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Mon, 10 May 2021 20:03:48 -0700 (PDT) Received: from hyeyoo ([183.99.11.150]) by smtp.gmail.com with ESMTPSA id k21sm1642639pgb.56.2021.05.10.20.03.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 May 2021 20:03:48 -0700 (PDT) Date: Tue, 11 May 2021 12:03:43 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Matthew Wilcox Cc: Vlastimil Babka , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: kmalloc_index: make compiler break when size is not supported Message-ID: <20210511030343.GB98904@hyeyoo> References: <20210508221328.7338-1-42.hyeyoo@gmail.com> <20210510135857.GA3594@hyeyoo> <9d0ffe49-a2e2-6c81-377b-4c8d2147dff8@suse.cz> <20210510150230.GA74915@hyeyoo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 69C6A20001D6 Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=QOYCuBvj; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf18.hostedemail.com: domain of 42hyeyoo@gmail.com designates 209.85.215.180 as permitted sender) smtp.mailfrom=42hyeyoo@gmail.com X-Rspamd-Server: rspam03 X-Stat-Signature: w4d7wp76w9mod58bzjqk9xhrmwgghubc Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from="<42.hyeyoo@gmail.com>"; helo=mail-pg1-f180.google.com; client-ip=209.85.215.180 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620702231-423563 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 Mon, May 10, 2021 at 04:44:09PM +0100, Matthew Wilcox wrote: > On Tue, May 11, 2021 at 12:02:30AM +0900, Hyeonggon Yoo wrote: > > @@ -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()"); > > we're being encouraged to use static_assert() these days. > https://en.cppreference.com/w/c/language/_Static_assert > can you tell me difference between static_assert and BUILD_BUG_ON? it seems that mm subsystem does not make use of it now.