[PATCH for-next v11 10/13] nvme: wire up fixed buffer support for nvme passthrough

[Anuj Gupta <anuj20.g@samsung.com>]

From: Kanchan Joshi <joshi.k@samsung.com>

if io_uring sends passthrough command with IORING_URING_CMD_FIXED flag,
use the pre-registered buffer for IO (non-vectored variant). Pass the
buffer/length to io_uring and get the bvec iterator for the range. Next,
pass this bvec to block-layer and obtain a bio/request for subsequent
processing.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
---
 drivers/nvme/host/ioctl.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index 4a7e45a263b6..25a68e8c60db 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -95,21 +95,31 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
 	void *meta = NULL;
 	int ret;
 
-	if (!vec)
-		ret = blk_rq_map_user(q, req, NULL, ubuffer, bufflen,
-			GFP_KERNEL);
-	else {
+	if (ioucmd && (ioucmd->flags & IORING_URING_CMD_FIXED)) {
+		struct iov_iter iter;
+
+		/* fixedbufs is only for non-vectored io */
+		if (WARN_ON_ONCE(vec))
+			return -EINVAL;
+		ret = io_uring_cmd_import_fixed(ubuffer, bufflen,
+				rq_data_dir(req), &iter, ioucmd);
+		if (ret < 0)
+			goto out;
+		ret = blk_rq_map_user_iov(q, req, NULL, &iter, GFP_KERNEL);
+	} else if (vec) {
 		struct iovec fast_iov[UIO_FASTIOV];
 		struct iovec *iov = fast_iov;
 		struct iov_iter iter;
 
-		ret = import_iovec(rq_data_dir(req), ubuffer, bufflen,
-				UIO_FASTIOV, &iov, &iter);
+		ret = import_iovec(rq_data_dir(req), nvme_to_user_ptr(ubuffer),
+				bufflen, UIO_FASTIOV, &iov, &iter);
 		if (ret < 0)
 			goto out;
-
 		ret = blk_rq_map_user_iov(q, req, NULL, &iter, GFP_KERNEL);
 		kfree(iov);
+	} else {
+		ret = blk_rq_map_user(q, req, NULL,
+				nvme_to_user_ptr(ubuffer), bufflen, GFP_KERNEL);
 	}
 	if (ret)
 		goto out;
-- 
2.25.1