Linux Virtualization - Aug 2013 - [PATCH] percpu ida: Switch to cpumask_t, add some comments

On Wed, 28 Aug 2013 12:55:17 -0700 Kent Overstreet <kmo at daterainc.com>
wrote:
> Fixup patch, addressing Andrew's review feedback:
Looks reasonable.
>  lib/idr.c           | 38 +++++++++++++++++++++-----------------
I still don't think it should be in this file.

You say that some as-yet-unmerged patches will tie the new code into
the old ida code.  But will it do it in a manner which requires that
the two reside in the same file?

On Wed, Aug 28, 2013 at 01:25:50PM -0700, Andrew Morton
wrote:
> On Wed, 28 Aug 2013 12:55:17 -0700 Kent Overstreet <kmo at
daterainc.com> wrote:
> 
> > Fixup patch, addressing Andrew's review feedback:
> 
> Looks reasonable.
> 
> >  lib/idr.c           | 38 +++++++++++++++++++++-----------------
> 
> I still don't think it should be in this file.
> 
> You say that some as-yet-unmerged patches will tie the new code into
> the old ida code.  But will it do it in a manner which requires that
> the two reside in the same file?
Not require, no - but it's just intimate enough with my ida rewrite that
I think it makes sense; it makes some use of stuff that should be
internal to the ida code.

Mostly just sharing the lock though, since I got rid of the ida
interfaces that don't do locking, but percpu ida needs a lock that also
covers what ida needs.

It also makes use of a ganged allocation interface, but there's no real
reason ida can't expose that, it's just unlikely to be useful to
anything but percpu ida.

The other reason I think it makes sense to live in idr.c is more for
users of the code; as you pointed out as far as the user's perspective
percpu ida isn't doing anything fundamentally different from ida, so I
think it makes sense for the code to live in the same place as a
kindness to future kernel developers who are trying to find their way
around the various library code.

On Wed, 28 Aug 2013 14:00:10 -0700 Kent Overstreet <kmo at daterainc.com>
wrote:
> On Wed, Aug 28, 2013 at 01:25:50PM -0700, Andrew Morton wrote:
> > On Wed, 28 Aug 2013 12:55:17 -0700 Kent Overstreet <kmo at
daterainc.com> wrote:
> > 
> > > Fixup patch, addressing Andrew's review feedback:
> > 
> > Looks reasonable.
> > 
> > >  lib/idr.c           | 38 +++++++++++++++++++++-----------------
> > 
> > I still don't think it should be in this file.
> > 
> > You say that some as-yet-unmerged patches will tie the new code into
> > the old ida code.  But will it do it in a manner which requires that
> > the two reside in the same file?
> 
> Not require, no - but it's just intimate enough with my ida rewrite
that
> I think it makes sense; it makes some use of stuff that should be
> internal to the ida code.
> 
> Mostly just sharing the lock though, since I got rid of the ida
> interfaces that don't do locking, but percpu ida needs a lock that also
> covers what ida needs.
> 
> It also makes use of a ganged allocation interface, but there's no real
> reason ida can't expose that, it's just unlikely to be useful to
> anything but percpu ida.
> 
> The other reason I think it makes sense to live in idr.c is more for
> users of the code; as you pointed out as far as the user's perspective
> percpu ida isn't doing anything fundamentally different from ida, so I
> think it makes sense for the code to live in the same place as a
> kindness to future kernel developers who are trying to find their way
> around the various library code.
I found things to be quite the opposite - it took 5 minutes of staring,
head-scratching, double-checking and penny-dropping before I was
confident that the newly-added code actually has nothing at all to do
with the current code.  Putting it in the same file was misleading, and
I got misled.