lvm2/lib/filters/filter-mpath.c

/*
 * Copyright (C) 2011 Red Hat, Inc. All rights reserved.
 *
 * This file is part of LVM2.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License v.2.1.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "lib.h"
#include "filter.h"
#include "activate.h"

#ifdef __linux__

#include <dirent.h>

#define MPATH_PREFIX "mpath-"

static const char *_get_sysfs_name(struct device *dev)
{
	const char *name;

	if (!(name = strrchr(dev_name(dev), '/'))) {
		log_error("Cannot find '/' in device name.");
		return NULL;
	}
	name++;

	if (!*name) {
		log_error("Device name is not valid.");
		return NULL;
	}

	return name;
}

static const char *_get_sysfs_name_by_devt(const char *sysfs_dir, dev_t devno,
					  char *buf, size_t buf_size)
{
	const char *name;
	char path[PATH_MAX];
	int size;

	if (dm_snprintf(path, sizeof(path), "%s/dev/block/%d:%d", sysfs_dir,
			(int) MAJOR(devno), (int) MINOR(devno)) < 0) {
		log_error("Sysfs path string is too long.");
		return NULL;
	}

	if ((size = readlink(path, buf, buf_size - 1)) < 0) {
		log_sys_error("readlink", path);
		return NULL;
	}
	buf[size] = '\0';

	if (!(name = strrchr(buf, '/'))) {
		log_error("Cannot find device name in sysfs path.");
		return NULL;
	}
	name++;

	return name;
}

static int _get_sysfs_string(const char *path, char *buffer, int max_size)
{
	FILE *fp;
	int r = 0;

	if (!(fp = fopen(path, "r"))) {
		log_sys_error("fopen", path);
		return 0;
	}

	if (!fgets(buffer, max_size, fp))
		log_sys_error("fgets", path);
	else
		r = 1;

	if (fclose(fp))
		log_sys_error("fclose", path);

	return r;
}

static int _get_sysfs_get_major_minor(const char *sysfs_dir, const char *kname, int *major, int *minor)
{
	char path[PATH_MAX], buffer[64];

	if (dm_snprintf(path, sizeof(path), "%s/block/%s/dev", sysfs_dir, kname) < 0) {
		log_error("Sysfs path string is too long.");
		return 0;
	}

	if (!_get_sysfs_string(path, buffer, sizeof(buffer)))
		return_0;

	if (sscanf(buffer, "%d:%d", major, minor) != 2) {
		log_error("Failed to parse major minor from %s", buffer);
		return 0;
	}

	return 1;
}

static int _get_parent_mpath(const char *dir, char *name, int max_size)
{
	struct dirent *d;
	DIR *dr;
	int r = 0;

	if (!(dr = opendir(dir))) {
		log_sys_error("opendir", dir);
		return 0;
	}

	*name = '\0';
	while ((d = readdir(dr))) {
		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
			continue;

		/* There should be only one holder if it is multipath */
		if (*name) {
			r = 0;
			break;
		}

		strncpy(name, d->d_name, max_size);
		r = 1;
	}

	if (closedir(dr))
		log_sys_error("closedir", dir);

	return r;
}

static int _dev_is_mpath(struct dev_filter *f, struct device *dev)
{
	struct dev_types *dt = (struct dev_types *) f->private;
	const char *part_name, *name;
	struct stat info;
	char path[PATH_MAX], parent_name[PATH_MAX];
	const char *sysfs_dir = dm_sysfs_dir();
	int major = MAJOR(dev->dev);
	int minor = MINOR(dev->dev);
	dev_t primary_dev;

	/* Limit this filter only to SCSI devices */
	if (!major_is_scsi_device(dt, MAJOR(dev->dev)))
		return 0;

	switch (dev_get_primary_dev(dt, dev, &primary_dev)) {
	case 2: /* The dev is partition. */
		part_name = dev_name(dev); /* name of original dev for log_debug msg */
		if (!(name = _get_sysfs_name_by_devt(sysfs_dir, primary_dev, parent_name, sizeof(parent_name))))
			return_0;
		log_debug_devs("%s: Device is a partition, using primary "
			       "device %s for mpath component detection",
			       part_name, name);
		break;
	case 1: /* The dev is already a primary dev. Just continue with the dev. */
		if (!(name = _get_sysfs_name(dev)))
			return_0;
		break;
	default: /* 0, error. */
		log_error("Failed to get primary device for %d:%d.", major, minor);
		return 0;
	}

	if (dm_snprintf(path, sizeof(path), "%s/block/%s/holders", sysfs_dir, name) < 0) {
		log_error("Sysfs path to check mpath is too long.");
		return 0;
	}

	/* also will filter out partitions */
	if (stat(path, &info))
		return 0;

	if (!S_ISDIR(info.st_mode)) {
		log_error("Path %s is not a directory.", path);
		return 0;
	}

	if (!_get_parent_mpath(path, parent_name, sizeof(parent_name)))
		return 0;

	if (!_get_sysfs_get_major_minor(sysfs_dir, parent_name, &major, &minor))
		return_0;

	if (major != dt->device_mapper_major)
		return 0;

	return lvm_dm_prefix_check(major, minor, MPATH_PREFIX);
}

static int _ignore_mpath(struct dev_filter *f, struct device *dev)
{
	if (_dev_is_mpath(f, dev) == 1) {
		log_debug_devs("%s: Skipping mpath component device", dev_name(dev));
		return 0;
	}

	return 1;
}

static void _destroy(struct dev_filter *f)
{
	if (f->use_count)
		log_error(INTERNAL_ERROR "Destroying mpath filter while in use %u times.", f->use_count);

	dm_free(f);
}

struct dev_filter *mpath_filter_create(struct dev_types *dt)
{
	const char *sysfs_dir = dm_sysfs_dir();
	struct dev_filter *f;

	if (!*sysfs_dir) {
		log_verbose("No proc filesystem found: skipping multipath filter");
		return NULL;
	}

	if (!(f = dm_zalloc(sizeof(*f)))) {
		log_error("mpath filter allocation failed");
		return NULL;
	}

	f->passes_filter = _ignore_mpath;
	f->destroy = _destroy;
	f->use_count = 0;
	f->private = dt;

	log_debug_devs("mpath filter initialised.");

	return f;
}

#else

struct dev_filter *mpath_filter_create(struct dev_types *dt)
{
	return NULL;
}

#endif