[RFC PATCH 10/12] nvme: submisssion/completion of uring_cmd to/from the registered queue

[Kanchan Joshi]

If IORING_URING_CMD_DIRECT flag is set, get the registered qid and
- submit the io_uring command via mq_ops->queue_uring_cmd.
- complete it via mq_ops->poll_uring_cmd.

If the command could not be submitted this way due to any reason,
abstract it and fallback to old way of submission.
This keeps IORING_URING_CMD_DIRECT flag advisory.

Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
---
 drivers/nvme/host/ioctl.c | 105 +++++++++++++++++++++++++++++++++-----
 drivers/nvme/host/nvme.h  |   4 ++
 2 files changed, 97 insertions(+), 12 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index 18f4f20f5e76..df86fb4f132b 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -653,6 +653,23 @@ static bool is_ctrl_ioctl(unsigned int cmd)
 	return false;
 }
 
+static int nvme_uring_cmd_io_direct(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
+		struct io_uring_cmd *ioucmd, unsigned int issue_flags)
+{
+	struct request_queue *q = ns ? ns->queue : ctrl->admin_q;
+	int qid = io_uring_cmd_import_qid(ioucmd);
+	struct nvme_uring_direct_pdu *pdu =
+		(struct nvme_uring_direct_pdu *)&ioucmd->pdu;
+
+	if ((issue_flags & IO_URING_F_IOPOLL) != IO_URING_F_IOPOLL)
+		return -EOPNOTSUPP;
+
+	pdu->ns = ns;
+	if (q->mq_ops && q->mq_ops->queue_uring_cmd)
+		return q->mq_ops->queue_uring_cmd(ioucmd, qid);
+	return -EOPNOTSUPP;
+}
+
 static int nvme_ctrl_ioctl(struct nvme_ctrl *ctrl, unsigned int cmd,
 		void __user *argp, fmode_t mode)
 {
@@ -763,6 +780,14 @@ static int nvme_ns_uring_cmd(struct nvme_ns *ns, struct io_uring_cmd *ioucmd,
 
 	switch (ioucmd->cmd_op) {
 	case NVME_URING_CMD_IO:
+		if (ioucmd->flags & IORING_URING_CMD_DIRECT) {
+			ret = nvme_uring_cmd_io_direct(ctrl, ns, ioucmd,
+					issue_flags);
+			if (ret == -EIOCBQUEUED)
+				return ret;
+			/* in case of any error, just fallback */
+			ioucmd->flags &= ~(IORING_URING_CMD_DIRECT);
+		}
 		ret = nvme_uring_cmd_io(ctrl, ns, ioucmd, issue_flags, false);
 		break;
 	case NVME_URING_CMD_IO_VEC:
@@ -783,6 +808,38 @@ int nvme_ns_chr_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags)
 	return nvme_ns_uring_cmd(ns, ioucmd, issue_flags);
 }
 
+/* similar to blk_mq_poll; may be possible to unify */
+int nvme_uring_cmd_iopoll_qid(struct request_queue *q,
+				 struct io_uring_cmd *ioucmd, int qid,
+				 struct io_comp_batch *iob,
+				 unsigned int flags)
+{
+	long state = get_current_state();
+	int ret;
+
+	if (!(q->mq_ops && q->mq_ops->poll_uring_cmd))
+		return 0;
+	do {
+		ret = q->mq_ops->poll_uring_cmd(ioucmd, qid, iob);
+		if (ret > 0) {
+			__set_current_state(TASK_RUNNING);
+			return ret;
+		}
+		if (signal_pending_state(state, current))
+			__set_current_state(TASK_RUNNING);
+		if (task_is_running(current))
+			return 1;
+
+		if (ret < 0 || (flags & BLK_POLL_ONESHOT))
+			break;
+		cpu_relax();
+
+	} while (!need_resched());
+
+	__set_current_state(TASK_RUNNING);
+	return 0;
+}
+
 int nvme_ns_chr_uring_cmd_iopoll(struct io_uring_cmd *ioucmd,
 				 struct io_comp_batch *iob,
 				 unsigned int poll_flags)
@@ -792,14 +849,26 @@ int nvme_ns_chr_uring_cmd_iopoll(struct io_uring_cmd *ioucmd,
 	struct nvme_ns *ns;
 	struct request_queue *q;
 
-	rcu_read_lock();
-	bio = READ_ONCE(ioucmd->cookie);
 	ns = container_of(file_inode(ioucmd->file)->i_cdev,
 			struct nvme_ns, cdev);
 	q = ns->queue;
-	if (test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && bio && bio->bi_bdev)
-		ret = bio_poll(bio, iob, poll_flags);
-	rcu_read_unlock();
+	if (!(ioucmd->flags & IORING_URING_CMD_DIRECT)) {
+		rcu_read_lock();
+		bio = READ_ONCE(ioucmd->cookie);
+		if (test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && bio && bio->bi_bdev)
+			ret = bio_poll(bio, iob, poll_flags);
+
+		rcu_read_unlock();
+	} else {
+		int qid = io_uring_cmd_import_qid(ioucmd);
+
+		if (qid <= 0)
+			return 0;
+		if (!percpu_ref_tryget(&q->q_usage_counter))
+			return 0;
+		ret = nvme_uring_cmd_iopoll_qid(q, ioucmd, qid, iob, poll_flags);
+		percpu_ref_put(&q->q_usage_counter);
+	}
 	return ret;
 }
 #ifdef CONFIG_NVME_MULTIPATH
@@ -952,13 +1021,25 @@ int nvme_ns_head_chr_uring_cmd_iopoll(struct io_uring_cmd *ioucmd,
 	struct request_queue *q;
 
 	if (ns) {
-		rcu_read_lock();
-		bio = READ_ONCE(ioucmd->cookie);
-		q = ns->queue;
-		if (test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && bio
-				&& bio->bi_bdev)
-			ret = bio_poll(bio, iob, poll_flags);
-		rcu_read_unlock();
+		if (!(ioucmd->flags & IORING_URING_CMD_DIRECT)) {
+			rcu_read_lock();
+			bio = READ_ONCE(ioucmd->cookie);
+			q = ns->queue;
+			if (test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && bio
+					&& bio->bi_bdev)
+				ret = bio_poll(bio, iob, poll_flags);
+			rcu_read_unlock();
+		} else {
+			int qid = io_uring_cmd_import_qid(ioucmd);
+
+			if (qid <= 0)
+				return 0;
+			if (!percpu_ref_tryget(&q->q_usage_counter))
+				return 0;
+			ret = nvme_uring_cmd_iopoll_qid(q, ioucmd, qid, iob,
+							poll_flags);
+			percpu_ref_put(&q->q_usage_counter);
+		}
 	}
 	srcu_read_unlock(&head->srcu, srcu_idx);
 	return ret;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 4eb45afc9484..2fd4432fbe12 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -176,6 +176,10 @@ struct nvme_uring_data {
 	__u32	timeout_ms;
 };
 
+struct nvme_uring_direct_pdu {
+	struct nvme_ns *ns;
+};
+
 /*
  * Mark a bio as coming in through the mpath node.
  */
-- 
2.25.1