migrate_disable() and rcu_read_lock() are used to together in many case in
bpf. However, when PREEMPT_RCU is not enabled, rcu_read_lock() will
disable preemption, which indicate migrate_disable(), so we don't need to
call it in this case.

In this series, we introduce rcu_read_lock_dont_migrate and
rcu_read_unlock_migrate, which will call migrate_disable and
migrate_enable only when PREEMPT_RCU enabled. And use
rcu_read_lock_dont_migrate in bpf subsystem.

Not sure if I should send the 1st patch to the RCU subsystem :/

Changes since V1:
* introduce rcu_read_lock_dont_migrate() instead of
  rcu_migrate_disable() + rcu_read_lock()

Menglong Dong (7):
  rcu: add rcu_read_lock_dont_migrate()
  bpf: use rcu_read_lock_dont_migrate() for bpf_cgrp_storage_free()
  bpf: use rcu_read_lock_dont_migrate() for bpf_inode_storage_free()
  bpf: use rcu_read_lock_dont_migrate() for bpf_iter_run_prog()
  bpf: use rcu_read_lock_dont_migrate() for bpf_task_storage_free()
  bpf: use rcu_read_lock_dont_migrate() for bpf_prog_run_array_cg()
  bpf: use rcu_read_lock_dont_migrate() for trampoline.c

 include/linux/rcupdate.h       | 24 ++++++++++++++++++++++++
 kernel/bpf/bpf_cgrp_storage.c  |  6 ++----
 kernel/bpf/bpf_inode_storage.c |  6 ++----
 kernel/bpf/bpf_iter.c          |  6 ++----
 kernel/bpf/bpf_task_storage.c  |  6 ++----
 kernel/bpf/cgroup.c            |  6 ++----
 kernel/bpf/trampoline.c        | 18 ++++++------------
 7 files changed, 40 insertions(+), 32 deletions(-)

-- 
2.50.1