Re: [dm-devel] [PATCH 0/9] Generate uevents for all DM events
From: Greg KH
Date: Wed Oct 05 2016 - 02:51:00 EST
On Wed, Oct 05, 2016 at 01:40:05AM +0100, Alasdair G Kergon wrote:
> On Tue, Oct 04, 2016 at 04:39:28PM -0700, Andy Grover wrote:
> > devicemapper is using uevents for:
> > a. dm-verity detected corruption
> > b. dm-multipath: path failed or reinstated
> > c. dm device renamed
> > d. there's also some use in md and bcache.
> > devicemapper uses DM_EVENT ioctl (yuck) for:
> > 1. dm-thin pool data/metadata filling up (hit a threshold)
> > 2. dm-cache is now clean
> > 3. dm-log flushed or log failed
> > 4. dm-raid error detected or sync complete
> > there doesn't seem to be much technical differentiation between the
> > two lists.
> The distinction in dm is that events in the first category may affect
> the availability of the device: they represent major (and hopefully
> rare) changes.
> Events in the second category are just notifications: no impact on /dev,
> no need to trigger udev rules, and their use will continue to be
> extended, and (rarely at the moment) could be frequent (which is no
> problem for the existing polling-based mechanism).
> > Instead of using uevent for everything, we could go to a separate
> > genetlink for 1-4 instead of making them use uevent like a-d, but we'd
> > end up with two different userspace notification techniques.
> We see these as two different categories of notifications, and prefer
> the greater flexibility a mechanism independent of uevents would
> provide. The team has discussed several alternatives over the years but
> didn't make a decision as we've not yet reached a point where we're
> straining the existing mechanism too far.
So, no changes need to be made? I'm confused here, who is wanting this