On Thu, Jan 7, 2021 at 12:04 PM Andrea Arcangeli [off-list ref] wrote:

However there are two cases that could wrprotecting exclusive anon
pages with only the mmap_read_lock:

I still think the real fix is "Don't do that then", and just take the
write lock.

The UFFDIO_WRITEPROTECT case simply isn't that critical. It's not a
normal operation. Same goes for softdirty.

Why have those become _so_ magical that they can break the VM for
everybody else?

         Linus