Re: [PATCH -mm -V7] mm, swap: fix race between swapoff and some swap operations

[Andrea Parri]

> Alternative implementation could be replacing disable preemption with
> rcu_read_lock_sched and stop_machine() with synchronize_sched().

JFYI, starting with v4.20-rc1, synchronize_rcu{,expedited}() also wait
for preempt-disable sections (the intent seems to retire the RCU-sched
update-side API), so that here you could instead use preempt-disable +
synchronize_rcu{,expedited}().  This LWN article gives an overview of
the latest RCU API/semantics changes: https://lwn.net/Articles/777036/.

  Andrea