Don't allow shrinking the shared store.

The kernel will never support it.

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

---
 tools/lvresize.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: lvm2/tools/lvresize.c
===================================================================
--- lvm2.orig/tools/lvresize.c
+++ lvm2/tools/lvresize.c
@@ -578,6 +578,11 @@ static int _lvresize(struct cmd_context 
 			return ECMD_FAILED;
 		}
 	}
+	if (lp->resize == LV_REDUCE &&
+	    lv_is_cow(lv) && lv->snapshot->status & SNAPSHOT_SHARED) {
+		log_error("Shared snapshot cannot be reduced.");
+		return ECMD_FAILED;
+	}
 
 	if ((lp->resize == LV_REDUCE) && lp->argc)
 		log_warn("Ignoring PVs on command line when reducing");