From: Valerie Aurora <vaurora@xxxxxxxxxx>
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 <valerie.aurora@xxxxxxxxx>
---
fs/namespace.c | 43 +++++++++++++++++++++++++++++++++++++++++++
1 files changed, 43 insertions(+), 0 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 12563ea..6486386 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1555,6 +1555,49 @@ 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
--
1.7.0.4
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