Introduce ocf_forward_write_zeros()

This is meant to be used in atomic mode to avoid allocating huge buffers
for zeroing data on drive.

Signed-off-by: Robert Baldyga <robert.baldyga@huawei.com>
Signed-off-by: Michal Mielewczyk <michal.mielewczyk@huawei.com>

inc/ocf_io.h

@@ -285,6 +285,20 @@ void ocf_forward_flush(ocf_volume_t volume, ocf_forward_token_t token);
 void ocf_forward_discard(ocf_volume_t volume, ocf_forward_token_t token,
 		uint64_t addr, uint64_t bytes);
 
+/**
+ * @brief Forward write_zeros to another subvolume
+ *
+ * Forwarding automatically increases forwarded io refcount, so at some
+ * point additional ocf_forward_end() needs to be called to balance it.
+ *
+ * @param[in] volume Volume to which IO is being submitted
+ * @param[in] token Token representing IO to be forwarded
+ * @param[in] addr Address to which IO is being submitted
+ * @param[in] bytes Length of the IO
+ */
+void ocf_forward_write_zeros(ocf_volume_t volume, ocf_forward_token_t token,
+		uint64_t addr, uint64_t bytes);
+
 /**
  * @brief Increment forwarded io refcount
  *

inc/ocf_volume.h

@@ -116,6 +116,19 @@ struct ocf_volume_ops {
 	void (*forward_discard)(ocf_volume_t volume, ocf_forward_token_t token,
 			uint64_t addr, uint64_t bytes);
 
+	/**
+	 * @brief Froward operation to write zeros to target address (including
+	 *        metadata extended LBAs in atomic mode)
+	 *
+	 * @param[in] volume Volume to which IO is being submitted
+	 * @param[in] token Token representing IO to be forwarded
+	 * @param[in] addr Address to which IO is being submitted
+	 * @param[in] bytes Length of the IO
+	 */
+	void (*forward_write_zeros)(ocf_volume_t volume,
+			ocf_forward_token_t token, uint64_t addr,
+			uint64_t bytes);
+
 	/**
 	 * @brief Volume initialization callback, called when volume object
 	 *        is being initialized