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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B8B55EB64DD for ; Mon, 14 Aug 2023 18:42:25 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-3.v29.lw.sourceforge.com) by sfs-ml-3.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1qVcWG-0004nP-PK; Mon, 14 Aug 2023 18:42:24 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-3.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qVcWF-0004nI-35 for linux-f2fs-devel@lists.sourceforge.net; Mon, 14 Aug 2023 18:42:23 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender: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=p7NSqNlR/lj2wuLjov6tI+cMdtQvjC+Lfxn7iYvHYEk=; b=QVWlVwqBF31HC2rrnCM/45mYnH sUGCsxdowhOgvOYDohMt/i8egMmCL7sP4MNPaNE4+LKpkfZILi8xxYgMCSlPeNL+1CehlGjCn2O3v MypCWwPXB2POgEInMORwf73lrpYeNBR4zhMX2dQfhQAE34dWGmEs11wGxiueDDdYFmq4=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender: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=p7NSqNlR/lj2wuLjov6tI+cMdtQvjC+Lfxn7iYvHYEk=; b=luzoISrhC4+YxgQNOSzgWVEY3O wwzK/wRH0Y/Uw21qs5vzx6UoAtPEh6yqJZxBlrObOgVaujqE4KA4fJ6Vf4VJUOXIwKXNmhlZxMGKy f53XHHvhDEshpNnmnt6MBntyhZQRL66kBZD/6SfFp1pJU98JVzXTisQgSCsv4uxZBLbo=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1qVcWE-005gRH-52 for linux-f2fs-devel@lists.sourceforge.net; Mon, 14 Aug 2023 18:42:22 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 90C976152F; Mon, 14 Aug 2023 18:42:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1DA8C433C8; Mon, 14 Aug 2023 18:42:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692038536; bh=cRZ0oe4bGlgMnSjDZmU1ziyvNS/S6FdTSbvDRpoiBVw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=smEVnz1dXlTZYP+snx+W94hNAvr5efHMO9iywxqCxACPnx7o1llXZSAd1PADdsTks W0JGwBYKhcQg2g00Wdv2eXHtHnL3NjvOq/ONxPrFmYKbzbmWAHaiYVUA47EXfNLzmz NJhUirjgDx4/MePzu1VQXsr4oH7h6/Wdjj2xzmglehsEkI4mtgBMHndjQe6ss4gRAj smEQKPTlw/5bi5eTEJBlIWLwrL0hWUltprMGyc8QCUTkJG9jqoJUUjiEI6izNDHqDe y2kDbQJxk4e2BwFanRKIZOq3MBEPR0ZLaBMT4kYFCSdFaYtG//kXD/GQdhRaqQMlm1 U1yogfMOOVlPA== Date: Mon, 14 Aug 2023 11:42:14 -0700 From: Eric Biggers To: Gabriel Krisman Bertazi Message-ID: <20230814184214.GB1171@sol.localdomain> References: <20230812004146.30980-1-krisman@suse.de> <20230812004146.30980-7-krisman@suse.de> <20230812024145.GD971@sol.localdomain> <87a5ut7k62.fsf@suse.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87a5ut7k62.fsf@suse.de> X-Headers-End: 1qVcWE-005gRH-52 Subject: Re: [f2fs-dev] [PATCH v5 06/10] libfs: Validate negative dentries in case-insensitive directories 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: brauner@kernel.org, tytso@mit.edu, linux-f2fs-devel@lists.sourceforge.net, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, jaegeuk@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 Mon, Aug 14, 2023 at 10:50:13AM -0400, Gabriel Krisman Bertazi wrote: > Eric Biggers writes: > > > On Fri, Aug 11, 2023 at 08:41:42PM -0400, Gabriel Krisman Bertazi wrote: > >> + /* > >> + * Filesystems will call into d_revalidate without setting > >> + * LOOKUP_ flags even for file creation (see lookup_one* > >> + * variants). Reject negative dentries in this case, since we > >> + * can't know for sure it won't be used for creation. > >> + */ > >> + if (!flags) > >> + return 0; > >> + > >> + /* > >> + * If the lookup is for creation, then a negative dentry can > >> + * only be reused if it's a case-sensitive match, not just a > >> + * case-insensitive one. This is needed to make the new file be > >> + * created with the name the user specified, preserving case. > >> + */ > >> + if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET)) { > >> + /* > >> + * ->d_name won't change from under us in the creation > >> + * path only, since d_revalidate during creation and > >> + * renames is always called with the parent inode > >> + * locked. It isn't the case for all lookup callpaths, > >> + * so ->d_name must not be touched outside > >> + * (LOOKUP_CREATE|LOOKUP_RENAME_TARGET) context. > >> + */ > >> + if (dentry->d_name.len != name->len || > >> + memcmp(dentry->d_name.name, name->name, name->len)) > >> + return 0; > >> + } > > > > This is still really confusing to me. Can you consider the below? The code is > > the same except for the reordering, but the explanation is reworked to be much > > clearer (IMO). Anything I am misunderstanding? > > > > /* > > * If the lookup is for creation, then a negative dentry can only be > > * reused if it's a case-sensitive match, not just a case-insensitive > > * one. This is needed to make the new file be created with the name > > * the user specified, preserving case. > > * > > * LOOKUP_CREATE or LOOKUP_RENAME_TARGET cover most creations. In these > > * cases, ->d_name is stable and can be compared to 'name' without > > * taking ->d_lock because the caller holds dir->i_rwsem for write. > > * (This is because the directory lock blocks the dentry from being > > * concurrently instantiated, and negative dentries are never moved.) > > * > > * All other creations actually use flags==0. These come from the edge > > * case of filesystems calling functions like lookup_one() that do a > > * lookup without setting the lookup flags at all. Such lookups might > > * or might not be for creation, and if not don't guarantee stable > > * ->d_name. Therefore, invalidate all negative dentries when flags==0. > > */ > > if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET)) { > > if (dentry->d_name.len != name->len || > > memcmp(dentry->d_name.name, name->name, name->len)) > > return 0; > > } > > if (!flags) > > return 0; > > I don't see it as particularly better or less confusing than the > original. but I also don't mind taking it into the next iteration. > Your commit message is still much longer and covers some quite different details which seem irrelevant to me. So if you don't see my explanation as being much different, I think we're still not on the same page. I hope that I'm not misunderstanding anything, in which I believe that what I wrote above is a good explanation and your commit message should be substantially simplified. Remember, longer != better. Keep things as simple as possible. - Eric _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel