s3: map routed write/delete errors and fall back on directory markers

Address review feedback on the routed fast paths:

- PutObject: map the response's machine-readable FilerError code to the same S3
  error the lock path produces (key-too-long, parent/existing-is-file,
  existing-is-directory, precondition), instead of re-wrapping resp.Error in a
  fresh error that filerErrorToS3Error can no longer match by sentinel. Unknown
  codes and in-band errors fall back to the lock path for exact semantics.

- DeleteObject: on any non-precondition routed error, fall back to the lock
  path instead of returning InternalError. This restores directory-marker
  handling (demote a marker that still has children rather than failing on a
  non-empty folder), which the raw DeleteEntry call lacks.

weed/s3api/s3api_object_handlers_delete.go

@@ -231,8 +231,10 @@ func (s3a *S3ApiServer) DeleteObjectHandler(w http.ResponseWriter, r *http.Reque
 				case resp.ErrorCode == filer_pb.FilerError_PRECONDITION_FAILED:
 					deleteCode, deleteHandled = s3err.ErrPreconditionFailed, true
 				case resp.Error != "":
-					glog.Errorf("DeleteObjectHandler: routed delete failed for %s/%s: %s", bucket, object, resp.Error)
-					deleteCode, deleteHandled = s3err.ErrInternalError, true
+					// Fall back to the lock path, which carries extra handling the
+					// raw DeleteEntry lacks (e.g. demoting a directory marker that
+					// still has children instead of failing on a non-empty folder).
+					glog.Warningf("DeleteObjectHandler: routed delete to %s returned %q for %s/%s, falling back to lock", owner, resp.Error, bucket, object)
 				default:
 					deleteCode, deleteHandled = s3err.ErrNone, true
 				}

weed/s3api/s3api_object_handlers_put.go

@@ -850,11 +850,17 @@ func (s3a *S3ApiServer) putToFiler(r *http.Request, filePath string, dataReader
 		switch {
 		case err != nil:
 			glog.Warningf("putToFiler: routed create to %s failed for %s, falling back to lock: %v", owner, filePath, err)
-		case resp.ErrorCode == filer_pb.FilerError_PRECONDITION_FAILED:
-			createCode, routed = s3err.ErrPreconditionFailed, true
+		case resp.ErrorCode != filer_pb.FilerError_OK:
+			// Map known filer error codes to the same S3 errors the lock path
+			// would produce; fall back for any code this does not recognize.
+			if code, mapped := filerErrorCodeToS3Error(resp.ErrorCode); mapped {
+				createCode, routed = code, true
+			} else {
+				glog.Warningf("putToFiler: routed create to %s returned code %v for %s, falling back to lock", owner, resp.ErrorCode, filePath)
+			}
 		case resp.Error != "":
-			createErr = fmt.Errorf("%s", resp.Error)
-			createCode, routed = filerErrorToS3Error(createErr), true
+			// In-band error without a code: fall back so the lock path maps it.
+			glog.Warningf("putToFiler: routed create to %s returned %q for %s, falling back to lock", owner, resp.Error, filePath)
 		default:
 			entryCreated, createCode, routed = true, s3err.ErrNone, true
 		}

weed/s3api/s3api_object_routed_write.go

@@ -128,6 +128,25 @@ func (s3a *S3ApiServer) createEntryOnFiler(owner pb.ServerAddress, req *filer_pb
 	return resp, err
 }
 
+// filerErrorCodeToS3Error maps a routed response's machine-readable FilerError
+// to the same S3 error the lock path produces via filerErrorToS3Error, so the
+// fast path keeps identical semantics. ok is false for codes it does not map,
+// signalling the caller to fall back to the lock path for exact behavior.
+func filerErrorCodeToS3Error(code filer_pb.FilerError) (s3err.ErrorCode, bool) {
+	switch code {
+	case filer_pb.FilerError_PRECONDITION_FAILED:
+		return s3err.ErrPreconditionFailed, true
+	case filer_pb.FilerError_ENTRY_NAME_TOO_LONG:
+		return s3err.ErrKeyTooLongError, true
+	case filer_pb.FilerError_PARENT_IS_FILE, filer_pb.FilerError_EXISTING_IS_FILE:
+		return s3err.ErrExistingObjectIsFile, true
+	case filer_pb.FilerError_EXISTING_IS_DIRECTORY:
+		return s3err.ErrExistingObjectIsDirectory, true
+	default:
+		return s3err.ErrNone, false
+	}
+}
+
 // buildDeleteCondition reduces a DeleteObject's If-Match header to a primitive.
 // DeleteObject only honors If-Match (matching checkDeleteIfMatch), so other
 // conditional headers are ignored here as they are on the existing path.