linux-kernel - Re: [PATCH 04/13] sysfs: Simplify sysfs_chmod

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Message-ID: <20091104045547.GA774@us.ibm.com>
Date:	Tue, 3 Nov 2009 22:55:47 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Benjamin LaHaise <bcrl@...et.ca>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 04/13] sysfs: Simplify sysfs_chmod_file semantics

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> "Serge E. Hallyn" <serue@...ibm.com> writes:
> 
> > Quoting Eric W. Biederman (ebiederm@...ssion.com):
> >> From: Eric W. Biederman <ebiederm@...ssion.com>
> >> 
> >> Currently every caller of sysfs_chmod_file happens at either
> >> file creation time to set a non-default mode or in response
> >> to a specific user requested space change in policy.  Making
> >> timestamps of when the chmod happens and notification of
> >> a file changing mode uninteresting.
> >
> > But these changes can occur by togging values in sysfs files
> > (i.e. f71805f.c), right?  Is this (specifically not doing inotify)
> > definately uncontroversial?
> 
> The fs_notify_change was not introduced to deliberately support
> a feature but as a side effect of other cleanups.  So there
> is no indication that anyone cares about inotify support.
> 
> > I can't exactly picture an admin sitting there watching
> > nautilus for a sysfs file to become writeable, but could
> > imagine some site's automation getting hung...  Or am I way
> > off base?
> 
> I would be stunned if the shell script in the automation that writes
> to a sysfs file to make things writeable doesn't on it's next line
> kick off whatever needs it to be writable.
> 
> With no benefit to using inotify and with only a handful of sysfs
> files affected I don't expect this change to break anything in
> userspace and I have been happily running with it for a year or so on
> all of our machines at work with no one problems.
> 
> The reason I am making the change is that the goal of this patchset is
> to get sysfs to act like any other distributed filesystem in linux,
> and to use the same interfaces in roughly the same ways as other
> distributed filesystems.  Unfortunately there is not a good interface
> for distributed filesystems to support inotify or I would use it.
> 
> Eric

Ok - I personally agree, but I know there are admins out there with
very different mindsets from mine

Acked-by: Serge Hallyn <serue@...ibm.com>

-serge
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