Currently, the view_update_generator::mutate_MV function acquires a
reference to the keyspace relevant to the operation, then it calls
max_concurrent_for_each and uses that reference inside the lambda passed
to that function. max_concurrent_for_each can preempt and there is no
mechanism that makes sure that the keyspace is alive until the view
updates are generated, so it is possible that the keyspace is freed by
the time the reference is used.
Fix the issue by precomputing the necessary information based on the
keyspace reference right away, and then passing that information by
value to the other parts of the code. It turns out that we only need to
know the replication factor of the datacenter and whether the keyspace
uses a network topology strategy.
Fixes: scylladb/scylladb#28925Closesscylladb/scylladb#28928
(cherry picked from commit 42d70baad3)
Closesscylladb/scylladb#28968Closesscylladb/scylladb#29095
bccc9be2b6