From: Anuj Gupta <anuj20.g@samsung.com>

Allow registering a dma-buf against an NVMe namespace character device
and using it as the data buffer of fixed uring_cmd passthrough I/O.
Complete through io_uring_cmd_hw_done(), so the dma-buf map is released
at hardware completion.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
---
 drivers/nvme/host/core.c  | 16 ++++++++++++++++
 drivers/nvme/host/ioctl.c |  5 +++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index a7a4d09644c1..33dbaa319bb9 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -8,6 +8,7 @@
 #include <linux/blkdev.h>
 #include <linux/blk-mq.h>
 #include <linux/blk-integrity.h>
+#include <linux/dma-buf-io.h>
 #include <linux/compat.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -4008,6 +4009,20 @@ static int nvme_ns_chr_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int nvme_ns_chr_init_dma_buf_io_ctx(struct file *file,
+					   struct dma_buf_io_ctx *ctx)
+{
+	struct nvme_ns *ns =
+		container_of(file_inode(file)->i_cdev, struct nvme_ns, cdev);
+	struct nvme_ctrl *ctrl = ns->ctrl;
+
+	if (ctx->dmabuf->size > UINT_MAX)
+		return -EINVAL;
+	if (!ctrl->ops->init_dma_buf_io_ctx)
+		return -EOPNOTSUPP;
+	return ctrl->ops->init_dma_buf_io_ctx(ctrl, ctx);
+}
+
 static const struct file_operations nvme_ns_chr_fops = {
 	.owner		= THIS_MODULE,
 	.open		= nvme_ns_chr_open,
@@ -4016,6 +4031,7 @@ static const struct file_operations nvme_ns_chr_fops = {
 	.compat_ioctl	= compat_ptr_ioctl,
 	.uring_cmd	= nvme_ns_chr_uring_cmd,
 	.uring_cmd_iopoll = nvme_ns_chr_uring_cmd_iopoll,
+	.init_dma_buf_io_ctx = nvme_ns_chr_init_dma_buf_io_ctx,
 };
 
 static void nvme_add_ns_cdev(struct nvme_ns *ns)
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index d342ccad067a..3f240c9a537f 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -472,7 +472,7 @@ static enum rq_end_io_ret nvme_uring_cmd_end_io(struct request *req,
 			blk_rq_unmap_user(pdu->bio);
 		__io_uring_cmd_done(ioucmd, 0);
 	} else {
-		io_uring_cmd_do_in_task_lazy(ioucmd, nvme_uring_task_cb);
+		io_uring_cmd_hw_done(ioucmd, nvme_uring_task_cb);
 	}
 	return RQ_END_IO_FREE;
 }
@@ -533,7 +533,8 @@ static int nvme_uring_cmd_io(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 					ddir, &iter, issue_flags);
 		else
 			ret = io_uring_cmd_import_fixed(d.addr, d.data_len,
-					ddir, &iter, ioucmd, issue_flags, 0);
+					ddir, &iter, ioucmd, issue_flags,
+					IO_URING_CMD_IMPORT_DMABUF);
 		if (ret < 0)
 			return ret;
 
-- 
2.43.0