Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757978AbbKSIzQ (ORCPT ); Thu, 19 Nov 2015 03:55:16 -0500 Received: from mail-ig0-f170.google.com ([209.85.213.170]:32853 "EHLO mail-ig0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754613AbbKSIzO (ORCPT ); Thu, 19 Nov 2015 03:55:14 -0500 Subject: Re: [PATCH v2 2/3] lib: Introduce 2 bit ops api: all_is_bit_{one,zero} To: xinhui , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org References: <1447915724-29709-1-git-send-email-hejianet@gmail.com> <1447915724-29709-3-git-send-email-hejianet@gmail.com> <564D8B14.9030509@linux.vnet.ibm.com> Cc: Andrew Morton , Rasmus Villemoes , Denys Vlasenko , Kyungmin Park , Michal Nazarewicz , Yury Norov , Tejun Heo , Martin Kepplinger , George Spelvin , Ingo Molnar , Arnd Bergmann From: hejianet Message-ID: <564D8E67.6030706@gmail.com> Date: Thu, 19 Nov 2015 16:55:03 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <564D8B14.9030509@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3027 Lines: 106 Thanks， I will add it in next verison B.R. Justin 在 11/19/15 4:40 PM, xinhui 写道: > hi, jia > Nice patch. But I have one minor question. see inline comments. > > On 2015/11/19 14:48, Jia He wrote: >> This patch introduces 2 lightweight bit api. >> all_bit_is_zero return 1 if the bit string is all zero. >> The addr is the start address, the size is the bit size of the bit >> string. >> all_bit_is_one is the opposite. >> >> Signed-off-by: Jia He >> --- >> lib/find_bit.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 50 insertions(+) >> >> diff --git a/lib/find_bit.c b/lib/find_bit.c >> index 18072ea..1d56d8d 100644 >> --- a/lib/find_bit.c >> +++ b/lib/find_bit.c >> @@ -131,6 +131,56 @@ unsigned long find_last_bit(const unsigned long >> *addr, unsigned long size) >> EXPORT_SYMBOL(find_last_bit); >> #endif >> >> +#ifndef all_bit_is_zero >> +/* >> + * return val: 1 means all bit is zero >> + */ >> +unsigned int all_bit_is_zero(const unsigned long *addr, unsigned size) >> +{ > Seems better that size should be type of "unsigned long". Otherwise > I'm afraid when we compare idx * BITS_PER_LONG with size, there might > be overflow issue. > >> + unsigned long idx; >> + unsigned long mask = size; >> + >> + if (unlikely(size == 0)) >> + return 1; >> + >> + if (size > BITS_PER_LONG) { >> + for (idx = 0; idx * BITS_PER_LONG < size; idx++) >> + if (addr[idx]) >> + return 0; >> + >> + mask = size - (idx - 1) * BITS_PER_LONG; >> + } >> + >> + return !(*addr & BITMAP_LAST_WORD_MASK(mask)); >> +} >> +EXPORT_SYMBOL(all_bit_is_zero); >> +#endif >> + >> +#ifndef all_bit_is_one >> +/* >> + * return val: 1 means all bit is one >> + */ >> +unsigned int all_bit_is_one(const unsigned long *addr, unsigned size) >> +{ > this argc of size should be type of "unsigned long", too. > > thanks > xinhui > >> + unsigned long idx; >> + unsigned long mask = size; >> + >> + if (unlikely(size == 0)) >> + return 1; >> + >> + if (size > BITS_PER_LONG) { >> + for (idx = 0; idx * BITS_PER_LONG < size; idx++) >> + if (~addr[idx]) >> + return 0; >> + >> + mask = size - (idx - 1) * BITS_PER_LONG; >> + } >> + >> + return !(~(*addr) & BITMAP_LAST_WORD_MASK(mask)); >> +} >> +EXPORT_SYMBOL(all_bit_is_one); >> +#endif >> + >> #ifdef __BIG_ENDIAN >> >> /* include/linux/byteorder does not support "unsigned long" type */ >> > > -- > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/