linux-kernel - Re: Why does ionice(1) ban the user to set back to 'none' class?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4FDF3AAA.9020101@landley.net>
Date:	Mon, 18 Jun 2012 09:26:50 -0500
From:	Rob Landley <rob@...dley.net>
To:	Jens Axboe <axboe@...nel.dk>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Why does ionice(1) ban the user to set back to 'none' class?

On 06/18/2012 06:48 AM, Zheng Liu wrote:
> 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.

Since I'm CC'd, I'll explicitly say I haven't a clue why it does this.

Rob
-- 
GNU/Linux isn't: Linux=GPLv2, GNU=GPLv3+, they can't share code.
Either it's "mere aggregation", or a license violation.  Pick one.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/