Added whiteout behavior option. ``-o whiteout=always'' is default mode

(it is established practice) and ``-o whiteout=whenneeded'' is less
disk-space using mode especially for resource restricted environments
like embedded environments. (Contributed by Ed Schouten. Thanks)

Submitted by:   Masanori Ozawa <ozawa@ongs.co.jp> (unionfs developer)
Reviewed by:    jeff, kensmith
Approved by:    re (kensmith)
MFC after:      1 week

3 files changed, 32 insertions, 2 deletions

diff --git a/sys/fs/unionfs/union.h b/sys/fs/unionfs/union.h
index 302b384..e97936d 100644
--- a/sys/fs/unionfs/union.h
+++ b/sys/fs/unionfs/union.h
@@ -45,11 +45,18 @@ typedef enum _unionfs_copymode {
 	UNIONFS_MASQUERADE
 } unionfs_copymode;
 
+/* whiteout policy of upper layer */
+typedef enum _unionfs_whitemode {
+       UNIONFS_WHITE_ALWAYS = 0,
+       UNIONFS_WHITE_WHENNEEDED
+} unionfs_whitemode;
+
 struct unionfs_mount {
 	struct vnode   *um_lowervp;	/* VREFed once */
 	struct vnode   *um_uppervp;	/* VREFed once */
 	struct vnode   *um_rootvp;	/* ROOT vnode */
 	unionfs_copymode um_copymode;
+	unionfs_whitemode um_whitemode;
 	uid_t		um_uid;
 	gid_t		um_gid;
 	u_short		um_udir;
diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c
index ea09895..3125f59 100644
--- a/sys/fs/unionfs/union_vfsops.c
+++ b/sys/fs/unionfs/union_vfsops.c
@@ -123,6 +123,7 @@ unionfs_domount(struct mount *mp, struct thread *td)
 	u_short		udir;
 	u_short		ufile;
 	unionfs_copymode copymode;
+	unionfs_whitemode whitemode;
 	struct componentname fakecn;
 	struct nameidata nd, *ndp;
 	struct vattr	va;
@@ -136,6 +137,7 @@ unionfs_domount(struct mount *mp, struct thread *td)
 	udir = 0;
 	ufile = 0;
 	copymode = UNIONFS_TRANSPARENT;	/* default */
+	whitemode = UNIONFS_WHITE_ALWAYS;
 	ndp = &nd;
 
 	if (mp->mnt_flag & MNT_ROOTFS) {
@@ -237,6 +239,20 @@ unionfs_domount(struct mount *mp, struct thread *td)
 				return (EINVAL);
 			}
 		}
+		if (vfs_getopt(mp->mnt_optnew, "whiteout", (void **)&tmp,
+		    NULL) == 0) {
+			if (tmp == NULL) {
+				vfs_mount_error(mp, "Invalid whiteout mode");
+				return (EINVAL);
+			} else if (strcasecmp(tmp, "always") == 0)
+				whitemode = UNIONFS_WHITE_ALWAYS;
+			else if (strcasecmp(tmp, "whenneeded") == 0)
+				whitemode = UNIONFS_WHITE_WHENNEEDED;
+			else {
+				vfs_mount_error(mp, "Invalid whiteout mode");
+				return (EINVAL);
+			}
+		}
 	}
 	/* If copymode is UNIONFS_TRADITIONAL, uid/gid is mounted user. */
 	if (copymode == UNIONFS_TRADITIONAL) {
@@ -286,6 +302,7 @@ unionfs_domount(struct mount *mp, struct thread *td)
 	ump->um_udir = udir;
 	ump->um_ufile = ufile;
 	ump->um_copymode = copymode;
+	ump->um_whitemode = whitemode;
 
 	MNT_ILOCK(mp);
 	if ((lowerrootvp->v_mount->mnt_kern_flag & MNTK_MPSAFE) &&
diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c
index 0437fe2..7a0cb60 100644
--- a/sys/fs/unionfs/union_vnops.c
+++ b/sys/fs/unionfs/union_vnops.c
@@ -939,6 +939,7 @@ unionfs_remove(struct vop_remove_args *ap)
 	int		error;
 	struct unionfs_node *dunp;
 	struct unionfs_node *unp;
+	struct unionfs_mount *ump;
 	struct vnode   *udvp;
 	struct vnode   *uvp;
 	struct vnode   *lvp;
@@ -960,7 +961,9 @@ unionfs_remove(struct vop_remove_args *ap)
 		return (EROFS);
 
 	if (uvp != NULLVP) {
-		cnp->cn_flags |= DOWHITEOUT;
+		ump = MOUNTTOUNIONFSMOUNT(ap->a_vp->v_mount);
+		if (ump->um_whitemode == UNIONFS_WHITE_ALWAYS || lvp != NULLVP)
+			cnp->cn_flags |= DOWHITEOUT;
 		error = VOP_REMOVE(udvp, uvp, cnp);
 	} else if (lvp != NULLVP)
 		error = unionfs_mkwhiteout(udvp, cnp, td, unp->un_path);
@@ -1290,6 +1293,7 @@ unionfs_rmdir(struct vop_rmdir_args *ap)
 	int		error;
 	struct unionfs_node *dunp;
 	struct unionfs_node *unp;
+	struct unionfs_mount *ump;
 	struct componentname *cnp;
 	struct thread  *td;
 	struct vnode   *udvp;
@@ -1319,7 +1323,9 @@ unionfs_rmdir(struct vop_rmdir_args *ap)
 			if (error != 0)
 				return (error);
 		}
-		cnp->cn_flags |= DOWHITEOUT;
+		ump = MOUNTTOUNIONFSMOUNT(ap->a_vp->v_mount);
+		if (ump->um_whitemode == UNIONFS_WHITE_ALWAYS || lvp != NULLVP)
+			cnp->cn_flags |= DOWHITEOUT;
 		error = VOP_RMDIR(udvp, uvp, cnp);
 	}
 	else if (lvp != NULLVP)