Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934086AbcCIUcf (ORCPT ); Wed, 9 Mar 2016 15:32:35 -0500 Received: from h2.hallyn.com ([78.46.35.8]:37980 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753522AbcCIUc0 (ORCPT ); Wed, 9 Mar 2016 15:32:26 -0500 Date: Wed, 9 Mar 2016 14:32:24 -0600 From: "Serge E. Hallyn" To: Seth Forshee Cc: "Eric W. Biederman" , Greg Kroah-Hartman , "Serge E. Hallyn" , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 2/2] debugfs: Make automount point inodes permanently empty Message-ID: <20160309203224.GA3734@mail.hallyn.com> References: <1457536687-32794-1-git-send-email-seth.forshee@canonical.com> <1457536687-32794-3-git-send-email-seth.forshee@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1457536687-32794-3-git-send-email-seth.forshee@canonical.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1763 Lines: 44 Quoting Seth Forshee (seth.forshee@canonical.com): > Starting with 4.1 the tracing subsystem has its own filesystem > which is automounted in the tracing subdirectory of debugfs. > Prior to this debugfs could be bind mounted in a cloned mount > namespace, but if tracefs has been mounted under debugfs this > now fails because there is a locked child mount. This creates > a regression for container software which bind mounts debugfs > to satisfy the assumption of some userspace software. > > In other pseudo filesystems such as proc and sysfs we're already > creating mountpoints like this in such a way that no dirents can > be created in the directories, allowing them to be exceptions to > some MNT_LOCKED tests. In fact we're already do this for the > tracefs mountpoint in sysfs. > > Do the same in debugfs_create_automount(), since the intention > here is clearly to create a mountpoint. This fixes the regression, > as locked child mounts on permanently empty directories do not > cause a bind mount to fail. > > Cc: stable@vger.kernel.org # v4.1+ > Signed-off-by: Seth Forshee Acked-by: Serge Hallyn > --- > fs/debugfs/inode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c > index bece948b363d..8580831ed237 100644 > --- a/fs/debugfs/inode.c > +++ b/fs/debugfs/inode.c > @@ -457,7 +457,7 @@ struct dentry *debugfs_create_automount(const char *name, > if (unlikely(!inode)) > return failed_creating(dentry); > > - inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; > + make_empty_dir_inode(inode); > inode->i_flags |= S_AUTOMOUNT; > inode->i_private = data; > dentry->d_fsdata = (void *)f; > -- > 1.9.1