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lvm2/lib/locking/file_locking.c
Peter Rajnoha 039bdad732 activation: flag temporary LVs internally
Add LV_TEMPORARY flag for LVs with limited existence during command
execution. Such LVs are temporary in way that they need to be activated,
some action done and then removed immediately. Such LVs are just like
any normal LV - the only difference is that they are removed during
LVM command execution. This is also the case for LVs representing
future pool metadata spare LVs which we need to initialize by using
the usual LV before they are declared as pool metadata spare.

We can optimize some other parts like udev to do a better job if
it knows that the LV is temporary and any processing on it is just
useless.

This flag is orthogonal to LV_NOSCAN flag introduced recently
as LV_NOSCAN flag is primarily used to mark an LV for the scanning
to be avoided before the zeroing of the device happens. The LV_TEMPORARY
flag makes a difference between a full-fledged LV visible in the system
and the LV just used as a temporary overlay for some action that needs to
be done on underlying PVs.

For example: lvcreate --thinpool POOL --zero n -L 1G vg

- first, the usual LV is created to do a clean up for pool metadata
  spare. The LV is activated, zeroed, deactivated.

- between "activated" and "zeroed" stage, the LV_NOSCAN flag is used
  to avoid any scanning in udev

- betwen "zeroed" and "deactivated" stage, we need to avoid the WATCH
  udev rule, but since the LV is just a usual LV, we can't make a
  difference. The LV_TEMPORARY internal LV flag helps here. If we
  create the LV with this flag, the DM_UDEV_DISABLE_DISK_RULES
  and DM_UDEV_DISABLE_OTHER_RULES flag are set (just like as it is
  with "invisible" and non-top-level LVs) - udev is directed to
  skip WATCH rule use.

- if the LV_TEMPORARY flag was not used, there would normally be
  a WATCH event generated once the LV is closed after "zeroed"
  stage. This will make problems with immediated deactivation that
  follows.
2013-10-23 14:09:37 +02:00

389 lines
9.0 KiB
C

/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2007 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 "locking.h"
#include "locking_types.h"
#include "activate.h"
#include "config.h"
#include "defaults.h"
#include "lvm-file.h"
#include "lvm-string.h"
#include "lvmcache.h"
#include <limits.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <fcntl.h>
#include <signal.h>
struct lock_list {
struct dm_list list;
int lf;
char *res;
};
static struct dm_list _lock_list;
static char _lock_dir[NAME_LEN];
static int _prioritise_write_locks;
static sig_t _oldhandler;
static sigset_t _fullsigset, _intsigset;
static volatile sig_atomic_t _handler_installed;
static void _undo_flock(const char *file, int fd)
{
struct stat buf1, buf2;
log_debug_locking("_undo_flock %s", file);
if (!flock(fd, LOCK_NB | LOCK_EX) &&
!stat(file, &buf1) &&
!fstat(fd, &buf2) &&
is_same_inode(buf1, buf2))
if (unlink(file))
log_sys_error("unlink", file);
if (close(fd) < 0)
log_sys_error("close", file);
}
static int _release_lock(const char *file, int unlock)
{
struct lock_list *ll;
struct dm_list *llh, *llt;
dm_list_iterate_safe(llh, llt, &_lock_list) {
ll = dm_list_item(llh, struct lock_list);
if (!file || !strcmp(ll->res, file)) {
dm_list_del(llh);
if (unlock) {
log_very_verbose("Unlocking %s", ll->res);
if (flock(ll->lf, LOCK_NB | LOCK_UN))
log_sys_error("flock", ll->res);
}
_undo_flock(ll->res, ll->lf);
dm_free(ll->res);
dm_free(llh);
if (file)
return 1;
}
}
return 0;
}
static void _fin_file_locking(void)
{
_release_lock(NULL, 1);
}
static void _reset_file_locking(void)
{
_release_lock(NULL, 0);
}
static void _remove_ctrl_c_handler(void)
{
siginterrupt(SIGINT, 0);
if (!_handler_installed)
return;
_handler_installed = 0;
sigprocmask(SIG_SETMASK, &_fullsigset, NULL);
if (signal(SIGINT, _oldhandler) == SIG_ERR)
log_sys_error("signal", "_remove_ctrl_c_handler");
}
static void _trap_ctrl_c(int sig __attribute__((unused)))
{
_remove_ctrl_c_handler();
log_error("CTRL-c detected: giving up waiting for lock");
}
static void _install_ctrl_c_handler(void)
{
_handler_installed = 1;
if ((_oldhandler = signal(SIGINT, _trap_ctrl_c)) == SIG_ERR) {
_handler_installed = 0;
return;
}
sigprocmask(SIG_SETMASK, &_intsigset, NULL);
siginterrupt(SIGINT, 1);
}
static int _do_flock(const char *file, int *fd, int operation, uint32_t nonblock)
{
int r = 1;
int old_errno;
struct stat buf1, buf2;
log_debug_locking("_do_flock %s %c%c", file,
operation == LOCK_EX ? 'W' : 'R', nonblock ? ' ' : 'B');
do {
if ((*fd > -1) && close(*fd))
log_sys_error("close", file);
if ((*fd = open(file, O_CREAT | O_APPEND | O_RDWR, 0777)) < 0) {
log_sys_error("open", file);
return 0;
}
if (nonblock)
operation |= LOCK_NB;
else
_install_ctrl_c_handler();
r = flock(*fd, operation);
old_errno = errno;
if (!nonblock)
_remove_ctrl_c_handler();
if (r) {
errno = old_errno;
log_sys_error("flock", file);
if (close(*fd))
log_sys_error("close", file);
return 0;
}
if (!stat(file, &buf1) && !fstat(*fd, &buf2) &&
is_same_inode(buf1, buf2))
return 1;
} while (!nonblock);
return_0;
}
#define AUX_LOCK_SUFFIX ":aux"
static int _do_write_priority_flock(const char *file, int *fd, int operation, uint32_t nonblock)
{
int r, fd_aux = -1;
char *file_aux = alloca(strlen(file) + sizeof(AUX_LOCK_SUFFIX));
strcpy(file_aux, file);
strcat(file_aux, AUX_LOCK_SUFFIX);
if ((r = _do_flock(file_aux, &fd_aux, LOCK_EX, 0))) {
if (operation == LOCK_EX) {
r = _do_flock(file, fd, operation, nonblock);
_undo_flock(file_aux, fd_aux);
} else {
_undo_flock(file_aux, fd_aux);
r = _do_flock(file, fd, operation, nonblock);
}
}
return r;
}
static int _lock_file(const char *file, uint32_t flags)
{
int operation;
uint32_t nonblock = flags & LCK_NONBLOCK;
int r;
struct lock_list *ll;
char state;
switch (flags & LCK_TYPE_MASK) {
case LCK_READ:
operation = LOCK_SH;
state = 'R';
break;
case LCK_WRITE:
operation = LOCK_EX;
state = 'W';
break;
case LCK_UNLOCK:
return _release_lock(file, 1);
default:
log_error("Unrecognised lock type: %d", flags & LCK_TYPE_MASK);
return 0;
}
if (!(ll = dm_malloc(sizeof(struct lock_list))))
return_0;
if (!(ll->res = dm_strdup(file))) {
dm_free(ll);
return_0;
}
ll->lf = -1;
log_very_verbose("Locking %s %c%c", ll->res, state,
nonblock ? ' ' : 'B');
(void) dm_prepare_selinux_context(file, S_IFREG);
if (_prioritise_write_locks)
r = _do_write_priority_flock(file, &ll->lf, operation, nonblock);
else
r = _do_flock(file, &ll->lf, operation, nonblock);
(void) dm_prepare_selinux_context(NULL, 0);
if (r)
dm_list_add(&_lock_list, &ll->list);
else {
dm_free(ll->res);
dm_free(ll);
stack;
}
return r;
}
static int _file_lock_resource(struct cmd_context *cmd, const char *resource,
uint32_t flags, struct logical_volume *lv)
{
char lockfile[PATH_MAX];
unsigned origin_only = (flags & LCK_ORIGIN_ONLY) ? 1 : 0;
unsigned revert = (flags & LCK_REVERT) ? 1 : 0;
switch (flags & LCK_SCOPE_MASK) {
case LCK_VG:
/* Skip cache refresh for VG_GLOBAL - the caller handles it */
if (strcmp(resource, VG_GLOBAL))
lvmcache_drop_metadata(resource, 0);
if (!strcmp(resource, VG_SYNC_NAMES))
fs_unlock();
/* LCK_CACHE does not require a real lock */
if (flags & LCK_CACHE)
break;
if (is_orphan_vg(resource) || is_global_vg(resource)) {
if (dm_snprintf(lockfile, sizeof(lockfile),
"%s/P_%s", _lock_dir, resource + 1) < 0) {
log_error("Too long locking filename %s/P_%s.",
_lock_dir, resource + 1);
return 0;
}
} else
if (dm_snprintf(lockfile, sizeof(lockfile),
"%s/V_%s", _lock_dir, resource) < 0) {
log_error("Too long locking filename %s/V_%s.",
_lock_dir, resource);
return 0;
}
if (!_lock_file(lockfile, flags))
return_0;
break;
case LCK_LV:
switch (flags & LCK_TYPE_MASK) {
case LCK_UNLOCK:
log_very_verbose("Unlocking LV %s%s%s", resource, origin_only ? " without snapshots" : "", revert ? " (reverting)" : "");
if (!lv_resume_if_active(cmd, resource, origin_only, 0, revert, lv_ondisk(lv)))
return 0;
break;
case LCK_NULL:
log_very_verbose("Locking LV %s (NL)", resource);
if (!lv_deactivate(cmd, resource, lv_ondisk(lv)))
return 0;
break;
case LCK_READ:
log_very_verbose("Locking LV %s (R)", resource);
if (!lv_activate_with_filter(cmd, resource, 0, lv->status & LV_NOSCAN ? 1 : 0,
lv->status & LV_TEMPORARY ? 1 : 0, lv_ondisk(lv)))
return 0;
break;
case LCK_PREAD:
log_very_verbose("Locking LV %s (PR) - ignored", resource);
break;
case LCK_WRITE:
log_very_verbose("Locking LV %s (W)%s", resource, origin_only ? " without snapshots" : "");
if (!lv_suspend_if_active(cmd, resource, origin_only, 0, lv_ondisk(lv), lv))
return 0;
break;
case LCK_EXCL:
log_very_verbose("Locking LV %s (EX)", resource);
if (!lv_activate_with_filter(cmd, resource, 1, lv->status & LV_NOSCAN ? 1 : 0,
lv->status & LV_TEMPORARY ? 1 : 0, lv_ondisk(lv)))
return 0;
break;
default:
break;
}
break;
default:
log_error("Unrecognised lock scope: %d",
flags & LCK_SCOPE_MASK);
return 0;
}
return 1;
}
int init_file_locking(struct locking_type *locking, struct cmd_context *cmd,
int suppress_messages)
{
int r;
const char *locking_dir;
locking->lock_resource = _file_lock_resource;
locking->reset_locking = _reset_file_locking;
locking->fin_locking = _fin_file_locking;
locking->flags = 0;
/* Get lockfile directory from config file */
locking_dir = find_config_tree_str(cmd, global_locking_dir_CFG, NULL);
if (strlen(locking_dir) >= sizeof(_lock_dir)) {
log_error("Path for locking_dir %s is invalid.", locking_dir);
return 0;
}
strcpy(_lock_dir, locking_dir);
_prioritise_write_locks =
find_config_tree_bool(cmd, global_prioritise_write_locks_CFG, NULL);
(void) dm_prepare_selinux_context(_lock_dir, S_IFDIR);
r = dm_create_dir(_lock_dir);
(void) dm_prepare_selinux_context(NULL, 0);
if (!r)
return 0;
/* Trap a read-only file system */
if ((access(_lock_dir, R_OK | W_OK | X_OK) == -1) && (errno == EROFS))
return 0;
dm_list_init(&_lock_list);
if (sigfillset(&_intsigset) || sigfillset(&_fullsigset)) {
log_sys_error_suppress(suppress_messages, "sigfillset",
"init_file_locking");
return 0;
}
if (sigdelset(&_intsigset, SIGINT)) {
log_sys_error_suppress(suppress_messages, "sigdelset",
"init_file_locking");
return 0;
}
return 1;
}