diff --git a/lib/datastruct/list.h b/lib/datastruct/list.h
index df3d32aea..a0054aa7f 100644
--- a/lib/datastruct/list.h
+++ b/lib/datastruct/list.h
@@ -63,26 +63,6 @@ static inline struct list *list_next(struct list *head, struct list *elem)
 	return (list_end(head, elem) ? NULL : elem->n);
 }
 
-#define list_iterate(v, head) \
-	for (v = (head)->n; v != head; v = v->n)
-
-#define list_uniterate(v, head, start) \
-	for (v = (start)->p; v != head; v = v->p)
-
-#define list_iterate_safe(v, t, head) \
-	for (v = (head)->n, t = v->n; v != head; v = t, t = v->n)
-
-static inline unsigned int list_size(const struct list *head)
-{
-	unsigned int s = 0;
-	const struct list *v;
-
-	list_iterate(v, head)
-	    s++;
-
-	return s;
-}
-
 #define list_item(v, t) \
     ((t *)((uintptr_t)(v) - (uintptr_t)&((t *) 0)->list))
 
@@ -96,4 +76,28 @@ static inline unsigned int list_size(const struct list *head)
 /* Given a known element in a known structure, locate the list head */
 #define list_head(v, t, e) struct_field(v, t, e, list)
 
+#define list_iterate(v, head) \
+	for (v = (head)->n; v != head; v = v->n)
+
+#define list_uniterate(v, head, start) \
+	for (v = (start)->p; v != head; v = v->p)
+
+#define list_iterate_safe(v, t, head) \
+	for (v = (head)->n, t = v->n; v != head; v = t, t = v->n)
+
+#define list_iterate_items(v, head) \
+	for (v = list_item((head)->n, typeof(*v)); &v->list != (head); \
+	     v = list_item(v->list.n, typeof(*v)))
+
+static inline unsigned int list_size(const struct list *head)
+{
+	unsigned int s = 0;
+	const struct list *v;
+
+	list_iterate(v, head)
+	    s++;
+
+	return s;
+}
+
 #endif
diff --git a/lib/format_text/export.c b/lib/format_text/export.c
index 1efe5add7..0396eaa0f 100644
--- a/lib/format_text/export.c
+++ b/lib/format_text/export.c
@@ -321,7 +321,6 @@ static int _print_pvs(struct formatter *f, struct volume_group *vg)
 	_inc_indent(f);
 
 	list_iterate(pvh, &vg->pvs) {
-
 		pv = list_item(pvh, struct pv_list)->pv;
 
 		if (!(name = _get_pv_name(f, pv))) {
@@ -522,7 +521,7 @@ static int _print_snapshots(struct formatter *f, struct volume_group *vg)
 
 static int _print_lvs(struct formatter *f, struct volume_group *vg)
 {
-	struct list *lvh, *segh;
+	struct list *lvh;
 	struct logical_volume *lv;
 	struct lv_segment *seg;
 	char buffer[256];
@@ -571,9 +570,7 @@ static int _print_lvs(struct formatter *f, struct volume_group *vg)
 		f->nl(f);
 
 		seg_count = 1;
-		list_iterate(segh, &lv->segments) {
-			seg = list_item(segh, struct lv_segment);
-
+		list_iterate_items(seg, &lv->segments) {
 			if (!_print_segment(f, vg, seg_count++, seg)) {
 				stack;
 				return 0;
diff --git a/lib/metadata/lv_alloc.h b/lib/metadata/lv_alloc.h
new file mode 100644
index 000000000..fc087b3cf
--- /dev/null
+++ b/lib/metadata/lv_alloc.h
@@ -0,0 +1,14 @@
+/*
+ * Copyright (C) 2003 Sistina Software (UK) Limited.
+ *
+ * This file is released under the LGPL.
+ *
+ * This is the in core representation of a volume group and its
+ * associated physical and logical volumes.
+ */
+
+#ifndef _LVM_LV_ALLOC_H
+#include "pool.h"
+
+struct lv_segment *alloc_lv_segment(struct pool *mem, uint32_t stripes);
+#endif
diff --git a/lib/metadata/lv_manip.c b/lib/metadata/lv_manip.c
index 7d1943060..93a95fd3e 100644
--- a/lib/metadata/lv_manip.c
+++ b/lib/metadata/lv_manip.c
@@ -10,6 +10,7 @@
 #include "pv_map.h"
 #include "lvm-string.h"
 #include "toolcontext.h"
+#include "lv_alloc.h"
 
 /*
  * These functions adjust the pe counts in pv's
@@ -49,7 +50,7 @@ static void _put_extents(struct lv_segment *seg)
 	}
 }
 
-static struct lv_segment *_alloc_segment(struct pool *mem, uint32_t stripes)
+struct lv_segment *alloc_lv_segment(struct pool *mem, uint32_t stripes)
 {
 	struct lv_segment *seg;
 	uint32_t len = sizeof(*seg) + (stripes * sizeof(seg->area[0]));
@@ -75,7 +76,7 @@ static int _alloc_stripe_area(struct logical_volume *lv, uint32_t stripes,
 	if (smallest < area_len)
 		area_len = smallest;
 
-	if (!(seg = _alloc_segment(lv->vg->cmd->mem, stripes))) {
+	if (!(seg = alloc_lv_segment(lv->vg->cmd->mem, stripes))) {
 		log_err("Couldn't allocate new stripe segment.");
 		return 0;
 	}
@@ -188,7 +189,7 @@ static int _alloc_linear_area(struct logical_volume *lv, uint32_t *ix,
 	if (count > remaining)
 		count = remaining;
 
-	if (!(seg = _alloc_segment(lv->vg->cmd->mem, 1))) {
+	if (!(seg = alloc_lv_segment(lv->vg->cmd->mem, 1))) {
 		log_err("Couldn't allocate new stripe segment.");
 		return 0;
 	}
@@ -224,7 +225,7 @@ static int _alloc_mirrored_area(struct logical_volume *lv, uint32_t *ix,
 	if (count > remaining)
 		count = remaining;
 
-	if (!(seg = _alloc_segment(lv->vg->cmd->mem, 2))) {
+	if (!(seg = alloc_lv_segment(lv->vg->cmd->mem, 2))) {
 		log_err("Couldn't allocate new mirrored segment.");
 		return 0;
 	}
@@ -731,8 +732,11 @@ int lock_lvs(struct cmd_context *cmd, struct list *lvs, int flags)
 		lv = list_item(lvh, struct lv_list)->lv;
 		if (!lock_vol(cmd, lv->lvid.s, flags)) {
 			log_error("Failed to lock %s", lv->name);
-			/* FIXME Only unlock the locked ones */
-			unlock_lvs(cmd, lvs);
+			list_uniterate(lvh, lvs, lvh) {
+				lv = list_item(lvh, struct lv_list)->lv;
+				unlock_lv(cmd, lv->lvid.s);
+			}
+
 			return 0;
 		}
 	}
diff --git a/lib/metadata/merge.c b/lib/metadata/merge.c
index af3217cf6..286a92b8c 100644
--- a/lib/metadata/merge.c
+++ b/lib/metadata/merge.c
@@ -6,6 +6,8 @@
 
 #include "lib.h"
 #include "metadata.h"
+#include "toolcontext.h"
+#include "lv_alloc.h"
 
 /*
  * Test whether two segments could be merged by the current merging code
@@ -100,3 +102,89 @@ int lv_check_segments(struct logical_volume *lv)
 	return 1;
 }
 
+/*
+ * Split the supplied segment at the supplied logical extent
+ */
+static int _lv_split_segment(struct logical_volume *lv, struct lv_segment *seg,
+			     uint32_t le)
+{
+	size_t len;
+	struct lv_segment *split_seg;
+	uint32_t s;
+	uint32_t offset = le - seg->le;
+
+	if (seg->type == SEG_SNAPSHOT) {
+		log_error("Unable to split the snapshot segment at LE %" PRIu32
+			  " in LV %s", le, lv->name);
+		return 0;
+	}
+
+	/* Clone the existing segment */
+	if (!(split_seg = alloc_lv_segment(lv->vg->cmd->mem,
+					   seg->area_count))) {
+		log_error("Couldn't allocate new LV segment.");
+		return 0;
+	}
+
+	len = sizeof(*seg) + (seg->area_count * sizeof(seg->area[0]));
+	memcpy(split_seg, seg, len);
+
+	/* In case of a striped segment, the offset has to be / stripes */
+	if (seg->type == SEG_STRIPED)
+		offset /= seg->area_count;
+
+	/* Adjust the PV mapping */
+	for (s = 0; s < seg->area_count; s++) {
+		/* Split area at the offset */
+		switch (seg->area[s].type) {
+		case AREA_LV:
+			split_seg->area[s].u.lv.le =
+			    seg->area[s].u.lv.le + offset;
+			break;
+
+		case AREA_PV:
+			split_seg->area[s].u.pv.pe =
+			    seg->area[s].u.pv.pe + offset;
+			break;
+
+		default:
+			log_error("Unrecognised segment type %u",
+				  seg->area[s].type);
+			return 0;
+		}
+	}
+
+	split_seg->area_len = seg->area_len - offset;
+	seg->area_len = offset;
+
+	/* Add split off segment to the list _after_ the original one */
+	list_add_h(&seg->list, &split_seg->list);
+
+	return 1;
+}
+
+/*
+ * Ensure there's a segment boundary at the given logical extent
+ */
+int lv_split_segment(struct logical_volume *lv, uint32_t le)
+{
+	struct lv_segment *seg;
+
+	if (!(seg = find_seg_by_le(lv, le))) {
+		log_error("Segment with extent %" PRIu32 " in LV %s not found",
+			  le, lv->name);
+		return 0;
+	}
+
+	/* This is a segment start already */
+	if (le == seg->le)
+		return 1;
+
+	if (!_lv_split_segment(lv, seg, le)) {
+		stack;
+		return 0;
+	}
+
+	return 1;
+}
+
diff --git a/lib/metadata/metadata.h b/lib/metadata/metadata.h
index 0e4d3ec0d..24e79fc37 100644
--- a/lib/metadata/metadata.h
+++ b/lib/metadata/metadata.h
@@ -468,6 +468,11 @@ int lv_check_segments(struct logical_volume *lv);
  */
 int lv_merge_segments(struct logical_volume *lv);
 
+/*
+ * Ensure there's a segment boundary at a given LE, splitting if necessary
+ */
+int lv_split_segment(struct logical_volume *lv, uint32_t le);
+
 /*
  * Useful functions for managing snapshots.
  */
diff --git a/libdm/datastruct/list.h b/libdm/datastruct/list.h
index df3d32aea..a0054aa7f 100644
--- a/libdm/datastruct/list.h
+++ b/libdm/datastruct/list.h
@@ -63,26 +63,6 @@ static inline struct list *list_next(struct list *head, struct list *elem)
 	return (list_end(head, elem) ? NULL : elem->n);
 }
 
-#define list_iterate(v, head) \
-	for (v = (head)->n; v != head; v = v->n)
-
-#define list_uniterate(v, head, start) \
-	for (v = (start)->p; v != head; v = v->p)
-
-#define list_iterate_safe(v, t, head) \
-	for (v = (head)->n, t = v->n; v != head; v = t, t = v->n)
-
-static inline unsigned int list_size(const struct list *head)
-{
-	unsigned int s = 0;
-	const struct list *v;
-
-	list_iterate(v, head)
-	    s++;
-
-	return s;
-}
-
 #define list_item(v, t) \
     ((t *)((uintptr_t)(v) - (uintptr_t)&((t *) 0)->list))
 
@@ -96,4 +76,28 @@ static inline unsigned int list_size(const struct list *head)
 /* Given a known element in a known structure, locate the list head */
 #define list_head(v, t, e) struct_field(v, t, e, list)
 
+#define list_iterate(v, head) \
+	for (v = (head)->n; v != head; v = v->n)
+
+#define list_uniterate(v, head, start) \
+	for (v = (start)->p; v != head; v = v->p)
+
+#define list_iterate_safe(v, t, head) \
+	for (v = (head)->n, t = v->n; v != head; v = t, t = v->n)
+
+#define list_iterate_items(v, head) \
+	for (v = list_item((head)->n, typeof(*v)); &v->list != (head); \
+	     v = list_item(v->list.n, typeof(*v)))
+
+static inline unsigned int list_size(const struct list *head)
+{
+	unsigned int s = 0;
+	const struct list *v;
+
+	list_iterate(v, head)
+	    s++;
+
+	return s;
+}
+
 #endif