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Subject: Re: [PATCH 1/2] blk-mq: not embed .mq_kobj and ctx->kobj into queue
 instance
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Guenter Roeck <linux@roeck-us.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org
References: <20181116032826.11901-1-ming.lei@redhat.com>
 <20181116032826.11901-2-ming.lei@redhat.com>
From: "jianchao.wang" <jianchao.w.wang@oracle.com>
Message-ID: <64abb411-f4af-a169-e878-2119f7c792d5@oracle.com>
Date: Fri, 16 Nov 2018 14:11:07 +0800
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On 11/16/18 11:28 AM, Ming Lei wrote:
...
>  
> +struct blk_mq_kobj {
> +	struct kobject kobj;
> +};
> +
>  static void blk_mq_sysfs_release(struct kobject *kobj)
>  {
> +	struct blk_mq_kobj *mq_kobj = container_of(kobj, struct blk_mq_kobj,
> +						   kobj);
> +	kfree(mq_kobj);
> +}
> +
...
>  
> -void blk_mq_sysfs_init(struct request_queue *q)
> +int blk_mq_sysfs_init(struct request_queue *q)
>  {
>  	struct blk_mq_ctx *ctx;
>  	int cpu;
> +	struct blk_mq_kobj *mq_kobj;
> +
> +	mq_kobj = kzalloc(sizeof(struct blk_mq_kobj), GFP_KERNEL);
> +	if (!mq_kobj)
> +		return -ENOMEM;
>  
> -	kobject_init(&q->mq_kobj, &blk_mq_ktype);
> +	kobject_init(&mq_kobj->kobj, &blk_mq_ktype);
>  
>  	for_each_possible_cpu(cpu) {
> -		ctx = per_cpu_ptr(q->queue_ctx, cpu);
> +		ctx = kzalloc_node(sizeof(*ctx), GFP_KERNEL, cpu_to_node(cpu));
> +		if (!ctx)
> +			goto fail;
> +		*per_cpu_ptr(q->queue_ctx, cpu) = ctx;
>  		kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
>  	}
> +	q->mq_kobj = &mq_kobj->kobj;
> +	return 0;
> +
> + fail:
> +	for_each_possible_cpu(cpu) {
> +		ctx = *per_cpu_ptr(q->queue_ctx, cpu);
> +		if (ctx)
> +			kobject_put(&ctx->kobj);
> +	}
> +	kobject_put(&mq_kobj->kobj);
> +	return -ENOMEM;
>  }


blk_mq_kobj looks meaningless, why do we need it, or do I miss something ?
And maybe we should allocate ctx in blk_mq_init_allocated_queue.

Thanks
Jianchao