Re: [PATCH 5/5] block: remove (__)blkdev_reread_part as an exported API

[Jan Kara <jack@suse.cz>]

On Wed 06-11-19 16:14:39, Christoph Hellwig wrote:
> In general drivers should never mess with partition tables directly.
> Unfortunately s390 and loop do for somewhat historic reasons, but they
> can use bdev_disk_changed directly instead when we export it as they
> satisfy the sanity checks we have in __blkdev_reread_part.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me. You can add:

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

								Honza

> ---
>  block/ioctl.c                   | 35 +++++----------------------------
>  drivers/block/loop.c            | 13 +++++++-----
>  drivers/s390/block/dasd_genhd.c |  4 +++-
>  fs/block_dev.c                  |  7 +++++++
>  include/linux/fs.h              |  2 --
>  5 files changed, 23 insertions(+), 38 deletions(-)
> 
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 52380c337078..2ed907ef0f01 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -155,46 +155,21 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
>  	}
>  }
>  
> -/*
> - * This is an exported API for the block driver, and will not
> - * acquire bd_mutex. This API should be used in case that
> - * caller has held bd_mutex already.
> - */
> -int __blkdev_reread_part(struct block_device *bdev)
> +static int blkdev_reread_part(struct block_device *bdev)
>  {
> +	int ret;
> +
>  	if (!disk_part_scan_enabled(bdev->bd_disk) || bdev != bdev->bd_contains)
>  		return -EINVAL;
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EACCES;
>  
> -	lockdep_assert_held(&bdev->bd_mutex);
> -
> -	return bdev_disk_changed(bdev, false);
> -}
> -EXPORT_SYMBOL(__blkdev_reread_part);
> -
> -/*
> - * This is an exported API for the block driver, and will
> - * try to acquire bd_mutex. If bd_mutex has been held already
> - * in current context, please call __blkdev_reread_part().
> - *
> - * Make sure the held locks in current context aren't required
> - * in open()/close() handler and I/O path for avoiding ABBA deadlock:
> - * - bd_mutex is held before calling block driver's open/close
> - *   handler
> - * - reading partition table may submit I/O to the block device
> - */
> -int blkdev_reread_part(struct block_device *bdev)
> -{
> -	int res;
> -
>  	mutex_lock(&bdev->bd_mutex);
> -	res = __blkdev_reread_part(bdev);
> +	ret = bdev_disk_changed(bdev, false);
>  	mutex_unlock(&bdev->bd_mutex);
>  
> -	return res;
> +	return ret;
>  }
> -EXPORT_SYMBOL(blkdev_reread_part);
>  
>  static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
>  		unsigned long arg, unsigned long flags)
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index f6f77eaa7217..64b16abee280 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -630,7 +630,9 @@ static void loop_reread_partitions(struct loop_device *lo,
>  {
>  	int rc;
>  
> -	rc = blkdev_reread_part(bdev);
> +	mutex_lock(&bdev->bd_mutex);
> +	rc = bdev_disk_changed(bdev, false);
> +	mutex_unlock(&bdev->bd_mutex);
>  	if (rc)
>  		pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
>  			__func__, lo->lo_number, lo->lo_file_name, rc);
> @@ -1154,10 +1156,11 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
>  		 * must be at least one and it can only become zero when the
>  		 * current holder is released.
>  		 */
> -		if (release)
> -			err = __blkdev_reread_part(bdev);
> -		else
> -			err = blkdev_reread_part(bdev);
> +		if (!release)
> +			mutex_lock(&bdev->bd_mutex);
> +		err = bdev_disk_changed(bdev, false);
> +		if (!release)
> +			mutex_unlock(&bdev->bd_mutex);
>  		if (err)
>  			pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
>  				__func__, lo_number, err);
> diff --git a/drivers/s390/block/dasd_genhd.c b/drivers/s390/block/dasd_genhd.c
> index 5542d9eadfe0..7d079154f849 100644
> --- a/drivers/s390/block/dasd_genhd.c
> +++ b/drivers/s390/block/dasd_genhd.c
> @@ -116,7 +116,9 @@ int dasd_scan_partitions(struct dasd_block *block)
>  		return -ENODEV;
>  	}
>  
> -	rc = blkdev_reread_part(bdev);
> +	mutex_lock(&bdev->bd_mutex);
> +	rc = bdev_disk_changed(bdev, false);
> +	mutex_unlock(&bdev->bd_mutex);
>  	if (rc)
>  		DBF_DEV_EVENT(DBF_ERR, block->base,
>  				"scan partitions error, rc %d", rc);
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index ae16466a67f7..9558a2f064b1 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1513,6 +1513,8 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
>  	struct gendisk *disk = bdev->bd_disk;
>  	int ret;
>  
> +	lockdep_assert_held(&bdev->bd_mutex);
> +
>  rescan:
>  	ret = blk_drop_partitions(disk, bdev);
>  	if (ret)
> @@ -1540,6 +1542,11 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
>  
>  	return ret;
>  }
> +/*
> + * Only exported for for loop and dasd for historic reasons.  Don't use in new
> + * code!
> + */
> +EXPORT_SYMBOL_GPL(bdev_disk_changed);
>  
>  /*
>   * bd_mutex locking:
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index d233dd661df7..ae6c5c37f3ae 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2632,8 +2632,6 @@ extern void bd_finish_claiming(struct block_device *bdev,
>  extern void bd_abort_claiming(struct block_device *bdev,
>  			      struct block_device *whole, void *holder);
>  extern void blkdev_put(struct block_device *bdev, fmode_t mode);
> -extern int __blkdev_reread_part(struct block_device *bdev);
> -extern int blkdev_reread_part(struct block_device *bdev);
>  
>  #ifdef CONFIG_SYSFS
>  extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
> -- 
> 2.20.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR