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Subject: Re: [PATCH] block, bfq: fix null pointer dereference in
 bfq_bio_bfqg()
To:     Jan Kara <jack@suse.cz>, Yu Kuai <yukuai1@huaweicloud.com>
Cc:     tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk,
        paolo.valente@linaro.org, cgroups@vger.kernel.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20221108103434.2853269-1-yukuai1@huaweicloud.com>
 <20221108124841.et6cddvczncp2cz7@quack3>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <6cd64e77-e14d-ff9c-d97f-055165a7b214@huaweicloud.com>
Date:   Tue, 8 Nov 2022 21:15:08 +0800
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Hi!

?? 2022/11/08 20:48, Jan Kara д??:
> 
> Hum, that is indeed contrieved ;). Your fixup makes sense so feel free to
> add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>

Thanks for the review, our test do many unusual operations together...

Thanks,
Kuai
> 
> 								Honza
> 
>>
>> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
>> index 144bca006463..7d624a3a3f0f 100644
>> --- a/block/bfq-cgroup.c
>> +++ b/block/bfq-cgroup.c
>> @@ -610,6 +610,10 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
>>   	struct bfq_group *bfqg;
>>   
>>   	while (blkg) {
>> +		if (!blkg->online) {
>> +			blkg = blkg->parent;
>> +			continue;
>> +		}
>>   		bfqg = blkg_to_bfqg(blkg);
>>   		if (bfqg->online) {
>>   			bio_associate_blkg_from_css(bio, &blkg->blkcg->css);
>> -- 
>> 2.31.1
>>