util: fix uses of spdk_posix_file_load_from_name

Changes for https://review.spdk.io/gerrit/c/spdk/spdk/+/21829 introduced a bug
in nvmf_ns_reservation_load_json(): non-existing file for ptpl was no longer
ignored.

spdk_posix_file_load_from_name changed to return an error code, in order to be
able to distinguish between different error conditions, and to prevent to rely
on global errno.

Signed-off-by: Dmitry Savitskiy <[email protected]>

include/spdk/file.h

@@ -31,10 +31,12 @@ void *spdk_posix_file_load(FILE *file, size_t *size);
  *
  * \param file_name File name.
  * \param size Size of bytes read from the file.
+ * \param file_data Pointer to write a pointer to the data containing the content on success, or
+ * NULL is written on failure.
  *
- * \return data containing the content on success, NULL on failure.
+ * \return 0 on success, negative errno error code on failure.
  */
-void *spdk_posix_file_load_from_name(const char *file_name, size_t *size);
+int spdk_posix_file_load_from_name(const char *file_name, size_t *size, void **file_data);
 
 #ifdef __cplusplus
 }

lib/event/app.c

@@ -956,8 +956,9 @@ spdk_app_start(struct spdk_app_opts *opts_user, spdk_msg_fn start_fn,
 			return 1;
 		}
 
-		g_spdk_app.json_data = spdk_posix_file_load_from_name(opts->json_config_file,
-				       &g_spdk_app.json_data_size);
+		spdk_posix_file_load_from_name(opts->json_config_file,
+					       &g_spdk_app.json_data_size,
+					       &g_spdk_app.json_data);
 		if (!g_spdk_app.json_data) {
 			SPDK_ERRLOG("Read JSON configuration file %s failed: %s\n",
 				    opts->json_config_file, spdk_strerror(errno));

lib/init/json_config.c

@@ -660,7 +660,7 @@ spdk_subsystem_init_from_json_config(const char *json_config_file, const char *r
 
 	assert(cb_fn);
 
-	json = spdk_posix_file_load_from_name(json_config_file, &json_size);
+	spdk_posix_file_load_from_name(json_config_file, &json_size, (void **)&json);
 	if (!json) {
 		SPDK_ERRLOG("Could not read JSON config file\n");
 		cb_fn(-EINVAL, cb_arg);

lib/nvmf/subsystem.c

@@ -2538,6 +2538,7 @@ static int
 nvmf_ns_reservation_load_json(const struct spdk_nvmf_ns *ns,
 			      struct spdk_nvmf_reservation_info *info)
 {
+	int err;
 	size_t json_size;
 	ssize_t values_cnt, rc;
 	void *json = NULL, *end;
@@ -2547,10 +2548,17 @@ nvmf_ns_reservation_load_json(const struct spdk_nvmf_ns *ns,
 	uint32_t i;
 
 	/* Load all persist file contents into a local buffer */
-	json = spdk_posix_file_load_from_name(file, &json_size);
+	err = spdk_posix_file_load_from_name(file, &json_size, &json);
+
+	/* It's not an error if the file does not exist */
+	if (err == -ENOENT) {
+		SPDK_NOTICELOG("Persist file %s does not exist\n", file);
+		return 0;
+	}
+
 	if (!json) {
-		SPDK_ERRLOG("Load persit file %s failed\n", file);
-		return -ENOMEM;
+		SPDK_ERRLOG("Load persist file %s failed: %s\n", file, strerror(-err));
+		return err;
 	}
 
 	rc = spdk_json_parse(json, json_size, NULL, 0, &end, 0);

lib/util/file.c

@@ -42,18 +42,24 @@ spdk_posix_file_load(FILE *file, size_t *size)
 	return NULL;
 }
 
-void *
-spdk_posix_file_load_from_name(const char *file_name, size_t *size)
+int
+spdk_posix_file_load_from_name(const char *file_name, size_t *size, void **file_data)
 {
 	FILE *file = fopen(file_name, "r");
-	void *data;
+
+	assert(file_data);
 
 	if (file == NULL) {
-		return NULL;
+		*file_data = NULL;
+		return -errno;
 	}
 
-	data = spdk_posix_file_load(file, size);
+	*file_data = spdk_posix_file_load(file, size);
 	fclose(file);
 
-	return data;
+	if (*file_data) {
+		return 0;
+	} else {
+		return -ENOMEM;
+	}
 }

test/app/fuzz/common/fuzz_common.h

@@ -105,7 +105,7 @@ read_json_into_buffer(const char *filename, struct spdk_json_val **values, void
 	size_t file_data_size;
 	ssize_t num_json_values = 0, rc;
 
-	*file_data = spdk_posix_file_load_from_name(filename, &file_data_size);
+	spdk_posix_file_load_from_name(filename, &file_data_size, file_data);
 	if (*file_data == NULL) {
 		return 0;
 	}

test/app/fuzz/llvm_nvme_fuzz/llvm_nvme_fuzz.c

@@ -932,7 +932,7 @@ nvme_fuzz_parse(int ch, char *arg)
 		}
 		break;
 	case 'N':
-		g_repro_data = spdk_posix_file_load_from_name(optarg, &g_repro_size);
+		spdk_posix_file_load_from_name(optarg, &g_repro_size, &g_repro_data);
 		if (g_repro_data == NULL) {
 			fprintf(stderr, "could not load data for file %s\n", optarg);
 			return -1;

test/app/fuzz/llvm_vfio_fuzz/llvm_vfio_fuzz.c

@@ -590,7 +590,7 @@ vfio_fuzz_parse(int ch, char *arg)
 		}
 		break;
 	case 'N':
-		g_repro_data = spdk_posix_file_load_from_name(optarg, &g_repro_size);
+		spdk_posix_file_load_from_name(optarg, &g_repro_size, &g_repro_data);
 		if (g_repro_data == NULL) {
 			fprintf(stderr, "could not load data for file %s\n", optarg);
 			return -1;