source/locking/shmem.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    Shared memory functions
   5    Copyright (C) Erik Devriendt 1996-1997
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20
  21 */
  22
  23 #include "includes.h"
  24
  25
  26 #ifdef FAST_SHARE_MODES
  27
  28
  29 extern int DEBUGLEVEL;
  30
  31
  32 #define SMB_SHM_MAGIC 0x53484100
  33 /* = "SHM" in hex */
  34
  35 #define SMB_SHM_VERSION 2
  36
  37 /* we need world read for smbstatus to function correctly */
  38 #ifdef SECURE_SHARE_MODES
  39 #define SHM_FILE_MODE 0600
  40 #else
  41 #define SHM_FILE_MODE 0644
  42 #endif
  43
  44 #define SHMEM_HASH_SIZE 113
  45
  46
  47 /* WARNING : offsets are used because mmap() does not guarantee that all processes have the
  48    shared memory mapped to the same address */
  49
  50 struct SmbShmHeader
  51 {
  52    int smb_shm_magic;
  53    int smb_shm_version;
  54    int total_size;      /* in bytes */
  55    BOOL consistent;
  56    int first_free_off;
  57    int userdef_off;    /* a userdefined offset. can be used to store root of tree or list */
  58    struct {             /* a cell is a range of bytes of sizeof(struct SmbShmBlockDesc) size */
  59       int cells_free;
  60       int cells_used;
  61       int cells_system; /* number of cells used as allocated block descriptors */
  62    } statistics;
  63 };
  64
  65 #define SMB_SHM_NOT_FREE_OFF (-1)
  66 struct SmbShmBlockDesc
  67 {
  68    int next;    /* offset of next block in the free list or SMB_SHM_NOT_FREE_OFF when block in use  */
  69    int          size;   /* user size in BlockDescSize units */
  70 };
  71
  72 #define EOList_Addr     (struct SmbShmBlockDesc *)( 0 )
  73 #define EOList_Off      (NULL_OFFSET)
  74
  75 #define CellSize        sizeof(struct SmbShmBlockDesc)
  76
  77 /* HeaderSize aligned on 8 byte boundary */
  78 #define AlignedHeaderSize       ((sizeof(struct SmbShmHeader)+7) & ~7)
  79
  80 static int  smb_shm_fd = -1;
  81 static pstring smb_shm_processreg_name = "";
  82
  83 static struct SmbShmHeader *smb_shm_header_p = (struct SmbShmHeader *)0;
  84 static int smb_shm_times_locked = 0;
  85
  86 static BOOL smb_shm_initialize_called = False;
  87
  88 static int read_only;
  89
  90 static BOOL smb_shm_global_lock(void)
  91 {
  92    if (smb_shm_fd < 0)
  93    {
  94       DEBUG(0,("ERROR smb_shm_global_lock : bad smb_shm_fd (%d)\n",smb_shm_fd));
  95       return False;
  96    }
  97
  98    smb_shm_times_locked++;
  99
 100    if(smb_shm_times_locked > 1)
 101    {
 102       DEBUG(5,("smb_shm_global_lock : locked %d times\n",smb_shm_times_locked));
 103       return True;
 104    }
 105
 106    if (read_only)
 107            return True;
 108
 109    /* Do an exclusive wait lock on the first byte of the file */
 110    if (fcntl_lock(smb_shm_fd, F_SETLKW, 0, 1, F_WRLCK) == False)
 111    {
 112       DEBUG(0,("ERROR smb_shm_global_lock : fcntl_lock failed with code %s\n",strerror(errno)));
 113       smb_shm_times_locked--;
 114       return False;
 115    }
 116
 117    return True;
 118
 119 }
 120
 121 static BOOL smb_shm_global_unlock(void)
 122 {
 123    if (smb_shm_fd < 0)
 124    {
 125       DEBUG(0,("ERROR smb_shm_global_unlock : bad smb_shm_fd (%d)\n",smb_shm_fd));
 126       return False;
 127    }
 128
 129    if(smb_shm_times_locked == 0)
 130    {
 131       DEBUG(0,("ERROR smb_shm_global_unlock : shmem not locked\n",smb_shm_fd));
 132       return False;
 133    }
 134
 135    smb_shm_times_locked--;
 136
 137    if(smb_shm_times_locked > 0)
 138    {
 139       DEBUG(5,("smb_shm_global_unlock : still locked %d times\n",smb_shm_times_locked));
 140       return True;
 141    }
 142
 143    if (read_only)
 144            return True;
 145
 146    /* Do a wait unlock on the first byte of the file */
 147    if (fcntl_lock(smb_shm_fd, F_SETLKW, 0, 1, F_UNLCK) == False)
 148    {
 149       DEBUG(0,("ERROR smb_shm_global_unlock : fcntl_lock failed with code %s\n",strerror(errno)));
 150       smb_shm_times_locked++;
 151       return False;
 152    }
 153
 154    return True;
 155
 156 }
 157
 158
 159 static void *smb_shm_offset2addr(int offset)
 160 {
 161    if (offset == NULL_OFFSET )
 162       return (void *)(0);
 163
 164    if (!smb_shm_header_p)
 165       return (void *)(0);
 166
 167    return (void *)((char *)smb_shm_header_p + offset );
 168 }
 169
 170 static int smb_shm_addr2offset(void *addr)
 171 {
 172    if (!addr)
 173       return NULL_OFFSET;
 174
 175    if (!smb_shm_header_p)
 176       return NULL_OFFSET;
 177
 178    return (int)((char *)addr - (char *)smb_shm_header_p);
 179 }
 180
 181
 182
 183 static int smb_shm_alloc(int size)
 184 {
 185    unsigned num_cells ;
 186    struct SmbShmBlockDesc *scanner_p;
 187    struct SmbShmBlockDesc *prev_p;
 188    struct SmbShmBlockDesc *new_p;
 189    int result_offset;
 190
 191
 192    if( !smb_shm_header_p )
 193    {
 194       /* not mapped yet */
 195       DEBUG(0,("ERROR smb_shm_alloc : shmem not mapped\n"));
 196       return NULL_OFFSET;
 197    }
 198
 199    smb_shm_global_lock();
 200
 201    if( !smb_shm_header_p->consistent)
 202    {
 203       DEBUG(0,("ERROR smb_shm_alloc : shmem not consistent\n"));
 204       smb_shm_global_unlock();
 205       return NULL_OFFSET;
 206    }
 207
 208
 209    /* calculate the number of cells */
 210    num_cells = (size + CellSize -1) / CellSize;
 211
 212    /* set start of scan */
 213    prev_p = (struct SmbShmBlockDesc *)smb_shm_offset2addr(smb_shm_header_p->first_free_off);
 214    scanner_p =  prev_p ;
 215
 216    /* scan the free list to find a matching free space */
 217    while ( ( scanner_p != EOList_Addr ) && ( scanner_p->size < num_cells ) )
 218    {
 219       prev_p = scanner_p;
 220       scanner_p = (struct SmbShmBlockDesc *)smb_shm_offset2addr(scanner_p->next);
 221    }
 222
 223    /* at this point scanner point to a block header or to the end of the list */
 224    if ( scanner_p == EOList_Addr )
 225    {
 226       DEBUG(0,("ERROR smb_shm_alloc : alloc of %d bytes failed, no free space found\n",size));
 227       smb_shm_global_unlock();
 228       return (NULL_OFFSET);
 229    }
 230
 231    /* going to modify shared mem */
 232    smb_shm_header_p->consistent = False;
 233
 234    /* if we found a good one : scanner == the good one */
 235    if ( scanner_p->size <= num_cells + 2 )
 236    {
 237       /* there is no use in making a new one, it will be too small anyway
 238       *  we will link out scanner
 239       */
 240       if ( prev_p == scanner_p )
 241       {
 242          smb_shm_header_p->first_free_off = scanner_p->next ;
 243       }
 244       else
 245       {
 246          prev_p->next = scanner_p->next ;
 247       }
 248       smb_shm_header_p->statistics.cells_free -= scanner_p->size;
 249       smb_shm_header_p->statistics.cells_used += scanner_p->size;
 250    }
 251    else
 252    {
 253       /* Make a new one */
 254       new_p = scanner_p + 1 + num_cells;
 255       new_p->size = scanner_p->size - num_cells - 1;
 256       new_p->next = scanner_p->next;
 257       scanner_p->size = num_cells;
 258       scanner_p->next = smb_shm_addr2offset(new_p);
 259
 260       if ( prev_p       != scanner_p )
 261       {
 262          prev_p->next      = smb_shm_addr2offset(new_p)  ;
 263       }
 264       else
 265       {
 266          smb_shm_header_p->first_free_off = smb_shm_addr2offset(new_p)  ;
 267       }
 268       smb_shm_header_p->statistics.cells_free -= num_cells+1;
 269       smb_shm_header_p->statistics.cells_used += num_cells;
 270       smb_shm_header_p->statistics.cells_system += 1;
 271    }
 272
 273    result_offset = smb_shm_addr2offset( &(scanner_p[1]) );
 274    scanner_p->next =    SMB_SHM_NOT_FREE_OFF ;
 275
 276    /* end modification of shared mem */
 277    smb_shm_header_p->consistent = True;
 278
 279    DEBUG(6,("smb_shm_alloc : request for %d bytes, allocated %d bytes at offset %d\n",size,scanner_p->size*CellSize,result_offset ));
 280
 281    smb_shm_global_unlock();
 282    return ( result_offset );
 283 }
 284
 285
 286
 287
 288 /*
 289  * Function to create the hash table for the share mode entries. Called
 290  * when smb shared memory is global locked.
 291  */
 292 static BOOL smb_shm_create_hash_table( unsigned int size )
 293 {
 294   size *= sizeof(int);
 295
 296   smb_shm_global_lock();
 297   smb_shm_header_p->userdef_off = smb_shm_alloc( size );
 298
 299   if(smb_shm_header_p->userdef_off == NULL_OFFSET)
 300     {
 301       DEBUG(0,("smb_shm_create_hash_table: Failed to create hash table of size %d\n",size));
 302       smb_shm_global_unlock();
 303       return False;
 304     }
 305
 306   /* Clear hash buckets. */
 307   memset( smb_shm_offset2addr(smb_shm_header_p->userdef_off), '\0', size);
 308   smb_shm_global_unlock();
 309   return True;
 310 }
 311
 312 static BOOL smb_shm_register_process(char *processreg_file, pid_t pid, BOOL *other_processes)
 313 {
 314    int smb_shm_processes_fd = -1;
 315    int nb_read;
 316    pid_t other_pid;
 317    int seek_back = -((int)sizeof(other_pid));
 318    int free_slot = -1;
 319    int erased_slot;
 320
 321    smb_shm_processes_fd = open(processreg_file,
 322                                read_only?O_RDONLY:(O_RDWR|O_CREAT),
 323                                SHM_FILE_MODE);
 324
 325    if ( smb_shm_processes_fd < 0 )
 326    {
 327       DEBUG(0,("ERROR smb_shm_register_process : processreg_file open failed with code %s\n",strerror(errno)));
 328       return False;
 329    }
 330
 331    *other_processes = False;
 332
 333    while ((nb_read = read(smb_shm_processes_fd, &other_pid, sizeof(other_pid))) > 0)
 334    {
 335       if(other_pid)
 336       {
 337          if(process_exists(other_pid))
 338             *other_processes = True;
 339          else
 340          {
 341             /* erase old pid */
 342             DEBUG(5,("smb_shm_register_process : erasing stale record for pid %d (seek_back = %d)\n",
 343                       other_pid, seek_back));
 344             other_pid = (pid_t)0;
 345             erased_slot = lseek(smb_shm_processes_fd, seek_back, SEEK_CUR);
 346             write(smb_shm_processes_fd, &other_pid, sizeof(other_pid));
 347             if(free_slot < 0)
 348                free_slot = erased_slot;
 349          }
 350       }
 351       else
 352          if(free_slot < 0)
 353             free_slot = lseek(smb_shm_processes_fd, seek_back, SEEK_CUR);
 354    }
 355    if (nb_read < 0)
 356    {
 357       DEBUG(0,("ERROR smb_shm_register_process : processreg_file read failed with code %s\n",strerror(errno)));
 358       close(smb_shm_processes_fd);
 359       return False;
 360    }
 361
 362    if(free_slot < 0)
 363       free_slot = lseek(smb_shm_processes_fd, 0, SEEK_END);
 364
 365    DEBUG(5,("smb_shm_register_process : writing record for pid %d at offset %d\n",pid,free_slot));
 366    lseek(smb_shm_processes_fd, free_slot, SEEK_SET);
 367    if(write(smb_shm_processes_fd, &pid, sizeof(pid)) < 0)
 368    {
 369       DEBUG(0,("ERROR smb_shm_register_process : processreg_file write failed with code %s\n",strerror(errno)));
 370       close(smb_shm_processes_fd);
 371       return False;
 372    }
 373
 374    close(smb_shm_processes_fd);
 375
 376    return True;
 377 }
 378
 379 static BOOL smb_shm_unregister_process(char *processreg_file, pid_t pid)
 380 {
 381    int smb_shm_processes_fd = -1;
 382    int nb_read;
 383    pid_t other_pid;
 384    int seek_back = -((int)sizeof(other_pid));
 385    int erased_slot;
 386    BOOL found = False;
 387
 388
 389    smb_shm_processes_fd = open(processreg_file, O_RDWR);
 390    if ( smb_shm_processes_fd < 0 )
 391    {
 392       DEBUG(0,("ERROR smb_shm_unregister_process : processreg_file open failed with code %s\n",strerror(errno)));
 393       return False;
 394    }
 395
 396    while ((nb_read = read(smb_shm_processes_fd, &other_pid, sizeof(other_pid))) > 0)
 397    {
 398       DEBUG(5,("smb_shm_unregister_process : read record for pid %d\n",other_pid));
 399       if(other_pid == pid)
 400       {
 401          /* erase pid */
 402          DEBUG(5,("smb_shm_unregister_process : erasing record for pid %d (seek_val = %d)\n",
 403                      other_pid, seek_back));
 404          other_pid = (pid_t)0;
 405          erased_slot = lseek(smb_shm_processes_fd, seek_back, SEEK_CUR);
 406          if(write(smb_shm_processes_fd, &other_pid, sizeof(other_pid)) < 0)
 407          {
 408             DEBUG(0,("ERROR smb_shm_unregister_process : processreg_file write failed with code %s\n",strerror(errno)));
 409             close(smb_shm_processes_fd);
 410             return False;
 411          }
 412
 413          found = True;
 414          break;
 415       }
 416    }
 417    if (nb_read < 0)
 418    {
 419       DEBUG(0,("ERROR smb_shm_unregister_process : processreg_file read failed with code %s\n",strerror(errno)));
 420       close(smb_shm_processes_fd);
 421       return False;
 422    }
 423
 424    if(!found)
 425    {
 426       DEBUG(0,("ERROR smb_shm_unregister_process : couldn't find pid %d in file %s\n",pid,processreg_file));
 427       close(smb_shm_processes_fd);
 428       return False;
 429    }
 430
 431
 432    close(smb_shm_processes_fd);
 433
 434    return True;
 435 }
 436
 437
 438 static BOOL smb_shm_validate_header(int size)
 439 {
 440    if( !smb_shm_header_p )
 441    {
 442       /* not mapped yet */
 443       DEBUG(0,("ERROR smb_shm_validate_header : shmem not mapped\n"));
 444       return False;
 445    }
 446
 447    if(smb_shm_header_p->smb_shm_magic != SMB_SHM_MAGIC)
 448    {
 449       DEBUG(0,("ERROR smb_shm_validate_header : bad magic\n"));
 450       return False;
 451    }
 452    if(smb_shm_header_p->smb_shm_version != SMB_SHM_VERSION)
 453    {
 454       DEBUG(0,("ERROR smb_shm_validate_header : bad version %X\n",smb_shm_header_p->smb_shm_version));
 455       return False;
 456    }
 457
 458    if(smb_shm_header_p->total_size != size)
 459    {
 460       DEBUG(0,("ERROR smb_shm_validate_header : shmem size mismatch (old = %d, new = %d)\n",smb_shm_header_p->total_size,size));
 461       return False;
 462    }
 463
 464    if(!smb_shm_header_p->consistent)
 465    {
 466       DEBUG(0,("ERROR smb_shm_validate_header : shmem not consistent\n"));
 467       return False;
 468    }
 469    return True;
 470 }
 471
 472 static BOOL smb_shm_initialize(int size)
 473 {
 474    struct SmbShmBlockDesc * first_free_block_p;
 475
 476    DEBUG(5,("smb_shm_initialize : initializing shmem file of size %d\n",size));
 477
 478    if( !smb_shm_header_p )
 479    {
 480       /* not mapped yet */
 481       DEBUG(0,("ERROR smb_shm_initialize : shmem not mapped\n"));
 482       return False;
 483    }
 484
 485    smb_shm_header_p->smb_shm_magic = SMB_SHM_MAGIC;
 486    smb_shm_header_p->smb_shm_version = SMB_SHM_VERSION;
 487    smb_shm_header_p->total_size = size;
 488    smb_shm_header_p->first_free_off = AlignedHeaderSize;
 489    smb_shm_header_p->userdef_off = NULL_OFFSET;
 490
 491    first_free_block_p = (struct SmbShmBlockDesc *)smb_shm_offset2addr(smb_shm_header_p->first_free_off);
 492    first_free_block_p->next = EOList_Off;
 493    first_free_block_p->size = ( size - AlignedHeaderSize - CellSize ) / CellSize ;
 494
 495    smb_shm_header_p->statistics.cells_free = first_free_block_p->size;
 496    smb_shm_header_p->statistics.cells_used = 0;
 497    smb_shm_header_p->statistics.cells_system = 1;
 498
 499    smb_shm_header_p->consistent = True;
 500
 501    smb_shm_initialize_called = True;
 502
 503    return True;
 504 }
 505
 506 static void smb_shm_solve_neighbors(struct SmbShmBlockDesc *head_p )
 507 {
 508    struct SmbShmBlockDesc *next_p;
 509
 510    /* Check if head_p and head_p->next are neighbors and if so join them */
 511    if ( head_p == EOList_Addr ) return ;
 512    if ( head_p->next == EOList_Off ) return ;
 513
 514    next_p = (struct SmbShmBlockDesc *)smb_shm_offset2addr(head_p->next);
 515    if ( ( head_p + head_p->size + 1 ) == next_p)
 516    {
 517       head_p->size += next_p->size +1 ; /* adapt size */
 518       head_p->next = next_p->next         ; /* link out */
 519
 520       smb_shm_header_p->statistics.cells_free += 1;
 521       smb_shm_header_p->statistics.cells_system -= 1;
 522    }
 523 }
 524
 525
 526
 527 static BOOL smb_shm_close( void )
 528 {
 529
 530    if(smb_shm_initialize_called == False)
 531      return True;
 532
 533    DEBUG(5,("smb_shm_close\n"));
 534    if(smb_shm_times_locked > 0)
 535       DEBUG(0,("WARNING smb_shm_close : shmem was still locked %d times\n",smb_shm_times_locked));;
 536    if ((smb_shm_header_p != NULL) &&
 537               (munmap((caddr_t)smb_shm_header_p, smb_shm_header_p->total_size) < 0))
 538    {
 539       DEBUG(0,("ERROR smb_shm_close : munmap failed with code %s\n",strerror(errno)));
 540    }
 541
 542    smb_shm_global_lock();
 543    DEBUG(5,("calling smb_shm_unregister_process(%s, %d)\n", smb_shm_processreg_name, getpid()));
 544    smb_shm_unregister_process(smb_shm_processreg_name, getpid());
 545    smb_shm_global_unlock();
 546
 547    close(smb_shm_fd);
 548
 549    smb_shm_fd = -1;
 550    smb_shm_processreg_name[0] = '\0';
 551
 552    smb_shm_header_p = (struct SmbShmHeader *)0;
 553    smb_shm_times_locked = 0;
 554
 555    return True;
 556 }
 557
 558
 559 static BOOL smb_shm_free(int offset)
 560 {
 561    struct SmbShmBlockDesc *header_p  ; /*       pointer to header of block to free */
 562    struct SmbShmBlockDesc *scanner_p ; /*       used to scan the list                      */
 563    struct SmbShmBlockDesc *prev_p          ; /* holds previous in the list                 */
 564
 565    if( !smb_shm_header_p )
 566    {
 567       /* not mapped yet */
 568       DEBUG(0,("ERROR smb_shm_free : shmem not mapped\n"));
 569       return False;
 570    }
 571
 572    smb_shm_global_lock();
 573
 574    if( !smb_shm_header_p->consistent)
 575    {
 576       DEBUG(0,("ERROR smb_shm_free : shmem not consistent\n"));
 577       smb_shm_global_unlock();
 578       return False;
 579    }
 580
 581    header_p = ( (struct SmbShmBlockDesc *)smb_shm_offset2addr(offset) - 1); /* make pointer to header of block */
 582
 583    if (header_p->next != SMB_SHM_NOT_FREE_OFF)
 584    {
 585       DEBUG(0,("ERROR smb_shm_free : bad offset (%d)\n",offset));
 586       smb_shm_global_unlock();
 587       return False;
 588    }
 589
 590    /* find a place in the free_list to put the header in */
 591
 592    /* set scanner and previous pointer to start of list */
 593    prev_p = (struct SmbShmBlockDesc *)smb_shm_offset2addr(smb_shm_header_p->first_free_off);
 594    scanner_p = prev_p ;
 595
 596    while ( ( scanner_p != EOList_Addr) && (scanner_p < header_p) ) /* while we didn't scan past its position */
 597    {
 598       prev_p = scanner_p ;
 599       scanner_p = (struct SmbShmBlockDesc *)smb_shm_offset2addr(scanner_p->next);
 600    }
 601
 602    smb_shm_header_p->consistent = False;
 603
 604    DEBUG(6,("smb_shm_free : freeing %d bytes at offset %d\n",header_p->size*CellSize,offset));
 605
 606    if ( scanner_p == prev_p )
 607    {
 608       smb_shm_header_p->statistics.cells_free += header_p->size;
 609       smb_shm_header_p->statistics.cells_used -= header_p->size;
 610
 611       /* we must free it at the beginning of the list */
 612       smb_shm_header_p->first_free_off = smb_shm_addr2offset(header_p);                                          /*     set     the free_list_pointer to this block_header */
 613
 614       /* scanner is the one that was first in the list */
 615       header_p->next = smb_shm_addr2offset(scanner_p);
 616       smb_shm_solve_neighbors( header_p ); /* if neighbors then link them */
 617
 618       smb_shm_header_p->consistent = True;
 619       smb_shm_global_unlock();
 620       return True;
 621    }
 622    else
 623    {
 624       smb_shm_header_p->statistics.cells_free += header_p->size;
 625       smb_shm_header_p->statistics.cells_used -= header_p->size;
 626
 627       prev_p->next = smb_shm_addr2offset(header_p);
 628       header_p->next = smb_shm_addr2offset(scanner_p);
 629       smb_shm_solve_neighbors(header_p) ;
 630       smb_shm_solve_neighbors(prev_p) ;
 631
 632       smb_shm_header_p->consistent = True;
 633       smb_shm_global_unlock();
 634       return True;
 635    }
 636 }
 637
 638 static int smb_shm_get_userdef_off(void)
 639 {
 640    if (!smb_shm_header_p)
 641       return NULL_OFFSET;
 642    else
 643       return smb_shm_header_p->userdef_off;
 644 }
 645
 646 /*******************************************************************
 647   Lock a particular hash bucket entry.
 648   ******************************************************************/
 649 static BOOL smb_shm_lock_hash_entry( unsigned int entry)
 650 {
 651   int start = (smb_shm_header_p->userdef_off + (entry * sizeof(int)));
 652
 653   if (smb_shm_fd < 0)
 654     {
 655       DEBUG(0,("ERROR smb_shm_lock_hash_entry : bad smb_shm_fd (%d)\n",smb_shm_fd));
 656       return False;
 657     }
 658
 659   /* Do an exclusive wait lock on the 4 byte region mapping into this entry  */
 660   if (fcntl_lock(smb_shm_fd, F_SETLKW, start, sizeof(int), F_WRLCK) == False)
 661     {
 662       DEBUG(0,("ERROR smb_shm_lock_hash_entry : fcntl_lock failed with code %s\n",strerror(errno)));
 663       return False;
 664     }
 665
 666   DEBUG(9,("smb_shm_lock_hash_entry: locked hash bucket %d\n", entry));
 667   return True;
 668 }
 669
 670 /*******************************************************************
 671   Unlock a particular hash bucket entry.
 672   ******************************************************************/
 673 static BOOL smb_shm_unlock_hash_entry( unsigned int entry )
 674 {
 675   int start = (smb_shm_header_p->userdef_off + (entry * sizeof(int)));
 676
 677   if (smb_shm_fd < 0)
 678     {
 679       DEBUG(0,("ERROR smb_shm_unlock_hash_entry : bad smb_shm_fd (%d)\n",smb_shm_fd));
 680       return False;
 681     }
 682
 683   /* Do a wait lock on the 4 byte region mapping into this entry  */
 684   if (fcntl_lock(smb_shm_fd, F_SETLKW, start, sizeof(int), F_UNLCK) == False)
 685     {
 686       DEBUG(0,("ERROR smb_shm_unlock_hash_entry : fcntl_lock failed with code %s\n",strerror(errno)));
 687       return False;
 688     }
 689
 690   DEBUG(9,("smb_shm_unlock_hash_entry: unlocked hash bucket %d\n", entry));
 691   return True;
 692 }
 693
 694 /*******************************************************************
 695   Gather statistics on shared memory usage.
 696   ******************************************************************/
 697 static BOOL smb_shm_get_usage(int *bytes_free,
 698                    int *bytes_used,
 699                    int *bytes_overhead)
 700 {
 701    if( !smb_shm_header_p )
 702    {
 703       /* not mapped yet */
 704       DEBUG(0,("ERROR smb_shm_free : shmem not mapped\n"));
 705       return False;
 706    }
 707    *bytes_free = smb_shm_header_p->statistics.cells_free * CellSize;
 708    *bytes_used = smb_shm_header_p->statistics.cells_used * CellSize;
 709    *bytes_overhead = smb_shm_header_p->statistics.cells_system * CellSize + AlignedHeaderSize;
 710
 711    return True;
 712 }
 713
 714 /*******************************************************************
 715 hash a number into a hash_entry
 716   ******************************************************************/
 717 static unsigned smb_shm_hash_size(void)
 718 {
 719         return SHMEM_HASH_SIZE;
 720 }
 721
 722 static struct shmem_ops shmops = {
 723         smb_shm_close,
 724         smb_shm_alloc,
 725         smb_shm_free,
 726         smb_shm_get_userdef_off,
 727         smb_shm_offset2addr,
 728         smb_shm_addr2offset,
 729         smb_shm_lock_hash_entry,
 730         smb_shm_unlock_hash_entry,
 731         smb_shm_get_usage,
 732         smb_shm_hash_size,
 733 };
 734
 735 /*******************************************************************
 736   open the shared memory
 737   ******************************************************************/
 738 struct shmem_ops *smb_shm_open(int ronly)
 739 {
 740         pstring file_name;
 741         int filesize;
 742         BOOL created_new = False;
 743         BOOL other_processes = True;
 744         int size = lp_shmem_size();
 745
 746         read_only = ronly;
 747
 748         pstrcpy(file_name,lp_lockdir());
 749         if (!directory_exist(file_name,NULL)) {
 750                 if (read_only) return NULL;
 751                 mkdir(file_name,0755);
 752         }
 753         trim_string(file_name,"","/");
 754         if (!*file_name) return(False);
 755         strcat(file_name, "/SHARE_MEM_FILE");
 756
 757    DEBUG(5,("smb_shm_open : using shmem file %s to be of size %d\n",file_name,size));
 758
 759    smb_shm_fd = open(file_name, read_only?O_RDONLY:(O_RDWR|O_CREAT),
 760                      SHM_FILE_MODE);
 761
 762    if ( smb_shm_fd < 0 )
 763    {
 764       DEBUG(0,("ERROR smb_shm_open : open failed with code %s\n",strerror(errno)));
 765       return NULL;
 766    }
 767
 768    if (!smb_shm_global_lock())
 769    {
 770       DEBUG(0,("ERROR smb_shm_open : can't do smb_shm_global_lock\n"));
 771       return NULL;
 772    }
 773
 774    if( (filesize = lseek(smb_shm_fd, 0, SEEK_END)) < 0)
 775    {
 776       DEBUG(0,("ERROR smb_shm_open : lseek failed with code %s\n",strerror(errno)));
 777       smb_shm_global_unlock();
 778       close(smb_shm_fd);
 779       return NULL;
 780    }
 781
 782    /* return the file offset to 0 to save on later seeks */
 783    lseek(smb_shm_fd,0,SEEK_SET);
 784
 785    if (filesize == 0)
 786    {
 787       /* we just created a new one */
 788       created_new = True;
 789    }
 790
 791    /* to find out if some other process is already mapping the file,
 792       we use a registration file containing the processids of the file mapping processes
 793       */
 794
 795    /* construct processreg file name */
 796    strcpy(smb_shm_processreg_name, file_name);
 797    strcat(smb_shm_processreg_name, ".processes");
 798
 799    if (!read_only &&
 800        !smb_shm_register_process(smb_shm_processreg_name, getpid(), &other_processes))
 801    {
 802       smb_shm_global_unlock();
 803       close(smb_shm_fd);
 804       return NULL;
 805    }
 806
 807    if (!read_only && (created_new || !other_processes))
 808    {
 809       /* we just created a new one, or are the first opener, lets set it size */
 810       if( ftruncate(smb_shm_fd, size) <0)
 811       {
 812          DEBUG(0,("ERROR smb_shm_open : ftruncate failed with code %s\n",strerror(errno)));
 813          smb_shm_unregister_process(smb_shm_processreg_name, getpid());
 814          smb_shm_global_unlock();
 815          close(smb_shm_fd);
 816          return NULL;
 817       }
 818
 819       /* paranoia */
 820       lseek(smb_shm_fd,0,SEEK_SET);
 821
 822       filesize = size;
 823    }
 824
 825    if (size != filesize )
 826    {
 827       /* the existing file has a different size and we are not the first opener.
 828          Since another process is still using it, we will use the file size */
 829       DEBUG(0,("WARNING smb_shm_open : filesize (%d) != expected size (%d), using filesize\n",filesize,size));
 830       size = filesize;
 831    }
 832
 833    smb_shm_header_p = (struct SmbShmHeader *)mmap(NULL, size,
 834                                                   read_only?PROT_READ:
 835                                                   (PROT_READ | PROT_WRITE),
 836                                                   MAP_FILE | MAP_SHARED,
 837                                                   smb_shm_fd, 0);
 838    /* WARNING, smb_shm_header_p can be different for different processes mapping the same file ! */
 839    if (smb_shm_header_p  == (struct SmbShmHeader *)(-1))
 840    {
 841       DEBUG(0,("ERROR smb_shm_open : mmap failed with code %s\n",strerror(errno)));
 842       smb_shm_unregister_process(smb_shm_processreg_name, getpid());
 843       smb_shm_global_unlock();
 844       close(smb_shm_fd);
 845       return NULL;
 846    }
 847
 848
 849    if (!read_only && (created_new || !other_processes))
 850    {
 851       smb_shm_initialize(size);
 852       /* Create the hash buckets for the share file entries. */
 853       smb_shm_create_hash_table(SHMEM_HASH_SIZE);
 854    }
 855    else if (!smb_shm_validate_header(size) )
 856    {
 857       /* existing file is corrupt, samba admin should remove it by hand */
 858       DEBUG(0,("ERROR smb_shm_open : corrupt shared mem file, remove it manually\n"));
 859       munmap((caddr_t)smb_shm_header_p, size);
 860       smb_shm_unregister_process(smb_shm_processreg_name, getpid());
 861       smb_shm_global_unlock();
 862       close(smb_shm_fd);
 863       return NULL;
 864    }
 865
 866    smb_shm_global_unlock();
 867    return &shmops;
 868 }
 869
 870
 871 #else /* FAST_SHARE_MODES */
 872  int shmem_dummy_procedure(void)
 873 {return 0;}
 874 #endif /* FAST_SHARE_MODES */