Re: [PATCH 06/26] brd: convert to blk_alloc_disk/blk_cleanup_disk

[Hannes Reinecke <hare@suse.de>]

On 5/21/21 7:50 AM, Christoph Hellwig wrote:
> Convert the brd driver to use the blk_alloc_disk and blk_cleanup_disk
> helpers to simplify gendisk and request_queue allocation.  This also
> allows to remove the request_queue pointer in struct request_queue,
> and to simplify the initialization as blk_cleanup_disk can be called
> on any disk returned from blk_alloc_disk.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/block/brd.c | 94 ++++++++++++++++-----------------------------
>   1 file changed, 33 insertions(+), 61 deletions(-)
> 
> diff --git a/drivers/block/brd.c b/drivers/block/brd.c
> index 7562cf30b14e..95694113e38e 100644
> --- a/drivers/block/brd.c
> +++ b/drivers/block/brd.c
> @@ -38,9 +38,7 @@
>    * device).
>    */
>   struct brd_device {
> -	int		brd_number;
> -
> -	struct request_queue	*brd_queue;
> +	int			brd_number;
>   	struct gendisk		*brd_disk;
>   	struct list_head	brd_list;
>   
> @@ -372,7 +370,7 @@ static LIST_HEAD(brd_devices);
>   static DEFINE_MUTEX(brd_devices_mutex);
>   static struct dentry *brd_debugfs_dir;
>   
> -static struct brd_device *brd_alloc(int i)
> +static int brd_alloc(int i)
>   {
>   	struct brd_device *brd;
>   	struct gendisk *disk;
> @@ -380,64 +378,55 @@ static struct brd_device *brd_alloc(int i)
>   
>   	brd = kzalloc(sizeof(*brd), GFP_KERNEL);
>   	if (!brd)
> -		goto out;
> +		return -ENOMEM;
>   	brd->brd_number		= i;
>   	spin_lock_init(&brd->brd_lock);
>   	INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
>   
> -	brd->brd_queue = blk_alloc_queue(NUMA_NO_NODE);
> -	if (!brd->brd_queue)
> -		goto out_free_dev;
> -
>   	snprintf(buf, DISK_NAME_LEN, "ram%d", i);
>   	if (!IS_ERR_OR_NULL(brd_debugfs_dir))
>   		debugfs_create_u64(buf, 0444, brd_debugfs_dir,
>   				&brd->brd_nr_pages);
>   
> -	/* This is so fdisk will align partitions on 4k, because of
> -	 * direct_access API needing 4k alignment, returning a PFN
> -	 * (This is only a problem on very small devices <= 4M,
> -	 *  otherwise fdisk will align on 1M. Regardless this call
> -	 *  is harmless)
> -	 */
> -	blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
> -	disk = brd->brd_disk = alloc_disk(max_part);
> +	disk = brd->brd_disk = blk_alloc_disk(NUMA_NO_NODE);
>   	if (!disk)
> -		goto out_free_queue;
> +		goto out_free_dev;
> +
>   	disk->major		= RAMDISK_MAJOR;
>   	disk->first_minor	= i * max_part;
> +	disk->minors		= max_part;
>   	disk->fops		= &brd_fops;
>   	disk->private_data	= brd;
>   	disk->flags		= GENHD_FL_EXT_DEVT;
>   	strlcpy(disk->disk_name, buf, DISK_NAME_LEN);
>   	set_capacity(disk, rd_size * 2);
> +	
> +	/*
> +	 * This is so fdisk will align partitions on 4k, because of
> +	 * direct_access API needing 4k alignment, returning a PFN
> +	 * (This is only a problem on very small devices <= 4M,
> +	 *  otherwise fdisk will align on 1M. Regardless this call
> +	 *  is harmless)
> +	 */
> +	blk_queue_physical_block_size(disk->queue, PAGE_SIZE);
>   

Maybe converting the comment to refer to 'PAGE_SIZE' instead of 4k while 
you're at it ...

>   	/* Tell the block layer that this is not a rotational device */
> -	blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue);
> -	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, brd->brd_queue);
> +	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
> +	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
> +	add_disk(disk);
> +	list_add_tail(&brd->brd_list, &brd_devices);
>   
> -	return brd;
> +	return 0;
>   
> -out_free_queue:
> -	blk_cleanup_queue(brd->brd_queue);
>   out_free_dev:
>   	kfree(brd);
> -out:
> -	return NULL;
> -}
> -
> -static void brd_free(struct brd_device *brd)
> -{
> -	put_disk(brd->brd_disk);
> -	blk_cleanup_queue(brd->brd_queue);
> -	brd_free_pages(brd);
> -	kfree(brd);
> +	return -ENOMEM;
>   }
>   
>   static void brd_probe(dev_t dev)
>   {
> -	struct brd_device *brd;
>   	int i = MINOR(dev) / max_part;
> +	struct brd_device *brd;
>   
>   	mutex_lock(&brd_devices_mutex);
>   	list_for_each_entry(brd, &brd_devices, brd_list) {
> @@ -445,13 +434,7 @@ static void brd_probe(dev_t dev)
>   			goto out_unlock;
>   	}
>   
> -	brd = brd_alloc(i);
> -	if (brd) {
> -		brd->brd_disk->queue = brd->brd_queue;
> -		add_disk(brd->brd_disk);
> -		list_add_tail(&brd->brd_list, &brd_devices);
> -	}
> -
> +	brd_alloc(i);
>   out_unlock:
>   	mutex_unlock(&brd_devices_mutex);
>   }
> @@ -460,7 +443,9 @@ static void brd_del_one(struct brd_device *brd)
>   {
>   	list_del(&brd->brd_list);
>   	del_gendisk(brd->brd_disk);
> -	brd_free(brd);
> +	blk_cleanup_disk(brd->brd_disk);
> +	brd_free_pages(brd);
> +	kfree(brd);
>   }
>   
>   static inline void brd_check_and_reset_par(void)
> @@ -485,7 +470,7 @@ static inline void brd_check_and_reset_par(void)
>   static int __init brd_init(void)
>   {
>   	struct brd_device *brd, *next;
> -	int i;
> +	int err, i;
>   
>   	/*
>   	 * brd module now has a feature to instantiate underlying device
> @@ -511,22 +496,11 @@ static int __init brd_init(void)
>   
>   	mutex_lock(&brd_devices_mutex);
>   	for (i = 0; i < rd_nr; i++) {
> -		brd = brd_alloc(i);
> -		if (!brd)
> +		err = brd_alloc(i);
> +		if (err)
>   			goto out_free;
> -		list_add_tail(&brd->brd_list, &brd_devices);
>   	}
>   
> -	/* point of no return */
> -
> -	list_for_each_entry(brd, &brd_devices, brd_list) {
> -		/*
> -		 * associate with queue just before adding disk for
> -		 * avoiding to mess up failure path
> -		 */
> -		brd->brd_disk->queue = brd->brd_queue;
> -		add_disk(brd->brd_disk);
> -	}
>   	mutex_unlock(&brd_devices_mutex);
>   
>   	pr_info("brd: module loaded\n");
> @@ -535,15 +509,13 @@ static int __init brd_init(void)
>   out_free:
>   	debugfs_remove_recursive(brd_debugfs_dir);
>   
> -	list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
> -		list_del(&brd->brd_list);
> -		brd_free(brd);
> -	}
> +	list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
> +		brd_del_one(brd);
>   	mutex_unlock(&brd_devices_mutex);
>   	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
>   
>   	pr_info("brd: module NOT loaded !!!\n");
> -	return -ENOMEM;
> +	return err;
>   }
>   
>   static void __exit brd_exit(void)
> 
Other than that:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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