Re: [PATCH v3] blk-throttle: fix race between blkcg_bio_issue_check() and cgroup_rmdir()

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Fine, I will do the corresponding changes and post v5.

Thanks,
Joseph

On 18/3/14 04:19, Tejun Heo wrote:
> Hello, Joseph.
> 
> On Mon, Mar 05, 2018 at 11:03:16PM +0800, Joseph Qi wrote:
>> +static void blkg_pd_offline(struct blkcg_gq *blkg)
>> +{
>> +	int i;
>> +
>> +	lockdep_assert_held(blkg->q->queue_lock);
>> +	lockdep_assert_held(&blkg->blkcg->lock);
>> +
>> +	for (i = 0; i < BLKCG_MAX_POLS; i++) {
>> +		struct blkcg_policy *pol = blkcg_policy[i];
>> +
>> +		if (blkg->pd[i] && !blkg->pd_offline[i] && pol->pd_offline_fn) {
>> +			pol->pd_offline_fn(blkg->pd[i]);
>> +			blkg->pd_offline[i] = true;
> 
> Can we move this flag into blkg_policy_data?
> 
>> +	while (!hlist_empty(&blkcg->blkg_list)) {
>> +		struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
>> +						    struct blkcg_gq,
>> +						    blkcg_node);
>> +		struct request_queue *q = blkg->q;
>> +
>> +		if (spin_trylock(q->queue_lock)) {
>> +			blkg_destroy(blkg);
>> +			spin_unlock(q->queue_lock);
>> +		} else {
>> +			spin_unlock_irq(&blkcg->lock);
>> +			cpu_relax();
>> +			spin_lock_irq(&blkcg->lock);
>> +		}
> 
> Can we factor out the above loop?  It's something subtle and painful
> and I think it'd be better to have it separated out and documented.
> 
> Other than that, looks great.
> 
> Thanks.
> 
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