Allowed unionfs to use whiteout not supporting file system as

upper layer. Until now, unionfs prevents to use that kind of
file system as upper layer. This time, I changed to allow
that kind of file system as upper layer. By this change, you
can use whiteout not supporting file system (e.g., especially
for tmpfs) as upper layer. It's very useful for combination of
tmpfs as upper layer and read only file system as lower layer.

By difinition, without whiteout support from the file system
backing the upper layer, there is no way that delete and rename
operations on lower layer objects can be done.  EOPNOTSUPP is
returned for this kind of operations as generated by VOP_WHITEOUT()
along with any others which would make modifica tions to the
lower layer, such as chmod(1).

This change is suggested by ed.

Submitted by:	ed

2 files changed, 4 insertions, 24 deletions

diff --git a/sbin/mount_unionfs/mount_unionfs.8 b/sbin/mount_unionfs/mount_unionfs.8
index 4f661b8..d120dd0 100644
--- a/sbin/mount_unionfs/mount_unionfs.8
+++ b/sbin/mount_unionfs/mount_unionfs.8
@@ -363,9 +363,10 @@ their intent to take it over.
 Without whiteout support from the file system backing the upper layer,
 there is no way that delete and rename operations on lower layer
 objects can be done.
-.Er EROFS
-is returned for this kind of operations along with any others
-which would make modifications to the lower layer, such as
+.Er EOPNOTSUPP
+is returned for this kind of operations as generated by VOP_WHITEOUT()
+along with any others which would make modifications to the lower 
+layer, such as
 .Xr chmod 1 .
 .Pp
 Running
diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c
index 604d4a3..e11219c 100644
--- a/sys/fs/unionfs/union_vfsops.c
+++ b/sys/fs/unionfs/union_vfsops.c
@@ -89,7 +89,6 @@ unionfs_domount(struct mount *mp)
 	u_short		ufile;
 	unionfs_copymode copymode;
 	unionfs_whitemode whitemode;
-	struct componentname fakecn;
 	struct nameidata nd, *ndp;
 	struct vattr	va;
 
@@ -280,26 +279,6 @@ unionfs_domount(struct mount *mp)
 	mp->mnt_flag |= ump->um_uppervp->v_mount->mnt_flag & MNT_RDONLY;
 
 	/*
-	 * Check whiteout
-	 */
-	if ((mp->mnt_flag & MNT_RDONLY) == 0) {
-		memset(&fakecn, 0, sizeof(fakecn));
-		fakecn.cn_nameiop = LOOKUP;
-		fakecn.cn_thread = td;
-		error = VOP_WHITEOUT(ump->um_uppervp, &fakecn, LOOKUP);
-		if (error) {
-			if (below) {
-				VOP_UNLOCK(ump->um_uppervp, 0);
-				vrele(upperrootvp);
-			} else
-				vput(ump->um_uppervp);
-			free(ump, M_UNIONFSMNT);
-			mp->mnt_data = NULL;
-			return (error);
-		}
-	}
-
-	/*
 	 * Unlock the node
 	 */
 	VOP_UNLOCK(ump->um_uppervp, 0);