Implement a shared store target in libdevmapper.

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

---
 libdm/libdevmapper.h  |    6 ++++++
 libdm/libdm-deptree.c |   32 +++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

Index: LVM2.2.02.70/libdm/libdevmapper.h
===================================================================
--- LVM2.2.02.70.orig/libdm/libdevmapper.h	2010-07-10 04:07:27.000000000 +0200
+++ LVM2.2.02.70/libdm/libdevmapper.h	2010-07-10 04:07:47.000000000 +0200
@@ -409,6 +409,12 @@ int dm_tree_node_add_snapshot_merge_targ
 					     const char *cow_uuid,
 					     const char *merge_uuid,
 					     uint32_t chunk_size);
+int dm_tree_node_add_snapshot_shared_target(struct dm_tree_node *node,
+					       uint64_t size,
+					       const char *origin_uuid,
+					       const char *cow_uuid,
+					       const char *exception_store,
+					       uint32_t chunk_size);
 int dm_tree_node_add_error_target(struct dm_tree_node *node,
 				     uint64_t size);
 int dm_tree_node_add_zero_target(struct dm_tree_node *node,
Index: LVM2.2.02.70/libdm/libdm-deptree.c
===================================================================
--- LVM2.2.02.70.orig/libdm/libdm-deptree.c	2010-07-10 04:07:27.000000000 +0200
+++ LVM2.2.02.70/libdm/libdm-deptree.c	2010-07-10 04:07:47.000000000 +0200
@@ -40,6 +40,7 @@ enum {
 	SEG_SNAPSHOT,
 	SEG_SNAPSHOT_ORIGIN,
 	SEG_SNAPSHOT_MERGE,
+	SEG_SNAPSHOT_SHARED,
 	SEG_STRIPED,
 	SEG_ZERO,
 };
@@ -59,6 +60,7 @@ struct {
 	{ SEG_SNAPSHOT, "snapshot" },
 	{ SEG_SNAPSHOT_ORIGIN, "snapshot-origin" },
 	{ SEG_SNAPSHOT_MERGE, "snapshot-merge" },
+	{ SEG_SNAPSHOT_SHARED, "multisnapshot" },
 	{ SEG_STRIPED, "striped" },
 	{ SEG_ZERO, "zero"},
 };
@@ -1704,6 +1706,14 @@ static int _emit_segment_line(struct dm_
 			return_0;
 		EMIT_PARAMS(pos, "%s", originbuf);
 		break;
+	case SEG_SNAPSHOT_SHARED:
+		if (!_build_dev_string(originbuf, sizeof(originbuf), seg->origin))
+			return_0;
+		if (!_build_dev_string(cowbuf, sizeof(cowbuf), seg->cow))
+			return_0;
+		EMIT_PARAMS(pos, "%s %s %d 0 %s 0", originbuf, cowbuf,
+			    seg->chunk_size, seg->exception_store);
+		break;
 	case SEG_STRIPED:
 		EMIT_PARAMS(pos, "%u %u ", seg->area_count, seg->stripe_size);
 		break;
@@ -1722,6 +1732,7 @@ static int _emit_segment_line(struct dm_
 	case SEG_SNAPSHOT:
 	case SEG_SNAPSHOT_ORIGIN:
 	case SEG_SNAPSHOT_MERGE:
+	case SEG_SNAPSHOT_SHARED:
 	case SEG_ZERO:
 		break;
 	case SEG_CRYPT:
@@ -2014,14 +2025,12 @@ static int _add_snapshot_target(struct d
 				   const char *origin_uuid,
 				   const char *cow_uuid,
 				   const char *merge_uuid,
+				   unsigned seg_type,
 				   const char *exception_store,
 				   uint32_t chunk_size)
 {
 	struct load_segment *seg;
 	struct dm_tree_node *origin_node, *cow_node, *merge_node;
-	unsigned seg_type;
-
-	seg_type = !merge_uuid ? SEG_SNAPSHOT : SEG_SNAPSHOT_MERGE;
 
 	if (!(seg = _add_segment(node, seg_type, size)))
 		return_0;
@@ -2080,7 +2089,8 @@ int dm_tree_node_add_snapshot_target(str
 				     uint32_t chunk_size)
 {
 	return _add_snapshot_target(node, size, origin_uuid, cow_uuid,
-				    NULL, exception_store, chunk_size);
+				    NULL, SEG_SNAPSHOT, exception_store,
+				    chunk_size);
 }
 
 int dm_tree_node_add_snapshot_merge_target(struct dm_tree_node *node,
@@ -2091,7 +2101,19 @@ int dm_tree_node_add_snapshot_merge_targ
 					   uint32_t chunk_size)
 {
 	return _add_snapshot_target(node, size, origin_uuid, cow_uuid,
-				    merge_uuid, "P", chunk_size);
+				    merge_uuid, SEG_SNAPSHOT_MERGE, "P",
+				    chunk_size);
+}
+
+int dm_tree_node_add_snapshot_shared_target(struct dm_tree_node *node,
+					       uint64_t size,
+					       const char *origin_uuid,
+					       const char *cow_uuid,
+					       const char *exception_store,
+					       uint32_t chunk_size)
+{
+	return _add_snapshot_target(node, size, origin_uuid, cow_uuid, NULL,
+			    SEG_SNAPSHOT_SHARED, exception_store, chunk_size);
 }
 
 int dm_tree_node_add_error_target(struct dm_tree_node *node,