From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valerie Aurora Subject: [PATCH 21/34] union-mount: Create prepare_mnt_union() and cleanup_mnt_union() Date: Thu, 16 Sep 2010 15:12:12 -0700 Message-ID: <1284675145-4391-22-git-send-email-vaurora@redhat.com> References: <1284675145-4391-1-git-send-email-vaurora@redhat.com> Cc: Miklos Szeredi , Christoph Hellwig , Andreas Gruenbacher , Nick Piggin , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Valerie Aurora To: Alexander Viro Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22796 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756542Ab0IPWOv (ORCPT ); Thu, 16 Sep 2010 18:14:51 -0400 In-Reply-To: <1284675145-4391-1-git-send-email-vaurora@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: prepare_mnt_union() ties together all the mount-time checks and setup for union mounts. It tests the layers for suitability and builds the root union stack. cleanup_mnt_union() unwinds everything prepare_mnt_union() does. Signed-off-by: Valerie Aurora --- fs/namespace.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 43 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 2bb4645..ff83cee 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1512,6 +1512,49 @@ out: return err; } +/** + * prepare_mnt_union - do setup necessary for a union mount + * + * @topmost_mnt: vfsmount of topmost layer + * @mntpnt: path of requested mountpoint + * + * We union every underlying file system that is mounted on the same + * mountpoint (well, pathname), read-only, and not shared. If we get + * at least one layer, we don't return an error, although we will + * complain in the kernel log if we hit a mount that can't be + * unioned. + * + * Caller needs namespace_sem, but can't have vfsmount_lock. + */ + +static int prepare_mnt_union(struct vfsmount *topmost_mnt, struct path *mntpnt) +{ + int err; + + err = check_topmost_union_mnt(topmost_mnt, topmost_mnt->mnt_flags); + if (err) + return err; + + err = clone_union_tree(topmost_mnt, mntpnt); + if (err) + return err; + + err = build_root_union(topmost_mnt); + if (err) + goto out; + + return 0; +out: + put_union_sb(topmost_mnt->mnt_sb); + return err; +} + +static void cleanup_mnt_union(struct vfsmount *topmost_mnt) +{ + d_free_unions(topmost_mnt->mnt_root); + put_union_sb(topmost_mnt->mnt_sb); +} + /* * @source_mnt : mount tree to be attached * @nd : place the mount tree @source_mnt is attached -- 1.6.3.3