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libutil: add function to get base device for blockdevice

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Some operations are only possible on base devices not on partitions.
Add functions to determine if a given device is a partition or a base
device and to get the base device to a given partition.

Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Stefan Haberland
2020-07-29 11:24:55 +02:00
committed by Jan Höppner
parent 7eb04cdc54
commit fa7a4dafa3
2 changed files with 102 additions and 0 deletions
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5
include/lib/util_sys.h
View File

@@ -12,6 +12,11 @@
#ifndef LIB_UTIL_SYS_H
#define LIB_UTIL_SYS_H
#include <stdbool.h>
int util_sys_get_dev_addr(const char *dev, char *addr);
bool util_sys_dev_is_partition(dev_t dev);
int util_sys_get_partnum(dev_t dev);
int util_sys_get_base_dev(dev_t dev, dev_t *base_dev);
#endif /** LIB_UTIL_SYS_H @} */

97
libutil/util_sys.c
View File

@@ -11,17 +11,114 @@
#include <err.h>
#include <errno.h>
#include <linux/fs.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <unistd.h>
#include "lib/util_file.h"
#include "lib/util_libc.h"
#include "lib/util_path.h"
#include "lib/util_sys.h"
/* lstat() doesn't work for sysfs files, a fixed size is therefore inevitable */
#define READLINK_SIZE 256
#define PAGE_SIZE 4096
/**
* Return the partition number of a given partition.
*
* @param[in] dev Device node of interest
*
* @retval int Partition number of the device
* @retval -1 Error when trying to read the partition number.
*/
int util_sys_get_partnum(dev_t dev)
{
int partnum = -1;
char *path;
path = util_path_sysfs("dev/block/%u:%u/partition",
major(dev), minor(dev));
if (util_file_read_i(&partnum, 10, path)) {
warnx("Could not read from path '%s'", path);
goto out;
}
if (partnum <= 0) {
warnx("Bad partition number in '%s'", path);
partnum = -1;
goto out;
}
out:
free(path);
return partnum;
}
/**
* Determine if the given device is a partition.
*
* @param[in] dev Device node of interest
*
* @retval true Device is partition
* @retval false Device is not a partition
*/
bool util_sys_dev_is_partition(dev_t dev)
{
bool is_part;
char *path;
path = util_path_sysfs("dev/block/%u:%u/partition",
major(dev), minor(dev));
is_part = util_path_exists(path);
free(path);
return is_part;
}
/**
* Determine base device
*
* This function determines the base device \p base_dev of a given
* device \p dev. If \p dev is a base device, \p base_dev becomes \p dev.
*
* @param[in] dev Device node of interest
* @param[out] base_dev Identified base device
*
* @retval 0 Success
* @retval -1 Error while reading device information or
* constructed path
*/
int util_sys_get_base_dev(dev_t dev, dev_t *base_dev)
{
int base_major, base_minor;
char buf[PAGE_SIZE];
char *path;
/* check if the device already is a base device */
if (!util_sys_dev_is_partition(dev)) {
*base_dev = makedev(major(dev), minor(dev));
return 0;
}
path = util_path_sysfs("dev/block/%d:%d/../dev",
major(dev), minor(dev));
if (util_file_read_line(buf, sizeof(buf), path)) {
warnx("Could not read from path '%s'", path);
free(path);
return -1;
}
free(path);
if (sscanf(buf, "%i:%i", &base_major, &base_minor) != 2) {
warn("Could not parse major:minor from string '%s'", buf);
return -1;
}
*base_dev = makedev(base_major, base_minor);
return 0;
}
/**
* Identify device address