volume: Introduce general IO forward mechanism

Allow the core volume IOs to be forwarded directly to backend volumes to
avoid unnecessary allocations.

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

inc/ocf_io.h

@@ -1,5 +1,6 @@
 /*
  * Copyright(c) 2012-2021 Intel Corporation
+ * Copyright(c) 2024 Huawei Technologies
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
@@ -235,4 +236,68 @@ void ocf_io_handle(struct ocf_io *io, void *opaque);
  */
 ocf_volume_t ocf_io_get_volume(struct ocf_io *io);
 
+/**
+ * @brief Get the original OCF IO associated with forward token
+ *
+ * @param[in] token Forward token
+ */
+struct ocf_io *ocf_forward_get_io(ocf_forward_token_t token);
+
+/**
+ * @brief Forward io 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] token Forward token
+ * @param[in] volume Volume to which IO is being submitted
+ * @param[in] token Token representing IO to be forwarded
+ * @param[in] dir Direction OCF_READ/OCF_WRITE
+ * @param[in] addr Address to which IO is being submitted
+ * @param[in] bytes Length of the IO
+ * @param[in] offset Offset within the IO data
+ */
+void ocf_forward_io(ocf_volume_t volume, ocf_forward_token_t token,
+		int dir, uint64_t addr, uint64_t bytes, uint64_t offset);
+
+/**
+ * @brief Forward flush 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
+ */
+void ocf_forward_flush(ocf_volume_t volume, ocf_forward_token_t token);
+
+/**
+ * @brief Forward discard 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_discard(ocf_volume_t volume, ocf_forward_token_t token,
+		uint64_t addr, uint64_t bytes);
+
+/**
+ * @brief Increment forwarded io refcount
+ *
+ * @param[in] token Forward token
+ */
+void ocf_forward_get(ocf_forward_token_t token);
+
+/**
+ * @brief Complete the forwarded io
+ *
+ * @param[in] token Forward token to be completed
+ * @param[in] error Completion status code
+ */
+void ocf_forward_end(ocf_forward_token_t token, int error);
+
 #endif /* __OCF_IO_H__ */

inc/ocf_types.h

@@ -1,5 +1,6 @@
 /*
  * Copyright(c) 2012-2021 Intel Corporation
+ * Copyright(c) 2024 Huawei Technologies
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
@@ -72,6 +73,17 @@ typedef struct ocf_volume_uuid *ocf_uuid_t;
  */
 typedef void ctx_data_t;
 
+/**
+ * @brief IO forward token
+ *
+ * The token is associated with IO that is being forwarded. It allows
+ * OCF to keep track of which IO has been forwarded where. It also has
+ * refcount which can be increased/decreased on each forward level, so
+ * that there is no need to introduce additional counters if at some
+ * level the forward needs to be splitted into several sub-forwards.
+ */
+typedef uint64_t ocf_forward_token_t;
+
 /**
  * @brief handle to I/O queue
  */

inc/ocf_volume.h

@@ -1,5 +1,6 @@
 /*
  * Copyright(c) 2012-2022 Intel Corporation
+ * Copyright(c) 2024 Huawei Technologies
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
@@ -82,6 +83,39 @@ struct ocf_volume_ops {
 	 */
 	void (*submit_write_zeroes)(struct ocf_io *io);
 
+	/**
+	 * @brief Forward the original io directly to the volume
+	 *
+	 * @param[in] volume Volume to which IO is being submitted
+	 * @param[in] token Token representing IO to be forwarded
+	 * @param[in] dir Direction OCF_READ/OCF_WRITE
+	 * @param[in] addr Address to which IO is being submitted
+	 * @param[in] bytes Length of the IO
+	 * @param[in] offset Offset within the IO data
+	 */
+	void (*forward_io)(ocf_volume_t volume, ocf_forward_token_t token,
+			int dir, uint64_t addr, uint64_t bytes,
+			uint64_t offset);
+
+	/**
+	 * @brief Forward the original flush io directly to the volume
+	 *
+	 * @param[in] volume Volume to which IO is being submitted
+	 * @param[in] token Token representing IO to be forwarded
+	 */
+	void (*forward_flush)(ocf_volume_t volume, ocf_forward_token_t token);
+
+	/**
+	 * @brief Forward the original discard io directly to the volume
+	 *
+	 * @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_discard)(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