From: Jan Kara jack@suse.cz
commit 09df6a75fffa68169c5ef9bef990cd7ba94f3eef upstream.
People are occasionally reporting a warning bfqq_request_over_limit() triggering reporting that BFQ's idea of cgroup hierarchy (and its depth) does not match what generic blkcg code thinks. This can actually happen when bfqq gets moved between BFQ groups while bfqq_request_over_limit() is running. Make sure the code is safe against BFQ queue being moved to a different BFQ group.
Fixes: 76f1df88bbc2 ("bfq: Limit number of requests consumed by each cgroup") CC: stable@vger.kernel.org Link: https://lore.kernel.org/all/CAJCQCtTw_2C7ZSz7as5Gvq=OmnDiio=HRkQekqWpKot84sQ... Reported-by: Chris Murphy lists@colorremedies.com Reported-by: "yukuai (C)" yukuai3@huawei.com Signed-off-by: Jan Kara jack@suse.cz Link: https://lore.kernel.org/r/20220407140738.9723-1-jack@suse.cz Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/bfq-iosched.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
--- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -569,7 +569,7 @@ static bool bfqq_request_over_limit(stru struct bfq_entity *entity = &bfqq->entity; struct bfq_entity *inline_entities[BFQ_LIMIT_INLINE_DEPTH]; struct bfq_entity **entities = inline_entities; - int depth, level; + int depth, level, alloc_depth = BFQ_LIMIT_INLINE_DEPTH; int class_idx = bfqq->ioprio_class - 1; struct bfq_sched_data *sched_data; unsigned long wsum; @@ -578,15 +578,21 @@ static bool bfqq_request_over_limit(stru if (!entity->on_st_or_in_serv) return false;
+retry: + spin_lock_irq(&bfqd->lock); /* +1 for bfqq entity, root cgroup not included */ depth = bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css.cgroup->level + 1; - if (depth > BFQ_LIMIT_INLINE_DEPTH) { + if (depth > alloc_depth) { + spin_unlock_irq(&bfqd->lock); + if (entities != inline_entities) + kfree(entities); entities = kmalloc_array(depth, sizeof(*entities), GFP_NOIO); if (!entities) return false; + alloc_depth = depth; + goto retry; }
- spin_lock_irq(&bfqd->lock); sched_data = entity->sched_data; /* Gather our ancestors as we need to traverse them in reverse order */ level = 0;