From patchwork Sat Jun 9 00:50:30 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Akinobu Mita X-Patchwork-Id: 163875 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id B1AE8B6FCC for ; Sat, 9 Jun 2012 10:51:51 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932748Ab2FIAu4 (ORCPT ); Fri, 8 Jun 2012 20:50:56 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:50988 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932201Ab2FIAuz (ORCPT ); Fri, 8 Jun 2012 20:50:55 -0400 Received: by pbbrp8 with SMTP id rp8so3196366pbb.19 for ; Fri, 08 Jun 2012 17:50:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:x-mailer; bh=CDFdq+v3/rICUGF2dZqx4x72lF2zQ5nokW62OSE4RVQ=; b=L/0rttHjpVrIy6eZc1zKsnimy6Pwd8+Y8/2ceCCm+HxeGL/Oa02BdiWkjVrNKZrZjU 2U+fKWTMrAa17Q3eItyrf7k8ysIGXXirPmewwRdDtTPW2Ck+IKlUMhNCG/yZ+HndI0jP YfVDIwyzCWKQRRa15mU3sqFPrsvzXNaFUvQKU9c6TPCfKAbno0IFy/kF77vneNBo1/Zw xYUJOSHLWCQ9qJiiJo1qT0k3WAtWCQzFF7wT1gojAam7LC/KMFA2C3DVqo5wUpLiYOM7 +giAz7lCpWNjEk2pyDFguJFwz1X43stele2XHb/mwdv3G91Mq6QTDSiTFzMuuG0htGcG yQng== Received: by 10.68.134.163 with SMTP id pl3mr467032pbb.167.1339203054188; Fri, 08 Jun 2012 17:50:54 -0700 (PDT) Received: from localhost.localdomain (p15023-ipngn1901hodogaya.kanagawa.ocn.ne.jp. [180.11.8.23]) by mx.google.com with ESMTPS id hc7sm9536241pbc.54.2012.06.08.17.50.49 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 08 Jun 2012 17:50:51 -0700 (PDT) From: Akinobu Mita To: linux-kernel@vger.kernel.org, akpm@linux-foundation.org Cc: Akinobu Mita , Anders Larsen , Alasdair Kergon , dm-devel@redhat.com, linux-fsdevel@vger.kernel.org, Laurent Pinchart , linux-media@vger.kernel.org, Mark Fasheh , Joel Becker , ocfs2-devel@oss.oracle.com, Jan Kara , linux-ext4@vger.kernel.org, Andreas Dilger , "Theodore Ts'o" , Matthew Wilcox Subject: [PATCH v3 1/9] string: introduce memweight Date: Sat, 9 Jun 2012 09:50:30 +0900 Message-Id: <1339203038-13069-1-git-send-email-akinobu.mita@gmail.com> X-Mailer: git-send-email 1.7.7.6 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org memweight() is the function that counts the total number of bits set in memory area. Unlike bitmap_weight(), memweight() takes pointer and size in bytes to specify a memory area which does not need to be aligned to long-word boundary. Signed-off-by: Akinobu Mita Cc: Anders Larsen Cc: Alasdair Kergon Cc: dm-devel@redhat.com Cc: linux-fsdevel@vger.kernel.org Cc: Laurent Pinchart Cc: linux-media@vger.kernel.org Cc: Mark Fasheh Cc: Joel Becker Cc: ocfs2-devel@oss.oracle.com Cc: Jan Kara Cc: linux-ext4@vger.kernel.org Cc: Andrew Morton Cc: Andreas Dilger Cc: "Theodore Ts'o" Cc: Matthew Wilcox --- v3: add comment for the last loop, adviced by Jan Kara v2: simplify memweight(), adviced by Jan Kara include/linux/string.h | 3 +++ lib/string.c | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 0 deletions(-) diff --git a/include/linux/string.h b/include/linux/string.h index e033564..ffe0442 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -145,4 +145,7 @@ static inline bool strstarts(const char *str, const char *prefix) return strncmp(str, prefix, strlen(prefix)) == 0; } #endif + +extern size_t memweight(const void *ptr, size_t bytes); + #endif /* _LINUX_STRING_H_ */ diff --git a/lib/string.c b/lib/string.c index e5878de..e467186 100644 --- a/lib/string.c +++ b/lib/string.c @@ -26,6 +26,7 @@ #include #include #include +#include #ifndef __HAVE_ARCH_STRNICMP /** @@ -824,3 +825,38 @@ void *memchr_inv(const void *start, int c, size_t bytes) return check_bytes8(start, value, bytes % 8); } EXPORT_SYMBOL(memchr_inv); + +/** + * memweight - count the total number of bits set in memory area + * @ptr: pointer to the start of the area + * @bytes: the size of the area + */ +size_t memweight(const void *ptr, size_t bytes) +{ + size_t w = 0; + size_t longs; + const unsigned char *bitmap = ptr; + + for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); + bytes--, bitmap++) + w += hweight8(*bitmap); + + longs = bytes / sizeof(long); + if (longs) { + BUG_ON(longs >= INT_MAX / BITS_PER_LONG); + w += bitmap_weight((unsigned long *)bitmap, + longs * BITS_PER_LONG); + bytes -= longs * sizeof(long); + bitmap += longs * sizeof(long); + } + /* + * The reason that this last loop is distinct from the preceding + * bitmap_weight() call is to compute 1-bits in the last region smaller + * than sizeof(long) properly on big-endian systems. + */ + for (; bytes > 0; bytes--, bitmap++) + w += hweight8(*bitmap); + + return w; +} +EXPORT_SYMBOL(memweight);