s390/partitions: make partition detection independent from DASD ioctls

In some usage scenarios it is desireable to work with disk images or
virtualized DASD devices. One problem that prevents such applications
is the partition detection in ibm.c. Currently it works only for
devices that support the BIODASDINFO2 ioctl, in other words, it only
works for devices that belong to the DASD device driver.

The information gained from the BIODASDINFO2 ioctl is only for a small
set of legacy cases abolutely necessary. All current VOL1, LNX1 and
CMS1 type of disk labels can be interpreted correctly without this
information, as long as the generic HDIO_GETGEO ioctl works and
provides a correct disk geometry.

This patch makes the ibm.c partition detection as independent as
possible from the BIODASDINFO2 ioctl. Only the following two cases are
still restricted to real DASDs:
- An FBA DASD, or LDL formatted ECKD DASD without any disk label.
- An old style LNX1 label (without large volume support) on a disk
  with inconsistent device geometry.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

block/partitions/ibm.c

@@ -1,9 +1,8 @@
 /*
- * File...........: linux/fs/partitions/ibm.c
  * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
  *                  Volker Sameske <sameske@de.ibm.com>
  * Bugreports.to..: <Linux390@de.ibm.com>
- * (C) IBM Corporation, IBM Deutschland Entwicklung GmbH, 1999,2000
+ * Copyright IBM Corp. 1999, 2012
  */
 
 #include <linux/buffer_head.h>
@@ -17,17 +16,23 @@
 #include "check.h"
 #include "ibm.h"
 
+
+union label_t {
+	struct vtoc_volume_label_cdl vol;
+	struct vtoc_volume_label_ldl lnx;
+	struct vtoc_cms_label cms;
+};
+
 /*
  * compute the block number from a
  * cyl-cyl-head-head structure
  */
-static sector_t
-cchh2blk (struct vtoc_cchh *ptr, struct hd_geometry *geo) {
-
+static sector_t cchh2blk(struct vtoc_cchh *ptr, struct hd_geometry *geo)
+{
 	sector_t cyl;
 	__u16 head;
 
-	/*decode cylinder and heads for large volumes */
+	/* decode cylinder and heads for large volumes */
 	cyl = ptr->hh & 0xFFF0;
 	cyl <<= 12;
 	cyl |= ptr->cc;
@@ -40,13 +45,12 @@ cchh2blk (struct vtoc_cchh *ptr, struct hd_geometry *geo) {
  * compute the block number from a
  * cyl-cyl-head-head-block structure
  */
-static sector_t
-cchhb2blk (struct vtoc_cchhb *ptr, struct hd_geometry *geo) {
-
+static sector_t cchhb2blk(struct vtoc_cchhb *ptr, struct hd_geometry *geo)
+{
 	sector_t cyl;
 	__u16 head;
 
-	/*decode cylinder and heads for large volumes */
+	/* decode cylinder and heads for large volumes */
 	cyl = ptr->hh & 0xFFF0;
 	cyl <<= 12;
 	cyl |= ptr->cc;
@@ -56,26 +60,243 @@ cchhb2blk (struct vtoc_cchhb *ptr, struct hd_geometry *geo) {
 		ptr->b;
 }
 
+static int find_label(struct parsed_partitions *state,
+		      dasd_information2_t *info,
+		      struct hd_geometry *geo,
+		      int blocksize,
+		      sector_t *labelsect,
+		      char name[],
+		      char type[],
+		      union label_t *label)
+{
+	Sector sect;
+	unsigned char *data;
+	sector_t testsect[3];
+	unsigned char temp[5];
+	int found = 0;
+	int i, testcount;
+
+	/* There a three places where we may find a valid label:
+	 * - on an ECKD disk it's block 2
+	 * - on an FBA disk it's block 1
+	 * - on an CMS formatted FBA disk it is sector 1, even if the block size
+	 *   is larger than 512 bytes (possible if the DIAG discipline is used)
+	 * If we have a valid info structure, then we know exactly which case we
+	 * have, otherwise we just search through all possebilities.
+	 */
+	if (info) {
+		if ((info->cu_type == 0x6310 && info->dev_type == 0x9336) ||
+		    (info->cu_type == 0x3880 && info->dev_type == 0x3370))
+			testsect[0] = info->label_block;
+		else
+			testsect[0] = info->label_block * (blocksize >> 9);
+		testcount = 1;
+	} else {
+		testsect[0] = 1;
+		testsect[1] = (blocksize >> 9);
+		testsect[2] = 2 * (blocksize >> 9);
+		testcount = 3;
+	}
+	for (i = 0; i < testcount; ++i) {
+		data = read_part_sector(state, testsect[i], &sect);
+		if (data == NULL)
+			continue;
+		memcpy(label, data, sizeof(*label));
+		memcpy(temp, data, 4);
+		temp[4] = 0;
+		EBCASC(temp, 4);
+		put_dev_sector(sect);
+		if (!strcmp(temp, "VOL1") ||
+		    !strcmp(temp, "LNX1") ||
+		    !strcmp(temp, "CMS1")) {
+			if (!strcmp(temp, "VOL1")) {
+				strncpy(type, label->vol.vollbl, 4);
+				strncpy(name, label->vol.volid, 6);
+			} else {
+				strncpy(type, label->lnx.vollbl, 4);
+				strncpy(name, label->lnx.volid, 6);
+			}
+			EBCASC(type, 4);
+			EBCASC(name, 6);
+			*labelsect = testsect[i];
+			found = 1;
+			break;
+		}
+	}
+	if (!found)
+		memset(label, 0, sizeof(*label));
+
+	return found;
+}
+
+static int find_vol1_partitions(struct parsed_partitions *state,
+				struct hd_geometry *geo,
+				int blocksize,
+				char name[],
+				union label_t *label)
+{
+	sector_t blk;
+	int counter;
+	char tmp[64];
+	Sector sect;
+	unsigned char *data;
+	loff_t offset, size;
+	struct vtoc_format1_label f1;
+	int secperblk;
+
+	snprintf(tmp, sizeof(tmp), "VOL1/%8s:", name);
+	strlcat(state->pp_buf, tmp, PAGE_SIZE);
+	/*
+	 * get start of VTOC from the disk label and then search for format1
+	 * and format8 labels
+	 */
+	secperblk = blocksize >> 9;
+	blk = cchhb2blk(&label->vol.vtoc, geo) + 1;
+	counter = 0;
+	data = read_part_sector(state, blk * secperblk, &sect);
+	while (data != NULL) {
+		memcpy(&f1, data, sizeof(struct vtoc_format1_label));
+		put_dev_sector(sect);
+		/* skip FMT4 / FMT5 / FMT7 labels */
+		if (f1.DS1FMTID == _ascebc['4']
+		    || f1.DS1FMTID == _ascebc['5']
+		    || f1.DS1FMTID == _ascebc['7']
+		    || f1.DS1FMTID == _ascebc['9']) {
+			blk++;
+			data = read_part_sector(state, blk * secperblk, &sect);
+			continue;
+		}
+		/* only FMT1 and 8 labels valid at this point */
+		if (f1.DS1FMTID != _ascebc['1'] &&
+		    f1.DS1FMTID != _ascebc['8'])
+			break;
+		/* OK, we got valid partition data */
+		offset = cchh2blk(&f1.DS1EXT1.llimit, geo);
+		size  = cchh2blk(&f1.DS1EXT1.ulimit, geo) -
+			offset + geo->sectors;
+		offset *= secperblk;
+		size *= secperblk;
+		if (counter >= state->limit)
+			break;
+		put_partition(state, counter + 1, offset, size);
+		counter++;
+		blk++;
+		data = read_part_sector(state, blk * secperblk, &sect);
+	}
+	strlcat(state->pp_buf, "\n", PAGE_SIZE);
+
+	if (!data)
+		return -1;
+
+	return 1;
+}
+
+static int find_lnx1_partitions(struct parsed_partitions *state,
+				struct hd_geometry *geo,
+				int blocksize,
+				char name[],
+				union label_t *label,
+				sector_t labelsect,
+				loff_t i_size,
+				dasd_information2_t *info)
+{
+	loff_t offset, geo_size, size;
+	char tmp[64];
+	int secperblk;
+
+	snprintf(tmp, sizeof(tmp), "LNX1/%8s:", name);
+	strlcat(state->pp_buf, tmp, PAGE_SIZE);
+	secperblk = blocksize >> 9;
+	if (label->lnx.ldl_version == 0xf2) {
+		size = label->lnx.formatted_blocks * secperblk;
+	} else {
+		/*
+		 * Formated w/o large volume support. If the sanity check
+		 * 'size based on geo == size based on i_size' is true, then
+		 * we can safely assume that we know the formatted size of
+		 * the disk, otherwise we need additional information
+		 * that we can only get from a real DASD device.
+		 */
+		geo_size = geo->cylinders * geo->heads
+			* geo->sectors * secperblk;
+		size = i_size >> 9;
+		if (size != geo_size) {
+			if (!info) {
+				strlcat(state->pp_buf, "\n", PAGE_SIZE);
+				return 1;
+			}
+			if (!strcmp(info->type, "ECKD"))
+				if (geo_size < size)
+					size = geo_size;
+			/* else keep size based on i_size */
+		}
+	}
+	/* first and only partition starts in the first block after the label */
+	offset = labelsect + secperblk;
+	put_partition(state, 1, offset, size - offset);
+	strlcat(state->pp_buf, "\n", PAGE_SIZE);
+	return 1;
+}
+
+static int find_cms1_partitions(struct parsed_partitions *state,
+				struct hd_geometry *geo,
+				int blocksize,
+				char name[],
+				union label_t *label,
+				sector_t labelsect)
+{
+	loff_t offset, size;
+	char tmp[64];
+	int secperblk;
+
+	/*
+	 * VM style CMS1 labeled disk
+	 */
+	blocksize = label->cms.block_size;
+	secperblk = blocksize >> 9;
+	if (label->cms.disk_offset != 0) {
+		snprintf(tmp, sizeof(tmp), "CMS1/%8s(MDSK):", name);
+		strlcat(state->pp_buf, tmp, PAGE_SIZE);
+		/* disk is reserved minidisk */
+		offset = label->cms.disk_offset * secperblk;
+		size = (label->cms.block_count - 1) * secperblk;
+	} else {
+		snprintf(tmp, sizeof(tmp), "CMS1/%8s:", name);
+		strlcat(state->pp_buf, tmp, PAGE_SIZE);
+		/*
+		 * Special case for FBA devices:
+		 * If an FBA device is CMS formatted with blocksize > 512 byte
+		 * and the DIAG discipline is used, then the CMS label is found
+		 * in sector 1 instead of block 1. However, the partition is
+		 * still supposed to start in block 2.
+		 */
+		if (labelsect == 1)
+			offset = 2 * secperblk;
+		else
+			offset = labelsect + secperblk;
+		size = label->cms.block_count * secperblk;
+	}
+
+	put_partition(state, 1, offset, size-offset);
+	strlcat(state->pp_buf, "\n", PAGE_SIZE);
+	return 1;
+}
+
+
 /*
+ * This is the main function, called by check.c
  */
 int ibm_partition(struct parsed_partitions *state)
 {
 	struct block_device *bdev = state->bdev;
 	int blocksize, res;
-	loff_t i_size, offset, size, fmt_size;
+	loff_t i_size, offset, size;
 	dasd_information2_t *info;
 	struct hd_geometry *geo;
 	char type[5] = {0,};
 	char name[7] = {0,};
-	union label_t {
-		struct vtoc_volume_label_cdl vol;
-		struct vtoc_volume_label_ldl lnx;
-		struct vtoc_cms_label cms;
-	} *label;
-	unsigned char *data;
-	Sector sect;
 	sector_t labelsect;
-	char tmp[64];
+	union label_t *label;
 
 	res = 0;
 	blocksize = bdev_logical_block_size(bdev);
@@ -84,7 +305,6 @@ int ibm_partition(struct parsed_partitions *state)
 	i_size = i_size_read(bdev->bd_inode);
 	if (i_size == 0)
 		goto out_exit;
-
 	info = kmalloc(sizeof(dasd_information2_t), GFP_KERNEL);
 	if (info == NULL)
 		goto out_exit;
@@ -94,176 +314,45 @@ int ibm_partition(struct parsed_partitions *state)
 	label = kmalloc(sizeof(union label_t), GFP_KERNEL);
 	if (label == NULL)
 		goto out_nolab;
-
-	if (ioctl_by_bdev(bdev, BIODASDINFO2, (unsigned long)info) != 0 ||
-	    ioctl_by_bdev(bdev, HDIO_GETGEO, (unsigned long)geo) != 0)
+	if (ioctl_by_bdev(bdev, HDIO_GETGEO, (unsigned long)geo) != 0)
 		goto out_freeall;
-
-	/*
-	 * Special case for FBA disks: label sector does not depend on
-	 * blocksize.
-	 */
-	if ((info->cu_type == 0x6310 && info->dev_type == 0x9336) ||
-	    (info->cu_type == 0x3880 && info->dev_type == 0x3370))
-		labelsect = info->label_block;
-	else
-		labelsect = info->label_block * (blocksize >> 9);
-
-	/*
-	 * Get volume label, extract name and type.
-	 */
-	data = read_part_sector(state, labelsect, &sect);
-	if (data == NULL)
-		goto out_readerr;
-
-	memcpy(label, data, sizeof(union label_t));
-	put_dev_sector(sect);
-
-	if ((!info->FBA_layout) && (!strcmp(info->type, "ECKD"))) {
-		strncpy(type, label->vol.vollbl, 4);
-		strncpy(name, label->vol.volid, 6);
-	} else {
-		strncpy(type, label->lnx.vollbl, 4);
-		strncpy(name, label->lnx.volid, 6);
+	if (ioctl_by_bdev(bdev, BIODASDINFO2, (unsigned long)info) != 0) {
+		kfree(info);
+		info = NULL;
 	}
-	EBCASC(type, 4);
-	EBCASC(name, 6);
-
-	res = 1;
 
-	/*
-	 * Three different formats: LDL, CDL and unformated disk
-	 *
-	 * identified by info->format
-	 *
-	 * unformated disks we do not have to care about
-	 */
-	if (info->format == DASD_FORMAT_LDL) {
-		if (strncmp(type, "CMS1", 4) == 0) {
-			/*
-			 * VM style CMS1 labeled disk
-			 */
-			blocksize = label->cms.block_size;
-			if (label->cms.disk_offset != 0) {
-				snprintf(tmp, sizeof(tmp), "CMS1/%8s(MDSK):", name);
-				strlcat(state->pp_buf, tmp, PAGE_SIZE);
-				/* disk is reserved minidisk */
-				offset = label->cms.disk_offset;
-				size = (label->cms.block_count - 1)
-					* (blocksize >> 9);
-			} else {
-				snprintf(tmp, sizeof(tmp), "CMS1/%8s:", name);
-				strlcat(state->pp_buf, tmp, PAGE_SIZE);
-				offset = (info->label_block + 1);
-				size = label->cms.block_count
-					* (blocksize >> 9);
-			}
-			put_partition(state, 1, offset*(blocksize >> 9),
-				      size-offset*(blocksize >> 9));
-		} else {
-			if (strncmp(type, "LNX1", 4) == 0) {
-				snprintf(tmp, sizeof(tmp), "LNX1/%8s:", name);
-				strlcat(state->pp_buf, tmp, PAGE_SIZE);
-				if (label->lnx.ldl_version == 0xf2) {
-					fmt_size = label->lnx.formatted_blocks
-						* (blocksize >> 9);
-				} else if (!strcmp(info->type, "ECKD")) {
-					/* formated w/o large volume support */
-					fmt_size = geo->cylinders * geo->heads
-					      * geo->sectors * (blocksize >> 9);
-				} else {
-					/* old label and no usable disk geometry
-					 * (e.g. DIAG) */
-					fmt_size = i_size >> 9;
-				}
-				size = i_size >> 9;
-				if (fmt_size < size)
-					size = fmt_size;
-				offset = (info->label_block + 1);
-			} else {
-				/* unlabeled disk */
-				strlcat(state->pp_buf, "(nonl)", PAGE_SIZE);
-				size = i_size >> 9;
-				offset = (info->label_block + 1);
-			}
-			put_partition(state, 1, offset*(blocksize >> 9),
-				      size-offset*(blocksize >> 9));
+	if (find_label(state, info, geo, blocksize, &labelsect, name, type,
+		       label)) {
+		if (!strncmp(type, "VOL1", 4)) {
+			res = find_vol1_partitions(state, geo, blocksize, name,
+						   label);
+		} else if (!strncmp(type, "LNX1", 4)) {
+			res = find_lnx1_partitions(state, geo, blocksize, name,
+						   label, labelsect, i_size,
+						   info);
+		} else if (!strncmp(type, "CMS1", 4)) {
+			res = find_cms1_partitions(state, geo, blocksize, name,
+						   label, labelsect);
 		}
-	} else if (info->format == DASD_FORMAT_CDL) {
-		/*
-		 * New style CDL formatted disk
-		 */
-		sector_t blk;
-		int counter;
-
+	} else if (info) {
 		/*
-		 * check if VOL1 label is available
-		 * if not, something is wrong, skipping partition detection
+		 * ugly but needed for backward compatibility:
+		 * If the block device is a DASD (i.e. BIODASDINFO2 works),
+		 * then we claim it in any case, even though it has no valid
+		 * label. If it has the LDL format, then we simply define a
+		 * partition as if it had an LNX1 label.
 		 */
-		if (strncmp(type, "VOL1",  4) == 0) {
-			snprintf(tmp, sizeof(tmp), "VOL1/%8s:", name);
-			strlcat(state->pp_buf, tmp, PAGE_SIZE);
-			/*
-			 * get block number and read then go through format1
-			 * labels
-			 */
-			blk = cchhb2blk(&label->vol.vtoc, geo) + 1;
-			counter = 0;
-			data = read_part_sector(state, blk * (blocksize/512),
-						&sect);
-			while (data != NULL) {
-				struct vtoc_format1_label f1;
-
-				memcpy(&f1, data,
-				       sizeof(struct vtoc_format1_label));
-				put_dev_sector(sect);
-
-				/* skip FMT4 / FMT5 / FMT7 labels */
-				if (f1.DS1FMTID == _ascebc['4']
-				    || f1.DS1FMTID == _ascebc['5']
-				    || f1.DS1FMTID == _ascebc['7']
-				    || f1.DS1FMTID == _ascebc['9']) {
-					blk++;
-					data = read_part_sector(state,
-						blk * (blocksize/512), &sect);
-					continue;
-				}
-
-				/* only FMT1 and 8 labels valid at this point */
-				if (f1.DS1FMTID != _ascebc['1'] &&
-				    f1.DS1FMTID != _ascebc['8'])
-					break;
-
-				/* OK, we got valid partition data */
-				offset = cchh2blk(&f1.DS1EXT1.llimit, geo);
-				size  = cchh2blk(&f1.DS1EXT1.ulimit, geo) -
-					offset + geo->sectors;
-				if (counter >= state->limit)
-					break;
-				put_partition(state, counter + 1,
-					      offset * (blocksize >> 9),
-					      size * (blocksize >> 9));
-				counter++;
-				blk++;
-				data = read_part_sector(state,
-						blk * (blocksize/512), &sect);
-			}
-
-			if (!data)
-				/* Are we not supposed to report this ? */
-				goto out_readerr;
-		} else
-			printk(KERN_INFO "Expected Label VOL1 not "
-			       "found, treating as CDL formated Disk");
-
-	}
-
-	strlcat(state->pp_buf, "\n", PAGE_SIZE);
-	goto out_freeall;
-
+		res = 1;
+		if (info->format == DASD_FORMAT_LDL) {
+			strlcat(state->pp_buf, "(nonl)", PAGE_SIZE);
+			size = i_size >> 9;
+			offset = (info->label_block + 1) * (blocksize >> 9);
+			put_partition(state, 1, offset, size-offset);
+			strlcat(state->pp_buf, "\n", PAGE_SIZE);
+		}
+	} else
+		res = 0;
 
-out_readerr:
-	res = -1;
 out_freeall:
 	kfree(label);
 out_nolab: