On Mon, 16 Aug 2021 17:17:50 -0700 Mike Kravetz [off-list ref] wrote:

quoted

And how does one know the operation has completed so the sysfs files
can be reloaded for another operation?

When the write to the file is complete, the operation has completed.
Not exactly sure what you mean by reloading the sysfs files for
another operation?

If userspace wishes to perform another demote operation, it must wait
for the preceding one to complete.

Presumably if thread A is blocked in a write to `demote' and thread B
concurrently tries to perform a demotion, thread B will be blocked as
well?  Was this tested?

Lots of things are to be added to changelogs & documentation, methinks.