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lvm2/lib/misc/lvm-wrappers.c
David Teigland 9048565093 devices: rework libudev usage
related to config settings:
  obtain_device_info_from_udev (controls if lvm gets
    a list of devices from readdir /dev or from libudev)
  external_device_info_source (controls if lvm asks
    libudev for device information)

. Make the obtain_device_list_from_udev setting
  affect only the choice of readdir /dev vs libudev.
  The setting no longer controls if udev is used for
  device type checks.

. Change obtain_device_list_from_udev default to 0.
  This helps avoid boot timeouts due to slow libudev
  queries, avoids reported failures from
  udev_enumerate_scan_devices, and avoids delays from
  "device not initialized in udev database" errors.
  Even without errors, for a system booting with 1024 PVs,
  lvm2-pvscan times improve from about 100 sec to 15 sec,
  and the pvscan command from about 64 sec to about 4 sec.

. For external_device_info_source="none", remove all
  libudev device info queries, and use only lvm
  native device info.

. For external_device_info_source="udev", first check
  lvm native device info, then check libudev info.

. Remove sleep/retry loop when attempting libudev
  queries for device info.  udev info will simply
  be skipped if it's not immediately available.

. Only set up a libdev connection if it will be used by
  obtain_device_list_from_udev/external_device_info_source.

. For native multipath component detection, use
  /etc/multipath/wwids.  If a device has a wwid
  matching an entry in the wwids file, then it's
  considered a multipath component.  This is
  necessary to natively detect multipath
  components when the mpath device is not set up.
2021-07-13 11:11:23 -05:00

175 lines
3.1 KiB
C

/*
* Copyright (C) 2006 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "lib/misc/lib.h"
#include <unistd.h>
#include <fcntl.h>
#ifdef UDEV_SYNC_SUPPORT
#include <libudev.h>
struct udev *_udev;
int udev_init_library_context(void)
{
if (_udev)
return 1;
if (getenv("DM_DISABLE_UDEV"))
return 0;
if (!(_udev = udev_new())) {
log_error("Failed to create udev library context.");
return 0;
}
if (!udev_is_running()) {
udev_unref(_udev);
_udev = NULL;
return 0;
}
return 1;
}
void udev_fin_library_context(void)
{
if (_udev)
udev_unref(_udev);
_udev = NULL;
}
int udev_is_running(void)
{
struct udev_queue *udev_queue;
int r;
if (!_udev) {
log_debug_activation("Udev library context not set.");
goto bad;
}
if (!(udev_queue = udev_queue_new(_udev))) {
log_debug_activation("Could not get udev state.");
goto bad;
}
r = udev_queue_get_udev_is_active(udev_queue);
udev_queue_unref(udev_queue);
return r;
bad:
log_debug_activation("Assuming udev is not running.");
return 0;
}
void *udev_get_library_context(void)
{
return _udev;
}
#else /* UDEV_SYNC_SUPPORT */
int udev_init_library_context(void)
{
return 1;
}
void *udev_get_library_context(void)
{
return NULL;
}
void udev_fin_library_context(void)
{
}
int udev_is_running(void)
{
return 0;
}
#endif
int lvm_getpagesize(void)
{
return getpagesize();
}
int read_urandom(void *buf, size_t len)
{
int fd;
/* FIXME: we should stat here, and handle other cases */
/* FIXME: use common _io() routine's open/read/close */
if ((fd = open("/dev/urandom", O_RDONLY)) < 0) {
log_sys_error("open", "read_urandom: /dev/urandom");
return 0;
}
if (read(fd, buf, len) != (ssize_t) len) {
log_sys_error("read", "read_urandom: /dev/urandom");
if (close(fd))
stack;
return 0;
}
if (close(fd))
stack;
return 1;
}
/*
* Return random integer in [0,max) interval
*
* The loop rejects numbers that come from an "incomplete" slice of the
* RAND_MAX space. Considering the number space [0, RAND_MAX] is divided
* into some "max"-sized slices and at most a single smaller slice,
* between [n*max, RAND_MAX] for suitable n, numbers from this last slice
* are discarded because they could distort the distribution in favour of
* smaller numbers.
*/
unsigned lvm_even_rand(unsigned *seed, unsigned max)
{
unsigned r, ret;
do {
r = (unsigned) rand_r(seed);
ret = r % max;
} while (r - ret > RAND_MAX - max);
return ret;
}
int clvmd_is_running(void)
{
#ifdef CLVMD_PIDFILE
return dm_daemon_is_running(CLVMD_PIDFILE);
#else
return 0;
#endif
}
int cmirrord_is_running(void)
{
#ifdef CMIRRORD_PIDFILE
return dm_daemon_is_running(CMIRRORD_PIDFILE);
#else
return 0;
#endif
}