diff options
| author | Waiman Long <longman@redhat.com> | 2022-11-04 20:59:02 -0400 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-11-16 16:58:44 -0700 |
| commit | dae590a6c96c799434e0ff8156ef29b88c257e60 (patch) | |
| tree | 47cc80856cb5e7b653e9ba8a70899b04c83ed850 /block/blk-cgroup.c | |
| parent | 3b8cc6298724021da845f2f9fd7dd4b6829a6817 (diff) | |
| download | linux-dae590a6c96c799434e0ff8156ef29b88c257e60.tar.bz2 | |
blk-cgroup: Flush stats at blkgs destruction path
As noted by Michal, the blkg_iostat_set's in the lockless list
hold reference to blkg's to protect against their removal. Those
blkg's hold reference to blkcg. When a cgroup is being destroyed,
cgroup_rstat_flush() is only called at css_release_work_fn() which is
called when the blkcg reference count reaches 0. This circular dependency
will prevent blkcg from being freed until some other events cause
cgroup_rstat_flush() to be called to flush out the pending blkcg stats.
To prevent this delayed blkcg removal, add a new cgroup_rstat_css_flush()
function to flush stats for a given css and cpu and call it at the blkgs
destruction path, blkcg_destroy_blkgs(), whenever there are still some
pending stats to be flushed. This will ensure that blkcg reference
count can reach 0 ASAP.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20221105005902.407297-4-longman@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-cgroup.c')
| -rw-r--r-- | block/blk-cgroup.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 3e03c0d13253..57941d2a8ba3 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1084,10 +1084,12 @@ struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css) */ static void blkcg_destroy_blkgs(struct blkcg *blkcg) { + int cpu; + might_sleep(); + css_get(&blkcg->css); spin_lock_irq(&blkcg->lock); - while (!hlist_empty(&blkcg->blkg_list)) { struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first, struct blkcg_gq, blkcg_node); @@ -1110,6 +1112,17 @@ static void blkcg_destroy_blkgs(struct blkcg *blkcg) } spin_unlock_irq(&blkcg->lock); + + /* + * Flush all the non-empty percpu lockless lists. + */ + for_each_possible_cpu(cpu) { + struct llist_head *lhead = per_cpu_ptr(blkcg->lhead, cpu); + + if (!llist_empty(lhead)) + cgroup_rstat_css_cpu_flush(&blkcg->css, cpu); + } + css_put(&blkcg->css); } /** |