Re: [PATCH] block: reopen the device in blkdev_reread_part

[Ming Lei <ming.lei@redhat.com>]

On Tue, Feb 23, 2021 at 04:18:22PM +0100, Christoph Hellwig wrote:
> Historically the BLKRRPART ioctls called into the now defunct ->revalidate
> method, which caused the sd driver to check if any media is present.
> When the ->revalidate method was removed this revalidation was lost,
> leading to lots of I/O errors when using the eject command.  Fix this by
> reopening the device to rescan the partitions, and thus calling the
> revalidation logic in the sd driver.
> 
> Fixes: 471bd0af544b ("sd: use bdev_check_media_change")
> Reported--by: Tom Seewald <tseewald@gmail.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Tested-by: Tom Seewald <tseewald@gmail.com>
> ---
>  block/ioctl.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/block/ioctl.c b/block/ioctl.c
> index d61d652078f41c..ff241e663c018f 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -81,20 +81,27 @@ static int compat_blkpg_ioctl(struct block_device *bdev,
>  }
>  #endif
>  
> -static int blkdev_reread_part(struct block_device *bdev)
> +static int blkdev_reread_part(struct block_device *bdev, fmode_t mode)
>  {
> -	int ret;
> +	struct block_device *tmp;
>  
>  	if (!disk_part_scan_enabled(bdev->bd_disk) || bdev_is_partition(bdev))
>  		return -EINVAL;
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EACCES;
>  
> -	mutex_lock(&bdev->bd_mutex);
> -	ret = bdev_disk_changed(bdev, false);
> -	mutex_unlock(&bdev->bd_mutex);
> +	/*
> +	 * Reopen the device to revalidate the driver state and force a
> +	 * partition rescan.
> +	 */
> +	mode &= ~FMODE_EXCL;
> +	set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
>  
> -	return ret;
> +	tmp = blkdev_get_by_dev(bdev->bd_dev, mode, NULL);
> +	if (IS_ERR(tmp))
> +		return PTR_ERR(tmp);
> +	blkdev_put(tmp, mode);
> +	return 0;
>  }
>  
>  static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
> @@ -498,7 +505,7 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
>  		bdev->bd_bdi->ra_pages = (arg * 512) / PAGE_SIZE;
>  		return 0;
>  	case BLKRRPART:
> -		return blkdev_reread_part(bdev);
> +		return blkdev_reread_part(bdev, mode);
>  	case BLKTRACESTART:
>  	case BLKTRACESTOP:
>  	case BLKTRACETEARDOWN:
> -- 
> 2.29.2
> 

Looks fine,

Reviewed-by: Ming Lei <ming.lei@redhat.com>


-- 
Ming