nvme/cuse: get functions for cuse ctrlr/ns names to accept a buffer

This was changed to better facilitate thread safety.
In next patch a lock will be held when going over the
cuse devices list.

Now user is expected to pass a buffer of a sufficient size
that will be filled with ctrlr or ns cuse device name.

Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Change-Id: I3202ef285e427111e3595389619463fda58dbef6
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/1978
Community-CI: Mellanox Build Bot
Community-CI: Broadcom CI
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>

include/spdk/nvme.h

@@ -3008,20 +3008,29 @@ void spdk_nvme_rdma_init_hooks(struct spdk_nvme_rdma_hooks *hooks);
  * Get name of cuse device associated with NVMe controller.
  *
  * \param ctrlr Opaque handle to NVMe controller.
+ * \param name	Buffer of be filled with cuse device name.
+ * \param size	Size of name buffer.
  *
- * \return Pointer to the name of device.
+ * \return 0 on success. Negated errno on the following error conditions:
+ * -ENODEV: No cuse device registered for the controller.
+ * -ENSPC: Too small buffer size passed. Value of size pointer changed to the required length.
  */
-char *spdk_nvme_cuse_get_ctrlr_name(struct spdk_nvme_ctrlr *ctrlr);
+int spdk_nvme_cuse_get_ctrlr_name(struct spdk_nvme_ctrlr *ctrlr, char *name, size_t *size);
 
 /**
  * Get name of cuse device associated with NVMe namespace.
  *
  * \param ctrlr Opaque handle to NVMe controller.
  * \param nsid	Namespace id.
+ * \param name	Buffer of be filled with cuse device name.
+ * \param size	Size of name buffer.
  *
- * \return Pointer to the name of device.
+ * \return 0 on success. Negated errno on the following error conditions:
+ * -ENODEV: No cuse device registered for the namespace.
+ * -ENSPC: Too small buffer size passed. Value of size pointer changed to the required length.
  */
-char *spdk_nvme_cuse_get_ns_name(struct spdk_nvme_ctrlr *ctrlr, uint32_t nsid);
+int spdk_nvme_cuse_get_ns_name(struct spdk_nvme_ctrlr *ctrlr, uint32_t nsid,
+			       char *name, size_t *size);
 
 /**
  * Create a character device at the path specified (Experimental)

lib/nvme/nvme_cuse.c

@@ -960,28 +960,44 @@ spdk_nvme_cuse_unregister(struct spdk_nvme_ctrlr *ctrlr)
 	return 0;
 }
 
-char *
+int
-spdk_nvme_cuse_get_ctrlr_name(struct spdk_nvme_ctrlr *ctrlr)
+spdk_nvme_cuse_get_ctrlr_name(struct spdk_nvme_ctrlr *ctrlr, char *name, size_t *size)
 {
 	struct cuse_device *ctrlr_device;
+	size_t req_len;
 
 	ctrlr_device = nvme_cuse_get_cuse_ctrlr_device(ctrlr);
 	if (!ctrlr_device) {
-		return NULL;
+		return -ENODEV;
 	}
 
-	return ctrlr_device->dev_name;
+	req_len = strnlen(ctrlr_device->dev_name, sizeof(ctrlr_device->dev_name));
+	if (*size < req_len) {
+		*size = req_len;
+		return -ENOSPC;
+	}
+	snprintf(name, req_len + 1, "%s", ctrlr_device->dev_name);
+
+	return 0;
 }
 
-char *
+int
-spdk_nvme_cuse_get_ns_name(struct spdk_nvme_ctrlr *ctrlr, uint32_t nsid)
+spdk_nvme_cuse_get_ns_name(struct spdk_nvme_ctrlr *ctrlr, uint32_t nsid, char *name, size_t *size)
 {
 	struct cuse_device *ns_device;
+	size_t req_len;
 
 	ns_device = nvme_cuse_get_cuse_ns_device(ctrlr, nsid);
 	if (!ns_device) {
-		return NULL;
+		return -ENODEV;
 	}
 
-	return ns_device->dev_name;
+	req_len = strnlen(ns_device->dev_name, sizeof(ns_device->dev_name));
+	if (*size < req_len) {
+		*size = req_len;
+		return -ENOSPC;
+	}
+	snprintf(name, req_len + 1, "%s", ns_device->dev_name);
+
+	return 0;
 }

module/bdev/nvme/bdev_nvme.c

@@ -765,12 +765,13 @@ bdev_nvme_dump_info_json(void *ctx, struct spdk_json_write_ctx *w)
 	spdk_json_write_object_end(w);
 
 #ifdef SPDK_CONFIG_NVME_CUSE
-	char *cuse_device;
+	size_t cuse_name_size = 128;
+	char cuse_name[cuse_name_size];
 
-	cuse_device = spdk_nvme_cuse_get_ns_name(nvme_bdev->nvme_bdev_ctrlr->ctrlr,
+	int rc = spdk_nvme_cuse_get_ns_name(nvme_bdev->nvme_bdev_ctrlr->ctrlr, spdk_nvme_ns_get_id(ns),
-			spdk_nvme_ns_get_id(ns));
+					    cuse_name, &cuse_name_size);
-	if (cuse_device) {
+	if (rc == 0) {
-		spdk_json_write_named_string(w, "cuse_device", cuse_device);
+		spdk_json_write_named_string(w, "cuse_device", cuse_name);
 	}
 #endif
 

module/bdev/nvme/bdev_nvme_rpc.c

@@ -355,11 +355,12 @@ spdk_rpc_dump_nvme_controller_info(struct spdk_json_write_ctx *w,
 	spdk_json_write_named_string(w, "name", nvme_bdev_ctrlr->name);
 
 #ifdef SPDK_CONFIG_NVME_CUSE
-	char *cuse_device;
+	size_t cuse_name_size = 128;
+	char cuse_name[cuse_name_size];
 
-	cuse_device = spdk_nvme_cuse_get_ctrlr_name(nvme_bdev_ctrlr->ctrlr);
+	int rc = spdk_nvme_cuse_get_ctrlr_name(nvme_bdev_ctrlr->ctrlr, cuse_name, &cuse_name_size);
-	if (cuse_device) {
+	if (rc == 0) {
-		spdk_json_write_named_string(w, "cuse_device", cuse_device);
+		spdk_json_write_named_string(w, "cuse_device", cuse_name);
 	}
 #endif