On Thu, Jul 22, 2021 at 09:53:58AM +0200, Christoph Hellwig wrote:
> Instead of acquiring an inode reference on open make sure partitions
> always hold device model references to the disk while alive, and switch
> open to grab only a device model reference to the opened block device.
> If that is a partition the disk reference is transitively held by the
> partition already.
> ---
> block/partitions/core.c | 9 ++++++-
> fs/block_dev.c | 60 ++++++++++++++++-------------------------
> 2 files changed, 31 insertions(+), 38 deletions(-)
>
> diff --git a/block/partitions/core.c b/block/partitions/core.c
> index 09c58a110a89..4f7a1a9cd544 100644
> --- a/block/partitions/core.c
> +++ b/block/partitions/core.c
> @@ -261,6 +261,7 @@ static void part_release(struct device *dev)
> {
> if (MAJOR(dev->devt) == BLOCK_EXT_MAJOR)
> blk_free_ext_minor(MINOR(dev->devt));
> + put_disk(dev_to_bdev(dev)->bd_disk);
> bdput(dev_to_bdev(dev));
> }
>
> @@ -349,9 +350,13 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
> if (xa_load(&disk->part_tbl, partno))
> return ERR_PTR(-EBUSY);
>
> + /* ensure we always have a reference to the whole disk */
> + get_device(disk_to_dev(disk));
> +
> + err = -ENOMEM;
> bdev = bdev_alloc(disk, partno);
> if (!bdev)
> - return ERR_PTR(-ENOMEM);
> + goto out_put_disk;
>
> bdev->bd_start_sect = start;
> bdev_set_nr_sectors(bdev, len);
> @@ -420,6 +425,8 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
> device_del(pdev);
> out_put:
> put_device(pdev);
> +out_put_disk:
> + put_disk(disk);
put_disk() is only needed for failure of bdev_alloc(). Once bdev->bd_device
is initialized, the disk reference will be dropped via part_release().
Thanks,
Ming
