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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 49BD8C433DF for ; Sat, 30 May 2020 17:59:31 +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 17F5120721; Sat, 30 May 2020 17:59:30 +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="QczUUmoC"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="ClsWKUvE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 17F5120721 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk 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-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1jf5la-0006aR-HG; Sat, 30 May 2020 17:59:30 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jf5lY-0006Zs-K6 for linux-f2fs-devel@lists.sourceforge.net; Sat, 30 May 2020 17:59:28 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Sender:In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding: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=I4Sl+k52E/CqXyjyic29wBCN4bpKoi5wMYDvduKAFNw=; b=QczUUmoC8g09fntmqPf8pimNg u+gsDamk65cCVYMurdPLTYPycqi8KYFrjS99Br2fL3fqXsg4b+u1xpyGi5OOXH6fCMRU21ow7sT7L A6OwvEB3XqiDf39faMWO70jMmY53sf+uJx8ML6pANgqHP37uSi8zXZs1Mx9RdkqYRXAeE=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Sender:In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-Transfer-Encoding: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=I4Sl+k52E/CqXyjyic29wBCN4bpKoi5wMYDvduKAFNw=; b=ClsWKUvE/xaJiIHrI3CMv3++x0 2szJp6DMPN4f3cbSjoqX5IRZXN2wSl9XGuMWckVxvOSXYKah/UYeunmUhvVgCI11Q15rlBXf93Os6 INMFkg/8lzlkDYKhrL9oH8MRgBoqDIkRq3JwB2/uy2R3+2KVzr8D/TI/mU2tZ49NslbI=; Received: from zeniv.linux.org.uk ([195.92.253.2]) by sfi-mx-3.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1jf5lW-00199f-V8 for linux-f2fs-devel@lists.sourceforge.net; Sat, 30 May 2020 17:59:28 +0000 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.93 #3 (Red Hat Linux)) id 1jf5lD-000X31-I7; Sat, 30 May 2020 17:59:07 +0000 Date: Sat, 30 May 2020 18:59:07 +0100 From: Al Viro To: Eric Biggers Message-ID: <20200530175907.GP23230@ZenIV.linux.org.uk> References: <20200530060216.221456-1-ebiggers@kernel.org> <20200530171814.GD19604@bombadil.infradead.org> <20200530173547.GA12299@sol.localdomain> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200530173547.GA12299@sol.localdomain> X-Headers-End: 1jf5lW-00199f-V8 Subject: Re: [f2fs-dev] [PATCH] ext4: avoid utf8_strncasecmp() with unstable name 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: Daniel Rosenberg , stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Gabriel Krisman Bertazi Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Sat, May 30, 2020 at 10:35:47AM -0700, Eric Biggers wrote: > On Sat, May 30, 2020 at 10:18:14AM -0700, Matthew Wilcox wrote: > > On Fri, May 29, 2020 at 11:02:16PM -0700, Eric Biggers wrote: > > > + if (len <= DNAME_INLINE_LEN - 1) { > > > + unsigned int i; > > > + > > > + for (i = 0; i < len; i++) > > > + strbuf[i] = READ_ONCE(str[i]); > > > + strbuf[len] = 0; > > > > This READ_ONCE is going to force the compiler to use byte accesses. > > What's wrong with using a plain memcpy()? > > > > It's undefined behavior when the source can be concurrently modified. > > Compilers can assume that it's not, and remove the memcpy() (instead just using > the source data directly) if they can prove that the destination array is never > modified again before it goes out of scope. > > Do you have any suggestions that don't involve undefined behavior? Even memcpy(strbuf, (volatile void *)str, len)? It's been a while since I've looked at these parts of C99... _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel