On Thu, Dec 19, 2024 at 01:18:23PM -0500, Liam R. Howlett wrote: > > For RCU lookups only the mas tree matters -- and its left present there. > > > > If you really want to block RCU readers, I would suggest punching a hole > > in the mm_mt. All the traditional code won't notice anyway, this is all > > with mmap_lock held for writing. > > We don't want to block all rcu readers, we want to block the rcu readers > that would see the problem - that is, anyone trying to read a particular > area. > > Right now we can page fault in unpopulated vmas while writing other vmas > to the tree. We are also moving more users to rcu reading to use the > vmas they need without waiting on writes to finish. > > Maybe I don't understand your suggestion, but I would think punching a > hole would lose this advantage? My suggestion was to remove the range stuck in mas_detach from mm_mt. That is exactly the affected range, no?
