From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f48.google.com (mail-wm1-f48.google.com [209.85.128.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E786828C872 for ; Wed, 16 Jul 2025 09:46:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752659184; cv=none; b=Wq3pe7aDDDRdTORamfvnl4VnqZyNqyNNgE9SMNdfcWo0LOApsR/AOwvw3YX4zXcQpxSHW4qquqHl/XUzzuU2gmrOmEWDGHcOiu2lf8QUNirZfMmBqgoVhEc60/S3EHBNT261HxLak6hDpy5u4cDzY1b7hL6fMo9TNU38SrnLeIo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752659184; c=relaxed/simple; bh=sK9WdAzJkT35n2OrnV74SnqD1oF6VrhrbQmeYrx4i6g=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=ZXoJ484gxXSCxzTQ3iJROvzfmzOVQJwq551IYpilq64SQodXKEAjtaagILcLxE113z7INwe65Pa0HKw+ehB5/DZ98mkdQGO6IQtUMhcxeB3WIdrGKkw1L4GBv+Sjbu3wjoK+AMvjKYjxwsAyCbdmA2O60nAX0iFZ2mupZ1iAjgU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=jFdWCxZO; arc=none smtp.client-ip=209.85.128.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="jFdWCxZO" Received: by mail-wm1-f48.google.com with SMTP id 5b1f17b1804b1-45617887276so25882725e9.2 for ; Wed, 16 Jul 2025 02:46:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1752659181; x=1753263981; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=unJc0BdBQI7iWQUSRrhzhQU8c9VKJ16+VGuE1/wwC/M=; b=jFdWCxZO/PWYEvCk3nk0q2hbPkOGwrsJD/viZjcHSiSpS5vGSVGXap6Va+ugR7wRqH hqVtn+K8KecePgedmF7iCmSXVLG58zTrFNhCFTKrjls/6FRkrhFUe1uaCHz1iiqA4TgN G0bsAJTvtQ4yCh9WEYSo9k4WoU1TVZg5fn34n1QkCNizJDhP3RNz58Ez3wtkLGzRyaTY p5vpPbH8r02mgTbH1aL1yYH7e9/9/0TzLqwhncQrLxOLwiWbu2posmQ/swQsq96WvSuF tt9ftwVRsKPadpBoDiSQtruzsFVuU7RmTbSGd0qtFRflM1XVw5jWrv7hsVHjD566c2dd lhCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752659181; x=1753263981; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=unJc0BdBQI7iWQUSRrhzhQU8c9VKJ16+VGuE1/wwC/M=; b=L73DvoC/oRPgF2HrbqRal/tmRorPrk16Sw+pTtmCFTcCMjDeDmO/GrjUgHvVx5FkGS e5+/nKs2sZ53nx86IOAnjnxoTNLjmjrRZ1oACyj4i1ggFyqIriYIoJjRSDxicgXPN2d6 RQ5n2qmUQ8lMT88io7+wQpTEPpEz1rzLRxs67DLttN3yhb1j0OBe9TC/HYwapuPGbcba FXmIBwgfK5LOgpQpSNDHy4eA7jlcOwmiGyfNZAWkNk8QxTKDz0IEaLXRFPZ7qVTQb39v OL9pHAby9hIlJxt3/GisJiWMpOMi2hXNBUSt3vgyGBoClseMUW3cR0HMPDwGgGalMSbx 01bQ== X-Forwarded-Encrypted: i=1; AJvYcCXjypL2W7swzARwWh7Vy04mEYPAJ3pqsGHruV0I2KL0HpT9MYHRKXfrgTcz1ykrI7e2sDuHgnoEb7srkrI=@vger.kernel.org X-Gm-Message-State: AOJu0Yxjra3jUvbNCWJzfOqHmjCIWk2DUVsc0noZzqv4BPtNFTiV1Ebl TLXj1LXP6L3qnU4MsT4CsjSxi7sM+Zm61UbXuUp69Sjqu38+JDYglSTObccb/l/Ta4PzIgA1tD3 F5MQlMBi8Jv28XpUViDGXzL1h+HtDHG51r42t/lKC X-Gm-Gg: ASbGnctqPB2XWIAg4sGwbL/8+zKsRourG+pgLmyMmK8Itk21SAeEYB8j+aeD0MULaXq mkoxQznIJWr06tPEoK7bzmxTfjtCgNXRcIZBgHYfJ4U79UP+uxGKA7S73DwhT9uUCsX5c74rowO 11Tvuijipic/88QSwBkStuZjow+1CBKAD5/M9PPk/75+AJ/H6eWIOuvALboy+COMDndZCfvBfKP uinA32s X-Google-Smtp-Source: AGHT+IGJvynLQXA/LQk6fcdvOGBEcRDrc5pxDlC+y97uzcPtpCoY1GOnLHBKt5EXqBGMRmyPCzJQVsWFQZFmSoofD4Y= X-Received: by 2002:a05:600c:c174:b0:456:1752:2b44 with SMTP id 5b1f17b1804b1-4562e39126cmr18086275e9.23.1752659181173; Wed, 16 Jul 2025 02:46:21 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250715-align-min-allocator-v1-0-3e1b2a5516c0@google.com> <20250715-align-min-allocator-v1-2-3e1b2a5516c0@google.com> In-Reply-To: From: Alice Ryhl Date: Wed, 16 Jul 2025 11:46:08 +0200 X-Gm-Features: Ac12FXzX7ouyqpx1LVbRHdVZq8jMUt7yI_ccMl1Rky0bxaMou6U-Kfx8iWXzP3g Message-ID: Subject: Re: [PATCH 2/2] rust: alloc: take the allocator into account for FOREIGN_ALIGN To: Danilo Krummrich Cc: Lorenzo Stoakes , "Liam R. Howlett" , Andrew Morton , Matthew Wilcox , Tamir Duberstein , Andreas Hindborg , Miguel Ojeda , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, Jul 15, 2025 at 4:19=E2=80=AFPM Danilo Krummrich = wrote: > > On Tue Jul 15, 2025 at 3:46 PM CEST, Alice Ryhl wrote: > > diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs > > index bffe72f44cb33a265018e67d92d9f0abe82f8e22..fd3f1e0b9c3b3437fb50d8f= 1b28c92bc7cefd565 100644 > > --- a/rust/kernel/alloc/kbox.rs > > +++ b/rust/kernel/alloc/kbox.rs > > @@ -400,12 +400,19 @@ fn try_init(init: impl Init, flags: Flag= s) -> Result > > } > > > > // SAFETY: The pointer returned by `into_foreign` comes from a well al= igned > > -// pointer to `T`. > > +// pointer to `T` allocated by `A`. > > unsafe impl ForeignOwnable for Box > > where > > A: Allocator, > > { > > - const FOREIGN_ALIGN: usize =3D core::mem::align_of::(); > > + const FOREIGN_ALIGN: usize =3D { > > + let mut align =3D core::mem::align_of::(); > > + if align < A::MIN_ALIGN { > > + align =3D A::MIN_ALIGN; > > + } > > + align > > + }; > > Pretty unfortunate that core::cmp::max() can't be used from const context= . :( > > What do you think about > > const FOREIGN_ALIGN: usize =3D > if core::mem::align_of::() < A::MIN_ALIGN { > A::MIN_ALIGN > } else { > core::mem::align_of::() > }; > > instead? I think that reads a bit better. I don't mind doing that instead. Alice