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lvm2/lib/locking/file_locking.c

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/*
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* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
*
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* This file is part of LVM2.
*
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* 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.
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*
* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
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#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;
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static volatile sig_atomic_t _handler_installed;
static void _undo_flock(const char *file, int fd)
{
struct stat buf1, buf2;
log_debug("_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);
}
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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);
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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)
{
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_release_lock(NULL, 1);
}
static void _reset_file_locking(void)
{
_release_lock(NULL, 0);
}
static void _remove_ctrl_c_handler(void)
{
siginterrupt(SIGINT, 0);
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if (!_handler_installed)
return;
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_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)
{
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_handler_installed = 1;
if ((_oldhandler = signal(SIGINT, _trap_ctrl_c)) == SIG_ERR) {
_handler_installed = 0;
return;
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}
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;
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int old_errno;
struct stat buf1, buf2;
log_debug("_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);
close(*fd);
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;
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char state;
switch (flags & LCK_TYPE_MASK) {
case LCK_READ:
operation = LOCK_SH;
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state = 'R';
break;
case LCK_WRITE:
operation = LOCK_EX;
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state = 'W';
break;
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case LCK_UNLOCK:
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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;
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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)
{
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:
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/* Skip cache refresh for VG_GLOBAL - the caller handles it */
if (strcmp(resource, VG_GLOBAL))
lvmcache_drop_metadata(resource, 0);
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if (!strcmp(resource, VG_SYNC_NAMES))
fs_unlock();
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/* LCK_CACHE does not require a real lock */
if (flags & LCK_CACHE)
break;
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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) {
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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))
return 0;
break;
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case LCK_NULL:
log_very_verbose("Locking LV %s (NL)", resource);
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if (!lv_deactivate(cmd, resource))
return 0;
break;
case LCK_READ:
log_very_verbose("Locking LV %s (R)", resource);
if (!lv_activate_with_filter(cmd, resource, 0))
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))
return 0;
break;
case LCK_EXCL:
log_very_verbose("Locking LV %s (EX)", resource);
if (!lv_activate_with_filter(cmd, resource, 1))
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;
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locking->reset_locking = _reset_file_locking;
locking->fin_locking = _fin_file_locking;
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locking->flags = 0;
/* Get lockfile directory from config file */
locking_dir = find_config_tree_str(cmd, "global/locking_dir",
DEFAULT_LOCK_DIR);
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",
DEFAULT_PRIORITISE_WRITE_LOCKS);
(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;
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/* 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;
}