Re: [PATCH v4 2/2] s390/dasd: remove ioctl_by_bdev calls

Christian Borntraeger
2020-10-07T09:34:28Z

On 19.05.20 16:22, Stefan Haberland wrote:
> The IBM partition parser requires device type specific information only
> available to the DASD driver to correctly register partitions. The
> current approach of using ioctl_by_bdev with a fake user space pointer
> is discouraged.
>
> Fix this by replacing IOCTL calls with direct in-kernel function calls.
>
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
> Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
> Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>

FWIW, this broken the ibm-partition code for virtio-blk, when CONFIG_DASD=m.

> ---
> MAINTAINERS | 1 +
> block/partitions/ibm.c | 24 +++++++++++++++++------
> drivers/s390/block/dasd_ioctl.c | 34 +++++++++++++++++++++++++++++++++
> include/linux/dasd_mod.h | 9 +++++++++
> 4 files changed, 62 insertions(+), 6 deletions(-)
> create mode 100644 include/linux/dasd_mod.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 1608ef8ce8d3..37f700187d74 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14625,6 +14625,7 @@ S: Supported
> W: http://www.ibm.com/developerworks/linux/linux390/
> F: block/partitions/ibm.c
> F: drivers/s390/block/dasd*
> +F: include/linux/dasd_mod.h
>
> S390 IOMMU (PCI)
> M: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> diff --git a/block/partitions/ibm.c b/block/partitions/ibm.c
> index 073faa6a69b8..d6e18df9c53c 100644
> --- a/block/partitions/ibm.c
> +++ b/block/partitions/ibm.c
> @@ -13,10 +13,11 @@
> #include <asm/ebcdic.h>
> #include <linux/uaccess.h>
> #include <asm/vtoc.h>
> +#include <linux/module.h>
> +#include <linux/dasd_mod.h>
>
> #include "check.h"
>
> -
> union label_t {
> struct vtoc_volume_label_cdl vol;
> struct vtoc_volume_label_ldl lnx;
> @@ -288,7 +289,9 @@ static int find_cms1_partitions(struct parsed_partitions *state,
> */
> int ibm_partition(struct parsed_partitions *state)
> {
> + int (*fn)(struct gendisk *disk, dasd_information2_t *info);
> struct block_device *bdev = state->bdev;
> + struct gendisk *disk = bdev->bd_disk;
> int blocksize, res;
> loff_t i_size, offset, size;
> dasd_information2_t *info;
> @@ -299,24 +302,31 @@ int ibm_partition(struct parsed_partitions *state)
> union label_t *label;
>
> res = 0;
> + if (!disk->fops->getgeo)
> + goto out_exit;
> + fn = symbol_get(dasd_biodasdinfo);
> + if (!fn)
> + goto out_exit;
> blocksize = bdev_logical_block_size(bdev);
> if (blocksize <= 0)
> - goto out_exit;
> + goto out_symbol;
> i_size = i_size_read(bdev->bd_inode);
> if (i_size == 0)
> - goto out_exit;
> + goto out_symbol;
> info = kmalloc(sizeof(dasd_information2_t), GFP_KERNEL);
> if (info == NULL)
> - goto out_exit;
> + goto out_symbol;
> geo = kmalloc(sizeof(struct hd_geometry), GFP_KERNEL);
> if (geo == NULL)
> goto out_nogeo;
> label = kmalloc(sizeof(union label_t), GFP_KERNEL);
> if (label == NULL)
> goto out_nolab;
> - if (ioctl_by_bdev(bdev, HDIO_GETGEO, (unsigned long)geo) != 0)
> + /* set start if not filled by getgeo function e.g. virtblk */
> + geo->start = get_start_sect(bdev);
> + if (disk->fops->getgeo(bdev, geo))
> goto out_freeall;
> - if (ioctl_by_bdev(bdev, BIODASDINFO2, (unsigned long)info) != 0) {
> + if (fn(disk, info)) {
> kfree(info);
> info = NULL;
> }
> @@ -359,6 +369,8 @@ int ibm_partition(struct parsed_partitions *state)
> kfree(geo);
> out_nogeo:
> kfree(info);
> +out_symbol:
> + symbol_put(dasd_biodasdinfo);
> out_exit:
> return res;
> }
> diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
> index 9b7782395c37..777734d1b4e5 100644
> --- a/drivers/s390/block/dasd_ioctl.c
> +++ b/drivers/s390/block/dasd_ioctl.c
> @@ -22,6 +22,7 @@
> #include <asm/schid.h>
> #include <asm/cmb.h>
> #include <linux/uaccess.h>
> +#include <linux/dasd_mod.h>
>
> /* This is ugly... */
> #define PRINTK_HEADER "dasd_ioctl:"
> @@ -664,3 +665,36 @@ int dasd_ioctl(struct block_device *bdev, fmode_t mode,
> dasd_put_device(base);
> return rc;
> }
> +
> +
> +/**
> + * dasd_biodasdinfo() - fill out the dasd information structure
> + * @disk [in]: pointer to gendisk structure that references a DASD
> + * @info [out]: pointer to the dasd_information2_t structure
> + *
> + * Provide access to DASD specific information.
> + * The gendisk structure is checked if it belongs to the DASD driver by
> + * comparing the gendisk->fops pointer.
> + * If it does not belong to the DASD driver -EINVAL is returned.
> + * Otherwise the provided dasd_information2_t structure is filled out.
> + *
> + * Returns:
> + * %0 on success and a negative error value on failure.
> + */
> +int dasd_biodasdinfo(struct gendisk *disk, struct dasd_information2_t *info)
> +{
> + struct dasd_device *base;
> + int error;
> +
> + if (disk->fops != &dasd_device_operations)
> + return -EINVAL;
> +
> + base = dasd_device_from_gendisk(disk);
> + if (!base)
> + return -ENODEV;
> + error = __dasd_ioctl_information(base->block, info);
> + dasd_put_device(base);
> + return error;
> +}
> +/* export that symbol_get in partition detection is possible */
> +EXPORT_SYMBOL_GPL(dasd_biodasdinfo);
> diff --git a/include/linux/dasd_mod.h b/include/linux/dasd_mod.h
> new file mode 100644
> index 000000000000..d39abad2ff6e
> --- /dev/null
> +++ b/include/linux/dasd_mod.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef DASD_MOD_H
> +#define DASD_MOD_H
> +
> +#include <asm/dasd.h>
> +
> +extern int dasd_biodasdinfo(struct gendisk *disk, dasd_information2_t *info);
> +
> +#endif
>