linux-kernel - Re: [PATCH 1/2] tools/lib/api/fs: Add procfs int read/write helpers

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Date:   Tue, 7 Feb 2017 12:00:45 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Robert Richter <rric@...nel.org>,
        Vince Weaver <vince@...ter.net>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] tools/lib/api/fs: Add procfs int read/write helpers

Em Tue, Feb 07, 2017 at 11:30:01AM +0100, Borislav Petkov escreveu:
> On Mon, Feb 06, 2017 at 10:43:56PM -0300, Arnaldo Carvalho de Melo wrote:
> > >  int sysctl__read_int(const char *sysctl, int *value);
> > 
> > Isn't sysctl__read_int() what you want?
> 
> Right, so looking at this: don't you think that having both sysctl__*
> and procfs__* is a little redundant?
> 
> The sysctl* things are doing the accesses over proc so shouldn't it all
> be procfs__* interfaces and no sysctl__* ones at all
> 
> or
> 
> at least the sysctl__* ones should call the procfs__* ones?

Well, I see this as: sysctls are implemented as files in procfs, but
could conceivably be implemented somewhere else, just like the events
file was implemented in debugfs but then was moved to a separate
filesystem type, tracefs.

So it being in procfs is an implementation detail, what I'm interested
are sysctls, and names for sysctls will be appended to wherever the
sysctl is made available in the file system.

For instance:

[root@...et ~]# sysctl kernel.watchdog
kernel.watchdog = 1
[root@...et ~]#

So the sysctl is "kernel.watchdog" and it is set to one.

So, I suggest you use:

	if (sysctl__read_int("kernel/watchdog", &watchdog_value) == 0)
		/* do whatever you want with it */

And forget that under the hood this is in something called "procfs".

:-)

- Arnaldo