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Mon, 10 May 2021 19:59:51 -0700 (PDT) Received: from hyeyoo ([183.99.11.150]) by smtp.gmail.com with ESMTPSA id 132sm12441756pfw.38.2021.05.10.19.59.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 May 2021 19:59:51 -0700 (PDT) Date: Tue, 11 May 2021 11:59:46 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Vlastimil Babka 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 Subject: Re: [PATCH v3] mm: change run-time assertion in kmalloc_index() to compile-time Message-ID: <20210511025946.GA98904@hyeyoo> References: <20210508221328.7338-1-42.hyeyoo@gmail.com> <20210510135857.GA3594@hyeyoo> <9d0ffe49-a2e2-6c81-377b-4c8d2147dff8@suse.cz> <20210510150230.GA74915@hyeyoo> <90591d7e-41e4-9ae5-54ae-ded467c498cf@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <90591d7e-41e4-9ae5-54ae-ded467c498cf@suse.cz> Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=NBm9MvSt; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf24.hostedemail.com: domain of 42hyeyoo@gmail.com designates 209.85.214.173 as permitted sender) smtp.mailfrom=42hyeyoo@gmail.com X-Stat-Signature: ycwtjrdi17ofnwaqzz4imunjof544usf X-Rspamd-Queue-Id: DA8BAA0003B9 X-Rspamd-Server: rspam02 Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf24; identity=mailfrom; envelope-from="<42.hyeyoo@gmail.com>"; helo=mail-pl1-f173.google.com; client-ip=209.85.214.173 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620701978-591118 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: >From c2b8fc4144f2c44b0ac5957a06207c385cc94d15 Mon Sep 17 00:00:00 2001 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> Date: Tue, 11 May 2021 11:53:23 +0900 Subject: [PATCH] mm, slub: change run-time assertion in kmalloc_index() to compile-time currently when size is not supported by kmalloc_index, compiler will generate a run-time BUG() while compile-time error is also possible, and better. so changed BUG to BUILD_BUG_ON_MSG to make compile-time check possible. 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 6d454886bcaf..df1937309df2 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -345,6 +345,9 @@ 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: there's no need to optimize kmalloc_index because it's evaluated + * in compile-time. */ static __always_inline unsigned int kmalloc_index(size_t size) { @@ -381,8 +384,8 @@ 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 fe8b68482670..97664bbe8147 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1192,8 +1192,8 @@ 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-32M. */ const struct kmalloc_info_struct kmalloc_info[] __initconst = { INIT_KMALLOC_INFO(0, 0), @@ -1221,8 +1221,7 @@ 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) }; /* -- 2.25.1