source/locking/brlock.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 3.0
   4    byte range locking code
   5    Updated to handle range splits/merges.
   6
   7    Copyright (C) Andrew Tridgell 1992-2000
   8    Copyright (C) Jeremy Allison 1992-2000
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program; if not, write to the Free Software
  22    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  23 */
  24
  25 /* This module implements a tdb based byte range locking service,
  26    replacing the fcntl() based byte range locking previously
  27    used. This allows us to provide the same semantics as NT */
  28
  29 #include "includes.h"
  30
  31 extern int DEBUGLEVEL;
  32
  33 /* This contains elements that differentiate locks. The smbpid is a
  34    client supplied pid, and is essentially the locking context for
  35    this client */
  36
  37 struct lock_context {
  38         uint16 smbpid;
  39         uint16 tid;
  40         pid_t pid;
  41 };
  42
  43 /* The data in brlock records is an unsorted linear array of these
  44    records.  It is unnecessary to store the count as tdb provides the
  45    size of the record */
  46
  47 struct lock_struct {
  48         struct lock_context context;
  49         br_off start;
  50         br_off size;
  51         int fnum;
  52         enum brl_type lock_type;
  53 };
  54
  55 /* The key used in the brlock database. */
  56
  57 struct lock_key {
  58         SMB_DEV_T device;
  59         SMB_INO_T inode;
  60 };
  61
  62 /* The open brlock.tdb database. */
  63
  64 static TDB_CONTEXT *tdb;
  65
  66 /****************************************************************************
  67  Create a locking key - ensuring zero filled for pad purposes.
  68 ****************************************************************************/
  69
  70 static TDB_DATA locking_key(SMB_DEV_T dev, SMB_INO_T inode)
  71 {
  72         static struct lock_key key;
  73         TDB_DATA kbuf;
  74
  75         memset(&key, '\0', sizeof(key));
  76         key.device = dev;
  77         key.inode = inode;
  78         kbuf.dptr = (char *)&key;
  79         kbuf.dsize = sizeof(key);
  80         return kbuf;
  81 }
  82
  83 /****************************************************************************
  84  See if two locking contexts are equal.
  85 ****************************************************************************/
  86
  87 static BOOL brl_same_context(struct lock_context *ctx1,
  88                              struct lock_context *ctx2)
  89 {
  90         return (ctx1->pid == ctx2->pid) &&
  91                 (ctx1->smbpid == ctx2->smbpid) &&
  92                 (ctx1->tid == ctx2->tid);
  93 }
  94
  95 /****************************************************************************
  96  See if lock2 can be added when lock1 is in place.
  97 ****************************************************************************/
  98
  99 static BOOL brl_conflict(struct lock_struct *lck1,
 100                          struct lock_struct *lck2)
 101 {
 102         if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK)
 103                 return False;
 104
 105         if (brl_same_context(&lck1->context, &lck2->context) &&
 106             lck2->lock_type == READ_LOCK && lck1->fnum == lck2->fnum) return False;
 107
 108         if (lck1->start >= (lck2->start + lck2->size) ||
 109             lck2->start >= (lck1->start + lck1->size)) return False;
 110
 111         return True;
 112 }
 113
 114
 115 /****************************************************************************
 116 delete a record if it is for a dead process
 117 ****************************************************************************/
 118 static int delete_fn(TDB_CONTEXT *ttdb, TDB_DATA kbuf, TDB_DATA dbuf, void *state)
 119 {
 120         struct lock_struct *locks;
 121         int count, i;
 122
 123         tdb_chainlock(tdb, kbuf);
 124
 125         locks = (struct lock_struct *)dbuf.dptr;
 126
 127         count = dbuf.dsize / sizeof(*locks);
 128         for (i=0; i<count; i++) {
 129                 struct lock_struct *lock = &locks[i];
 130
 131                 if (process_exists(lock->context.pid)) continue;
 132
 133                 if (count > 1 && i < count-1) {
 134                         memmove(&locks[i], &locks[i+1],
 135                                 sizeof(*locks)*((count-1) - i));
 136                 }
 137                 count--;
 138                 i--;
 139         }
 140
 141         if (count == 0) {
 142                 tdb_delete(tdb, kbuf);
 143         } else if (count < (dbuf.dsize / sizeof(*locks))) {
 144                 dbuf.dsize = count * sizeof(*locks);
 145                 tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
 146         }
 147
 148         tdb_chainunlock(tdb, kbuf);
 149         return 0;
 150 }
 151
 152 /****************************************************************************
 153  Open up the brlock.tdb database.
 154 ****************************************************************************/
 155 void brl_init(int read_only)
 156 {
 157         if (tdb) return;
 158         tdb = tdb_open(lock_path("brlock.tdb"), 0, TDB_CLEAR_IF_FIRST,
 159                        read_only?O_RDONLY:(O_RDWR|O_CREAT), 0644);
 160         if (!tdb) {
 161                 DEBUG(0,("Failed to open byte range locking database\n"));
 162                 return;
 163         }
 164
 165         /* delete any dead locks */
 166         if (!read_only) {
 167                 tdb_traverse(tdb, delete_fn, NULL);
 168         }
 169 }
 170
 171
 172 /****************************************************************************
 173  Lock a range of bytes.
 174 ****************************************************************************/
 175
 176 BOOL brl_lock(SMB_DEV_T dev, SMB_INO_T ino, int fnum,
 177               uint16 smbpid, pid_t pid, uint16 tid,
 178               br_off start, br_off size,
 179               enum brl_type lock_type)
 180 {
 181         TDB_DATA kbuf, dbuf;
 182         int count, i;
 183         struct lock_struct lock, *locks;
 184
 185         kbuf = locking_key(dev,ino);
 186
 187         dbuf.dptr = NULL;
 188
 189         tdb_chainlock(tdb, kbuf);
 190         dbuf = tdb_fetch(tdb, kbuf);
 191
 192         lock.context.smbpid = smbpid;
 193         lock.context.pid = pid;
 194         lock.context.tid = tid;
 195         lock.start = start;
 196         lock.size = size;
 197         lock.fnum = fnum;
 198         lock.lock_type = lock_type;
 199
 200         if (dbuf.dptr) {
 201                 /* there are existing locks - make sure they don't conflict */
 202                 locks = (struct lock_struct *)dbuf.dptr;
 203                 count = dbuf.dsize / sizeof(*locks);
 204                 for (i=0; i<count; i++) {
 205                         if (brl_conflict(&locks[i], &lock)) {
 206                                 goto fail;
 207                         }
 208                 }
 209         }
 210
 211         /* no conflicts - add it to the list of locks */
 212         dbuf.dptr = Realloc(dbuf.dptr, dbuf.dsize + sizeof(*locks));
 213         if (!dbuf.dptr) goto fail;
 214         memcpy(dbuf.dptr + dbuf.dsize, &lock, sizeof(lock));
 215         dbuf.dsize += sizeof(lock);
 216         tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
 217
 218         free(dbuf.dptr);
 219         tdb_chainunlock(tdb, kbuf);
 220         return True;
 221
 222  fail:
 223         if (dbuf.dptr) free(dbuf.dptr);
 224         tdb_chainunlock(tdb, kbuf);
 225         return False;
 226 }
 227
 228 /****************************************************************************
 229  Unlock a range of bytes.
 230 ****************************************************************************/
 231
 232 BOOL brl_unlock(SMB_DEV_T dev, SMB_INO_T ino, int fnum,
 233                 uint16 smbpid, pid_t pid, uint16 tid,
 234                 br_off start, br_off size)
 235 {
 236         TDB_DATA kbuf, dbuf;
 237         int count, i;
 238         struct lock_struct *locks;
 239         struct lock_context context;
 240
 241         kbuf = locking_key(dev,ino);
 242
 243         dbuf.dptr = NULL;
 244
 245         tdb_chainlock(tdb, kbuf);
 246         dbuf = tdb_fetch(tdb, kbuf);
 247
 248         if (!dbuf.dptr) {
 249                 DEBUG(10,("brl_unlock: tdb_fetch failed !\n"));
 250                 goto fail;
 251         }
 252
 253         context.smbpid = smbpid;
 254         context.pid = pid;
 255         context.tid = tid;
 256
 257         /* there are existing locks - find a match */
 258         locks = (struct lock_struct *)dbuf.dptr;
 259         count = dbuf.dsize / sizeof(*locks);
 260         for (i=0; i<count; i++) {
 261
 262                 struct lock_struct *lock = &locks[i];
 263
 264 #if 0
 265                 /* JRATEST - DEBUGGING INFO */
 266                 if(!brl_same_context(&lock->context, &context)) {
 267                         DEBUG(10,("brl_unlock: Not same context. l_smbpid = %u, l_pid = %u, l_tid = %u: \
 268 smbpid = %u, pid = %u, tid = %u\n",
 269                                 lock->context.smbpid, lock->context.pid, lock->context.tid,
 270                                 context.smbpid, context.pid, context.tid ));
 271
 272                 }
 273                 /* JRATEST */
 274 #endif
 275
 276                 if (brl_same_context(&lock->context, &context) &&
 277                     lock->fnum == fnum &&
 278                     lock->start == start &&
 279                     lock->size == size) {
 280                         /* found it - delete it */
 281                         if (count == 1) {
 282                                 tdb_delete(tdb, kbuf);
 283                         } else {
 284                                 if (i < count-1) {
 285                                         memmove(&locks[i], &locks[i+1],
 286                                                 sizeof(*locks)*((count-1) - i));
 287                                 }
 288                                 dbuf.dsize -= sizeof(*locks);
 289                                 tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
 290                         }
 291
 292                         free(dbuf.dptr);
 293                         tdb_chainunlock(tdb, kbuf);
 294                         return True;
 295                 }
 296         }
 297
 298         /* we didn't find it */
 299
 300  fail:
 301         if (dbuf.dptr) free(dbuf.dptr);
 302         tdb_chainunlock(tdb, kbuf);
 303         return False;
 304 }
 305
 306 /****************************************************************************
 307  Test if we could add a lock if we wanted to.
 308 ****************************************************************************/
 309
 310 BOOL brl_locktest(SMB_DEV_T dev, SMB_INO_T ino, int fnum,
 311                   uint16 smbpid, pid_t pid, uint16 tid,
 312                   br_off start, br_off size,
 313                   enum brl_type lock_type)
 314 {
 315         TDB_DATA kbuf, dbuf;
 316         int count, i;
 317         struct lock_struct lock, *locks;
 318
 319         kbuf = locking_key(dev,ino);
 320
 321         dbuf.dptr = NULL;
 322
 323         tdb_chainlock(tdb, kbuf);
 324         dbuf = tdb_fetch(tdb, kbuf);
 325
 326         lock.context.smbpid = smbpid;
 327         lock.context.pid = pid;
 328         lock.context.tid = tid;
 329         lock.start = start;
 330         lock.size = size;
 331         lock.fnum = fnum;
 332         lock.lock_type = lock_type;
 333
 334         if (dbuf.dptr) {
 335                 /* there are existing locks - make sure they don't conflict */
 336                 locks = (struct lock_struct *)dbuf.dptr;
 337                 count = dbuf.dsize / sizeof(*locks);
 338                 for (i=0; i<count; i++) {
 339                         if (brl_conflict(&locks[i], &lock)) {
 340                                 goto fail;
 341                         }
 342                 }
 343         }
 344
 345         /* no conflicts - we could have added it */
 346         free(dbuf.dptr);
 347         tdb_chainunlock(tdb, kbuf);
 348         return True;
 349
 350  fail:
 351         if (dbuf.dptr) free(dbuf.dptr);
 352         tdb_chainunlock(tdb, kbuf);
 353         return False;
 354 }
 355
 356 /****************************************************************************
 357  Remove any locks associated with a open file.
 358 ****************************************************************************/
 359
 360 void brl_close(SMB_DEV_T dev, SMB_INO_T ino, pid_t pid, int tid, int fnum)
 361 {
 362         TDB_DATA kbuf, dbuf;
 363         int count, i, dcount=0;
 364         struct lock_struct *locks;
 365
 366         kbuf = locking_key(dev,ino);
 367
 368         dbuf.dptr = NULL;
 369
 370         tdb_chainlock(tdb, kbuf);
 371         dbuf = tdb_fetch(tdb, kbuf);
 372
 373         if (!dbuf.dptr) goto fail;
 374
 375         /* there are existing locks - remove any for this fnum */
 376         locks = (struct lock_struct *)dbuf.dptr;
 377         count = dbuf.dsize / sizeof(*locks);
 378         for (i=0; i<count; i++) {
 379                 struct lock_struct *lock = &locks[i];
 380
 381                 if (lock->context.tid == tid &&
 382                     lock->context.pid == pid &&
 383                     lock->fnum == fnum) {
 384                         /* found it - delete it */
 385                         if (count > 1 && i < count-1) {
 386                                 memmove(&locks[i], &locks[i+1],
 387                                         sizeof(*locks)*((count-1) - i));
 388                         }
 389                         count--;
 390                         i--;
 391                         dcount++;
 392                 }
 393         }
 394
 395         if (count == 0) {
 396                 tdb_delete(tdb, kbuf);
 397         } else if (count < (dbuf.dsize / sizeof(*locks))) {
 398                 dbuf.dsize -= dcount * sizeof(*locks);
 399                 tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
 400         }
 401
 402         /* we didn't find it */
 403  fail:
 404         if (dbuf.dptr) free(dbuf.dptr);
 405         tdb_chainunlock(tdb, kbuf);
 406 }
 407
 408 /****************************************************************************
 409  Traverse the whole database with this function, calling traverse_callback
 410  on each lock.
 411 ****************************************************************************/
 412
 413 static int traverse_fn(TDB_CONTEXT *ttdb, TDB_DATA kbuf, TDB_DATA dbuf, void *state)
 414 {
 415         struct lock_struct *locks;
 416         struct lock_key *key;
 417         int i;
 418
 419         BRLOCK_FN(traverse_callback) = (BRLOCK_FN_CAST())state;
 420
 421         locks = (struct lock_struct *)dbuf.dptr;
 422         key = (struct lock_key *)kbuf.dptr;
 423
 424         for (i=0;i<dbuf.dsize/sizeof(*locks);i++) {
 425                 traverse_callback(key->device, key->inode,
 426                                   locks[i].context.pid,
 427                                   locks[i].lock_type,
 428                                   locks[i].start,
 429                                   locks[i].size);
 430         }
 431         return 0;
 432 }
 433
 434 /*******************************************************************
 435  Call the specified function on each lock in the database.
 436 ********************************************************************/
 437
 438 int brl_forall(BRLOCK_FN(fn))
 439 {
 440         if (!tdb) return 0;
 441         return tdb_traverse(tdb, traverse_fn, (void *)fn);
 442 }