Re: Filesystem configuration parsers - (was: Re: [RESEND][PATCH] xfs: add online uevent for mount operation)

[Dave Chinner <david@fromorbit.com>]

On Thu, Aug 24, 2017 at 08:04:41PM +0200, Luis R. Rodriguez wrote:
> While all this is nice, I'm sure we're all aware of the dangers of setting
> things in stone through sysfs, its likely already decided for the above
> tunables, but adding a uevent *is* yet another layer of user interface
> which userspace can *expect* and we should be certain we want this so
> we won't regress userspace later.
> 
> Just saying, we better damn be sure this is the way we want to go.

I'm not sure what you are trying to warn us about? :/

These are events on an XFS specific kobj, it's not a generic VFS
filesystem event we are generating here. It's no different from a
hardware device generating it's own uevents to tell userspace
something changed in the device.

A quick grep would have told you that GFS2 already has it's own
online/offline uevents (e.g. gfs2_online_uevent()), as does the
DLM code. Orangefs seems to use quite a few of uevent notifications,
too. So it's not like we're doing something controversial or unique
here, nor something that locks us out of a non-existent VFS event
notification mechanism.

Please, talk all you want about a Grand Unified VFS Event
Notification infrastructure and filesystem tool libraries, but
please don't hijack an unrelated discussion to do it.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com