s390/dasd: remove ioctl_by_bdev calls

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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

MAINTAINERS

@@ -14628,6 +14628,7 @@ 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>

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;
 }

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);

include/linux/dasd_mod.h

+/* 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