Re: [PATCH v3 0/5] dax: add PROBE_PREFER_ASYNCHRONOUS to all the dax drivers

[<dan.j.williams@intel.com>]

Michal Clapinski wrote:
> Comments in linux/device/driver.h say that the goal is to do async
> probing on all devices. The current behavior unnecessarily slows down
> the boot by synchronously probing dax devices, so let's change that.
> 
> For thousands of devices, this change saves >1s of boot time.
> 
> Michal Clapinski (5):
>   dax: add PROBE_PREFER_ASYNCHRONOUS to the pmem driver
>   dax: add PROBE_PREFER_ASYNCHRONOUS to the kmem driver
>   dax: add PROBE_PREFER_ASYNCHRONOUS to the cxl driver
>   dax: add PROBE_PREFER_ASYNCHRONOUS to the hmem drivers
>   dax: add PROBE_PREFER_ASYNCHRONOUS to the dax device driver

After seeing the trouble this causes with libdaxctl and failing to find
a quick fix I wonder if you should just go through route of eating the
potential regressions in your own environment.

I.e. instead of making it a problem that the kernel needs to debug for
all legacy users, how about you just boot with the command line option:

   driver_async_probe=device_dax

...or add the following to your mopdrobe configuration:

   options device_dax async_probe

I.e. do you really need to change this policy globally for everyone at
this point?

I do want to improve this, but I think it will take time for libdaxctl
to get ready for this flag day.