From dfd6200a095440b663099d8d42f1efb0175a1ce3 Mon Sep 17 00:00:00 2001 From: Yu Kuai Date: Thu, 19 Jan 2023 19:03:49 +0800 Subject: blk-cgroup: support to track if policy is online A new field 'online' is added to blkg_policy_data to fix following 2 problem: 1) In blkcg_activate_policy(), if pd_alloc_fn() with 'GFP_NOWAIT' failed, 'queue_lock' will be dropped and pd_alloc_fn() will try again without 'GFP_NOWAIT'. In the meantime, remove cgroup can race with it, and pd_offline_fn() will be called without pd_init_fn() and pd_online_fn(). This way null-ptr-deference can be triggered. 2) In order to synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy(), 'list_del_init(&blkg->q_node)' will be delayed to blkg_free_workfn(), hence pd_offline_fn() can be called first in blkg_destroy(), and then blkcg_deactivate_policy() will call it again, we must prevent it. The new field 'online' will be set after pd_online_fn() and will be cleared after pd_offline_fn(), in the meantime pd_offline_fn() will only be called if 'online' is set. Signed-off-by: Yu Kuai Acked-by: Tejun Heo Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20230119110350.2287325-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe --- block/blk-cgroup.h | 1 + 1 file changed, 1 insertion(+) (limited to 'block/blk-cgroup.h') diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 1e94e404eaa8..b13ee84f358e 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -135,6 +135,7 @@ struct blkg_policy_data { /* the blkg and policy id this per-policy data belongs to */ struct blkcg_gq *blkg; int plid; + bool online; }; /* -- cgit