add option for O_SYNC writes for standalone FS backend (#9581)

cmd/config/constants.go

@@ -32,6 +32,7 @@ const (
 	EnvRegionName   = "MINIO_REGION_NAME"
 	EnvPublicIPs    = "MINIO_PUBLIC_IPS"
 	EnvEndpoints    = "MINIO_ENDPOINTS"
+	EnvFSOSync      = "MINIO_FS_OSYNC"
 
 	// API sub-system
 	EnvAPIRequestsMax      = "MINIO_API_REQUESTS_MAX"

cmd/config/errors.go

@@ -24,6 +24,12 @@ var (
 		"Browser can only accept `on` and `off` values. To disable web browser access, set this value to `off`",
 	)
 
+	ErrInvalidFSOSyncValue = newErrFn(
+		"Invalid O_SYNC value",
+		"Please check the passed value",
+		"Can only accept `on` and `off` values. To enable O_SYNC for fs backend, set this value to `on`",
+	)
+
 	ErrInvalidDomainValue = newErrFn(
 		"Invalid domain value",
 		"Please check the passed value",