lib/tdb_compat/tdb_compat.c

   1 #include <tdb_compat.h>
   2
   3 /* Note: for the moment, we only need this file for TDB2, so we can
   4  * assume waf. */
   5 #if BUILD_TDB2
   6 TDB_DATA tdb_null = { NULL, 0 };
   7
   8 /* Proxy which sets waitflag to false so we never block. */
   9 static int lock_nonblock(int fd, int rw, off_t off, off_t len, bool waitflag,
  10                          void *_orig)
  11 {
  12         struct tdb_attribute_flock *orig = _orig;
  13
  14         return orig->lock(fd, rw, off, len, false, orig->data);
  15 }
  16
  17 enum TDB_ERROR tdb_transaction_start_nonblock(struct tdb_context *tdb)
  18 {
  19         union tdb_attribute locking, orig;
  20         enum TDB_ERROR ecode;
  21
  22         orig.base.attr = TDB_ATTRIBUTE_FLOCK;
  23         ecode = tdb_get_attribute(tdb, &orig);
  24         if (ecode != TDB_SUCCESS)
  25                 return ecode;
  26
  27         /* Replace locking function with our own. */
  28         locking = orig;
  29         locking.flock.data = &orig;
  30         locking.flock.lock = lock_nonblock;
  31
  32         ecode = tdb_set_attribute(tdb, &locking);
  33         if (ecode != TDB_SUCCESS)
  34                 return ecode;
  35
  36         ecode = tdb_transaction_start(tdb);
  37         tdb_unset_attribute(tdb, TDB_ATTRIBUTE_FLOCK);
  38         return ecode;
  39 }
  40
  41 /*
  42  * This handles TDB_CLEAR_IF_FIRST.
  43  */
  44 static enum TDB_ERROR clear_if_first(int fd, void *unused)
  45 {
  46         /* We hold a lock offset 63 always, so we can tell if anyone else is. */
  47         struct flock fl;
  48
  49         fl.l_type = F_WRLCK;
  50         fl.l_whence = SEEK_SET;
  51         fl.l_start = 63;
  52         fl.l_len = 1;
  53
  54         if (fcntl(fd, F_SETLK, &fl) == 0) {
  55                 /* We must be first ones to open it w/ TDB_CLEAR_IF_FIRST! */
  56                 if (ftruncate(fd, 0) != 0) {
  57                         return TDB_ERR_IO;
  58                 }
  59         }
  60         fl.l_type = F_RDLCK;
  61         if (fcntl(fd, F_SETLKW, &fl) != 0) {
  62                 return TDB_ERR_IO;
  63         }
  64         return TDB_SUCCESS;
  65 }
  66
  67 struct tdb_context *
  68 tdb_open_compat_(const char *name, int hash_size_unused,
  69                  int tdb_flags, int open_flags, mode_t mode,
  70                  void (*log_fn)(struct tdb_context *,
  71                                 enum tdb_log_level,
  72                                 const char *message,
  73                                 void *data),
  74                  void *log_data)
  75 {
  76         union tdb_attribute cif, log, *attr = NULL;
  77
  78         if (log_fn) {
  79                 log.log.base.attr = TDB_ATTRIBUTE_LOG;
  80                 log.log.base.next = NULL;
  81                 log.log.fn = log_fn;
  82                 log.log.data = log_data;
  83                 attr = &log;
  84         }
  85
  86         if (tdb_flags & TDB_CLEAR_IF_FIRST) {
  87                 cif.openhook.base.attr = TDB_ATTRIBUTE_OPENHOOK;
  88                 cif.openhook.base.next = attr;
  89                 cif.openhook.fn = clear_if_first;
  90                 attr = &cif;
  91                 tdb_flags &= ~TDB_CLEAR_IF_FIRST;
  92         }
  93
  94         /* Testsuite uses this to speed things up. */
  95         if (getenv("TDB_NO_FSYNC")) {
  96                 tdb_flags |= TDB_NOSYNC;
  97         }
  98
  99         return tdb_open(name, tdb_flags|TDB_ALLOW_NESTING, open_flags, mode,
 100                         attr);
 101 }
 102 #endif