Re: [PATCH 2/2] mmc: switch to blk_mq_alloc_disk

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi

On 16.06.2021 07:39, Christoph Hellwig wrote:
> Use the blk_mq_alloc_disk to allocate the request_queue and gendisk
> together.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

This patch landed recently in linux-next as commit 281ea6a5bfdc ("mmc: 
switch to blk_mq_alloc_disk"). It triggers the following warning during 
boot on all my systems with MMC devices:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 10 at block/genhd.c:491 __device_add_disk+0x4e8/0x630
Modules linked in:
CPU: 0 PID: 10 Comm: kworker/0:1 Not tainted 
5.13.0-rc3-00090-g281ea6a5bfdc #3542
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: events_freezable mmc_rescan
[<c0111844>] (unwind_backtrace) from [<c010d014>] (show_stack+0x10/0x14)
[<c010d014>] (show_stack) from [<c0b6f84c>] (dump_stack+0xa4/0xc4)
[<c0b6f84c>] (dump_stack) from [<c0127630>] (__warn+0x118/0x11c)
[<c0127630>] (__warn) from [<c01276e8>] (warn_slowpath_fmt+0xb4/0xbc)
[<c01276e8>] (warn_slowpath_fmt) from [<c052a52c>] 
(__device_add_disk+0x4e8/0x630)
[<c052a52c>] (__device_add_disk) from [<c08a8e10>] (mmc_add_disk+0x24/0x120)
[<c08a8e10>] (mmc_add_disk) from [<c08a9e68>] (mmc_blk_probe+0x420/0x65c)
[<c08a9e68>] (mmc_blk_probe) from [<c06bece4>] (really_probe+0x250/0x4dc)
[<c06bece4>] (really_probe) from [<c06beff4>] 
(driver_probe_device+0x84/0x1e4)
[<c06beff4>] (driver_probe_device) from [<c06bcc70>] 
(bus_for_each_drv+0x78/0xbc)
[<c06bcc70>] (bus_for_each_drv) from [<c06be9f4>] 
(__device_attach+0xe8/0x180)
[<c06be9f4>] (__device_attach) from [<c06bda1c>] 
(bus_probe_device+0x88/0x90)
[<c06bda1c>] (bus_probe_device) from [<c06bb5f0>] (device_add+0x4c8/0x874)
[<c06bb5f0>] (device_add) from [<c089ac6c>] (mmc_add_card+0x110/0x2d0)
[<c089ac6c>] (mmc_add_card) from [<c089ebd8>] (mmc_attach_mmc+0xc8/0x180)
[<c089ebd8>] (mmc_attach_mmc) from [<c089a5c4>] (mmc_rescan+0x2ec/0x334)
[<c089a5c4>] (mmc_rescan) from [<c014a994>] (process_one_work+0x30c/0x884)
[<c014a994>] (process_one_work) from [<c014af64>] (worker_thread+0x58/0x594)
[<c014af64>] (worker_thread) from [<c0151f34>] (kthread+0x154/0x19c)
[<c0151f34>] (kthread) from [<c010011c>] (ret_from_fork+0x14/0x38)
Exception stack(0xc1d25fb0 to 0xc1d25ff8)
...
irq event stamp: 3653
hardirqs last  enabled at (3667): [<c0100b4c>] __irq_svc+0x8c/0xb0
hardirqs last disabled at (3678): [<c0b749c4>] __schedule+0x54c/0x9dc
softirqs last  enabled at (3648): [<c0101790>] __do_softirq+0x528/0x63c
softirqs last disabled at (3641): [<c01311b8>] irq_exit+0x214/0x220
---[ end trace e60288107691b657 ]---

It looks that something is missing in this conversion.

> ---
>   drivers/mmc/core/block.c | 14 +++-----------
>   drivers/mmc/core/queue.c | 23 ++++++++++-------------
>   drivers/mmc/core/queue.h |  2 +-
>   3 files changed, 14 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 947624e76c33..6652e1f1d4b2 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -2310,27 +2310,21 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>   	 */
>   	md->read_only = mmc_blk_readonly(card);
>   
> -	md->disk = alloc_disk(perdev_minors);
> -	if (md->disk == NULL) {
> -		ret = -ENOMEM;
> +	md->disk = mmc_init_queue(&md->queue, card);
> +	if (IS_ERR(md->disk)) {
> +		ret = PTR_ERR(md->disk);
>   		goto err_kfree;
>   	}
>   
>   	INIT_LIST_HEAD(&md->part);
>   	INIT_LIST_HEAD(&md->rpmbs);
>   	md->usage = 1;
> -
> -	ret = mmc_init_queue(&md->queue, card);
> -	if (ret)
> -		goto err_putdisk;
> -
>   	md->queue.blkdata = md;
>   
>   	md->disk->major	= MMC_BLOCK_MAJOR;
>   	md->disk->first_minor = devidx * perdev_minors;
>   	md->disk->fops = &mmc_bdops;
>   	md->disk->private_data = md;
> -	md->disk->queue = md->queue.queue;
>   	md->parent = parent;
>   	set_disk_ro(md->disk, md->read_only || default_ro);
>   	md->disk->flags = GENHD_FL_EXT_DEVT;
> @@ -2379,8 +2373,6 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>   
>   	return md;
>   
> - err_putdisk:
> -	put_disk(md->disk);
>    err_kfree:
>   	kfree(md);
>    out:
> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index d600e0a4a460..cc3261777637 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -424,9 +424,10 @@ static inline bool mmc_merge_capable(struct mmc_host *host)
>    *
>    * Initialise a MMC card request queue.
>    */
> -int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card)
> +struct gendisk *mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card)
>   {
>   	struct mmc_host *host = card->host;
> +	struct gendisk *disk;
>   	int ret;
>   
>   	mq->card = card;
> @@ -464,26 +465,22 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card)
>   
>   	ret = blk_mq_alloc_tag_set(&mq->tag_set);
>   	if (ret)
> -		return ret;
> +		return ERR_PTR(ret);
> +		
>   
> -	mq->queue = blk_mq_init_queue(&mq->tag_set);
> -	if (IS_ERR(mq->queue)) {
> -		ret = PTR_ERR(mq->queue);
> -		goto free_tag_set;
> +	disk = blk_mq_alloc_disk(&mq->tag_set, mq);
> +	if (IS_ERR(disk)) {
> +		blk_mq_free_tag_set(&mq->tag_set);
> +		return disk;
>   	}
> +	mq->queue = disk->queue;
>   
>   	if (mmc_host_is_spi(host) && host->use_spi_crc)
>   		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, mq->queue);
> -
> -	mq->queue->queuedata = mq;
>   	blk_queue_rq_timeout(mq->queue, 60 * HZ);
>   
>   	mmc_setup_queue(mq, card);
> -	return 0;
> -
> -free_tag_set:
> -	blk_mq_free_tag_set(&mq->tag_set);
> -	return ret;
> +	return disk;
>   }
>   
>   void mmc_queue_suspend(struct mmc_queue *mq)
> diff --git a/drivers/mmc/core/queue.h b/drivers/mmc/core/queue.h
> index 3319d8ab57d0..9ade3bcbb714 100644
> --- a/drivers/mmc/core/queue.h
> +++ b/drivers/mmc/core/queue.h
> @@ -94,7 +94,7 @@ struct mmc_queue {
>   	struct work_struct	complete_work;
>   };
>   
> -extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *);
> +struct gendisk *mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card);
>   extern void mmc_cleanup_queue(struct mmc_queue *);
>   extern void mmc_queue_suspend(struct mmc_queue *);
>   extern void mmc_queue_resume(struct mmc_queue *);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland