[PATCH v4 0/4] blk-cgroup: fix blkg list and policy data races

[Yu Kuai]

From: Yu Kuai <yukuai@xxxxxxx>

This set fix some problems that are reported long time ago with minimal changes,
the blkcg_mutex refactor I'm working on can fix these problems as well, but it's
complicated and may not land in this merge window. So I think this set should land
in this merge window first.

Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
blkcg_mutex.

Patches 2-3 fix races between blkcg_activate_policy() and concurrent
blkg destruction.

Patch 4 factors the policy data teardown loop into a helper after the
race fixes.

Changes since v3:
- Rebase on the latest for-7.3/block branch.

Changes since v2:
- Rebase on the latest block-7.2 branch.

Changes since v1:
- Drop the BFQ q->blkg_list patch because the current block tree already
  has a stronger fix in commit 17b2d950a3c0 ("block, bfq: protect async
  queue reset with blkcg locks").
- Add Reviewed-by tags from Tang Yizhou.

Yu Kuai (1):
  blk-cgroup: protect q->blkg_list iteration in blkg_destroy_all() with
    blkcg_mutex

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/blk-cgroup.c | 65 +++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 30 deletions(-)

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2.51.0