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Date: Thu, 18 Nov 2010 18:08:20 -0800
From: Greg KH <greg@kroah.com>
To: Yehuda Sadeh Weinraub <yehuda@hq.newdream.net>
Cc: sage@newdream.net, ceph-devel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rbd: replace the rbd sysfs interface
Message-ID: <20101119020820.GB18767@kroah.com>
References: <1289953929-30896-1-git-send-email-yehuda@hq.newdream.net> <20101117171924.GC12050@kroah.com> <AANLkTims_MjBS1SdHkOjOWvGqg1aRABH23MWk8J-E+-Y@mail.gmail.com> <20101118013002.GC8558@kroah.com> <AANLkTi=7z40CNBUmfVUEa68J+1R=7nbn9d8vM7ETpajA@mail.gmail.com>
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On Thu, Nov 18, 2010 at 02:53:35PM -0800, Yehuda Sadeh Weinraub wrote:
> On Wed, Nov 17, 2010 at 5:30 PM, Greg KH <greg@kroah.com> wrote:
> > On Wed, Nov 17, 2010 at 03:00:17PM -0800, Yehuda Sadeh Weinraub wrote:
> >> On Wed, Nov 17, 2010 at 9:19 AM, Greg KH <greg@kroah.com> wrote:
> >> > On Tue, Nov 16, 2010 at 04:32:09PM -0800, Yehuda Sadeh wrote:
> >> >> Hi Greg,
> >> >>
> >> >> Following is the new rbd sysfs interface. It lists devices in their own
> >> >> subdirectories, as well as their underlying snapshots. Please let us
> >> >> know if there's any issue you think we missed or did wrong.
> >> >>
> >> >> Thanks,
> >> >> Yehuda
> >> >>
> >> >> ---
> >> >>
> >> >> The new interface creates directories per mapped image
> >> >> and under each it creates a subdir per available snapshot.
> >> >> This allows keeping a cleaner interface within the sysfs
> >> >> guidelines. The ABI documentation was updated too.
> >> >>
> >> >> Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
> >> >> ---
> >> >> ?Documentation/ABI/testing/sysfs-class-rbd | ? 83 +++
> >> >> ?drivers/block/rbd.c ? ? ? ? ? ? ? ? ? ? ? | ?775 +++++++++++++++++------------
> >> >> ?2 files changed, 547 insertions(+), 311 deletions(-)
> >> >>
> >> >> diff --git a/Documentation/ABI/testing/sysfs-class-rbd b/Documentation/ABI/testing/sysfs-class-rbd
> >> >> new file mode 100644
> >> >> index 0000000..4d96618
> >> >> --- /dev/null
> >> >> +++ b/Documentation/ABI/testing/sysfs-class-rbd
> >> >> @@ -0,0 +1,83 @@
> >> >> +What: ? ? ? ? ? ? ? ?/sys/class/rbd/
> >> >
> >> > I thought I mentioned that you should not add new classes to the kernel.
> >> > Please don't do that, make it a bus_type instead.
> >>
> >>
> >> Ahmm.. apparently not in the rbd related threads. So moving things
> >> around and having rbd under /sys/bus we'll have the following:
> >>
> >> /sys/bus/rbd/drivers/rbd/..
> >> ? ? add - add a device
> >> ? ? remove - remove a device
> >
> > These files could go in /sys/bus/rbd/ directly instead of burying under
> > 2 more layers, right?
> >
> >>
> >> /sys/bus/rbd/devices/<id>
> >> ? ?name
> >> ? ?pool
> >> ? ?...
> >>
> >> /sys/bus/rbd/devices/<id>/snaps/<name>
> >> ? ? id
> >> ? ? size
> >> ? ? ...
> >>
> >>
> >> Would this work?
> >
> > With the change mentioned above, I think that seems sane, do you?
> >
> 
> Yes, pretty much. One problem that I do see is that if we define the
> snaps/ as a device (and not just as a kobj) as you suggested before,
> it'll automatically create a 'uevent' entry under it which can be a
> real issue in the case we have a snapshot named like that. Shouldn't
> we just create it as a kobj in that case?

No.  Just use the subdirectory option of an attribute group to handle
that and you will not need to create any device or kobject with that
name, the driver core will handle it all automatically for you.

hope this helps,

greg k-h