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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 709F2C77B73 for ; Tue, 30 May 2023 12:42:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231658AbjE3Mmw (ORCPT ); Tue, 30 May 2023 08:42:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229821AbjE3Mmu (ORCPT ); Tue, 30 May 2023 08:42:50 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 645E8A1; Tue, 30 May 2023 05:42:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BB3FC62F82; Tue, 30 May 2023 12:42:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78B3CC433D2; Tue, 30 May 2023 12:42:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685450538; bh=AjbhKWnLkbzSGImSCtxRr31JpRn/bFy4QpGd/SOJtsQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=U+6p+TL98fxRHUAbLkCHzfVMO5xsp5WqmINUupyMMLssUcIgc7Kmxv+V5Kds/fS0N yzdgl57dIZFTnAnMYhyai0TY9oiFNDAeL90OBvAgWMy8D7OVhPQfEttMLr8iPJCiJa PdOkheBNknMRnIRgb67UOyGSZX4jrtc6jAD6hFbXNk9vZfqEQi6Jkd/SIVZf0VVWcY TDax/ezF+3aGAVkJzc+V/S2laopkDQr19jiOqZOAfD6tWfhr9herMBemtwqsN43Oyk fqM1pNJGwLAhDlCQ0WyBCzAlWxBBawRN6NTDWgG2e5AfzdYsZQ/b1Bkm6gyqiAMOp9 Gg6KXHzh3jOkQ== Date: Tue, 30 May 2023 14:42:07 +0200 From: Christian Brauner To: Jan Kara Cc: Al Viro , linux-fsdevel@vger.kernel.org, Miklos Szeredi , "Darrick J. Wong" , Ted Tso , Jaegeuk Kim , linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 4/6] fs: Establish locking order for unrelated directories Message-ID: <20230530-darauf-nordost-4e631cd8f1d0@brauner> References: <20230525100654.15069-1-jack@suse.cz> <20230525101624.15814-4-jack@suse.cz> <20230526-polarstern-herrichten-32fc46c63bfc@brauner> <20230529124131.gbb3fmhrspl332i6@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230529124131.gbb3fmhrspl332i6@quack3> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Mon, May 29, 2023 at 02:41:31PM +0200, Jan Kara wrote: > On Fri 26-05-23 11:45:15, Christian Brauner wrote: > > On Thu, May 25, 2023 at 12:16:10PM +0200, Jan Kara wrote: > > > Currently the locking order of inode locks for directories that are not > > > in ancestor relationship is not defined because all operations that > > > needed to lock two directories like this were serialized by > > > sb->s_vfs_rename_mutex. However some filesystems need to lock two > > > subdirectories for RENAME_EXCHANGE operations and for this we need the > > > locking order established even for two tree-unrelated directories. > > > Provide a helper function lock_two_inodes() that establishes lock > > > ordering for any two inodes and use it in lock_two_directories(). > > > > > > CC: stable@vger.kernel.org > > > Signed-off-by: Jan Kara > > > --- > > > fs/inode.c | 34 ++++++++++++++++++++++++++++++++++ > > > fs/internal.h | 2 ++ > > > fs/namei.c | 4 ++-- > > > 3 files changed, 38 insertions(+), 2 deletions(-) > > > > > > diff --git a/fs/inode.c b/fs/inode.c > > > index 577799b7855f..2015fa50d34a 100644 > > > --- a/fs/inode.c > > > +++ b/fs/inode.c > > > @@ -1103,6 +1103,40 @@ void discard_new_inode(struct inode *inode) > > > } > > > EXPORT_SYMBOL(discard_new_inode); > > > > > > +/** > > > + * lock_two_inodes - lock two inodes (may be regular files but also dirs) > > > + * > > > + * Lock any non-NULL argument. The caller must make sure that if he is passing > > > + * in two directories, one is not ancestor of the other. Zero, one or two > > > + * objects may be locked by this function. > > > + * > > > + * @inode1: first inode to lock > > > + * @inode2: second inode to lock > > > + * @subclass1: inode lock subclass for the first lock obtained > > > + * @subclass2: inode lock subclass for the second lock obtained > > > + */ > > > +void lock_two_inodes(struct inode *inode1, struct inode *inode2, > > > + unsigned subclass1, unsigned subclass2) > > > +{ > > > + if (!inode1 || !inode2) > > > + goto lock; > > > > Before this change in > > > > lock_two_nondirectories(struct inode *inode1, struct inode *inode2) > > > > the swap() would cause the non-NULL inode to always be locked with > > I_MUTEX_NONDIR2. Now it can be either I_MUTEX_NORMAL or I_MUTEX_NONDIR2. > > Is that change intentional? > > Kind of. I don't think we really care so I didn't bother to complicate the > code for this. If you think keeping the lockdep class consistent is worth > it, I can modify the patch... Either a short comment or consistent lockdep class would be nice. I know it probably doesn't matter much but otherwise someone may end up wondering whether that's ok or not.