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: LVM2.2.02.73/lib/metadata/lv_manip.c
===================================================================
--- LVM2.2.02.73.orig/lib/metadata/lv_manip.c	2010-09-10 17:44:56.000000000 +0200
+++ LVM2.2.02.73/lib/metadata/lv_manip.c	2010-09-10 17:45:05.000000000 +0200
@@ -2008,6 +2008,7 @@ struct logical_volume *alloc_lv(struct d
 	}
 
 	lv->snapshot = NULL;
+	lv->shared_snapshot = NULL;
 	dm_list_init(&lv->snapshot_segs);
 	dm_list_init(&lv->segments);
 	dm_list_init(&lv->tags);
@@ -3095,6 +3096,17 @@ 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: LVM2.2.02.73/lib/metadata/metadata-exported.h
===================================================================
--- LVM2.2.02.73.orig/lib/metadata/metadata-exported.h	2010-09-10 17:44:56.000000000 +0200
+++ LVM2.2.02.73/lib/metadata/metadata-exported.h	2010-09-10 17:45:05.000000000 +0200
@@ -419,6 +419,9 @@ struct logical_volume {
 	struct replicator_device *rdevice;/* For replicator-devs, rimages, slogs - reference to rdevice */
 	struct dm_list rsites;	/* For replicators - all sites */
 
+	/* 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;
@@ -721,6 +724,7 @@ int lv_is_virtual_origin(const struct lo
 int lv_is_cow(const struct logical_volume *lv);
 int lv_is_merging_origin(const struct logical_volume *origin);
 int lv_is_merging_cow(const struct logical_volume *snapshot);
+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: LVM2.2.02.73/lib/metadata/snapshot_manip.c
===================================================================
--- LVM2.2.02.73.orig/lib/metadata/snapshot_manip.c	2010-09-10 17:44:56.000000000 +0200
+++ LVM2.2.02.73/lib/metadata/snapshot_manip.c	2010-09-10 17:45:05.000000000 +0200
@@ -30,6 +30,11 @@ int lv_is_cow(const struct logical_volum
 	return (!lv_is_origin(lv) && 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)
@@ -116,6 +121,15 @@ int init_snapshot_seg(struct lv_segment 
 	if (merge)
 		init_snapshot_merge(seg, origin);
 
+	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;
@@ -169,6 +183,11 @@ 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)))
@@ -211,6 +230,9 @@ int vg_remove_snapshot(struct logical_vo
 		}
 	}
 
+	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);