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Thu, 13 May 2021 05:08:34 -0700 (PDT) Received: from hyeyoo ([121.135.181.35]) by smtp.gmail.com with ESMTPSA id c201sm1991044pfc.38.2021.05.13.05.08.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 May 2021 05:08:34 -0700 (PDT) Date: Thu, 13 May 2021 21:08:29 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Vlastimil Babka Cc: Marco Elver , Andrew Morton , iamjoonsoo.kim@lge.com, rientjes@google.com, penberg@kernel.org, cl@linux.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 42.hyeyoo@gmail.com Subject: Re: [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time Message-ID: <20210513120829.GB772931@hyeyoo> References: <20210511173448.GA54466@hyeyoo> <20210512195227.245000695c9014242e9a00e5@linux-foundation.org> <20210513031220.GA133011@hyeyoo> <20210512204024.401ff3de38649d7d0f5a45e8@linux-foundation.org> <20210513062809.GA319973@hyeyoo> <90c1b2ae-a5c1-07d1-b056-5b3699b6cc77@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <90c1b2ae-a5c1-07d1-b056-5b3699b6cc77@suse.cz> Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=UwxoaNjR; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf17.hostedemail.com: domain of 42hyeyoo@gmail.com designates 209.85.214.180 as permitted sender) smtp.mailfrom=42hyeyoo@gmail.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 174334080F56 X-Stat-Signature: 3dzdggkwy4wnodn99cfuwg3mjj51n3hg Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from="<42.hyeyoo@gmail.com>"; helo=mail-pl1-f180.google.com; client-ip=209.85.214.180 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620907709-224563 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, May 13, 2021 at 01:37:38PM +0200, Vlastimil Babka wrote: > > See my suggestion below that builds on Andrew's size_is_constant but > > would retain the old interface and support testing. > > I can accept that, but please also modify/expand the newly added comment. Now > it's *normally* evaluated in compile-time. And there should be warning that > anyone calling it with size_is_constant == false should do that only in context > where performance (and code bloat, most likely too) doesn't matter, such as unit > test. > > Thanks, Vlastimil > > > Thanks, I completely agree on what Vlastimil said. there should be comment saying that generally you should not use kmalloc_index with size_is_const == true. and the caller MUST guarantee that size_is_const is correct. if not, it would be so confusing.