Re: [ndctl PATCH 04/10] libdaxctl: add an API to determine if memory is movable

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Fri, 2019-10-18 at 11:54 -0700, Dan Williams wrote:
> On Wed, Oct 2, 2019 at 4:49 PM Vishal Verma <vishal.l.verma@intel.com> wrote:
> > By default, daxctl always attempts to online new memory sections as
> > 'movable' so that routine kernel allocations aren't serviced from this
> > memory, and the memory is later removable via hot-unplug.
> > 
> > System configuration, or other agents (such as udev rules) may race
> > 'daxctl' to online memory, and this may result in the memory not being
> > 'movable'. Add an interface to query the movability of a memory object
> > associated with a dax device.
> > 
> > This is in preparation to both display a 'movable' attribute in device
> > listings, as well as optionally allowing memory to be onlined as
> > non-movable.
> > 
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Reported-by: Ben Olson <ben.olson@intel.com>
> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> > ---
> >  daxctl/lib/libdaxctl-private.h | 20 +++++++++
> >  daxctl/lib/libdaxctl.c         | 77 ++++++++++++++++++++++++++++++++--
> >  daxctl/lib/libdaxctl.sym       |  5 +++
> >  daxctl/libdaxctl.h             |  1 +
> >  4 files changed, 100 insertions(+), 3 deletions(-)
> > 
> > diff --git a/daxctl/lib/libdaxctl-private.h b/daxctl/lib/libdaxctl-private.h
> > index 7ba3c46..82939bb 100644
> > --- a/daxctl/lib/libdaxctl-private.h
> > +++ b/daxctl/lib/libdaxctl-private.h
> > @@ -44,6 +44,25 @@ enum memory_op {
> >         MEM_SET_ONLINE,
> >         MEM_IS_ONLINE,
> >         MEM_COUNT,
> > +       MEM_FIND_ZONE,
> 
> This is private so the naming is not too big a concern, but isn't this
> a MEM_GET_ZONE? A find operation to me is something that can succeed
> to find nothing, whereas a get operation fail assumes the association
> can always be retrieved barring exceptional conditions.

Hm, my personal view of find vs. get was that 'get' grabs a reference
(or similar) to something which we know how to get to (have a pointer
directly) etc. 'Find' is more of a 'go searching for' something - and it
may involve walking and looping over data structures.

But I'm not too opposed to this, and can change to 'get' if that follows
convention better.


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