=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=K+pI64PXKp5kbWfEETD9BEr7htHXoTf64q22dAJJqYtWlMtVW4J1dmvU4GoeDjUzAkElBC0IG/ivwXAlUy6cfHyRdosPQ0j7YebpzHTUGd1y9xf1yrePcFbxX3WgDK93Nc/VOSOM2P72kLPq0pbezxzg92hMKGFDkbU01oHPcHw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=p0zWxKpX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="p0zWxKpX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94D2DC4CEF4; Tue, 26 Aug 2025 11:32:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756207958; bh=hINt2RYz1hVIanxuI5wet5r9iqwDzvv59AaIMHlnR54=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p0zWxKpX9W+/zDx305vggs3SfsCNXM+ScT1PLBbB5/ZwjTqfuX8VOSpdZ+nT8CmCZ 3U1JS5b860DEg4VnkEPCTkkDHrIwWAHVzP8UObxG0sf5BnUykRBxl+C4W9RUz7TDbF pagzaTzpQzpy4zylcHzGykEAp/5IAmvnB9xhVT+o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alice Ryhl , Danilo Krummrich , Sasha Levin Subject: [PATCH 6.16 352/457] rust: alloc: replace aligned_size() with Kmalloc::aligned_layout() Date: Tue, 26 Aug 2025 13:10:36 +0200 Message-ID: <20250826110946.020935439@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110937.289866482@linuxfoundation.org> References: <20250826110937.289866482@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Danilo Krummrich [ Upstream commit fde578c86281f27b182680c7642836a0dbbd0be7 ] aligned_size() dates back to when Rust did support kmalloc() only, but is now used in ReallocFunc::call() and hence for all allocators. However, the additional padding applied by aligned_size() is only required by the kmalloc() allocator backend. Hence, replace aligned_size() with Kmalloc::aligned_layout() and use it for the affected allocators, i.e. kmalloc() and kvmalloc(), only. While at it, make Kmalloc::aligned_layout() public, such that Rust abstractions, which have to call subsystem specific kmalloc() based allocation primitives directly, can make use of it. Fixes: 8a799831fc63 ("rust: alloc: implement `ReallocFunc`") Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250731154919.4132-2-dakr@kernel.org [ Remove `const` from Kmalloc::aligned_layout(). - Danilo ] Signed-off-by: Danilo Krummrich Signed-off-by: Sasha Levin --- rust/kernel/alloc/allocator.rs | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index aa2dfa9dca4c..2692cf90c948 100644 --- a/rust/kernel/alloc/allocator.rs +++ b/rust/kernel/alloc/allocator.rs @@ -43,17 +43,6 @@ pub struct Vmalloc; /// For more details see [self]. pub struct KVmalloc; -/// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. -fn aligned_size(new_layout: Layout) -> usize { - // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. - let layout = new_layout.pad_to_align(); - - // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()` - // which together with the slab guarantees means the `krealloc` will return a properly aligned - // object (see comments in `kmalloc()` for more information). - layout.size() -} - /// # Invariants /// /// One of the following: `krealloc`, `vrealloc`, `kvrealloc`. @@ -88,7 +77,7 @@ impl ReallocFunc { old_layout: Layout, flags: Flags, ) -> Result, AllocError> { - let size = aligned_size(layout); + let size = layout.size(); let ptr = match ptr { Some(ptr) => { if old_layout.size() == 0 { @@ -123,6 +112,17 @@ impl ReallocFunc { } } +impl Kmalloc { + /// Returns a [`Layout`] that makes [`Kmalloc`] fulfill the requested size and alignment of + /// `layout`. + pub fn aligned_layout(layout: Layout) -> Layout { + // Note that `layout.size()` (after padding) is guaranteed to be a multiple of + // `layout.align()` which together with the slab guarantees means that `Kmalloc` will return + // a properly aligned object (see comments in `kmalloc()` for more information). + layout.pad_to_align() + } +} + // SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that // - memory remains valid until it is explicitly freed, // - passing a pointer to a valid memory allocation is OK, @@ -135,6 +135,8 @@ unsafe impl Allocator for Kmalloc { old_layout: Layout, flags: Flags, ) -> Result, AllocError> { + let layout = Kmalloc::aligned_layout(layout); + // SAFETY: `ReallocFunc::call` has the same safety requirements as `Allocator::realloc`. unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags) } } @@ -176,6 +178,10 @@ unsafe impl Allocator for KVmalloc { old_layout: Layout, flags: Flags, ) -> Result, AllocError> { + // `KVmalloc` may use the `Kmalloc` backend, hence we have to enforce a `Kmalloc` + // compatible layout. + let layout = Kmalloc::aligned_layout(layout); + // TODO: Support alignments larger than PAGE_SIZE. if layout.align() > bindings::PAGE_SIZE { pr_warn!("KVmalloc does not support alignments larger than PAGE_SIZE yet.\n"); -- 2.50.1