blobfs: add a new API to return file's unique ID

Change-Id: I066085a0606d64a0d95ab2d28340aa35d83efdf7
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-on: https://review.gerrithub.io/423504
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>

include/spdk/blobfs.h

@@ -388,6 +388,17 @@ void spdk_file_set_priority(struct spdk_file *file, uint32_t priority);
  */
 int spdk_file_sync(struct spdk_file *file, struct spdk_io_channel *channel);
 
+/**
+ * Get the unique ID for the file.
+ *
+ * \param file File to get the ID.
+ * \param id ID buffer.
+ * \param size Size of the ID buffer.
+ *
+ * \return the length of ID on success.
+ */
+int spdk_file_get_id(struct spdk_file *file, void *id, size_t size);
+
 #ifdef __cplusplus
 }
 #endif

lib/blobfs/blobfs.c

@@ -2576,6 +2576,18 @@ spdk_file_close(struct spdk_file *file, struct spdk_io_channel *_channel)
 	return args->rc;
 }
 
+int
+spdk_file_get_id(struct spdk_file *file, void *id, size_t size)
+{
+	if (size < sizeof(spdk_blob_id)) {
+		return -EINVAL;
+	}
+
+	memcpy(id, &file->blobid, sizeof(spdk_blob_id));
+
+	return sizeof(spdk_blob_id);
+}
+
 static void
 cache_free_buffers(struct spdk_file *file)
 {

lib/rocksdb/env_spdk.cc

@@ -308,10 +308,16 @@ public:
 			return Status::IOError(spdk_file_get_name(mFile), strerror(errno));
 		}
 	}
-	virtual size_t GetUniqueId(__attribute__((unused)) char *id,
-				   __attribute__((unused)) size_t max_size) const override
+	virtual size_t GetUniqueId(char *id, size_t max_size) const override
 	{
-		return 0;
+		int rc;
+
+		rc = spdk_file_get_id(mFile, id, max_size);
+		if (rc < 0) {
+			return 0;
+		} else {
+			return rc;
+		}
 	}
 };