diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index a680c76..737d388 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -713,6 +713,9 @@
 	if (r)
 		goto bad;
 
+	if (bdev_size > THIN_METADATA_MAX_SECTORS)
+		bdev_size = THIN_METADATA_MAX_SECTORS;
+
 	disk_super = dm_block_data(sblock);
 	disk_super->magic = cpu_to_le64(THIN_SUPERBLOCK_MAGIC);
 	disk_super->version = cpu_to_le32(THIN_VERSION);
diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index 859c168..ed4725e 100644
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -11,6 +11,19 @@
 
 #define THIN_METADATA_BLOCK_SIZE 4096
 
+/*
+ * The metadata device is currently limited in size.
+ *
+ * We have one block of index, which can hold 255 index entries.  Each
+ * index entry contains allocation info about 16k metadata blocks.
+ */
+#define THIN_METADATA_MAX_SECTORS (255 * (1 << 14) * (THIN_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))
+
+/*
+ * A metadata device larger than 16GB triggers a warning.
+ */
+#define THIN_METADATA_MAX_SECTORS_WARNING (16 * (1024 * 1024 * 1024 >> SECTOR_SHIFT))
+
 /*----------------------------------------------------------------*/
 
 struct dm_pool_metadata;
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index bcb1433..2378ee8 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -33,16 +33,6 @@
 #define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
 
 /*
- * The metadata device is currently limited in size.  The limitation is
- * checked lower down in dm-space-map-metadata, but we also check it here
- * so we can fail early.
- *
- * We have one block of index, which can hold 255 index entries.  Each
- * index entry contains allocation info about 16k metadata blocks.
- */
-#define METADATA_DEV_MAX_SECTORS (255 * (1 << 14) * (THIN_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))
-
-/*
  * Device id is restricted to 24 bits.
  */
 #define MAX_DEV_ID ((1 << 24) - 1)
@@ -1736,6 +1726,7 @@
 	dm_block_t low_water_blocks;
 	struct dm_dev *metadata_dev;
 	sector_t metadata_dev_size;
+	char b[BDEVNAME_SIZE];
 
 	/*
 	 * FIXME Remove validation from scope of lock.
@@ -1757,11 +1748,9 @@
 	}
 
 	metadata_dev_size = i_size_read(metadata_dev->bdev->bd_inode) >> SECTOR_SHIFT;
-	if (metadata_dev_size > METADATA_DEV_MAX_SECTORS) {
-		ti->error = "Metadata device is too large";
-		r = -EINVAL;
-		goto out_metadata;
-	}
+	if (metadata_dev_size > THIN_METADATA_MAX_SECTORS_WARNING)
+		DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
+		       bdevname(metadata_dev->bdev, b), THIN_METADATA_MAX_SECTORS);
 
 	r = dm_get_device(ti, argv[1], FMODE_READ | FMODE_WRITE, &data_dev);
 	if (r) {