external/gpl2/lvm2/dist/lib/locking/file_locking.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
   5  * Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
   6  *
   7  * This file is part of LVM2.
   8  *
   9  * This copyrighted material is made available to anyone wishing to use,
  10  * modify, copy, or redistribute it subject to the terms and conditions
  11  * of the GNU Lesser General Public License v.2.1.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this program; if not, write to the Free Software Foundation,
  15  * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  16  */
  17
  18 #include "lib.h"
  19 #include "locking.h"
  20 #include "locking_types.h"
  21 #include "activate.h"
  22 #include "config.h"
  23 #include "defaults.h"
  24 #include "lvm-file.h"
  25 #include "lvm-string.h"
  26 #include "lvmcache.h"
  27
  28 #include <limits.h>
  29 #include <unistd.h>
  30 #include <sys/stat.h>
  31 #include <sys/file.h>
  32 #include <fcntl.h>
  33 #include <signal.h>
  34
  35 struct lock_list {
  36         struct dm_list list;
  37         int lf;
  38         char *res;
  39 };
  40
  41 static struct dm_list _lock_list;
  42 static char _lock_dir[NAME_LEN];
  43 static int _prioritise_write_locks;
  44
  45 static sig_t _oldhandler;
  46 static sigset_t _fullsigset, _intsigset;
  47 static volatile sig_atomic_t _handler_installed;
  48
  49 static void _undo_flock(const char *file, int fd)
  50 {
  51         struct stat buf1, buf2;
  52
  53         log_debug("_undo_flock %s", file);
  54         if (!flock(fd, LOCK_NB | LOCK_EX) &&
  55             !stat(file, &buf1) &&
  56             !fstat(fd, &buf2) &&
  57             is_same_inode(buf1, buf2))
  58                 if (unlink(file))
  59                         log_sys_error("unlink", file);
  60
  61         if (close(fd) < 0)
  62                 log_sys_error("close", file);
  63 }
  64
  65 static int _release_lock(const char *file, int unlock)
  66 {
  67         struct lock_list *ll;
  68         struct dm_list *llh, *llt;
  69
  70         dm_list_iterate_safe(llh, llt, &_lock_list) {
  71                 ll = dm_list_item(llh, struct lock_list);
  72
  73                 if (!file || !strcmp(ll->res, file)) {
  74                         dm_list_del(llh);
  75                         if (unlock) {
  76                                 log_very_verbose("Unlocking %s", ll->res);
  77                                 if (flock(ll->lf, LOCK_NB | LOCK_UN))
  78                                         log_sys_error("flock", ll->res);
  79                         }
  80
  81                         _undo_flock(ll->res, ll->lf);
  82
  83                         dm_free(ll->res);
  84                         dm_free(llh);
  85
  86                         if (file)
  87                                 return 1;
  88                 }
  89         }
  90
  91         return 0;
  92 }
  93
  94 static void _fin_file_locking(void)
  95 {
  96         _release_lock(NULL, 1);
  97 }
  98
  99 static void _reset_file_locking(void)
 100 {
 101         _release_lock(NULL, 0);
 102 }
 103
 104 static void _remove_ctrl_c_handler(void)
 105 {
 106         siginterrupt(SIGINT, 0);
 107         if (!_handler_installed)
 108                 return;
 109
 110         _handler_installed = 0;
 111
 112         sigprocmask(SIG_SETMASK, &_fullsigset, NULL);
 113         if (signal(SIGINT, _oldhandler) == SIG_ERR)
 114                 log_sys_error("signal", "_remove_ctrl_c_handler");
 115 }
 116
 117 static void _trap_ctrl_c(int sig __attribute((unused)))
 118 {
 119         _remove_ctrl_c_handler();
 120         log_error("CTRL-c detected: giving up waiting for lock");
 121 }
 122
 123 static void _install_ctrl_c_handler()
 124 {
 125         _handler_installed = 1;
 126
 127         if ((_oldhandler = signal(SIGINT, _trap_ctrl_c)) == SIG_ERR) {
 128                 _handler_installed = 0;
 129                 return;
 130         }
 131
 132         sigprocmask(SIG_SETMASK, &_intsigset, NULL);
 133         siginterrupt(SIGINT, 1);
 134 }
 135
 136 static int _do_flock(const char *file, int *fd, int operation, uint32_t nonblock)
 137 {
 138         int r = 1;
 139         int old_errno;
 140         struct stat buf1, buf2;
 141
 142         log_debug("_do_flock %s %c%c",
 143                   file, operation == LOCK_EX ? 'W' : 'R', nonblock ? ' ' : 'B');
 144         do {
 145                 if ((*fd > -1) && close(*fd))
 146                         log_sys_error("close", file);
 147
 148                 if ((*fd = open(file, O_CREAT | O_APPEND | O_RDWR, 0777)) < 0) {
 149                         log_sys_error("open", file);
 150                         return 0;
 151                 }
 152
 153                 if (nonblock)
 154                         operation |= LOCK_NB;
 155                 else
 156                         _install_ctrl_c_handler();
 157
 158                 r = flock(*fd, operation);
 159                 old_errno = errno;
 160                 if (!nonblock)
 161                         _remove_ctrl_c_handler();
 162
 163                 if (r) {
 164                         errno = old_errno;
 165                         log_sys_error("flock", file);
 166                         close(*fd);
 167                         return 0;
 168                 }
 169
 170                 if (!stat(file, &buf1) && !fstat(*fd, &buf2) &&
 171                     is_same_inode(buf1, buf2))
 172                         return 1;
 173         } while (!nonblock);
 174
 175         return_0;
 176 }
 177
 178 #define AUX_LOCK_SUFFIX ":aux"
 179
 180 static int _do_write_priority_flock(const char *file, int *fd, int operation, uint32_t nonblock)
 181 {
 182         int r, fd_aux = -1;
 183         char *file_aux = alloca(strlen(file) + sizeof(AUX_LOCK_SUFFIX));
 184
 185         strcpy(file_aux, file);
 186         strcat(file_aux, AUX_LOCK_SUFFIX);
 187
 188         if ((r = _do_flock(file_aux, &fd_aux, LOCK_EX, 0))) {
 189                 if (operation == LOCK_EX) {
 190                         r = _do_flock(file, fd, operation, nonblock);
 191                         _undo_flock(file_aux, fd_aux);
 192                 } else {
 193                         _undo_flock(file_aux, fd_aux);
 194                         r = _do_flock(file, fd, operation, nonblock);
 195                 }
 196         }
 197
 198         return r;
 199 }
 200
 201 static int _lock_file(const char *file, uint32_t flags)
 202 {
 203         int operation;
 204         uint32_t nonblock = flags & LCK_NONBLOCK;
 205         int r;
 206
 207         struct lock_list *ll;
 208         char state;
 209
 210         switch (flags & LCK_TYPE_MASK) {
 211         case LCK_READ:
 212                 operation = LOCK_SH;
 213                 state = 'R';
 214                 break;
 215         case LCK_WRITE:
 216                 operation = LOCK_EX;
 217                 state = 'W';
 218                 break;
 219         case LCK_UNLOCK:
 220                 return _release_lock(file, 1);
 221         default:
 222                 log_error("Unrecognised lock type: %d", flags & LCK_TYPE_MASK);
 223                 return 0;
 224         }
 225
 226         if (!(ll = dm_malloc(sizeof(struct lock_list))))
 227                 return_0;
 228
 229         if (!(ll->res = dm_strdup(file))) {
 230                 dm_free(ll);
 231                 return_0;
 232         }
 233
 234         ll->lf = -1;
 235
 236         log_very_verbose("Locking %s %c%c", ll->res, state,
 237                          nonblock ? ' ' : 'B');
 238
 239         if (_prioritise_write_locks)
 240                 r = _do_write_priority_flock(file, &ll->lf, operation, nonblock);
 241         else
 242                 r = _do_flock(file, &ll->lf, operation, nonblock);
 243
 244         if (r)
 245                 dm_list_add(&_lock_list, &ll->list);
 246         else {
 247                 dm_free(ll->res);
 248                 dm_free(ll);
 249                 stack;
 250         }
 251
 252         return r;
 253 }
 254
 255 static int _file_lock_resource(struct cmd_context *cmd, const char *resource,
 256                                uint32_t flags)
 257 {
 258         char lockfile[PATH_MAX];
 259
 260         switch (flags & LCK_SCOPE_MASK) {
 261         case LCK_VG:
 262                 /* Skip cache refresh for VG_GLOBAL - the caller handles it */
 263                 if (strcmp(resource, VG_GLOBAL))
 264                         lvmcache_drop_metadata(resource);
 265
 266                 /* LCK_CACHE does not require a real lock */
 267                 if (flags & LCK_CACHE)
 268                         break;
 269
 270                 if (*resource == '#')
 271                         dm_snprintf(lockfile, sizeof(lockfile),
 272                                      "%s/P_%s", _lock_dir, resource + 1);
 273                 else
 274                         dm_snprintf(lockfile, sizeof(lockfile),
 275                                      "%s/V_%s", _lock_dir, resource);
 276
 277                 if (!_lock_file(lockfile, flags))
 278                         return_0;
 279                 break;
 280         case LCK_LV:
 281                 switch (flags & LCK_TYPE_MASK) {
 282                 case LCK_UNLOCK:
 283                         log_very_verbose("Unlocking LV %s", resource);
 284                         if (!lv_resume_if_active(cmd, resource))
 285                                 return 0;
 286                         break;
 287                 case LCK_NULL:
 288                         log_very_verbose("Locking LV %s (NL)", resource);
 289                         if (!lv_deactivate(cmd, resource))
 290                                 return 0;
 291                         break;
 292                 case LCK_READ:
 293                         log_very_verbose("Locking LV %s (R)", resource);
 294                         if (!lv_activate_with_filter(cmd, resource, 0))
 295                                 return 0;
 296                         break;
 297                 case LCK_PREAD:
 298                         log_very_verbose("Locking LV %s (PR) - ignored", resource);
 299                         break;
 300                 case LCK_WRITE:
 301                         log_very_verbose("Locking LV %s (W)", resource);
 302                         if (!lv_suspend_if_active(cmd, resource))
 303                                 return 0;
 304                         break;
 305                 case LCK_EXCL:
 306                         log_very_verbose("Locking LV %s (EX)", resource);
 307                         if (!lv_activate_with_filter(cmd, resource, 1))
 308                                 return 0;
 309                         break;
 310                 default:
 311                         break;
 312                 }
 313                 break;
 314         default:
 315                 log_error("Unrecognised lock scope: %d",
 316                           flags & LCK_SCOPE_MASK);
 317                 return 0;
 318         }
 319
 320         return 1;
 321 }
 322
 323 int init_file_locking(struct locking_type *locking, struct cmd_context *cmd)
 324 {
 325         locking->lock_resource = _file_lock_resource;
 326         locking->reset_locking = _reset_file_locking;
 327         locking->fin_locking = _fin_file_locking;
 328         locking->flags = 0;
 329
 330         /* Get lockfile directory from config file */
 331         strncpy(_lock_dir, find_config_tree_str(cmd, "global/locking_dir",
 332                                                 DEFAULT_LOCK_DIR),
 333                 sizeof(_lock_dir));
 334
 335         _prioritise_write_locks =
 336             find_config_tree_bool(cmd, "global/prioritise_write_locks",
 337                                   DEFAULT_PRIORITISE_WRITE_LOCKS);
 338
 339         if (!dm_create_dir(_lock_dir))
 340                 return 0;
 341
 342         /* Trap a read-only file system */
 343         if ((access(_lock_dir, R_OK | W_OK | X_OK) == -1) && (errno == EROFS))
 344                 return 0;
 345
 346         dm_list_init(&_lock_list);
 347
 348         if (sigfillset(&_intsigset) || sigfillset(&_fullsigset)) {
 349                 log_sys_error("sigfillset", "init_file_locking");
 350                 return 0;
 351         }
 352
 353         if (sigdelset(&_intsigset, SIGINT)) {
 354                 log_sys_error("sigdelset", "init_file_locking");
 355                 return 0;
 356         }
 357
 358         return 1;
 359 }