From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E400C43603 for ; Fri, 20 Dec 2019 14:07:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5BA421D7D for ; Fri, 20 Dec 2019 14:07:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="feMhg1+K" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727414AbfLTOHK (ORCPT ); Fri, 20 Dec 2019 09:07:10 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48478 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727346AbfLTOHK (ORCPT ); Fri, 20 Dec 2019 09:07:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=srmu36watHtwo/Ix7kyaxDlauHh4Ta8GCTLUGNooItA=; b=feMhg1+KIpswvyXGH+AssiHvr TU7whlsxtBck2xgW+ykcgGnsKVSZBc1MP0fIcVlr7g3iv7wsqJ9lVyX8seHxdNAOvW79D9pfGUtY+ lTH0n2EVymEVir4WhI4wQZbBZW3EXkNeOmUQkkRAkAs2bOVDefmUOmngEKC5SRHf6gLQzCqAVxUaW RfoARvSVLDhp9uysm0V5RJ8m5r4YJnQtanGk+psNH1XuZOcI5er6JDZnUfIA892XgP+9jz8OcXIUg IY/vK9ILRIvtvxQx/LHa7YPbiSZg3v0N/NW/aUY4o2q/RF1zSN7xqqdO21Ssew1R77G6qLAfUvKAW 4iqRUQK8Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iiIvh-00013n-Ll; Fri, 20 Dec 2019 14:06:57 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 31F7130073C; Fri, 20 Dec 2019 15:05:31 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 23A21203A8993; Fri, 20 Dec 2019 15:06:55 +0100 (CET) Date: Fri, 20 Dec 2019 15:06:55 +0100 From: Peter Zijlstra To: Marc Gonzalez Cc: Greg Kroah-Hartman , Rafael Wysocki , LKML , Linux ARM , Robin Murphy , Dmitry Torokhov , Alexey Brodkin , Will Deacon , Russell King , Bjorn Andersson , Tejun Heo , Mark Brown Subject: Re: [RFC PATCH v1] devres: align devres.data strictly only for devm_kmalloc() Message-ID: <20191220140655.GN2827@hirez.programming.kicks-ass.net> References: <74ae22cd-08c1-d846-3e1d-cbc38db87442@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 20, 2019 at 11:19:27AM +0100, Marc Gonzalez wrote: > Would anyone else have any suggestions, comments, insights, recommendations, > improvements, guidance, or wisdom? :-) Flip devres upside down! **WARNING, wear protective glasses when reading the below** struct devres { struct devres_node node; void *data; }; /* * We place struct devres at the tail of the memory allocation * such that data retains the ARCH_KMALLOC_MINALIGN alignment. * struct devres itself is just 4 pointers and should therefore * only require trivial alignment. */ static inline struct devres *data2devres(void *data) { return (struct devres *)(data + ksize(data) - sizeof(struct devres)); } void *alloc_dr(...) { struct devres *dr; void *data; data = kmalloc(size + sizeof(struct devres), GFP_KERNEL); dr = data2devres(data); WARN_ON((unsigned long)dr & __alignof(*dr)-1); INIT_LIST_HEAD(&dr->node.entry); dr->node.release = release; dr->data = data; return dr; } void devres_free(void *data) { if (data) { struct devres *dr = data2devres(data); BUG_ON(!list_empty(dr->node.entry)); kfree(data); } } static int release_nodes(...) { ... list_for_each_entry_safe_reverse(dr, ...) { ... kfree(dr->data); } }