rbd: add wrapper for rbd_pool_metadata_remove()

Add wrapper for rbd_pool_metadata_remove() function which removes pool
metadata associated with a given key.

Signed-off-by: Mudit Agarwal <muagarwa@redhat.com>

rbd/pool_nautilus.go

@@ -1,7 +1,7 @@
 // +build !luminous,!mimic
 //
 // Ceph Nautilus is the first release that includes rbd_pool_metadata_get(),
-// rbd_pool_metadata_set().
+// rbd_pool_metadata_set() and rbd_pool_metadata_remove().
 
 package rbd
 
@@ -60,3 +60,15 @@ func SetPoolMetadata(ioctx *rados.IOContext, key, value string) error {
 	ret := C.rbd_pool_metadata_set(cephIoctx(ioctx), cKey, cValue)
 	return getError(ret)
 }
+
+// RemovePoolMetadata removes the pool metadata value for a given pool metadata key.
+//
+// Implements:
+//  int rbd_pool_metadata_remove(rados_ioctx_t io_ctx, const char *key)
+func RemovePoolMetadata(ioctx *rados.IOContext, key string) error {
+	cKey := C.CString(key)
+	defer C.free(unsafe.Pointer(cKey))
+
+	ret := C.rbd_pool_metadata_remove(cephIoctx(ioctx), cKey)
+	return getError(ret)
+}

rbd/pool_nautilus_test.go

@@ -59,4 +59,25 @@ func TestPoolMetadata(t *testing.T) {
 		assert.NoError(t, err)
 		assert.Equal(t, keyLen, len(myVal))
 	})
+
+	t.Run("removeNonExistingKey", func(t *testing.T) {
+		err := RemovePoolMetadata(ioctx, "someKey")
+		assert.Error(t, err)
+	})
+
+	t.Run("removeExistingKey", func(t *testing.T) {
+		var (
+			myKey = "myKey"
+			myVal = "myVal"
+		)
+		assert.NoError(t, SetPoolMetadata(ioctx, myKey, myVal))
+		_, err := GetPoolMetadata(ioctx, myKey)
+		assert.NoError(t, err)
+
+		// Remove the key.
+		err = RemovePoolMetadata(ioctx, myKey)
+		assert.NoError(t, err)
+		_, err = GetPoolMetadata(ioctx, myKey)
+		assert.Error(t, err)
+	})
 }