diff --git a/Documentation/device-mapper/snapshot.txt b/Documentation/device-mapper/snapshot.txt
index 0d5bc46..ad6949b 100644
--- a/Documentation/device-mapper/snapshot.txt
+++ b/Documentation/device-mapper/snapshot.txt
@@ -41,9 +41,13 @@
 the amount of free space and expand the <COW device> before it fills up.
 
 <persistent?> is P (Persistent) or N (Not persistent - will not survive
-after reboot).
-The difference is that for transient snapshots less metadata must be
-saved on disk - they can be kept in memory by the kernel.
+after reboot).  O (Overflow) can be added as a persistent store option
+to allow userspace to advertise its support for seeing "Overflow" in the
+snapshot status.  So supported store types are "P", "PO" and "N".
+
+The difference between persistent and transient is with transient
+snapshots less metadata must be saved on disk - they can be kept in
+memory by the kernel.
 
 
 * snapshot-merge <origin> <COW device> <persistent> <chunksize>
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index ebaa4f8..192bb8b 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -203,7 +203,7 @@
 		return -EINVAL;
 	}
 
-	tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
+	tmp_store = kzalloc(sizeof(*tmp_store), GFP_KERNEL);
 	if (!tmp_store) {
 		ti->error = "Exception store allocation failed";
 		return -ENOMEM;
@@ -215,7 +215,7 @@
 	else if (persistent == 'N')
 		type = get_type("N");
 	else {
-		ti->error = "Persistent flag is not P or N";
+		ti->error = "Exception store type is not P or N";
 		r = -EINVAL;
 		goto bad_type;
 	}
@@ -233,7 +233,7 @@
 	if (r)
 		goto bad;
 
-	r = type->ctr(tmp_store, 0, NULL);
+	r = type->ctr(tmp_store, (strlen(argv[0]) > 1 ? &argv[0][1] : NULL));
 	if (r) {
 		ti->error = "Exception store type constructor failed";
 		goto bad;
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
index 0b25362..fae34e7 100644
--- a/drivers/md/dm-exception-store.h
+++ b/drivers/md/dm-exception-store.h
@@ -42,8 +42,7 @@
 	const char *name;
 	struct module *module;
 
-	int (*ctr) (struct dm_exception_store *store,
-		    unsigned argc, char **argv);
+	int (*ctr) (struct dm_exception_store *store, char *options);
 
 	/*
 	 * Destroys this object when you've finished with it.
@@ -123,6 +122,8 @@
 	unsigned chunk_shift;
 
 	void *context;
+
+	bool userspace_supports_overflow;
 };
 
 /*
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index bf71583..aeacad9 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -7,6 +7,7 @@
 
 #include "dm-exception-store.h"
 
+#include <linux/ctype.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/vmalloc.h>
@@ -843,8 +844,7 @@
 		DMWARN("write header failed");
 }
 
-static int persistent_ctr(struct dm_exception_store *store,
-			  unsigned argc, char **argv)
+static int persistent_ctr(struct dm_exception_store *store, char *options)
 {
 	struct pstore *ps;
 
@@ -873,6 +873,16 @@
 		return -ENOMEM;
 	}
 
+	if (options) {
+		char overflow = toupper(options[0]);
+		if (overflow == 'O')
+			store->userspace_supports_overflow = true;
+		else {
+			DMERR("Unsupported persistent store option: %s", options);
+			return -EINVAL;
+		}
+	}
+
 	store->context = ps;
 
 	return 0;
@@ -888,7 +898,8 @@
 	case STATUSTYPE_INFO:
 		break;
 	case STATUSTYPE_TABLE:
-		DMEMIT(" P %llu", (unsigned long long)store->chunk_size);
+		DMEMIT(" %s %llu", store->userspace_supports_overflow ? "PO" : "P",
+		       (unsigned long long)store->chunk_size);
 	}
 
 	return sz;
diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
index 1ce9a25..9b7c8c8 100644
--- a/drivers/md/dm-snap-transient.c
+++ b/drivers/md/dm-snap-transient.c
@@ -70,8 +70,7 @@
 	*metadata_sectors = 0;
 }
 
-static int transient_ctr(struct dm_exception_store *store,
-			 unsigned argc, char **argv)
+static int transient_ctr(struct dm_exception_store *store, char *options)
 {
 	struct transient_c *tc;
 
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index c0bcd65..c06b74e 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1098,7 +1098,7 @@
 }
 
 /*
- * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
+ * Construct a snapshot mapping: <origin_dev> <COW-dev> <p|po|n> <chunk-size>
  */
 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 {
@@ -1302,6 +1302,7 @@
 
 	u.store_swap = snap_dest->store;
 	snap_dest->store = snap_src->store;
+	snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
 	snap_src->store = u.store_swap;
 
 	snap_dest->store->snap = snap_dest;
@@ -1739,8 +1740,11 @@
 
 			pe = __find_pending_exception(s, pe, chunk);
 			if (!pe) {
-				s->snapshot_overflowed = 1;
-				DMERR("Snapshot overflowed: Unable to allocate exception.");
+				if (s->store->userspace_supports_overflow) {
+					s->snapshot_overflowed = 1;
+					DMERR("Snapshot overflowed: Unable to allocate exception.");
+				} else
+					__invalidate_snapshot(s, -ENOMEM);
 				r = -EIO;
 				goto out_unlock;
 			}
@@ -2365,7 +2369,7 @@
 
 static struct target_type snapshot_target = {
 	.name    = "snapshot",
-	.version = {1, 14, 0},
+	.version = {1, 15, 0},
 	.module  = THIS_MODULE,
 	.ctr     = snapshot_ctr,
 	.dtr     = snapshot_dtr,
@@ -2379,7 +2383,7 @@
 
 static struct target_type merge_target = {
 	.name    = dm_snapshot_merge_target_name,
-	.version = {1, 3, 0},
+	.version = {1, 4, 0},
 	.module  = THIS_MODULE,
 	.ctr     = snapshot_ctr,
 	.dtr     = snapshot_dtr,