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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 B77ABC433ED for ; Mon, 10 May 2021 15:21:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9782361139 for ; Mon, 10 May 2021 15:21:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237433AbhEJPWQ (ORCPT ); Mon, 10 May 2021 11:22:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:56766 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234617AbhEJPVI (ORCPT ); Mon, 10 May 2021 11:21:08 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 56046AD5C; Mon, 10 May 2021 15:20:02 +0000 (UTC) Subject: Re: [PATCH v2] mm: kmalloc_index: make compiler break when size is not supported To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Matthew Wilcox , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210508221328.7338-1-42.hyeyoo@gmail.com> <20210510135857.GA3594@hyeyoo> <9d0ffe49-a2e2-6c81-377b-4c8d2147dff8@suse.cz> <20210510150230.GA74915@hyeyoo> From: Vlastimil Babka Message-ID: <90591d7e-41e4-9ae5-54ae-ded467c498cf@suse.cz> Date: Mon, 10 May 2021 17:19:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210510150230.GA74915@hyeyoo> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/10/21 5:02 PM, Hyeonggon Yoo wrote: > updated patch. let me know if something is wrong! > > > 0001-mm-kmalloc_index-make-compiler-break-when-size-is-no.patch > > From 8fe7ecdfb0f5bd5b08771512303d72f1c6447362 Mon Sep 17 00:00:00 2001 > From: Hyeonggon Yoo <42.hyeyoo@gmail.com> > Date: Mon, 10 May 2021 23:57:34 +0900 > Subject: [PATCH] mm: kmalloc_index: make compiler break when size is not > supported I'd rephrase the subject: mm, slub: change run-time assertion in kmalloc_index() to compile-time > currently when size is not supported by kmalloc_index, compiler will not > break. "... compiler will generate a run-time BUG() while a compile-time error is also possible, and better" > so changed BUG to BUILD_BUG_ON_MSG to make compiler break if size is > wrong. this is done in compile time. > > also removed code that allocates more than 32MB because current > implementation supports only up to 32MB. > > Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > --- > include/linux/slab.h | 7 +++++-- > mm/slab_common.c | 7 +++---- > 2 files changed, 8 insertions(+), 6 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 0c97d788762c..fd0c7229d105 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -346,6 +346,9 @@ static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags) > * 1 = 65 .. 96 bytes > * 2 = 129 .. 192 bytes > * n = 2^(n-1)+1 .. 2^n > + * > + * Note: you don't need to optimize kmalloc_index because it's evaluated "there's no need to..." > + * in compile-time. > */ > static __always_inline unsigned int kmalloc_index(size_t size) > { > @@ -382,8 +385,8 @@ static __always_inline unsigned int kmalloc_index(size_t size) > if (size <= 8 * 1024 * 1024) return 23; > if (size <= 16 * 1024 * 1024) return 24; > if (size <= 32 * 1024 * 1024) return 25; > - if (size <= 64 * 1024 * 1024) return 26; > - BUG(); > + > + BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); > > /* Will never be reached. Needed because the compiler may complain */ > return -1; > diff --git a/mm/slab_common.c b/mm/slab_common.c > index f8833d3e5d47..39d4eca8cf9b 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -745,8 +745,8 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) > > /* > * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time. > - * kmalloc_index() supports up to 2^26=64MB, so the final entry of the table is > - * kmalloc-67108864. > + * kmalloc_index() supports up to 2^25=32MB, so the final entry of the table is > + * kmalloc-33554432. kmalloc-32M > */ > const struct kmalloc_info_struct kmalloc_info[] __initconst = { > INIT_KMALLOC_INFO(0, 0), > @@ -774,8 +774,7 @@ const struct kmalloc_info_struct kmalloc_info[] __initconst = { > INIT_KMALLOC_INFO(4194304, 4M), > INIT_KMALLOC_INFO(8388608, 8M), > INIT_KMALLOC_INFO(16777216, 16M), > - INIT_KMALLOC_INFO(33554432, 32M), > - INIT_KMALLOC_INFO(67108864, 64M) > + INIT_KMALLOC_INFO(33554432, 32M) > }; > > /* > Thanks