[PATCH 13/17] nvme: allow user passthrough commands to poll

[Kanchan Joshi]

From: Keith Busch <kbusch at kernel.org>

The block layer knows how to deal with polled requests. Let the NVMe
driver use the previously reserved user "flags" fields to define an
option to allocate the request from the polled hardware contexts. If
polling is not enabled, then the block layer will automatically fallback
to a non-polled request.[1]

[1] https://lore.kernel.org/linux-block/20210517171443.GB2709391@dhcp-10-100-145-180.wdc.com/

Signed-off-by: Keith Busch <kbusch at kernel.org>
---
 drivers/nvme/host/ioctl.c       | 30 ++++++++++++++++--------------
 include/uapi/linux/nvme_ioctl.h |  4 ++++
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index a4cde210aab9..a6712fb3eb98 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -132,7 +132,7 @@ static int nvme_submit_user_cmd(struct request_queue *q,
 		struct nvme_command *cmd, u64 ubuffer,
 		unsigned bufflen, void __user *meta_buffer, unsigned meta_len,
 		u32 meta_seed, u64 *result, unsigned timeout,
-		struct io_uring_cmd *ioucmd)
+		struct io_uring_cmd *ioucmd, unsigned int rq_flags)
 {
 	bool write = nvme_is_write(cmd);
 	struct nvme_ns *ns = q->queuedata;
@@ -140,7 +140,6 @@ static int nvme_submit_user_cmd(struct request_queue *q,
 	struct request *req;
 	struct bio *bio = NULL;
 	void *meta = NULL;
-	unsigned int rq_flags = 0;
 	blk_mq_req_flags_t blk_flags = 0;
 	int ret;
 
@@ -216,11 +215,12 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 	struct nvme_command c;
 	unsigned length, meta_len;
 	void __user *metadata;
+	unsigned int rq_flags = 0;
 
 	if (copy_from_user(&io, uio, sizeof(io)))
 		return -EFAULT;
-	if (io.flags)
-		return -EINVAL;
+	if (io.flags & NVME_HIPRI)
+		rq_flags |= REQ_POLLED;
 
 	switch (io.opcode) {
 	case nvme_cmd_write:
@@ -258,7 +258,7 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 
 	memset(&c, 0, sizeof(c));
 	c.rw.opcode = io.opcode;
-	c.rw.flags = io.flags;
+	c.rw.flags = 0;
 	c.rw.nsid = cpu_to_le32(ns->head->ns_id);
 	c.rw.slba = cpu_to_le64(io.slba);
 	c.rw.length = cpu_to_le16(io.nblocks);
@@ -270,7 +270,7 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 
 	return nvme_submit_user_cmd(ns->queue, &c,
 			io.addr, length, metadata, meta_len,
-			lower_32_bits(io.slba), NULL, 0, NULL);
+			lower_32_bits(io.slba), NULL, 0, NULL, rq_flags);
 }
 
 static bool nvme_validate_passthru_nsid(struct nvme_ctrl *ctrl,
@@ -292,6 +292,7 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 {
 	struct nvme_passthru_cmd cmd;
 	struct nvme_command c;
+	unsigned int rq_flags = 0;
 	unsigned timeout = 0;
 	u64 result;
 	int status;
@@ -300,14 +301,14 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 		return -EACCES;
 	if (copy_from_user(&cmd, ucmd, sizeof(cmd)))
 		return -EFAULT;
-	if (cmd.flags)
-		return -EINVAL;
+	if (cmd.flags & NVME_HIPRI)
+		rq_flags |= REQ_POLLED;
 	if (!nvme_validate_passthru_nsid(ctrl, ns, cmd.nsid))
 		return -EINVAL;
 
 	memset(&c, 0, sizeof(c));
 	c.common.opcode = cmd.opcode;
-	c.common.flags = cmd.flags;
+	c.common.flags = 0;
 	c.common.nsid = cpu_to_le32(cmd.nsid);
 	c.common.cdw2[0] = cpu_to_le32(cmd.cdw2);
 	c.common.cdw2[1] = cpu_to_le32(cmd.cdw3);
@@ -323,7 +324,7 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 
 	status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c,
 			cmd.addr, cmd.data_len, nvme_to_user_ptr(cmd.metadata),
-			cmd.metadata_len, 0, &result, timeout, NULL);
+			cmd.metadata_len, 0, &result, timeout, NULL, rq_flags);
 
 	if (status >= 0) {
 		if (put_user(result, &ucmd->result))
@@ -339,6 +340,7 @@ static int nvme_user_cmd64(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 {
 	struct nvme_passthru_cmd64 cmd, *cptr;
 	struct nvme_command c;
+	unsigned int rq_flags = 0;
 	unsigned timeout = 0;
 	int status;
 
@@ -353,14 +355,14 @@ static int nvme_user_cmd64(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 			return -EINVAL;
 		cptr = (struct nvme_passthru_cmd64 *)ioucmd->cmd;
 	}
-	if (cptr->flags)
-		return -EINVAL;
+	if (cptr->flags & NVME_HIPRI)
+		rq_flags |= REQ_POLLED;
 	if (!nvme_validate_passthru_nsid(ctrl, ns, cptr->nsid))
 		return -EINVAL;
 
 	memset(&c, 0, sizeof(c));
 	c.common.opcode = cptr->opcode;
-	c.common.flags = cptr->flags;
+	c.common.flags = 0;
 	c.common.nsid = cpu_to_le32(cptr->nsid);
 	c.common.cdw2[0] = cpu_to_le32(cptr->cdw2);
 	c.common.cdw2[1] = cpu_to_le32(cptr->cdw3);
@@ -377,7 +379,7 @@ static int nvme_user_cmd64(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 	status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c,
 			cptr->addr, cptr->data_len,
 			nvme_to_user_ptr(cptr->metadata), cptr->metadata_len,
-			0, &cptr->result, timeout, ioucmd);
+			0, &cptr->result, timeout, ioucmd, rq_flags);
 
 	if (!ioucmd && status >= 0) {
 		if (put_user(cptr->result, &ucmd->result))
diff --git a/include/uapi/linux/nvme_ioctl.h b/include/uapi/linux/nvme_ioctl.h
index d99b5a772698..df2c138c38d9 100644
--- a/include/uapi/linux/nvme_ioctl.h
+++ b/include/uapi/linux/nvme_ioctl.h
@@ -9,6 +9,10 @@
 
 #include <linux/types.h>
 
+enum nvme_io_flags {
+	NVME_HIPRI      = 1 << 0, /* use polling queue if available */
+};
+
 struct nvme_user_io {
 	__u8	opcode;
 	__u8	flags;
-- 
2.25.1