[v7,0/3] blk-cgroup: Optimize blkcg_rstat_flush()

Message

Waiman Long Oct. 3, 2022, 3:44 p.m. UTC

v7:
  - Drop patch 1 ("blk-cgroup: Correctly free percpu iostat_cpu in blkg
    on error exit") as it is found to be unnecessary.
  - Add a new llist patch to provide a lockless list variant terminated
    by a sentinel node.
  - Modified patch 3 to use the new sllist API and move percpu_ref_put()
    later in the blkcg_rstat_flush() loop to prevent potential
    use-after-free problem.

 v6:
  - Add a missing free_percpu() into blkcg_css_free() in patch 3.
  - Integrating the documentation patch 4 back into patch 3.

 v5:
  - Add a new patch 2 to eliminate the use of intermediate "ret"
    variable in blkcg_css_alloc() to fix compilation warning reported
    by kernel test robot.

This patch series improves blkcg_rstat_flush() performance by eliminating
unnecessary blkg enumeration and flush operations for those blkg's and
blkg_iostat_set's that haven't been updated since the last flush.

Waiman Long (3):
  llist: Add a lock-less list variant terminated by a sentinel node
  blk-cgroup: Return -ENOMEM directly in blkcg_css_alloc() error path
  blk-cgroup: Optimize blkcg_rstat_flush()

 block/blk-cgroup.c    |  85 ++++++++++++++++++++++-----
 block/blk-cgroup.h    |   9 +++
 include/linux/llist.h | 132 +++++++++++++++++++++++++++++++++++++++++-
 lib/llist.c           |  79 ++++++++++++++++++++++++-
 4 files changed, 289 insertions(+), 16 deletions(-)