[RFC PATCH 08/12] io_uring: support OP_READ/OP_WRITE for fused slave request

[Ming Lei <ming.lei@redhat.com>]

Start to allow fused slave request to support OP_READ/OP_WRITE, and
the buffer can be retrieved from master request.

Once the slave request is completed, the master buffer will be returned
back.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 io_uring/opdef.c |  2 ++
 io_uring/rw.c    | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 63b90e8e65f8..f044629e5475 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -235,6 +235,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.ioprio			= 1,
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
+		.fused_slave		= 1,
 		.prep			= io_prep_rw,
 		.issue			= io_read,
 	},
@@ -248,6 +249,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.ioprio			= 1,
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
+		.fused_slave		= 1,
 		.prep			= io_prep_rw,
 		.issue			= io_write,
 	},
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 4c233910e200..36d31a943317 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -19,6 +19,7 @@
 #include "kbuf.h"
 #include "rsrc.h"
 #include "rw.h"
+#include "fused_cmd.h"
 
 struct io_rw {
 	/* NOTE: kiocb has the file as the first member, so don't do it here */
@@ -371,6 +372,17 @@ static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
 	size_t sqe_len;
 	ssize_t ret;
 
+	/*
+	 * SLAVE OP passes buffer offset from sqe->addr actually, since
+	 * the fused cmd kbuf's mapped start address is zero.
+	 */
+	if (req->flags & REQ_F_FUSED_SLAVE) {
+		ret = io_import_kbuf_for_slave(rw->addr, rw->len, ddir, iter, req);
+		if (ret)
+			return ERR_PTR(ret);
+		return NULL;
+	}
+
 	if (opcode == IORING_OP_READ_FIXED || opcode == IORING_OP_WRITE_FIXED) {
 		ret = io_import_fixed(ddir, iter, req->imu, rw->addr, rw->len);
 		if (ret)
@@ -428,11 +440,19 @@ static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
  */
 static ssize_t loop_rw_iter(int ddir, struct io_rw *rw, struct iov_iter *iter)
 {
+	struct io_kiocb *req = cmd_to_io_kiocb(rw);
 	struct kiocb *kiocb = &rw->kiocb;
 	struct file *file = kiocb->ki_filp;
 	ssize_t ret = 0;
 	loff_t *ppos;
 
+	/*
+	 * Fused slave req hasn't user buffer, so ->read/->write can't
+	 * be supported
+	 */
+	if (req->flags & REQ_F_FUSED_SLAVE)
+		return -EOPNOTSUPP;
+
 	/*
 	 * Don't support polled IO through this interface, and we can't
 	 * support non-blocking either. For the latter, this just causes
-- 
2.31.1