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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 0C124C43603 for ; Wed, 11 Dec 2019 04:00:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7E982073B for ; Wed, 11 Dec 2019 04:00:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726718AbfLKEA2 (ORCPT ); Tue, 10 Dec 2019 23:00:28 -0500 Received: from mail.loongson.cn ([114.242.206.163]:47994 "EHLO loongson.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726642AbfLKEA2 (ORCPT ); Tue, 10 Dec 2019 23:00:28 -0500 Received: from [10.130.0.36] (unknown [123.138.236.242]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9DxDxe3afBd0nEJAA--.6S3; Wed, 11 Dec 2019 12:00:08 +0800 (CST) Subject: Re: [PATCH v5] fs: introduce is_dot_or_dotdot helper for cleanup To: Eric Biggers , Matthew Wilcox References: <1576030801-8609-1-git-send-email-yangtiezhu@loongson.cn> <20191211024858.GB732@sol.localdomain> Cc: Alexander Viro , "Theodore Y. Ts'o" , Jaegeuk Kim , Chao Yu , Tyler Hicks , linux-fsdevel@vger.kernel.org, ecryptfs@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org From: Tiezhu Yang Message-ID: Date: Wed, 11 Dec 2019 11:59:40 +0800 User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20191211024858.GB732@sol.localdomain> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CM-TRANSID: AQAAf9DxDxe3afBd0nEJAA--.6S3 X-Coremail-Antispam: 1UD129KBjvJXoW7Aw4rXryxJFW5WFyDWF4DArb_yoW8Zr1UpF y5CFZYyF1IgFyUZF4vyw4fZF4Yvrs3XFyjy347K3s8AF1aqFnaqrW5Kr1093Z3JrZ5ZF1S gay3WFyYk398AaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvEb7Iv0xC_tr1lb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Gr0_Xr1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8Jr0_Cr1UM28EF7xvwV C2z280aVCY1x0267AKxVWxJr0_GcWle2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xv F2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r 4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwACI402YVCY1x02628vn2kIc2xK xwCYjI0SjxkI62AI1cAE67vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r 1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CE b7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0x vE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_WFyUJVCq3wCI 42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWI evJa73UjIFyTuYvjxU2rcTDUUUU X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ Sender: linux-fscrypt-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org On 12/11/2019 10:48 AM, Eric Biggers wrote: > On Wed, Dec 11, 2019 at 10:20:01AM +0800, Tiezhu Yang wrote: >> diff --git a/include/linux/namei.h b/include/linux/namei.h >> index 7fe7b87..0fd9315 100644 >> --- a/include/linux/namei.h >> +++ b/include/linux/namei.h >> @@ -92,4 +92,14 @@ retry_estale(const long error, const unsigned int flags) >> return error == -ESTALE && !(flags & LOOKUP_REVAL); >> } >> >> +static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len) >> +{ >> + if (unlikely(name[0] == '.')) { >> + if (len == 1 || (len == 2 && name[1] == '.')) >> + return true; >> + } >> + >> + return false; >> +} >> + >> #endif /* _LINUX_NAMEI_H */ > I had suggested adding a len >= 1 check to handle the empty name case correctly. > What I had in mind was > > static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len) > { > if (len >= 1 && unlikely(name[0] == '.')) { > if (len < 2 || (len == 2 && name[1] == '.')) > return true; > } > > return false; > } > > As is, you're proposing that it always dereference the first byte even when > len=0, which seems like a bad idea for a shared helper function. Did you check > whether it's okay for all the existing callers? fscrypt_fname_disk_to_usr() is > called from 6 places, did you check all of them? > > How about keeping the existing optimized code for the hot path in fs/namei.c > (i.e. not using the helper function), while having the helper function do the > extra check to handle len=0 correctly? Hi Eric, Thank you for reminding me. How about using the following helper for all callers? static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len) { if (len == 1 && name[0] == '.') return true; if (len == 2 && name[0] == '.' && name[1] == '.') return true; return false; } Hi Matthew, How do you think? I think the performance influence is very small due to is_dot_or_dotdot() is a such short static inline function. Thanks, Tiezhu Yang > > - Eric 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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 458B5C43603 for ; Wed, 11 Dec 2019 04:00:33 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EE32D2073B; Wed, 11 Dec 2019 04:00:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sourceforge.net header.i=@sourceforge.net header.b="YUbofKV4"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="CO1jW56W" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EE32D2073B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1ietAu-0002bW-Bi; Wed, 11 Dec 2019 04:00:32 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ietAs-0002bN-1t for linux-f2fs-devel@lists.sourceforge.net; Wed, 11 Dec 2019 04:00:30 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:Cc:References:To:Subject:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=SXh3KYgMsPS5RG5pnVp/ro4tCSM6bG5RdmmTkHZWnyM=; b=YUbofKV4n5WNLjJABuYIWxDaUM yqIreCjOgW7pChAPuPk5NZWpawJorelPeKty/0d1pZTXs7N1OgT8k+J2h2dz3Z0jhZ92aGrSrgC4t F6yHMWPy04Q4muN41Qwi8fK7zY9qLmvR+TutkAHkCZcJkJZIwy9Y5YW4rp/Zy+MjAvgo=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:MIME-Version:Date: Message-ID:From:Cc:References:To:Subject:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=SXh3KYgMsPS5RG5pnVp/ro4tCSM6bG5RdmmTkHZWnyM=; b=CO1jW56WE6MPQVT8l4fFGgHDVe xo9FI0M790cCwBdjaFZLm851wdSapx4TpRttOB6y6hJrshrmOFdZune3UqI2D0b14KauqFem2Qasf 8C6IhO7h4nnQfwIm6kFANh4cmf4fJ/odbJn5fStodUvYGaq6C1Y922DPw0xoVfHReSeA=; Received: from mail.loongson.cn ([114.242.206.163] helo=loongson.cn) by sfi-mx-3.v28.lw.sourceforge.com with esmtp (Exim 4.92.2) id 1ietAn-000XcZ-1V for linux-f2fs-devel@lists.sourceforge.net; Wed, 11 Dec 2019 04:00:30 +0000 Received: from [10.130.0.36] (unknown [123.138.236.242]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9DxDxe3afBd0nEJAA--.6S3; Wed, 11 Dec 2019 12:00:08 +0800 (CST) To: Eric Biggers , Matthew Wilcox References: <1576030801-8609-1-git-send-email-yangtiezhu@loongson.cn> <20191211024858.GB732@sol.localdomain> From: Tiezhu Yang Message-ID: Date: Wed, 11 Dec 2019 11:59:40 +0800 User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20191211024858.GB732@sol.localdomain> X-CM-TRANSID: AQAAf9DxDxe3afBd0nEJAA--.6S3 X-Coremail-Antispam: 1UD129KBjvJXoW7Aw4rXryxJFW5WFyDWF4DArb_yoW8Zr1UpF y5CFZYyF1IgFyUZF4vyw4fZF4Yvrs3XFyjy347K3s8AF1aqFnaqrW5Kr1093Z3JrZ5ZF1S gay3WFyYk398AaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvEb7Iv0xC_tr1lb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Gr0_Xr1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8Jr0_Cr1UM28EF7xvwV C2z280aVCY1x0267AKxVWxJr0_GcWle2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xv F2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r 4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwACI402YVCY1x02628vn2kIc2xK xwCYjI0SjxkI62AI1cAE67vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r 1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CE b7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0x vE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_WFyUJVCq3wCI 42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWI evJa73UjIFyTuYvjxU2rcTDUUUU X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Headers-End: 1ietAn-000XcZ-1V Subject: Re: [f2fs-dev] [PATCH v5] fs: introduce is_dot_or_dotdot helper for cleanup X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ecryptfs@vger.kernel.org, "Theodore Y. Ts'o" , linux-kernel@vger.kernel.org, Tyler Hicks , linux-fscrypt@vger.kernel.org, Alexander Viro , linux-fsdevel@vger.kernel.org, Jaegeuk Kim , linux-f2fs-devel@lists.sourceforge.net Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 12/11/2019 10:48 AM, Eric Biggers wrote: > On Wed, Dec 11, 2019 at 10:20:01AM +0800, Tiezhu Yang wrote: >> diff --git a/include/linux/namei.h b/include/linux/namei.h >> index 7fe7b87..0fd9315 100644 >> --- a/include/linux/namei.h >> +++ b/include/linux/namei.h >> @@ -92,4 +92,14 @@ retry_estale(const long error, const unsigned int flags) >> return error == -ESTALE && !(flags & LOOKUP_REVAL); >> } >> >> +static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len) >> +{ >> + if (unlikely(name[0] == '.')) { >> + if (len == 1 || (len == 2 && name[1] == '.')) >> + return true; >> + } >> + >> + return false; >> +} >> + >> #endif /* _LINUX_NAMEI_H */ > I had suggested adding a len >= 1 check to handle the empty name case correctly. > What I had in mind was > > static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len) > { > if (len >= 1 && unlikely(name[0] == '.')) { > if (len < 2 || (len == 2 && name[1] == '.')) > return true; > } > > return false; > } > > As is, you're proposing that it always dereference the first byte even when > len=0, which seems like a bad idea for a shared helper function. Did you check > whether it's okay for all the existing callers? fscrypt_fname_disk_to_usr() is > called from 6 places, did you check all of them? > > How about keeping the existing optimized code for the hot path in fs/namei.c > (i.e. not using the helper function), while having the helper function do the > extra check to handle len=0 correctly? Hi Eric, Thank you for reminding me. How about using the following helper for all callers? static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len) { if (len == 1 && name[0] == '.') return true; if (len == 2 && name[0] == '.' && name[1] == '.') return true; return false; } Hi Matthew, How do you think? I think the performance influence is very small due to is_dot_or_dotdot() is a such short static inline function. Thanks, Tiezhu Yang > > - Eric _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel