[RFC 07/13] nvme: enable passthrough with fixed-buffer

[Kanchan Joshi <joshi.k@samsung.com>]

Add support to carry out passthrough command with pre-mapped buffers.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
---
 block/blk-map.c           | 46 +++++++++++++++++++++++++++++++++++++++
 drivers/nvme/host/ioctl.c | 30 +++++++++++++++----------
 include/linux/blk-mq.h    |  3 +++
 3 files changed, 67 insertions(+), 12 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index 4526adde0156..9aa9864eab55 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -8,6 +8,7 @@
 #include <linux/bio.h>
 #include <linux/blkdev.h>
 #include <linux/uio.h>
+#include <linux/io_uring.h>
 
 #include "blk.h"
 
@@ -577,6 +578,51 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
 }
 EXPORT_SYMBOL(blk_rq_map_user);
 
+/* Unlike blk_rq_map_user () this is only for fixed-buffer async passthrough. */
+int blk_rq_map_user_fixedb(struct request_queue *q, struct request *rq,
+		     u64 ubuf, unsigned long len, gfp_t gfp_mask,
+		     struct io_uring_cmd *ioucmd)
+{
+	struct iov_iter iter;
+	size_t iter_count, nr_segs;
+	struct bio *bio;
+	int ret;
+
+	/*
+	 * Talk to io_uring to obtain BVEC iterator for the buffer.
+	 * And use that iterator to form bio/request.
+	 */
+	ret = io_uring_cmd_import_fixed(ubuf, len, rq_data_dir(rq), &iter,
+			ioucmd);
+	if (unlikely(ret < 0))
+		return ret;
+	iter_count = iov_iter_count(&iter);
+	nr_segs = iter.nr_segs;
+
+	if (!iter_count || (iter_count >> 9) > queue_max_hw_sectors(q))
+		return -EINVAL;
+	if (nr_segs > queue_max_segments(q))
+		return -EINVAL;
+	/* no iovecs to alloc, as we already have a BVEC iterator */
+	bio = bio_alloc(gfp_mask, 0);
+	if (!bio)
+		return -ENOMEM;
+
+	bio->bi_opf |= req_op(rq);
+	ret = bio_iov_iter_get_pages(bio, &iter);
+	if (ret)
+		goto out_free;
+
+	blk_rq_bio_prep(rq, bio, nr_segs);
+	return 0;
+
+out_free:
+	bio_release_pages(bio, false);
+	bio_put(bio);
+	return ret;
+}
+EXPORT_SYMBOL(blk_rq_map_user_fixedb);
+
 /**
  * blk_rq_unmap_user - unmap a request with user data
  * @bio:	       start of bio list
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index 7d9c51d9c0a8..dc6a5f1b81ca 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -131,8 +131,13 @@ static void *nvme_add_user_metadata(struct bio *bio, void __user *ubuf,
 	return ERR_PTR(ret);
 }
 
+static inline bool nvme_is_fixedb_passthru(struct io_uring_cmd *ioucmd)
+{
+	return ((ioucmd) && (ioucmd->flags & URING_CMD_FIXEDBUFS));
+}
+
 static int nvme_submit_user_cmd(struct request_queue *q,
-		struct nvme_command *cmd, void __user *ubuffer,
+		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)
@@ -154,8 +159,12 @@ static int nvme_submit_user_cmd(struct request_queue *q,
 	nvme_req(req)->flags |= NVME_REQ_USERCMD;
 
 	if (ubuffer && bufflen) {
-		ret = blk_rq_map_user(q, req, NULL, ubuffer, bufflen,
-				GFP_KERNEL);
+		if (likely(!nvme_is_fixedb_passthru(ioucmd)))
+			ret = blk_rq_map_user(q, req, NULL, nvme_to_user_ptr(ubuffer),
+					bufflen, GFP_KERNEL);
+		else
+			ret = blk_rq_map_user_fixedb(q, req, ubuffer, bufflen,
+					GFP_KERNEL, ioucmd);
 		if (ret)
 			goto out;
 		bio = req->bio;
@@ -254,9 +263,8 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 	c.rw.appmask = cpu_to_le16(io.appmask);
 
 	return nvme_submit_user_cmd(ns->queue, &c,
-			nvme_to_user_ptr(io.addr), length,
-			metadata, meta_len, lower_32_bits(io.slba), NULL, 0,
-			NULL);
+			io.addr, length, metadata, meta_len,
+			lower_32_bits(io.slba), NULL, 0, NULL);
 }
 
 static bool nvme_validate_passthru_nsid(struct nvme_ctrl *ctrl,
@@ -308,9 +316,8 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 		timeout = msecs_to_jiffies(cmd.timeout_ms);
 
 	status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c,
-			nvme_to_user_ptr(cmd.addr), cmd.data_len,
-			nvme_to_user_ptr(cmd.metadata), cmd.metadata_len,
-			0, &result, timeout, NULL);
+			cmd.addr, cmd.data_len, nvme_to_user_ptr(cmd.metadata),
+			cmd.metadata_len, 0, &result, timeout, NULL);
 
 	if (status >= 0) {
 		if (put_user(result, &ucmd->result))
@@ -355,9 +362,8 @@ static int nvme_user_cmd64(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 		timeout = msecs_to_jiffies(cmd.timeout_ms);
 
 	status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c,
-			nvme_to_user_ptr(cmd.addr), cmd.data_len,
-			nvme_to_user_ptr(cmd.metadata), cmd.metadata_len,
-			0, &cmd.result, timeout, ioucmd);
+			cmd.addr, cmd.data_len, nvme_to_user_ptr(cmd.metadata),
+			cmd.metadata_len, 0, &cmd.result, timeout, ioucmd);
 
 	if (!ioucmd && status >= 0) {
 		if (put_user(cmd.result, &ucmd->result))
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 30e54ab05333..a82b054eebde 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -922,6 +922,9 @@ struct rq_map_data {
 
 int blk_rq_map_user(struct request_queue *, struct request *,
 		struct rq_map_data *, void __user *, unsigned long, gfp_t);
+int blk_rq_map_user_fixedb(struct request_queue *, struct request *,
+		     u64 ubuf, unsigned long, gfp_t,
+		     struct io_uring_cmd *);
 int blk_rq_map_user_iov(struct request_queue *, struct request *,
 		struct rq_map_data *, const struct iov_iter *, gfp_t);
 int blk_rq_unmap_user(struct bio *);
-- 
2.25.1