[ewg] Re: pkey change handling patch

[Roland Dreier]

 > So, this all turned out looking much more hairy than I thought it would be.
 > Maybe option 1 is better? How about adding new types of events, and
 > generating them once cache has been updated?

Well, I had another idea that I've been meaning to post.  How about
adding a can_block flag to the methods query the cache.  If can_block
is set, just wait for the cache to be up-to-date, and if it is not
set, then return ESTALE (or maybe EAGAIN to match non-blocking file
methods even more closely).

That forces us to think about every use of the cache queries, but I'm
not sure that's a bad think.

 - R.