nvmet: add ns write protect support

This patch implements the Namespace Write Protect feature described in
"NVMe TP 4005a Namespace Write Protect". In this version, we implement
No Write Protect and Write Protect states for target ns which can be
toggled by set-features commands from the host side.

For write-protect state transition, we need to flush the ns specified
as a part of command so we also add helpers for carrying out synchronous
flush operations.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
[hch: fixed an incorrect endianess conversion, minor cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/admin-cmd.c

@@ -372,6 +372,8 @@ 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 */
+
 	status = nvmet_copy_to_sgl(req, 0, id, sizeof(*id));
 
 	kfree(id);
@@ -433,6 +435,8 @@ static void nvmet_execute_identify_ns(struct nvmet_req *req)
 
 	id->lbaf[0].ds = ns->blksize_shift;
 
+	if (ns->readonly)
+		id->nsattr |= (1 << 0);
 	nvmet_put_namespace(ns);
 done:
 	status = nvmet_copy_to_sgl(req, 0, id, sizeof(*id));
@@ -545,6 +549,52 @@ static void nvmet_execute_abort(struct nvmet_req *req)
 	nvmet_req_complete(req, 0);
 }
 
+static u16 nvmet_write_protect_flush_sync(struct nvmet_req *req)
+{
+	u16 status;
+
+	if (req->ns->file)
+		status = nvmet_file_flush(req);
+	else
+		status = nvmet_bdev_flush(req);
+
+	if (status)
+		pr_err("write protect flush failed nsid: %u\n", req->ns->nsid);
+	return status;
+}
+
+static u16 nvmet_set_feat_write_protect(struct nvmet_req *req)
+{
+	u32 write_protect = le32_to_cpu(req->cmd->common.cdw10[1]);
+	struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
+	u16 status = NVME_SC_FEATURE_NOT_CHANGEABLE;
+
+	req->ns = nvmet_find_namespace(req->sq->ctrl, req->cmd->rw.nsid);
+	if (unlikely(!req->ns))
+		return status;
+
+	mutex_lock(&subsys->lock);
+	switch (write_protect) {
+	case NVME_NS_WRITE_PROTECT:
+		req->ns->readonly = true;
+		status = nvmet_write_protect_flush_sync(req);
+		if (status)
+			req->ns->readonly = false;
+		break;
+	case NVME_NS_NO_WRITE_PROTECT:
+		req->ns->readonly = false;
+		status = 0;
+		break;
+	default:
+		break;
+	}
+
+	if (!status)
+		nvmet_ns_changed(subsys, req->ns->nsid);
+	mutex_unlock(&subsys->lock);
+	return status;
+}
+
 static void nvmet_execute_set_features(struct nvmet_req *req)
 {
 	struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
@@ -575,6 +625,9 @@ static void nvmet_execute_set_features(struct nvmet_req *req)
 	case NVME_FEAT_HOST_ID:
 		status = NVME_SC_CMD_SEQ_ERROR | NVME_SC_DNR;
 		break;
+	case NVME_FEAT_WRITE_PROTECT:
+		status = nvmet_set_feat_write_protect(req);
+		break;
 	default:
 		status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
 		break;
@@ -583,6 +636,26 @@ static void nvmet_execute_set_features(struct nvmet_req *req)
 	nvmet_req_complete(req, status);
 }
 
+static u16 nvmet_get_feat_write_protect(struct nvmet_req *req)
+{
+	struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
+	u32 result;
+
+	req->ns = nvmet_find_namespace(req->sq->ctrl, req->cmd->common.nsid);
+	if (!req->ns)
+		return NVME_SC_INVALID_NS | NVME_SC_DNR;
+
+	mutex_lock(&subsys->lock);
+	if (req->ns->readonly == true)
+		result = NVME_NS_WRITE_PROTECT;
+	else
+		result = NVME_NS_NO_WRITE_PROTECT;
+	nvmet_set_result(req, result);
+	mutex_unlock(&subsys->lock);
+
+	return 0;
+}
+
 static void nvmet_execute_get_features(struct nvmet_req *req)
 {
 	struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
@@ -634,6 +707,9 @@ static void nvmet_execute_get_features(struct nvmet_req *req)
 		status = nvmet_copy_to_sgl(req, 0, &req->sq->ctrl->hostid,
 				sizeof(req->sq->ctrl->hostid));
 		break;
+	case NVME_FEAT_WRITE_PROTECT:
+		status = nvmet_get_feat_write_protect(req);
+		break;
 	default:
 		status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
 		break;

drivers/nvme/target/core.c

@@ -180,7 +180,7 @@ out_unlock:
 	mutex_unlock(&ctrl->lock);
 }
 
-static void nvmet_ns_changed(struct nvmet_subsys *subsys, u32 nsid)
+void nvmet_ns_changed(struct nvmet_subsys *subsys, u32 nsid)
 {
 	struct nvmet_ctrl *ctrl;
 
@@ -609,6 +609,21 @@ static inline u16 nvmet_check_ana_state(struct nvmet_port *port,
 	return 0;
 }
 
+static inline u16 nvmet_io_cmd_check_access(struct nvmet_req *req)
+{
+	if (unlikely(req->ns->readonly)) {
+		switch (req->cmd->common.opcode) {
+		case nvme_cmd_read:
+		case nvme_cmd_flush:
+			break;
+		default:
+			return NVME_SC_NS_WRITE_PROTECTED;
+		}
+	}
+
+	return 0;
+}
+
 static u16 nvmet_parse_io_cmd(struct nvmet_req *req)
 {
 	struct nvme_command *cmd = req->cmd;
@@ -622,6 +637,9 @@ static u16 nvmet_parse_io_cmd(struct nvmet_req *req)
 	if (unlikely(!req->ns))
 		return NVME_SC_INVALID_NS | NVME_SC_DNR;
 	ret = nvmet_check_ana_state(req->port, req->ns);
+	if (unlikely(ret))
+		return ret;
+	ret = nvmet_io_cmd_check_access(req);
 	if (unlikely(ret))
 		return ret;
 

drivers/nvme/target/io-cmd-bdev.c

@@ -124,6 +124,13 @@ static void nvmet_bdev_execute_flush(struct nvmet_req *req)
 	submit_bio(bio);
 }
 
+u16 nvmet_bdev_flush(struct nvmet_req *req)
+{
+	if (blkdev_issue_flush(req->ns->bdev, GFP_KERNEL, NULL))
+		return NVME_SC_INTERNAL | NVME_SC_DNR;
+	return 0;
+}
+
 static u16 nvmet_bdev_discard_range(struct nvmet_ns *ns,
 		struct nvme_dsm_range *range, struct bio **bio)
 {

drivers/nvme/target/io-cmd-file.c

@@ -211,14 +211,18 @@ static void nvmet_file_execute_rw_buffered_io(struct nvmet_req *req)
 	queue_work(buffered_io_wq, &req->f.work);
 }
 
+u16 nvmet_file_flush(struct nvmet_req *req)
+{
+	if (vfs_fsync(req->ns->file, 1) < 0)
+		return NVME_SC_INTERNAL | NVME_SC_DNR;
+	return 0;
+}
+
 static void nvmet_file_flush_work(struct work_struct *w)
 {
 	struct nvmet_req *req = container_of(w, struct nvmet_req, f.work);
-	int ret;
 
-	ret = vfs_fsync(req->ns->file, 1);
-
-	nvmet_req_complete(req, ret < 0 ? NVME_SC_INTERNAL | NVME_SC_DNR : 0);
+	nvmet_req_complete(req, nvmet_file_flush(req));
 }
 
 static void nvmet_file_execute_flush(struct nvmet_req *req)

drivers/nvme/target/nvmet.h

@@ -58,6 +58,7 @@ struct nvmet_ns {
 	struct percpu_ref	ref;
 	struct block_device	*bdev;
 	struct file		*file;
+	bool			readonly;
 	u32			nsid;
 	u32			blksize_shift;
 	loff_t			size;
@@ -429,6 +430,9 @@ int nvmet_bdev_ns_enable(struct nvmet_ns *ns);
 int nvmet_file_ns_enable(struct nvmet_ns *ns);
 void nvmet_bdev_ns_disable(struct nvmet_ns *ns);
 void nvmet_file_ns_disable(struct nvmet_ns *ns);
+u16 nvmet_bdev_flush(struct nvmet_req *req);
+u16 nvmet_file_flush(struct nvmet_req *req);
+void nvmet_ns_changed(struct nvmet_subsys *subsys, u32 nsid);
 
 static inline u32 nvmet_rw_len(struct nvmet_req *req)
 {