Changes in v2:
 - check dying blkg early in patch 4;
 - add patch 7 to fix rq_qos_mutex related deadlocks;

This series fixes race conditions between blkcg_activate_policy() and
blkg destruction, and optimizes the policy activation path.

Patches 1-2 add missing blkcg_mutex protection for q->blkg_list iteration.

Patches 3-5 from Zheng Qixing fix use-after-free and memory leak issues
caused by races between policy activation and blkg destruction.

Patch 6 restructures blkcg_activate_policy() to allocate pds before
freezing the queue. This is a prep patch to fix deadlocks related to
percpu allocation with queue frozen, since some policies like iocost
and iolatency do percpu allocation in pd_alloc_fn().

Patch 7 reduces freeze queue contex by moving rq_qos_mutex into
rq_qos_add/del, so that allocate memory without queue frozen.

Yu Kuai (4):
  blk-cgroup: protect q->blkg_list iteration in blkg_destroy_all() with
    blkcg_mutex
  bfq: protect q->blkg_list iteration in bfq_end_wr_async() with
    blkcg_mutex
  blk-cgroup: allocate pds before freezing queue in
    blkcg_activate_policy()
  blk-rq-qos: move rq_qos_mutex acquisition inside rq_qos_add/del

Zheng Qixing (3):
  blk-cgroup: fix race between policy activation and blkg destruction
  blk-cgroup: skip dying blkg in blkcg_activate_policy()
  blk-cgroup: factor policy pd teardown loop into helper

 block/bfq-cgroup.c  |   3 +-
 block/bfq-iosched.c |   2 +
 block/blk-cgroup.c  | 200 ++++++++++++++------------------------------
 block/blk-cgroup.h  |   2 -
 block/blk-iocost.c  |  11 +--
 block/blk-rq-qos.c  |  31 ++++---
 block/blk-wbt.c     |   2 -
 7 files changed, 90 insertions(+), 161 deletions(-)

-- 
2.51.0