From patchwork Mon Oct 3 00:46:33 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Kent X-Patchwork-Id: 9359891 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CCB6B60459 for ; Mon, 3 Oct 2016 00:51:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DCA7528A45 for ; Mon, 3 Oct 2016 00:51:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D15A928A59; Mon, 3 Oct 2016 00:51:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 472FC28A45 for ; Mon, 3 Oct 2016 00:51:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752723AbcJCAvH (ORCPT ); Sun, 2 Oct 2016 20:51:07 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:56941 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751621AbcJCAqh (ORCPT ); Sun, 2 Oct 2016 20:46:37 -0400 Received: from compute7.internal (compute7.nyi.internal [10.202.2.47]) by mailout.nyi.internal (Postfix) with ESMTP id 5B70C205BA; Sun, 2 Oct 2016 20:46:36 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute7.internal (MEProxy); Sun, 02 Oct 2016 20:46:36 -0400 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=themaw.net; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-sasl-enc :x-sasl-enc; s=mesmtp; bh=0pKX6c1KB+tKG4xdbqwAX77kcF0=; b=uUHGzo odU1N0FFYqIEHVcoQTy75CQ+AXyQN7uHrvw0txfGQOrJrdLWht61a/ZqIqJyZY3N 6joj23MZjQZiFgYj3i4mrXIbm6L/JBinFbBxLNlue3xBQ8aWWxqgxLgIrxb9ZY/P QgQvgvorbRwAy2m+WqcrkqfFDE5kZLRWkDy90= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-sasl-enc:x-sasl-enc; s=smtpout; bh=0pKX6c1KB+tKG4x dbqwAX77kcF0=; b=XnrBcv70MQWlScr0ubXNlDRYUjpCee1MUB6i8GZdowD3Yud 6fJPb9gaQZM9MN1kMd68Ve5CShSCxdlp4Gnk1M3tKPll9g6ejzJ77WgYnLUwzwfv JC2HqRrYl/fBy5dlz/l/9inY1soxnlXWEIsk6CEbXwt+rPrhzI4kCk4xX/DM= X-Sasl-enc: Dlqo8Va5sHh/X0Ssa3pcBJUUoniggDTOhHJ8olO/HbKl 1475455595 Received: from pluto.themaw.net (58-6-77-201.dyn.iinet.net.au [58.6.77.201]) by mail.messagingengine.com (Postfix) with ESMTPA id C8FF3CC083; Sun, 2 Oct 2016 20:46:35 -0400 (EDT) Received: from pluto.themaw.net (localhost [127.0.0.1]) by pluto.themaw.net (Postfix) with ESMTP id 81A9CA008E; Mon, 3 Oct 2016 08:46:33 +0800 (AWST) Subject: [RFC PATCH 2/8] vfs - add path_is_mountpoint() helper From: Ian Kent To: Kernel Mailing List Cc: autofs mailing list , Al Viro , linux-fsdevel , Omar Sandoval , Andrew Morton , "Eric W. Biederman" Date: Mon, 03 Oct 2016 08:46:33 +0800 Message-ID: <20161003004633.4865.1482.stgit@pluto.themaw.net> In-Reply-To: <20161003003646.4865.42500.stgit@pluto.themaw.net> References: <20161003003646.4865.42500.stgit@pluto.themaw.net> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 a given dentry that may be in a different namespace. Add helper functions, path_is_mountpoint() and an rcu version , that checks if a struct path is a mountpoint for this case. Signed-off-by: Ian Kent Cc: Al Viro Cc: Eric W. Biederman Cc: Omar Sandoval --- fs/namespace.c | 43 +++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 2 ++ 2 files changed, 45 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/namespace.c b/fs/namespace.c index 7bb2cda..ca1faaa 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1153,6 +1153,49 @@ struct vfsmount *mntget(struct vfsmount *mnt) } EXPORT_SYMBOL(mntget); +static bool __path_is_mountpoint(struct path *path) +{ + struct mount *mount; + struct vfsmount *mnt; + unsigned seq; + + do { + seq = read_seqbegin(&mount_lock); + mount = __lookup_mnt(path->mnt, path->dentry); + mnt = mount ? &mount->mnt : NULL; + } while (mnt && + !(mnt->mnt_flags & MNT_SYNC_UMOUNT) && + read_seqretry(&mount_lock, seq)); + + return mnt != NULL; +} + +/* Check if path is a mount in current namespace */ +bool path_is_mountpoint(struct path *path) +{ + bool res; + + if (!d_mountpoint(path->dentry)) + return 0; + + rcu_read_lock(); + res = __path_is_mountpoint(path); + rcu_read_unlock(); + + return res; +} +EXPORT_SYMBOL(path_is_mountpoint); + +/* Check if path is a mount in current namespace */ +bool path_is_mountpoint_rcu(struct path *path) +{ + if (!d_mountpoint(path->dentry)) + return 0; + + return __path_is_mountpoint(path); +} +EXPORT_SYMBOL(path_is_mountpoint_rcu); + struct vfsmount *mnt_clone_internal(struct path *path) { struct mount *p; diff --git a/include/linux/fs.h b/include/linux/fs.h index 901e25d..d588b26 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2117,6 +2117,8 @@ extern int vfs_ustat(dev_t, struct kstatfs *); extern int freeze_super(struct super_block *super); extern int thaw_super(struct super_block *super); extern bool our_mnt(struct vfsmount *mnt); +extern bool path_is_mountpoint(struct path *); +extern bool path_is_mountpoint_rcu(struct path *); extern int current_umask(void);