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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 32A0CC352A4 for ; Mon, 10 Feb 2020 23:44:54 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 0561720708 for ; Mon, 10 Feb 2020 23:44:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="SRYv4BxU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0561720708 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=iz2s5XJv0nEoQVijWl3uODvqziY1raERMDiz+G20ZdE=; b=SRYv4BxUqTX2oD LCEK8dP49kcLitQEW4nIggLIzo53iDYwU5TSMXOn+/cP34ANu5bMrqMMsjg/TPj86z0cRGiKlqywJ 7MYRZfnkFPQPpoKH7iQtUe4XJtoOgk6XOh2dE4Dq1XJNrUBlNxL5+7KOvqWtK+nQiGJKpkYUjtEIH IlOdjWIdUd+yYdaB1Uq6r0yOu3U4CGXCEet+FEuQHwLuU9ticz00GR7iVhASZkmm/1yuYZ0Sjc9kO SFcCWiJXCY8ExrOnwdnTx/s1/klqUw/qH/CHGlVZqulyWA74T08wM4WstOW6ePnr6PmzXsmmswT4/ V2O1/ppbyx4IK8HMQ+UA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1Ij9-0005y7-4x; Mon, 10 Feb 2020 23:44:31 +0000 Received: from zeniv.linux.org.uk ([195.92.253.2]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1Ij5-0005ZZ-Gd for linux-mtd@lists.infradead.org; Mon, 10 Feb 2020 23:44:29 +0000 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1Igp-00AcMq-LS; Mon, 10 Feb 2020 23:42:07 +0000 Date: Mon, 10 Feb 2020 23:42:07 +0000 From: Al Viro To: Daniel Rosenberg Subject: Re: [PATCH v7 2/8] fs: Add standard casefolding support Message-ID: <20200210234207.GJ23230@ZenIV.linux.org.uk> References: <20200208013552.241832-1-drosen@google.com> <20200208013552.241832-3-drosen@google.com> <20200208021216.GE23230@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200210_154427_551210_32B29E08 X-CRM114-Status: GOOD ( 10.61 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel-team@android.com, Theodore Ts'o , Jonathan Corbet , Richard Weinberger , Andreas Dilger , Chao Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Eric Biggers , linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, Jaegeuk Kim , linux-ext4@vger.kernel.org, Gabriel Krisman Bertazi Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Mon, Feb 10, 2020 at 03:11:13PM -0800, Daniel Rosenberg wrote: > On Fri, Feb 7, 2020 at 6:12 PM Al Viro wrote: > > > > On Fri, Feb 07, 2020 at 05:35:46PM -0800, Daniel Rosenberg wrote: > > > > > > Again, is that safe in case when the contents of the string str points to > > keeps changing under you? > > I'm not sure what you mean. I thought it was safe to use the str and > len passed into d_compare. Even if it gets changed under RCU > conditions I thought there was some code to ensure that the name/len > pair passed in is consistent, and any other inconsistencies would get > caught by d_seq later. Are there unsafe code paths that can follow? If you ever fetch the same byte twice, you might see different values. You need a fairly careful use of READ_ONCE() or equivalents to make sure that you don't get screwed over by that. Sure, ->d_seq mismatch will throw the result out, but you need to make sure you won't oops/step on uninitialized memory/etc. in process. It's not impossible to get right, but it's not trivial and you need all code working with that much more careful than normal for string handling. ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/