8:14 a.m.
On Thu, Nov 8, 2018 at 12:57 PM Jeff Moyer <jmoyer(a)redhat.com> wrote:
Dan Williams <dan.j.williams(a)intel.com> writes:
> In support of the kernel's conversion of the dax-subsystem from a
> 'class' to a 'bus', teach the libdaxctl subsystem-layout-specific
code
> to parse the new layout. The kernel changes do not effect the primary
> ndctl use case of putting namespaces into 'dax' mode since that uses
> libnvdimm namespace device relative paths, but it does break 'ndctl list
> -X' and 'daxctl list'. For that reason the kernel provides a
> dax_pmem_compat driver to support the old layout and give time for
> userspace components to switch.
>
> Installation of the latest libdaxctl package arranges for a daxctl
> configuration file to be dropped in /etc/modprobe.d. The modprobe
> configuration blacklists dax_pmem_compat modules and sets the proper
> alias for the dax_pmem module. The modprobe configuration upgrades the
> default kernel handling to the /sys/bus/dax scheme.
OK, one other snafu: pmdk also uses the /sys/class/dax path (see
src/common/file.c). Since ndctl isn't the only consumer, we'd have to
coordinate the class->bus switch among all parties.
Yes, the only way I can see to do this is to whack-a-mole convert
/sys/class/dax users over to libdaxctl. At a minimum I need to
disconnect the opt-in from a package upgrade and make it an explicit
command with a man page explaining the details and consequences.
Is there a way to just keep the class-based paths working alongside
the
bus interface?
Unfortunately, devices can't have a 'class' and 'bus' association at
the same time because they will collide on the 'subsystem'
designation. The subsystem association is 1:1.