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=-1.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 C1009C433B4 for ; Thu, 13 May 2021 13:09:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C88261435 for ; Thu, 13 May 2021 13:09:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233842AbhEMNKL (ORCPT ); Thu, 13 May 2021 09:10:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230498AbhEMNKE (ORCPT ); Thu, 13 May 2021 09:10:04 -0400 Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60D88C061574 for ; Thu, 13 May 2021 06:08:54 -0700 (PDT) Received: by mail-pf1-x42a.google.com with SMTP id v191so21663989pfc.8 for ; Thu, 13 May 2021 06:08:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=gXNGtSr5Jfwp0sWTm9YEqRolUceYdaH5fX4XDPsA5Wo=; b=IEah8HvzvcEfL+hYEKAPPzkpt1lA/Enb+VxQKD8zSURITes1ef/i/y8nUuSsZ+q/yO M4L2uj2v3/0H9O7xwyk8SE6DJ9Q+Qi2hKTB35/m+ctU8KGPKUOupZKcivs1MwV8LA498 iokoEyVwXMoeT5Wj6r1akF8KQ6Vq19jqw7X7fWfzmE6ZLUXExk4rZx50apD5CKNxk1AC ZxQisNERvhjLrItOeOeXqtp4bY36SgZcSiR7GPVbL7pef3dtGukxCDRkXqfGknQUeGyI +tdV5iY0yPEfjvWOeJ7agFBQ8N1yP0IWRTVdeShE7ePZ60JYMXfR1Q9gGmD5DWrvMy6a IYcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=gXNGtSr5Jfwp0sWTm9YEqRolUceYdaH5fX4XDPsA5Wo=; b=iiIj6aK5uQgZDa0R6AeqTFQn+TjFjWew146bbIPDRp65pYjtGNgZwMaywbuNyYCh4N VVsV8E1+m/l9hqJ3WpCT1ZUp4naPhN9QeKiMYC71sJS8C3AdnFmTVd7klKngZwFTPP/j OiKZfqweOxUrTlTCKZxdB5gRsSIKZ5mn0QsF/fF8hriR9FmrLbH7jgN6LyrO+tRfW0YC MBwJUzukieequ0E4COnE0CJoekVpIJoGH7jXAm4HL0W8rld+A6l8Zy173JbauDpiBnkB oXRUSLDh5GzOpFLPy68ywBBa40yl+APNlq8aRgjxFx32gAoqHczKyuQNIYyvM7+wT657 yazg== X-Gm-Message-State: AOAM533+WpbZnOgAlyR/ij6koo7HkfbfgFfYNBotvJvBPb4wVyNSn2JH NzU2MnMmNNHOnbRk8UBcGsI= X-Google-Smtp-Source: ABdhPJyGxU2t9N4d1gexGsfQJoEiMS20c+Z6tN85lIBMVtzxpNBn92piE0I/17OqF1NO1aWquPU5Dg== X-Received: by 2002:a05:6a00:b46:b029:2d3:3504:88d9 with SMTP id p6-20020a056a000b46b02902d3350488d9mr839174pfo.39.1620911333958; Thu, 13 May 2021 06:08:53 -0700 (PDT) Received: from hyeyoo ([121.135.181.35]) by smtp.gmail.com with ESMTPSA id w14sm2164690pff.94.2021.05.13.06.08.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 May 2021 06:08:53 -0700 (PDT) Date: Thu, 13 May 2021 22:08:48 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Marco Elver Cc: Vlastimil Babka , Andrew Morton , Joonsoo Kim , David Rientjes , Pekka Enberg , Christoph Lameter , Linux Memory Management List , LKML Subject: Re: [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time Message-ID: <20210513130848.GA778609@hyeyoo> References: <20210511173448.GA54466@hyeyoo> <20210512195227.245000695c9014242e9a00e5@linux-foundation.org> <20210513031220.GA133011@hyeyoo> <20210512204024.401ff3de38649d7d0f5a45e8@linux-foundation.org> <20210513062809.GA319973@hyeyoo> <20210513120339.GA772931@hyeyoo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 13, 2021 at 02:29:13PM +0200, Marco Elver wrote: > This doesn't solve the problem. We want the compiler to complain > whenever kmalloc_index() is used with non-constant in normal code. But > it should be possible to use it in allocator tests regardless of size. > Either that or export kmalloc_slab(), but I think that's worse. I'll > send my patch with an updated comment. to explain in more detail, in include/linux/slab.h: static __always_inline void *kmalloc(size_t size, gfp_t flags) { if (__builtin_constant_p(size)) { #ifndef CONFIG_SLOB unsigned int index; #endif if (size > KMALLOC_MAX_CACHE_SIZE) return kmalloc_large(size, flags); #ifndef CONFIG_SLOB index = kmalloc_index(size); it checks if size is bigger than KMALLOC_MAX_CACHE_SIZE. so kmalloc_index works safely because the size was already checked. and definition of KMALLOC_MAX_CACHE_SIZE is in include/linux/slab.h: #ifdef CONFIG_SLAB #define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \ (MAX_ORDER + PAGE_SHIFT - 1) : 25) #define KMALLOC_SHIFT_MAX KMALLOC_SHIFT_HIGH #ifndef KMALLOC_SHIFT_LOW #define KMALLOC_SHIFT_LOW 5 #endif #endif #ifdef CONFIG_SLUB #define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1) #define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1) #ifndef KMALLOC_SHIFT_LOW #define KMALLOC_SHIFT_LOW 3 #endif #endif #ifdef CONFIG_SLOB #define KMALLOC_SHIFT_HIGH PAGE_SHIFT #define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1) #ifndef KMALLOC_SHIFT_LOW #define KMALLOC_SHIFT_LOW 3 #endif #endif so if kmalloc_index is called from another place other than kmalloc, it's not safe to assume that the supported size is 32MB. Thanks, Hyeonggon