[PATCH V4 1/2] ublk_cmd.h: add one new ublk command: UBLK_IO_NEED_GET_DATA

[ZiyangZhang <ZiyangZhang@linux.alibaba.com>]

Add one new ublk command: UBLK_IO_NEED_GET_DATA. It is prepared for a new
feature designed for a user application who wants to allocate IO buffer
and set IO buffer address only after it receives an IO request from
ublksrv.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
---
 include/uapi/linux/ublk_cmd.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index ca33092354ab..51a1ef9051ab 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -28,12 +28,21 @@
  *      this IO request, request's handling result is committed to ublk
  *      driver, meantime FETCH_REQ is piggyback, and FETCH_REQ has to be
  *      handled before completing io request.
+ *
+ * NEED_GET_DATA: only used for write requests to set io addr and copy data
+ *      When NEED_GET_DATA is set, ublksrv has to issue UBLK_IO_NEED_GET_DATA
+ *      command after ublk driver returns UBLK_IO_RES_NEED_GET_DATA.
+ *
+ *      It is only used if ublksrv set UBLK_F_NEED_GET_DATA flag
+ *      while starting a ublk device.
  */
 #define	UBLK_IO_FETCH_REQ		0x20
 #define	UBLK_IO_COMMIT_AND_FETCH_REQ	0x21
+#define	UBLK_IO_NEED_GET_DATA	0x22
 
 /* only ABORT means that no re-fetch */
 #define UBLK_IO_RES_OK			0
+#define UBLK_IO_RES_NEED_GET_DATA	1
 #define UBLK_IO_RES_ABORT		(-ENODEV)
 
 #define UBLKSRV_CMD_BUF_OFFSET	0
@@ -54,6 +63,15 @@
  */
 #define UBLK_F_URING_CMD_COMP_IN_TASK	(1ULL << 1)
 
+/*
+ * User should issue io cmd again for write requests to
+ * set io buffer address and copy data from bio vectors
+ * to the userspace io buffer.
+ *
+ * In this mode, task_work is not used.
+ */
+#define UBLK_F_NEED_GET_DATA (1UL << 2)
+
 /* device state */
 #define UBLK_S_DEV_DEAD	0
 #define UBLK_S_DEV_LIVE	1
-- 
2.34.1