linux-kernel - Re: [PATCH 2/7] blk-mq: add blk_mq_init_allocated_queue and export blk_mq_register

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Message-ID: <CACVXFVNO5Z1_+ienhx9Jujp_uyCDjthuTf5hjwRpfzxcZydNgw@mail.gmail.com>
Date:	Thu, 12 Mar 2015 16:10:40 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Mike Snitzer <snitzer@...hat.com>
Cc:	Jens Axboe <axboe@...nel.dk>, Keith Busch <keith.busch@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	dm-devel@...hat.com
Subject: Re: [PATCH 2/7] blk-mq: add blk_mq_init_allocated_queue and export blk_mq_register_disk

On Thu, Mar 12, 2015 at 11:56 AM, Mike Snitzer <snitzer@...hat.com> wrote:
> Add a variant of blk_mq_init_queue that allows a previously allocated
> queue to be initialized.  blk_mq_init_allocated_queue models
> blk_init_allocated_queue -- which was also created for DM's use.
>
> DM's approach to device creation requires a placeholder request_queue be
> allocated for use with alloc_dev() but the decision about what type of
> request_queue will be ultimately created is deferred until all component
> devices referenced in the DM table are processed to determine the table
> type (request-based, blk-mq request-based, or bio-based).
>
> Signed-off-by: Mike Snitzer <snitzer@...hat.com>
> ---
>  block/blk-mq-sysfs.c   |  1 +
>  block/blk-mq.c         | 28 +++++++++++++++++++---------
>  include/linux/blk-mq.h |  2 ++
>  3 files changed, 22 insertions(+), 9 deletions(-)
>
> diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
> index 1630a20..b79685e 100644
> --- a/block/blk-mq-sysfs.c
> +++ b/block/blk-mq-sysfs.c
> @@ -436,6 +436,7 @@ int blk_mq_register_disk(struct gendisk *disk)
>
>         return 0;
>  }
> +EXPORT_SYMBOL_GPL(blk_mq_register_disk);
>
>  void blk_mq_sysfs_unregister(struct request_queue *q)
>  {
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 459840c..d576a78 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1891,9 +1891,25 @@ void blk_mq_release(struct request_queue *q)
>
>  struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
>  {
> +       struct request_queue *uninit_q, *q;
> +
> +       uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
> +       if (!uninit_q)
> +               return ERR_PTR(-ENOMEM);
> +
> +       q = blk_mq_init_allocated_queue(set, uninit_q);
> +       if (!q)
> +               blk_cleanup_queue(uninit_q);
> +
> +       return q;

Current drivers suppose that queue won't be returned as null, and
looks you need to change the check of !q as IS_ERR(q) and return
ERR_PTR() if it is true.

> +}
> +EXPORT_SYMBOL(blk_mq_init_queue);
> +
> +struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
> +                                                 struct request_queue *q)
> +{
>         struct blk_mq_hw_ctx **hctxs;
>         struct blk_mq_ctx __percpu *ctx;
> -       struct request_queue *q;
>         unsigned int *map;
>         int i;
>
> @@ -1928,10 +1944,6 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
>                 hctxs[i]->queue_num = i;
>         }
>
> -       q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
> -       if (!q)
> -               goto err_hctxs;
> -
>         /*
>          * Init percpu_ref in atomic mode so that it's faster to shutdown.
>          * See blk_register_queue() for details.
> @@ -1981,7 +1993,7 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
>         blk_mq_init_cpu_queues(q, set->nr_hw_queues);
>
>         if (blk_mq_init_hw_queues(q, set))
> -               goto err_hw;
> +               goto err_hctxs;
>
>         mutex_lock(&all_q_mutex);
>         list_add_tail(&q->all_q_node, &all_q_list);
> @@ -1993,8 +2005,6 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
>
>         return q;
>
> -err_hw:
> -       blk_cleanup_queue(q);
>  err_hctxs:
>         kfree(map);
>         for (i = 0; i < set->nr_hw_queues; i++) {
> @@ -2009,7 +2019,7 @@ err_percpu:
>         free_percpu(ctx);
>         return ERR_PTR(-ENOMEM);
>  }
> -EXPORT_SYMBOL(blk_mq_init_queue);
> +EXPORT_SYMBOL(blk_mq_init_allocated_queue);
>
>  void blk_mq_free_queue(struct request_queue *q)
>  {
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index 7aec861..9a75c88 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -164,6 +164,8 @@ enum {
>                 << BLK_MQ_F_ALLOC_POLICY_START_BIT)
>
>  struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
> +struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
> +                                                 struct request_queue *q);
>  void blk_mq_finish_init(struct request_queue *q);
>  int blk_mq_register_disk(struct gendisk *);
>  void blk_mq_unregister_disk(struct gendisk *);
> --
> 1.9.5 (Apple Git-50.3)
>
> --
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-- 
Ming Lei
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