From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752262AbcJKFeK (ORCPT ); Tue, 11 Oct 2016 01:34:10 -0400 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:46721 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751691AbcJKFeG (ORCPT ); Tue, 11 Oct 2016 01:34:06 -0400 X-Sasl-enc: oWJn6fV3PfVQL6/BB6xpqHDtMamCKi0JfUO4adabPjVx 1476164045 Subject: [PATCH 3/8] vfs - add path_has_submounts() From: Ian Kent To: Andrew Morton Cc: autofs mailing list , Kernel Mailing List , "Eric W. Biederman" , linux-fsdevel , Omar Sandoval , Al Viro Date: Tue, 11 Oct 2016 13:34:03 +0800 Message-ID: <20161011053403.27645.55242.stgit@pluto.themaw.net> In-Reply-To: <20161011053352.27645.83962.stgit@pluto.themaw.net> References: <20161011053352.27645.83962.stgit@pluto.themaw.net> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ian Kent d_mountpoint() can only be used reliably to establish if a dentry is not mounted in any namespace. It isn't aware of the possibility there may be multiple mounts using the given dentry, possibly in a different namespace. Add function, path_has_submounts(), that checks is a struct path contains mounts (or is a mountpoint itself) to handle this case. Signed-off-by: Ian Kent Cc: Al Viro Cc: Eric W. Biederman Cc: Omar Sandoval --- fs/dcache.c | 35 +++++++++++++++++++++++++++++++++++ include/linux/dcache.h | 1 + 2 files changed, 36 insertions(+) diff --git a/fs/dcache.c b/fs/dcache.c index 5c7cc95..872f04e 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1306,6 +1306,41 @@ int have_submounts(struct dentry *parent) } EXPORT_SYMBOL(have_submounts); +struct check_mount { + struct vfsmount *mnt; + unsigned int mounted; +}; + +static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry) +{ + struct check_mount *info = data; + struct path path = { .mnt = info->mnt, .dentry = dentry }; + + if (path_is_mountpoint(&path)) { + info->mounted = 1; + return D_WALK_QUIT; + } + return D_WALK_CONTINUE; +} + +/** + * path_has_submounts - check for mounts over a dentry in the + * current namespace. + * @parent: path to check. + * + * Return true if the parent or its subdirectories contain + * a mount point in the current namespace. + */ +int path_has_submounts(struct path *parent) +{ + struct check_mount data = { .mnt = parent->mnt, .mounted = 0 }; + + d_walk(parent->dentry, &data, path_check_mount, NULL); + + return data.mounted; +} +EXPORT_SYMBOL(path_has_submounts); + /* * Called by mount code to set a mountpoint and check if the mountpoint is * reachable (e.g. NFS can unhash a directory dentry and then the complete diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 798bc04..e351646 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -255,6 +255,7 @@ extern void d_prune_aliases(struct inode *); /* test whether we have any submounts in a subdir tree */ extern int have_submounts(struct dentry *); +extern int path_has_submounts(struct path *); /* * This adds the entry to the hash queues.