[PATCH 2/4] io_uring: add iopoll infrastructure for io_uring_cmd

[Kanchan Joshi]

Put this up in the same way as iopoll is done for regular read/write IO.
Make place for storing a cookie into struct io_uring_cmd on its
submission. Perform the completion using the ->uring_cmd_iopoll handler.

Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
Signed-off-by: Pankaj Raghav <p.raghav at samsung.com>
---
 include/linux/io_uring.h |  8 ++++++--
 io_uring/io_uring.c      |  6 ++++++
 io_uring/opdef.c         |  1 +
 io_uring/rw.c            |  8 +++++++-
 io_uring/uring_cmd.c     | 11 +++++++++--
 5 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 4a2f6cc5a492..58676c0a398f 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -20,8 +20,12 @@ enum io_uring_cmd_flags {
 struct io_uring_cmd {
 	struct file	*file;
 	const void	*cmd;
-	/* callback to defer completions to task context */
-	void (*task_work_cb)(struct io_uring_cmd *cmd);
+	union {
+		/* callback to defer completions to task context */
+		void (*task_work_cb)(struct io_uring_cmd *cmd);
+		/* used for polled completion */
+		void *cookie;
+	};
 	u32		cmd_op;
 	u32		pad;
 	u8		pdu[32]; /* available inline for free use */
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index b54218da075c..48a430a86b50 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1296,6 +1296,12 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
 			    wq_list_empty(&ctx->iopoll_list))
 				break;
 		}
+
+		if (task_work_pending(current)) {
+			mutex_unlock(&ctx->uring_lock);
+			io_run_task_work();
+			mutex_lock(&ctx->uring_lock);
+		}
 		ret = io_do_iopoll(ctx, !min);
 		if (ret < 0)
 			break;
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 72dd2b2d8a9d..9a0df19306fe 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -466,6 +466,7 @@ const struct io_op_def io_op_defs[] = {
 		.needs_file		= 1,
 		.plug			= 1,
 		.name			= "URING_CMD",
+		.iopoll			= 1,
 		.async_size		= uring_cmd_pdu_size(1),
 		.prep			= io_uring_cmd_prep,
 		.issue			= io_uring_cmd,
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 2b784795103c..1a4fb8a44b9a 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -1005,7 +1005,13 @@ int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
 		if (READ_ONCE(req->iopoll_completed))
 			break;
 
-		ret = rw->kiocb.ki_filp->f_op->iopoll(&rw->kiocb, &iob, poll_flags);
+		if (req->opcode == IORING_OP_URING_CMD) {
+			struct io_uring_cmd *ioucmd = (struct io_uring_cmd *)rw;
+
+			ret = req->file->f_op->uring_cmd_iopoll(ioucmd);
+		} else
+			ret = rw->kiocb.ki_filp->f_op->iopoll(&rw->kiocb, &iob,
+							poll_flags);
 		if (unlikely(ret < 0))
 			return ret;
 		else if (ret)
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 0a421ed51e7e..5cc339fba8b8 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -49,7 +49,11 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2)
 	io_req_set_res(req, 0, ret);
 	if (req->ctx->flags & IORING_SETUP_CQE32)
 		io_req_set_cqe32_extra(req, res2, 0);
-	__io_req_complete(req, 0);
+	if (req->ctx->flags & IORING_SETUP_IOPOLL)
+		/* order with io_iopoll_req_issued() checking ->iopoll_completed */
+		smp_store_release(&req->iopoll_completed, 1);
+	else
+		__io_req_complete(req, 0);
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_done);
 
@@ -89,8 +93,11 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 		issue_flags |= IO_URING_F_SQE128;
 	if (ctx->flags & IORING_SETUP_CQE32)
 		issue_flags |= IO_URING_F_CQE32;
-	if (ctx->flags & IORING_SETUP_IOPOLL)
+	if (ctx->flags & IORING_SETUP_IOPOLL) {
 		issue_flags |= IO_URING_F_IOPOLL;
+		req->iopoll_completed = 0;
+		WRITE_ONCE(ioucmd->cookie, NULL);
+	}
 
 	if (req_has_async_data(req))
 		ioucmd->cmd = req->async_data;
-- 
2.25.1