zipl_helper.device-mapper: Fix imprecise is_device_mapper() predicate

Fix is_device_mapper() predicate to not base on checking a hardcoded
major number (253), which not always correct, since on some systems
dm-devices have different majors".

Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Eduard Shishkin <edward6@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

include/lib/util_proc.h

@@ -31,6 +31,7 @@ struct util_proc_dev_entry {
 #define UTIL_PROC_DEV_ENTRY_SD       "sd"
 #define UTIL_PROC_DEV_ENTRY_BLKEXT   "blkext"
 #define UTIL_PROC_DEV_ENTRY_MD       "md"
+#define UTIL_PROC_DEV_ENTRY_DM       "device-mapper"
 
 int util_proc_part_get_entry(dev_t device, struct util_proc_part_entry *entry);
 void util_proc_part_free_entry(struct util_proc_part_entry *entry);

zipl/include/misc.h

@@ -58,6 +58,7 @@ int misc_check_writable_device(const char* devno, int blockdev, int chardev);
 void misc_ebcdic_to_ascii(unsigned char *from, unsigned char *to);
 void misc_ascii_to_ebcdic(unsigned char *from, unsigned char *to);
 unsigned int misc_check_secure_boot(void);
+void misc_warn_on_failed_pdge(dev_t device);
 
 #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
 #endif /* not MISC_H */

zipl/src/disk.c

@@ -509,10 +509,7 @@ static void set_driver_name(int fd, struct disk_info *info, dev_t device)
 			info->drv_name = misc_strdup(dev_entry.name);
 		util_proc_dev_free_entry(&dev_entry);
 	} else {
-		fprintf(stderr, "Warning: Could not determine driver name for "
-			"major %d from /proc/devices\n", major(device));
-		fprintf(stderr, "Warning: Preparing a logical device for boot "
-			"might fail\n");
+		misc_warn_on_failed_pdge(device);
 	}
 }
 

zipl/src/misc.c

@@ -18,6 +18,7 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <sys/sysmacros.h>
 #include <unistd.h>
 
 #include "error.h"
@@ -662,4 +663,14 @@ void misc_ascii_to_ebcdic(unsigned char *from, unsigned char *to)
 		*from = ascebc[*from];
 }
 
-
+/**
+ *  zipl-specific response on failed util_proc_dev_get_entry()
+ */
+void misc_warn_on_failed_pdge(dev_t device)
+{
+	fprintf(stderr,
+		"Warning: Could not determine driver name for major %d from /proc/devices\n",
+		major(device));
+	fprintf(stderr,
+		"Warning: Preparing a logical device for boot might fail\n");
+}

zipl/src/zipl_helper.device-mapper.c

@@ -180,7 +180,6 @@ struct helper {
 #define SCSI_PARTN_MASK 0x0f
 
 #define MD_MAJOR 9
-#define DEVICE_MAPPER_MAJOR 253
 
 /* Internal constants */
 enum dev_type {
@@ -231,9 +230,19 @@ static int error_on(const char *state, const char *this, const char *fixup,
 	return 0;
 }
 
-static int is_device_mapper(unsigned int major)
+static int is_device_mapper(dev_t device)
 {
-	return major == DEVICE_MAPPER_MAJOR;
+	struct util_proc_dev_entry pde;
+	int result = 0;
+
+	if (util_proc_dev_get_entry(device, 1, &pde) == 0) {
+		if (strcmp(pde.name, UTIL_PROC_DEV_ENTRY_DM) == 0)
+			result = 1;
+		util_proc_dev_free_entry(&pde);
+	} else {
+		misc_warn_on_failed_pdge(device);
+	}
+	return result;
 }
 
 static void get_type_name(char *name, unsigned short type)
@@ -1705,7 +1714,7 @@ static int md_mirror_to_params(unsigned int major, unsigned int minor,
 		ERR("Unsupported configuration: nested md devices\n");
 		return -1;
 	}
-	if (is_device_mapper(major)) {
+	if (is_device_mapper(dev)) {
 		struct ext_dev xdev = {dev, data_start_md + fs_start_md};
 		char *name;