[RFC PATCH] nvme: allow NVME_IOCTL_IO_CMD on controller char dev even when multiple ns

[Niklas Cassel]

From: Niklas Cassel <niklas.cassel@xxxxxxx>

Currently when doing NVME_IOCTL_IO_CMD on the controller character device,
the command is rejected if there is more than one namespace in the
ctrl->namespaces list.

There is not really any reason for this restriction.
Instead, check the nsid value specified in the passthru command, and try
to find the matching namespace in ctrl->namespaces list.
If found, call nvme_user_cmd() on the namespace.
If not found, reject the command.

While at it, remove the warning that says that NVME_IOCTL_IO_CMD is
deprecated on the controller character device.
There is no comment saying why it is deprecated.
It might be very unsafe to send a passthru command, but if that is
the issue with this IOCTL, then we should add a warning about that
instead.

Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
---
 drivers/nvme/host/core.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index a50352ea3f7b..b50fdf143b90 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3264,35 +3264,31 @@ static int nvme_dev_release(struct inode *inode, struct file *file)
 
 static int nvme_dev_user_cmd(struct nvme_ctrl *ctrl, void __user *argp)
 {
+	struct nvme_passthru_cmd cmd;
 	struct nvme_ns *ns;
 	int ret;
 
 	down_read(&ctrl->namespaces_rwsem);
 	if (list_empty(&ctrl->namespaces)) {
-		ret = -ENOTTY;
-		goto out_unlock;
+		up_read(&ctrl->namespaces_rwsem);
+		return -ENOTTY;
 	}
+	up_read(&ctrl->namespaces_rwsem);
 
-	ns = list_first_entry(&ctrl->namespaces, struct nvme_ns, list);
-	if (ns != list_last_entry(&ctrl->namespaces, struct nvme_ns, list)) {
-		dev_warn(ctrl->device,
-			"NVME_IOCTL_IO_CMD not supported when multiple namespaces present!\n");
-		ret = -EINVAL;
-		goto out_unlock;
-	}
+	if (copy_from_user(&cmd, argp, sizeof(cmd)))
+		return -EFAULT;
 
-	dev_warn(ctrl->device,
-		"using deprecated NVME_IOCTL_IO_CMD ioctl on the char device!\n");
-	kref_get(&ns->kref);
-	up_read(&ctrl->namespaces_rwsem);
+	ns = nvme_find_get_ns(ctrl, cmd.nsid);
+	if (!ns) {
+		dev_err(ctrl->device,
+			"%s: could not find namespace with nsid %u\n",
+			current->comm, cmd.nsid);
+		return -EINVAL;
+	}
 
 	ret = nvme_user_cmd(ctrl, ns, argp);
 	nvme_put_ns(ns);
 	return ret;
-
-out_unlock:
-	up_read(&ctrl->namespaces_rwsem);
-	return ret;
 }
 
 static long nvme_dev_ioctl(struct file *file, unsigned int cmd,
-- 
2.30.2