On Fri 17-02-23 10:22:00, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> As explained in commit 36369f46e917 ("block: Do not reread partition table
> on exclusively open device"), reread partition on the device that is
> exclusively opened by someone else is problematic.
>
> This patch will make sure partition scan will only be proceed if current
> thread open the device exclusively, or the device is not opened
> exclusively, and in the later case, other scanners and exclusive openers
> will be blocked temporarily until partition scan is done.
>
> Fixes: 10c70d95c0f2 ("block: remove the bd_openers checks in blk_drop_partitions")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Suggested-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
Looks good to me, just two minor comments below:
> diff --git a/block/genhd.c b/block/genhd.c
> index b30d5538710c..3ee5577e1586 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -359,6 +359,7 @@ EXPORT_SYMBOL_GPL(disk_uevent);
> int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
> {
> struct block_device *bdev;
> + int ret = 0;
>
> if (disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN))
> return -EINVAL;
> @@ -368,11 +369,27 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
> return -EBUSY;
>
> set_bit(GD_NEED_PART_SCAN, &disk->state);
I'd move the set_bit() after we are sure we have exclusive access to the
bdev. Otherwise we could set GD_NEED_PART_SCAN on a device exclusively open
by someone else and if we race with open in an unfortunate way, we could
trigger unexpected partition scan...
> - bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);
> + /*
> + * If the device is opened exclusively by current thread already, it's
> + * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
> + * synchronize with other exclusive openers and other partition
> + * scanners.
> + */
> + if (!(mode & FMODE_EXCL)) {
> + ret = bd_prepare_to_claim(disk->part0, disk_scan_partitions);
> + if (ret)
> + return ret;
> + }
> +
> + bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL);
> if (IS_ERR(bdev))
> - return PTR_ERR(bdev);
> - blkdev_put(bdev, mode);
> - return 0;
> + ret = PTR_ERR(bdev);
> + else
> + blkdev_put(bdev, mode);
> +
> + if (!(mode & FMODE_EXCL))
> + bd_abort_claiming(disk->part0, disk_scan_partitions);
> + return ret;
> }
>
> /**
> @@ -494,6 +511,11 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
> if (ret)
> goto out_unregister_bdi;
>
> + /* Make sure the first partition scan will be proceed */
^^^^^^ "will happen"
probably makes more sense here.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
