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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 23E08C43460 for ; Fri, 7 May 2021 01:02:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 024D1613BA for ; Fri, 7 May 2021 01:02:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234024AbhEGBD5 (ORCPT ); Thu, 6 May 2021 21:03:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:43592 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233989AbhEGBD4 (ORCPT ); Thu, 6 May 2021 21:03:56 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 46095613B9; Fri, 7 May 2021 01:02:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620349377; bh=VrbFDMhnmKozbCUdDW+wmZFhJv3fkUY9RFAPLsn1U48=; h=Date:From:To:Subject:In-Reply-To:From; b=RUA7632QjOrpPQGdc12Hg77mhoZPNurRdJZKSkTktqMHt2SmZ1gfhGI6d66zPmI1p mBeqMOYFZXqRuDvC+9/ghMr2nexZzHN+DaaEEDg9XVaRD1NZg+RUX+hYTOoCp9O4z1 vTMfhyUYFZo7JBnRJBm30S0eSb0qUSssxKTD9p/8= Date: Thu, 06 May 2021 18:02:56 -0700 From: Andrew Morton To: aklimov@redhat.com, akpm@linux-foundation.org, andy.shevchenko@gmail.com, arnd@arndb.de, dalias@libc.org, dennis@kernel.org, dsterba@suse.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, jianpeng.ma@intel.com, joe@perches.com, jpoimboe@redhat.com, linux-mm@kvack.org, linux@rasmusvillemoes.dk, mm-commits@vger.kernel.org, richard.weiyang@linux.alibaba.com, sbrivio@redhat.com, torvalds@linux-foundation.org, wsa+renesas@sang-engineering.com, ysato@users.osdn.me, yury.norov@gmail.com Subject: [patch 18/91] lib: extend the scope of small_const_nbits() macro Message-ID: <20210507010256.tFwkkKmV2%akpm@linux-foundation.org> In-Reply-To: <20210506180126.03e1baee7ca52bedb6cc6003@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Yury Norov Subject: lib: extend the scope of small_const_nbits() macro find_bit would also benefit from small_const_nbits() optimizations. The detailed comment is provided by Rasmus Villemoes. Link: https://lkml.kernel.org/r/20210401003153.97325-6-yury.norov@gmail.com Suggested-by: Rasmus Villemoes Signed-off-by: Yury Norov Acked-by: Rasmus Villemoes Acked-by: Andy Shevchenko Cc: Alexey Klimov Cc: Arnd Bergmann Cc: David Sterba Cc: Dennis Zhou Cc: Geert Uytterhoeven Cc: Jianpeng Ma Cc: Joe Perches Cc: John Paul Adrian Glaubitz Cc: Josh Poimboeuf Cc: Rich Felker Cc: Stefano Brivio Cc: Wei Yang Cc: Wolfram Sang Cc: Yoshinori Sato Signed-off-by: Andrew Morton --- include/asm-generic/bitsperlong.h | 12 ++++++++++++ include/linux/bitmap.h | 8 -------- 2 files changed, 12 insertions(+), 8 deletions(-) --- a/include/asm-generic/bitsperlong.h~lib-extend-the-scope-of-small_const_nbits-macro +++ a/include/asm-generic/bitsperlong.h @@ -23,4 +23,16 @@ #define BITS_PER_LONG_LONG 64 #endif +/* + * small_const_nbits(n) is true precisely when it is known at compile-time + * that BITMAP_SIZE(n) is 1, i.e. 1 <= n <= BITS_PER_LONG. This allows + * various bit/bitmap APIs to provide a fast inline implementation. Bitmaps + * of size 0 are very rare, and a compile-time-known-size 0 is most likely + * a sign of error. They will be handled correctly by the bit/bitmap APIs, + * but using the out-of-line functions, so that the inline implementations + * can unconditionally dereference the pointer(s). + */ +#define small_const_nbits(nbits) \ + (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) + #endif /* __ASM_GENERIC_BITS_PER_LONG */ --- a/include/linux/bitmap.h~lib-extend-the-scope-of-small_const_nbits-macro +++ a/include/linux/bitmap.h @@ -223,14 +223,6 @@ extern int bitmap_print_to_pagebuf(bool #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) -/* - * The static inlines below do not handle constant nbits==0 correctly, - * so make such users (should any ever turn up) call the out-of-line - * versions. - */ -#define small_const_nbits(nbits) \ - (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) - static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); _