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SubjectRe: [PATCH -next RFC 2/3] block: factor out the setting of GD_NEED_PART_SCAN
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On 2/12/23 10:26, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
>
> In order to prevent scan partition for a device that is opened
> exclusively by someone else, new conditions will be added to
> disk_scan_partitions() in the next patch. Hence if device is opened
> exclusively between bdev_add() and disk_scan_partitions(), the first
> partition scan will fail unexpected. This patch factor out the setting
> of GD_NEED_PART_SCAN to prevent the problem.
>
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
> block/genhd.c | 2 +-
> block/ioctl.c | 1 +
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 075d8da284f5..c0d1220bd798 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -367,7 +367,6 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
> if (disk->open_partitions)
> return -EBUSY;
>
> - set_bit(GD_NEED_PART_SCAN, &disk->state);
> bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);
> if (IS_ERR(bdev))
> return PTR_ERR(bdev);
> @@ -493,6 +492,7 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
> if (ret)
> goto out_unregister_bdi;
>
> + set_bit(GD_NEED_PART_SCAN, &disk->state);
> bdev_add(disk->part0, ddev->devt);
> if (get_capacity(disk))
> disk_scan_partitions(disk, FMODE_READ);
Usual caveat:
What happens if the flag is already set here?
Wouldn't that imply that another scan is underway?
And wouldn't it be better to use 'test_and_set()'?


> diff --git a/block/ioctl.c b/block/ioctl.c
> index 6dd49d877584..0eefcdb936a0 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -528,6 +528,7 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
> return -EACCES;
> if (bdev_is_partition(bdev))
> return -EINVAL;
> + set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
> return disk_scan_partitions(bdev->bd_disk, mode & ~FMODE_EXCL);
> case BLKTRACESTART:
> case BLKTRACESTOP:
Similar here.

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

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