return ENOENT if trying to attach missing target

include/bake-server.h

@@ -55,16 +55,14 @@ int bake_provider_register(margo_instance_id                     mid,
 int bake_provider_deregister(bake_provider_t provider);
 
 /**
- * Makes the provider start managing a target.
- * The target must have been previously created with bake_makepool,
- * and it should not be managed by another provider (whether in this
- * proccess or another).
+ * Makes the provider start managing a target.  The target must have already
+ * been created in the past.
  *
  * @param provider Bake provider
  * @param target_name path to pmem target
  * @param target_id resulting id identifying the target
  *
- * @return 0 on success, -1 on failure
+ * @return BAKE_SUCCESS or BAKE_ERR*
  */
 int bake_provider_attach_target(bake_provider_t   provider,
                                 const char*       target_name,

include/bake.h

@@ -55,7 +55,9 @@ typedef struct {
 #define BAKE_ERR_FORBIDDEN      (-12) /* Forbidden operation */
 #define BAKE_ERR_BACKEND_TYPE   (-13) /* Unknown backend type */
 #define BAKE_ERR_IO             (-14) /* Back-end I/O error */
-#define BAKE_ERR_END            (-15) /* End of valid bake error codes */
+#define BAKE_ERR_NOENT          (-15) /* entry does not exist */
+#define BAKE_ERR_EXIST          (-16) /* entry already exists */
+#define BAKE_ERR_END            (-17) /* End of valid bake error codes */
 
 /**
  * Print bake errors in human-friendly form

src/bake-file-backend.c

@@ -215,7 +215,7 @@ static int bake_file_backend_initialize(bake_provider_t    provider,
     if (new_entry->log_fd < 0) {
         BAKE_ERROR(provider->mid, "open(): %s on %s",
                    strerror(-new_entry->log_fd), path);
-        ret = BAKE_ERR_IO;
+        ret = BAKE_ERR_NOENT;
         goto error_cleanup;
     }
 

src/bake-pmem-backend.c

@@ -106,7 +106,7 @@ static int bake_pmem_backend_initialize(bake_provider_t    provider,
         free(new_context->filename);
         free(new_context->root);
         free(new_context);
-        return BAKE_ERR_PMEM;
+        return BAKE_ERR_NOENT;
     }
 
     /* check to make sure the root is properly set */

src/util.c

@@ -51,6 +51,12 @@ static char* bake_err_str(int ret)
     case BAKE_ERR_OP_UNSUPPORTED:
         return "Operation not supported";
         break;
+    case BAKE_ERR_NOENT:
+        return "Entry does not exist";
+        break;
+    case BAKE_ERR_EXIST:
+        return "Entry already exists";
+        break;
     default:
         return "Unknown error";
         break;