Re: [PATCH] block: don't set GD_NEED_PART_SCAN if scan partition failed

[Yu Kuai]

Hi, Jens!

在 2023/03/22 11:59, Yu Kuai 写道:
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> Currently if disk_scan_partitions() failed, GD_NEED_PART_SCAN will still
> set, and partition scan will be proceed again when blkdev_get_by_dev()
> is called. However, this will cause a problem that re-assemble partitioned
> raid device will creat partition for underlying disk.
>
> Test procedure:
>
> mdadm -CR /dev/md0 -l 1 -n 2 /dev/sda /dev/sdb -e 1.0
> sgdisk -n 0:0:+100MiB /dev/md0
> blockdev --rereadpt /dev/sda
> blockdev --rereadpt /dev/sdb
> mdadm -S /dev/md0
> mdadm -A /dev/md0 /dev/sda /dev/sdb
>
> Test result: underlying disk partition and raid partition can be
> observed at the same time
>
> Note that this can still happen in come corner cases that
> GD_NEED_PART_SCAN can be set for underlying disk while re-assemble raid
> device.

Can you apply this patch?

Thanks,
Kuai
> Fixes: e5cfefa97bcc ("block: fix scan partition for exclusively open device again")
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
>   block/genhd.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 08bb1a9ec22c..a72e27d6779d 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -368,7 +368,6 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
>   	if (disk->open_partitions)
>   		return -EBUSY;
>   
> -	set_bit(GD_NEED_PART_SCAN, &disk->state);
>   	/*
>   	 * If the device is opened exclusively by current thread already, it's
>   	 * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
> @@ -381,12 +380,19 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
>   			return ret;
>   	}
>   
> +	set_bit(GD_NEED_PART_SCAN, &disk->state);
>   	bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL);
>   	if (IS_ERR(bdev))
>   		ret =  PTR_ERR(bdev);
>   	else
>   		blkdev_put(bdev, mode & ~FMODE_EXCL);
>   
> +	/*
> +	 * If blkdev_get_by_dev() failed early, GD_NEED_PART_SCAN is still set,
> +	 * and this will cause that re-assemble partitioned raid device will
> +	 * creat partition for underlying disk.
> +	 */
> +	clear_bit(GD_NEED_PART_SCAN, &disk->state);
>   	if (!(mode & FMODE_EXCL))
>   		bd_abort_claiming(disk->part0, disk_scan_partitions);
>   	return ret;