Re: [PATCH 04/13] block: add a disk_openers helper

[Jan Kara <jack@suse.cz>]

On Thu 24-03-22 08:51:10, Christoph Hellwig wrote:
> Add a helper that returns the openers for a given gendisk to avoid having
> drivers poke into disk->part0 to get at this information in a somewhat
> cumbersome way.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  drivers/block/nbd.c           |  4 ++--
>  drivers/block/zram/zram_drv.c |  4 ++--
>  include/linux/blkdev.h        | 15 +++++++++++++++
>  3 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 795f65a5c9661..93af7587d5ed6 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1219,7 +1219,7 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
>  
>  static void nbd_bdev_reset(struct nbd_device *nbd)
>  {
> -	if (nbd->disk->part0->bd_openers > 1)
> +	if (disk_openers(nbd->disk) > 1)
>  		return;
>  	set_capacity(nbd->disk, 0);
>  }
> @@ -1578,7 +1578,7 @@ static void nbd_release(struct gendisk *disk, fmode_t mode)
>  	struct nbd_device *nbd = disk->private_data;
>  
>  	if (test_bit(NBD_RT_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
> -			disk->part0->bd_openers == 0)
> +			disk_openers(disk) == 0)
>  		nbd_disconnect_and_put(nbd);
>  
>  	nbd_config_put(nbd);
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 863606f1722b1..2362385f782a9 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1800,7 +1800,7 @@ static ssize_t reset_store(struct device *dev,
>  
>  	mutex_lock(&disk->open_mutex);
>  	/* Do not reset an active device or claimed device */
> -	if (disk->part0->bd_openers || zram->claim) {
> +	if (disk_openers(disk) || zram->claim) {
>  		mutex_unlock(&disk->open_mutex);
>  		return -EBUSY;
>  	}
> @@ -1990,7 +1990,7 @@ static int zram_remove(struct zram *zram)
>  	bool claimed;
>  
>  	mutex_lock(&zram->disk->open_mutex);
> -	if (zram->disk->part0->bd_openers) {
> +	if (disk_openers(zram->disk)) {
>  		mutex_unlock(&zram->disk->open_mutex);
>  		return -EBUSY;
>  	}
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index eb27312a1b8f3..9824ebc9b4d31 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -176,6 +176,21 @@ static inline bool disk_live(struct gendisk *disk)
>  	return !inode_unhashed(disk->part0->bd_inode);
>  }
>  
> +/**
> + * disk_openers - returns how many openers are there for a disk
> + * @disk: disk to check
> + *
> + * This returns the number of openers for a disk.  Note that this value is only
> + * stable if disk->open_mutex is held.
> + *
> + * Note: Due to a quirk in the block layer open code, each open partition is
> + * only counted once even if there are multiple openers.
> + */
> +static inline unsigned int disk_openers(struct gendisk *disk)
> +{
> +	return disk->part0->bd_openers;
> +}
> +
>  /*
>   * The gendisk is refcounted by the part0 block_device, and the bd_device
>   * therein is also used for device model presentation in sysfs.
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR