Hi Jens, I meet a problem when I use ionice(1) to adjust a process's io priority. I do the following operations: $ ionice -p${pid} none: prio 0 $ ionice -p${pid} -c2 -n4 $ ionice -p${pid} best-effort: prio 4 $ ionice -p${pid} -c0 -n0 $ ionice -p${pid} best-effort: prio 0 So I cannot set scheduling class back to 'none'. If I call ioprio_set(2) directly, it will be fine. But if I use ionice(1), I cannot change it. I read the docs about ionice in [1]. I notice this code: switch (ioprio_class) { case IOPRIO_CLASS_NONE: ioprio_class = IOPRIO_CLASS_BE; ^^^^^^^^^^^^^^^^ *It means that we cannot set back to none.* break; case IOPRIO_CLASS_RT: case IOPRIO_CLASS_BE: break; case IOPRIO_CLASS_IDLE: ioprio = 7; break; default: printf("bad prio class %d\n", ioprio_class); return 1; } My question is why we need to ban the user to set back to 'none'. Is there some reasons? Thank you. [Sorry, I don't subscribe linux-doc and linux-kernel mailing list. Please CC to me.] 1. ${linux_src}/Documentation/block/ioprio.txt. Regards, Zheng -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html