Make pointer from the origin volume to the shared store.

There may be only one shared store, so we do not need to build a list.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 lib/metadata/lv_manip.c          |   12 ++++++++++++
 lib/metadata/metadata-exported.h |    4 ++++
 lib/metadata/snapshot_manip.c    |   22 ++++++++++++++++++++++
 3 files changed, 38 insertions(+)

Index: LVM2.2.02.53/lib/metadata/lv_manip.c
===================================================================
--- LVM2.2.02.53.orig/lib/metadata/lv_manip.c	2009-10-13 01:52:59.000000000 +0200
+++ LVM2.2.02.53/lib/metadata/lv_manip.c	2009-10-13 02:04:47.000000000 +0200
@@ -1872,6 +1872,7 @@ int vg_max_lv_reached(struct volume_grou
 void lv_init(struct logical_volume *lv)
 {
 	lv->snapshot = NULL;
+	lv->shared_snapshot = NULL;
 	dm_list_init(&lv->snapshot_segs);
 	dm_list_init(&lv->segments);
 	dm_list_init(&lv->tags);
@@ -2930,6 +2931,17 @@ int lv_create_single(struct volume_group
 					  "supported yet.");
 				return 0;
 			}
+			if (lv_is_multisnap_origin(org)) {
+				log_error("It is not allowed to create more "
+					  "shared snapshot stores.");
+				return 0;
+			}
+			if (lv_is_origin(org) && !lv_is_multisnap_origin(org) &&
+			    lp->shared_store) {
+				log_error("It is not allowed to mix shared "
+					  "and unshared snapshots.");
+				return 0;
+			}
 			if (org->status & LOCKED) {
 				log_error("Snapshots of locked devices are not "
 					  "supported yet");
Index: LVM2.2.02.53/lib/metadata/metadata-exported.h
===================================================================
--- LVM2.2.02.53.orig/lib/metadata/metadata-exported.h	2009-10-13 01:53:18.000000000 +0200
+++ LVM2.2.02.53/lib/metadata/metadata-exported.h	2009-10-13 02:04:47.000000000 +0200
@@ -322,6 +322,9 @@ struct logical_volume {
 	struct dm_list snapshot_segs;
 	struct lv_segment *snapshot;
 
+	/* A shared-snapshot segment for this origin */
+	struct lv_segment *shared_snapshot;
+
 	struct dm_list segments;
 	struct dm_list tags;
 	struct dm_list segs_using_this_lv;
@@ -605,6 +608,7 @@ struct lv_segment *first_seg(const struc
 int lv_is_origin(const struct logical_volume *lv);
 int lv_is_virtual_origin(const struct logical_volume *lv);
 int lv_is_cow(const struct logical_volume *lv);
+int lv_is_multisnap_origin(const struct logical_volume *lv);
 
 /* Test if given LV is visible from user's perspective */
 int lv_is_visible(const struct logical_volume *lv);
Index: LVM2.2.02.53/lib/metadata/snapshot_manip.c
===================================================================
--- LVM2.2.02.53.orig/lib/metadata/snapshot_manip.c	2009-10-13 01:54:33.000000000 +0200
+++ LVM2.2.02.53/lib/metadata/snapshot_manip.c	2009-10-13 02:06:03.000000000 +0200
@@ -28,6 +28,11 @@ int lv_is_cow(const struct logical_volum
 	return lv->snapshot ? 1 : 0;
 }
 
+int lv_is_multisnap_origin(const struct logical_volume *lv)
+{
+	return lv_is_origin(lv) && lv->shared_snapshot;
+}
+
 int lv_is_visible(const struct logical_volume *lv)
 {
 	if (lv->status & SNAPSHOT)
@@ -90,6 +95,15 @@ int init_snapshot_seg(struct lv_segment 
 		}
 	}
 
+	if (seg->status & SNAPSHOT_SHARED) {
+		if (!origin->shared_snapshot) {
+			origin->shared_snapshot = seg;
+		} else {
+			log_err("Origin '%s' has already a shared snapshot.", origin->name);
+			return_0;
+		}
+	}
+
 	dm_list_add(&origin->snapshot_segs, &seg->origin_list);
 
 	return 1;
@@ -116,6 +130,11 @@ int vg_add_snapshot(struct logical_volum
 		return 0;
 	}
 
+	if (snapshot_flags & SNAPSHOT_SHARED && origin->shared_snapshot) {
+		log_error("Origin has already a shared snapshot.");
+		return 0;
+	}
+
 	if (!(snap = lv_create_empty("snapshot%d",
 				     lvid, LVM_READ | LVM_WRITE | VISIBLE_LV,
 				     ALLOC_INHERIT, origin->vg)))
@@ -136,6 +155,9 @@ int vg_remove_snapshot(struct logical_vo
 	dm_list_del(&cow->snapshot->origin_list);
 	cow->snapshot->origin->origin_count--;
 
+	if (cow->snapshot->origin->shared_snapshot == cow->snapshot)
+		cow->snapshot->origin->shared_snapshot = NULL;
+
 	if (!lv_remove(cow->snapshot->lv)) {
 		log_error("Failed to remove internal snapshot LV %s",
 			  cow->snapshot->lv->name);