On Fri, Oct 08, 2021 at 03:27:20PM +0800, Yu Kuai wrote:
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index eb48090eefce..00e1d97621ea 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -226,6 +226,20 @@ struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
}
EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
+static void blkg_check_pd(struct request_queue *q, struct blkcg_gq *blkg)
+{
+ int i;
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (blkg->pd[i] && !blkcg_policy_enabled(q, pol)) {
+ pol->pd_free_fn(blkg->pd[i]);
+ blkg->pd[i] = NULL;
+ }
+ }
+}
+
/*
* If @new_blkg is %NULL, this function tries to allocate a new one as
* necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
@@ -252,6 +266,9 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
goto err_free_blkg;
}
+ if (new_blkg)
+ blkg_check_pd(q, new_blkg);
+
Can't this happen the other way around too? ie. Linking a pd which doesn't
have an entry for a policy which got enabled inbetween? And what if an
existing policy was de-registered and another policy got the policy id
inbetween? I think the correct solution here would be synchronizing alloc -
create blocks against policy deactivation rather than trying to patch an
allocated blkg later. Deactivation being a really slow path, there are
plenty of options. The main challenge would making it difficult to make
mistakes with, I guess.
Thanks.