On Tue 17-10-23 20:48:20, Christoph Hellwig wrote:
> From: Christian Brauner <brauner@xxxxxxxxxx>
>
> The logic for disk->open_partitions is:
>
> blkdev_get_by_*()
> -> bdev_is_partition()
> -> blkdev_get_part()
> -> blkdev_get_whole() // bdev_whole->bd_openers++
> -> if (part->bd_openers == 0)
> disk->open_partitions++
> part->bd_openers
>
> In other words, when we first claim/open a partition we increment
> disk->open_partitions and only when all part->bd_openers are closed will
> disk->open_partitions be zero. That should mean that
> disk->open_partitions is always > 0 as long as there's anyone that
> has an open partition.
>
> So the check for disk->open_partitions should meand that we can never
> remove an active partition that has a holder and holder ops set. Assert
> that in the code. The main disk isn't removed so that check doesn't work
> for disk->part0 which is what we want. After all we only care about
> partition not about the main disk.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> block/partitions/core.c | 30 +++++++++++++++++-------------
> 1 file changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/block/partitions/core.c b/block/partitions/core.c
> index b0585536b407a5..f47ffcfdfcec22 100644
> --- a/block/partitions/core.c
> +++ b/block/partitions/core.c
> @@ -274,17 +274,6 @@ void drop_partition(struct block_device *part)
> put_device(&part->bd_device);
> }
>
> -static void delete_partition(struct block_device *part)
> -{
> - /*
> - * Remove the block device from the inode hash, so that it cannot be
> - * looked up any more even when openers still hold references.
> - */
> - remove_inode_hash(part->bd_inode);
> - bdev_mark_dead(part, false);
> - drop_partition(part);
> -}
> -
> static ssize_t whole_disk_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> @@ -674,8 +663,23 @@ int bdev_disk_changed(struct gendisk *disk, bool invalidate)
> sync_blockdev(disk->part0);
> invalidate_bdev(disk->part0);
>
> - xa_for_each_start(&disk->part_tbl, idx, part, 1)
> - delete_partition(part);
> + xa_for_each_start(&disk->part_tbl, idx, part, 1) {
> + /*
> + * Remove the block device from the inode hash, so that
> + * it cannot be looked up any more even when openers
> + * still hold references.
> + */
> + remove_inode_hash(part->bd_inode);
> +
> + /*
> + * If @disk->open_partitions isn't elevated but there's
> + * still an active holder of that block device things
> + * are broken.
> + */
> + WARN_ON_ONCE(atomic_read(&part->bd_openers));
> + invalidate_bdev(part);
> + drop_partition(part);
> + }
> clear_bit(GD_NEED_PART_SCAN, &disk->state);
>
> /*
> --
> 2.39.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
