[PATCH V2 2/4] nvmet: allow user to set the ns readonly

[Chaitanya Kulkarni]

User may want to export readonly ns to host in order to export
read-only snapshots. Right now we don't have configfs attribute to
allow user to mark readonly & export ns.

Add a configfs attribute "write_protect" such that user can set the ns
and export ns readonly when it is not enabled.

Also, when user is setting the ns write protected from configfs we set
ns write protect state to NVME_NS_WRITE_PROTECT_PERMANENT and don't
allow user to change the value for the ns-write-protect feature.

We also update the id->nwpc to indicate the support for namespace
write protect permanent state. For RPMB clear the bit 1 of the field
Namesapce Write Protection Authentication Control to indicate Set
Features command which attenpts to set the namespace write protection
state to permanent write protect will fail.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
---
 drivers/nvme/target/admin-cmd.c |  9 ++++++++-
 drivers/nvme/target/configfs.c  | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 263cfff6ddd4..44ff847db83e 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -457,7 +457,8 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 	id->psd[0].entry_lat = cpu_to_le32(0x10);
 	id->psd[0].exit_lat = cpu_to_le32(0x4);
 
-	id->nwpc = 1 << 0; /* write protect and no write protect */
+	/* write protect permanent, write protect and no write protect */
+	id->nwpc = 1 << 2 | 1 << 0;
 
 	status = nvmet_copy_to_sgl(req, 0, id, sizeof(*id));
 
@@ -711,6 +712,11 @@ static u16 nvmet_set_feat_write_protect(struct nvmet_req *req)
 	}
 
 	mutex_lock(&subsys->lock);
+	if (req->ns->write_protect == NVME_NS_WRITE_PROTECT_PERMANENT) {
+		req->error_loc = offsetof(struct nvme_common_command, nsid);
+		goto out;
+	}
+
 	switch (write_protect) {
 	case NVME_NS_WRITE_PROTECT:
 		status = nvmet_write_protect_flush_sync(req);
@@ -729,6 +735,7 @@ static u16 nvmet_set_feat_write_protect(struct nvmet_req *req)
 
 	if (!status)
 		nvmet_ns_changed(subsys, req->ns->nsid);
+out:
 	mutex_unlock(&subsys->lock);
 	return status;
 }
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 37e1d7784e17..5d8ee00b8fd0 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -595,6 +595,38 @@ static ssize_t nvmet_ns_revalidate_size_store(struct config_item *item,
 
 CONFIGFS_ATTR_WO(nvmet_ns_, revalidate_size);
 
+static ssize_t nvmet_ns_write_protect_show(struct config_item *item, char *page)
+{
+	return sprintf(page, "%d\n", to_nvmet_ns(item)->write_protect);
+}
+
+static ssize_t nvmet_ns_write_protect_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct nvmet_ns *ns = to_nvmet_ns(item);
+	bool val;
+
+	if (strtobool(page, &val))
+		return -EINVAL;
+
+	mutex_lock(&ns->subsys->lock);
+	if (ns->enabled) {
+		pr_err("disable ns before setting write_protect value.\n");
+		mutex_unlock(&ns->subsys->lock);
+		return -EINVAL;
+	}
+
+	if (val)
+		ns->write_protect = NVME_NS_WRITE_PROTECT_PERMANENT;
+	else
+		ns->write_protect = NVME_NS_NO_WRITE_PROTECT;
+
+	mutex_unlock(&ns->subsys->lock);
+	return count;
+}
+
+CONFIGFS_ATTR(nvmet_ns_, write_protect);
+
 static struct configfs_attribute *nvmet_ns_attrs[] = {
 	&nvmet_ns_attr_device_path,
 	&nvmet_ns_attr_device_nguid,
@@ -603,6 +635,7 @@ static struct configfs_attribute *nvmet_ns_attrs[] = {
 	&nvmet_ns_attr_enable,
 	&nvmet_ns_attr_buffered_io,
 	&nvmet_ns_attr_revalidate_size,
+	&nvmet_ns_attr_write_protect,
 #ifdef CONFIG_PCI_P2PDMA
 	&nvmet_ns_attr_p2pmem,
 #endif
-- 
2.22.1