/src/samba/lib/tdb/common/lock.c

Source
 /*
   Unix SMB/CIFS implementation.

   trivial database library

   Copyright (C) Andrew Tridgell              1999-2005
   Copyright (C) Paul `Rusty' Russell      2000
   Copyright (C) Jeremy Allison        2000-2003

     ** NOTE! The following LGPL license applies to the tdb
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "tdb_private.h"

_PUBLIC_ void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr)
{
  tdb->interrupt_sig_ptr = ptr;
}

static int fcntl_lock(struct tdb_context *tdb,
          int rw, off_t off, off_t len, bool waitflag)
{
  struct flock fl;
  int cmd;

#ifdef USE_TDB_MUTEX_LOCKING
  {
    int ret;
    if (tdb_mutex_lock(tdb, rw, off, len, waitflag, &ret)) {
      return ret;
    }
  }
#endif

  fl.l_type = rw;
  fl.l_whence = SEEK_SET;
  fl.l_start = off;
  fl.l_len = len;
  fl.l_pid = 0;

  cmd = waitflag ? F_SETLKW : F_SETLK;

  return fcntl(tdb->fd, cmd, &fl);
}

static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len)
{
  struct flock fl;
#if 0 /* Check they matched up locks and unlocks correctly. */
  char line[80];
  FILE *locks;
  bool found = false;

  locks = fopen("/proc/locks", "r");

  while (fgets(line, 80, locks)) {
    char *p;
    int type, start, l;

    /* eg. 1: FLOCK  ADVISORY  WRITE 2440 08:01:2180826 0 EOF */
    p = strchr(line, ':') + 1;
    if (strncmp(p, " POSIX  ADVISORY  ", strlen(" POSIX  ADVISORY  ")))
      continue;
    p += strlen(" FLOCK  ADVISORY  ");
    if (strncmp(p, "READ  ", strlen("READ  ")) == 0)
      type = F_RDLCK;
    else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0)
      type = F_WRLCK;
    else
      abort();
    p += 6;
    if (atoi(p) != getpid())
      continue;
    p = strchr(strchr(p, ' ') + 1, ' ') + 1;
    start = atoi(p);
    p = strchr(p, ' ') + 1;
    if (strncmp(p, "EOF", 3) == 0)
      l = 0;
    else
      l = atoi(p) - start + 1;

    if (off == start) {
      if (len != l) {
        fprintf(stderr, "Len %u should be %u: %s",
          (int)len, l, line);
        abort();
      }
      if (type != rw) {
        fprintf(stderr, "Type %s wrong: %s",
          rw == F_RDLCK ? "READ" : "WRITE", line);
        abort();
      }
      found = true;
      break;
    }
  }

  if (!found) {
    fprintf(stderr, "Unlock on %u@%u not found!\n",
      (int)off, (int)len);
    abort();
  }

  fclose(locks);
#endif

#ifdef USE_TDB_MUTEX_LOCKING
  {
    int ret;
    if (tdb_mutex_unlock(tdb, rw, off, len, &ret)) {
      return ret;
    }
  }
#endif

  fl.l_type = F_UNLCK;
  fl.l_whence = SEEK_SET;
  fl.l_start = off;
  fl.l_len = len;
  fl.l_pid = 0;

  return fcntl(tdb->fd, F_SETLKW, &fl);
}

/*
 * Calculate the lock offset for a list
 *
 * list -1 is the freelist, otherwise a hash chain.
 *
 * Note that we consistently (but without real reason) lock hash chains at an
 * offset that is 4 bytes below the real offset of the corresponding list head
 * in the db.
 *
 * This is the memory layout of the hashchain array:
 *
 * FREELIST_TOP + 0 = freelist
 * FREELIST_TOP + 4 = hashtable list 0
 * FREELIST_TOP + 8 = hashtable list 1
 * ...
 *
 * Otoh lock_offset computes:
 *
 * freelist = FREELIST_TOP - 4
 * list 0   = FREELIST_TOP + 0
 * list 1   = FREELIST_TOP + 4
 * ...
 *
 * Unfortunately we can't change this calculation in order to align the locking
 * offset with the memory layout, as that would make the locking incompatible
 * between different tdb versions.
 */
static tdb_off_t lock_offset(int list)
{
  return FREELIST_TOP + 4*list;
}

/* a byte range locking function - return 0 on success
   this functions locks/unlocks "len" byte at the specified offset.

   On error, errno is also set so that errors are passed back properly
   through tdb_open().

   note that a len of zero means lock to end of file
*/
int tdb_brlock(struct tdb_context *tdb,
         int rw_type, tdb_off_t offset, size_t len,
         enum tdb_lock_flags flags)
{
  int ret;

  if (tdb->flags & TDB_NOLOCK) {
    return 0;
  }

  if (flags & TDB_LOCK_MARK_ONLY) {
    return 0;
  }

  if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
    tdb->ecode = TDB_ERR_RDONLY;
    return -1;
  }

  do {
    ret = fcntl_lock(tdb, rw_type, offset, len,
         flags & TDB_LOCK_WAIT);
    /* Check for a sigalarm break. */
    if (ret == -1 && errno == EINTR &&
        tdb->interrupt_sig_ptr &&
        *tdb->interrupt_sig_ptr) {
      break;
    }
  } while (ret == -1 && errno == EINTR);

  if (ret == -1) {
    tdb->ecode = TDB_ERR_LOCK;
    /* Generic lock error. errno set by fcntl.
     * EAGAIN is an expected return from non-blocking
     * locks. */
    if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) {
      TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %u rw_type=%d flags=%d len=%zu\n",
         tdb->fd, offset, rw_type, flags, len));
    }
    return -1;
  }
  return 0;
}

int tdb_brunlock(struct tdb_context *tdb,
     int rw_type, tdb_off_t offset, size_t len)
{
  int ret;

  if (tdb->flags & TDB_NOLOCK) {
    return 0;
  }

  do {
    ret = fcntl_unlock(tdb, rw_type, offset, len);
  } while (ret == -1 && errno == EINTR);

  if (ret == -1) {
    TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brunlock failed (fd=%d) at offset %u rw_type=%u len=%zu\n",
       tdb->fd, offset, rw_type, len));
  }
  return ret;
}

/*
 * Do a tdb_brlock in a loop. Some OSes (such as solaris) have too
 * conservative deadlock detection and claim a deadlock when progress can be
 * made. For those OSes we may loop for a while.
 */

static int tdb_brlock_retry(struct tdb_context *tdb,
          int rw_type, tdb_off_t offset, size_t len,
          enum tdb_lock_flags flags)
{
  int count = 1000;

  while (count--) {
    struct timeval tv;
    int ret;

    ret = tdb_brlock(tdb, rw_type, offset, len, flags);
    if (ret == 0) {
      return 0;
    }
    if (errno != EDEADLK) {
      break;
    }
    /* sleep for as short a time as we can - more portable than usleep() */
    tv.tv_sec = 0;
    tv.tv_usec = 1;
    select(0, NULL, NULL, NULL, &tv);
  }
  return -1;
}

/*
  upgrade a read lock to a write lock.
*/
int tdb_allrecord_upgrade(struct tdb_context *tdb)
{
  int ret;

  if (tdb->allrecord_lock.count != 1) {
    TDB_LOG((tdb, TDB_DEBUG_ERROR,
       "tdb_allrecord_upgrade failed: count %u too high\n",
       tdb->allrecord_lock.count));
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (tdb->allrecord_lock.off != 1) {
    TDB_LOG((tdb, TDB_DEBUG_ERROR,
       "tdb_allrecord_upgrade failed: already upgraded?\n"));
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (tdb_have_mutexes(tdb)) {
    ret = tdb_mutex_allrecord_upgrade(tdb);
    if (ret == -1) {
      goto fail;
    }
    ret = tdb_brlock_retry(tdb, F_WRLCK, lock_offset(tdb->hash_size),
               0, TDB_LOCK_WAIT|TDB_LOCK_PROBE);
    if (ret == -1) {
      tdb_mutex_allrecord_downgrade(tdb);
    }
  } else {
    ret = tdb_brlock_retry(tdb, F_WRLCK, FREELIST_TOP, 0,
               TDB_LOCK_WAIT|TDB_LOCK_PROBE);
  }

  if (ret == 0) {
    tdb->allrecord_lock.ltype = F_WRLCK;
    tdb->allrecord_lock.off = 0;
    return 0;
  }
fail:
  TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_allrecord_upgrade failed\n"));
  return -1;
}

static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
             tdb_off_t offset)
{
  int i;

  for (i=0; i<tdb->num_lockrecs; i++) {
    if (tdb->lockrecs[i].off == offset) {
      return &tdb->lockrecs[i];
    }
  }
  return NULL;
}

/* lock an offset in the database. */
int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype,
      enum tdb_lock_flags flags)
{
  struct tdb_lock_type *new_lck;

  if (offset >= lock_offset(tdb->hash_size)) {
    tdb->ecode = TDB_ERR_LOCK;
    TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid offset %u for ltype=%d\n",
       offset, ltype));
    return -1;
  }
  if (tdb->flags & TDB_NOLOCK)
    return 0;

  new_lck = find_nestlock(tdb, offset);
  if (new_lck) {
    if ((new_lck->ltype == F_RDLCK) && (ltype == F_WRLCK)) {
      if (!tdb_have_mutexes(tdb)) {
        int ret;
        /*
         * Upgrade the underlying fcntl
         * lock. Mutexes don't do readlocks,
         * so this only applies to fcntl
         * locking.
         */
        ret = tdb_brlock(tdb, ltype, offset, 1, flags);
        if (ret != 0) {
          return ret;
        }
      }
      new_lck->ltype = F_WRLCK;
    }
    /*
     * Just increment the in-memory struct, posix locks
     * don't stack.
     */
    new_lck->count++;
    return 0;
  }

  if (tdb->num_lockrecs == tdb->lockrecs_array_length) {
    new_lck = (struct tdb_lock_type *)realloc(
      tdb->lockrecs,
      sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
    if (new_lck == NULL) {
      errno = ENOMEM;
      return -1;
    }
    tdb->lockrecs_array_length = tdb->num_lockrecs+1;
    tdb->lockrecs = new_lck;
  }

  /* Since fcntl locks don't nest, we do a lock for the first one,
     and simply bump the count for future ones */
  if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
    return -1;
  }

  new_lck = &tdb->lockrecs[tdb->num_lockrecs];

  new_lck->off = offset;
  new_lck->count = 1;
  new_lck->ltype = ltype;
  tdb->num_lockrecs++;

  return 0;
}

static int tdb_lock_and_recover(struct tdb_context *tdb)
{
  int ret;

  /* We need to match locking order in transaction commit. */
  if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) {
    return -1;
  }

  if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) {
    tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
    return -1;
  }

  ret = tdb_transaction_recover(tdb);

  tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1);
  tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);

  return ret;
}

static bool have_data_locks(const struct tdb_context *tdb)
{
  int i;

  for (i = 0; i < tdb->num_lockrecs; i++) {
    if (tdb->lockrecs[i].off >= lock_offset(-1))
      return true;
  }
  return false;
}

/*
 * A allrecord lock allows us to avoid per chain locks. Check if the allrecord
 * lock is strong enough.
 */
static int tdb_lock_covered_by_allrecord_lock(struct tdb_context *tdb,
                int ltype)
{
  if (ltype == F_RDLCK) {
    /*
     * The allrecord_lock is equal (F_RDLCK) or stronger
     * (F_WRLCK). Pass.
     */
    return 0;
  }

  if (tdb->allrecord_lock.ltype == F_RDLCK) {
    /*
     * We ask for ltype==F_WRLCK, but the allrecord_lock
     * is too weak. We can't upgrade here, so fail.
     */
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  /*
   * Asking for F_WRLCK, allrecord is F_WRLCK as well. Pass.
   */
  return 0;
}

static int tdb_lock_list(struct tdb_context *tdb, int list, int ltype,
       enum tdb_lock_flags waitflag)
{
  int ret;
  bool check = false;

  if (tdb->allrecord_lock.count) {
    return tdb_lock_covered_by_allrecord_lock(tdb, ltype);
  }

  /*
   * Check for recoveries: Someone might have kill -9'ed a process
   * during a commit.
   */
  check = !have_data_locks(tdb);
  ret = tdb_nest_lock(tdb, lock_offset(list), ltype, waitflag);

  if (ret == 0 && check && tdb_needs_recovery(tdb)) {
    tdb_nest_unlock(tdb, lock_offset(list), ltype, false);

    if (tdb_lock_and_recover(tdb) == -1) {
      return -1;
    }
    return tdb_lock_list(tdb, list, ltype, waitflag);
  }
  return ret;
}

/* lock a list in the database. list -1 is the alloc list */
int tdb_lock(struct tdb_context *tdb, int list, int ltype)
{
  int ret;

  ret = tdb_lock_list(tdb, list, ltype, TDB_LOCK_WAIT);
  if (ret) {
    TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
       "ltype=%d (%s)\n",  list, ltype, strerror(errno)));
  }
  return ret;
}

/* lock a list in the database. list -1 is the alloc list. non-blocking lock */
_PUBLIC_ int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype);
_PUBLIC_ int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
{
  return tdb_lock_list(tdb, list, ltype, TDB_LOCK_NOWAIT);
}


int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype,
        bool mark_lock)
{
  int ret = -1;
  struct tdb_lock_type *lck;

  if (tdb->flags & TDB_NOLOCK)
    return 0;

  /* Sanity checks */
  if (offset >= lock_offset(tdb->hash_size)) {
    TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->hash_size));
    return ret;
  }

  lck = find_nestlock(tdb, offset);
  if ((lck == NULL) || (lck->count == 0)) {
    TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n"));
    return -1;
  }

  if (lck->count > 1) {
    lck->count--;
    return 0;
  }

  /*
   * This lock has count==1 left, so we need to unlock it in the
   * kernel. We don't bother with decrementing the in-memory array
   * element, we're about to overwrite it with the last array element
   * anyway.
   */

  if (mark_lock) {
    ret = 0;
  } else {
    ret = tdb_brunlock(tdb, ltype, offset, 1);
  }

  /*
   * Shrink the array by overwriting the element just unlocked with the
   * last array element.
   */
  *lck = tdb->lockrecs[--tdb->num_lockrecs];

  /*
   * We don't bother with realloc when the array shrinks, but if we have
   * a completely idle tdb we should get rid of the locked array.
   */

  if (ret)
    TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));
  return ret;
}

_PUBLIC_ int tdb_unlock(struct tdb_context *tdb, int list, int ltype);
_PUBLIC_ int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
{
  /* a global lock allows us to avoid per chain locks */
  if (tdb->allrecord_lock.count) {
    return tdb_lock_covered_by_allrecord_lock(tdb, ltype);
  }

  return tdb_nest_unlock(tdb, lock_offset(list), ltype, false);
}

/*
  get the transaction lock
 */
int tdb_transaction_lock(struct tdb_context *tdb, int ltype,
       enum tdb_lock_flags lockflags)
{
  return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags);
}

/*
  release the transaction lock
 */
int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
{
  return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);
}

/* Returns 0 if all done, -1 if error, 1 if ok. */
static int tdb_allrecord_check(struct tdb_context *tdb, int ltype,
             enum tdb_lock_flags flags, bool upgradable)
{
  /* There are no locks on read-only dbs */
  if (tdb->read_only || tdb->traverse_read) {
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (tdb->allrecord_lock.count &&
      tdb->allrecord_lock.ltype == (uint32_t)ltype) {
    tdb->allrecord_lock.count++;
    return 0;
  }

  if (tdb->allrecord_lock.count) {
    /* a global lock of a different type exists */
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (tdb_have_extra_locks(tdb)) {
    /* can't combine global and chain locks */
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (upgradable && ltype != F_RDLCK) {
    /* tdb error: you can't upgrade a write lock! */
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }
  return 1;
}

/* We only need to lock individual bytes, but Linux merges consecutive locks
 * so we lock in contiguous ranges. */
static int tdb_chainlock_gradual(struct tdb_context *tdb,
         int ltype, enum tdb_lock_flags flags,
         size_t off, size_t len)
{
  int ret;
  enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);

  if (len <= 4) {
    /* Single record.  Just do blocking lock. */
    return tdb_brlock(tdb, ltype, off, len, flags);
  }

  /* First we try non-blocking. */
  ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
  if (ret == 0) {
    return 0;
  }

  /* Try locking first half, then second. */
  ret = tdb_chainlock_gradual(tdb, ltype, flags, off, len / 2);
  if (ret == -1)
    return -1;

  ret = tdb_chainlock_gradual(tdb, ltype, flags,
            off + len / 2, len - len / 2);
  if (ret == -1) {
    tdb_brunlock(tdb, ltype, off, len / 2);
    return -1;
  }
  return 0;
}

/* lock/unlock entire database.  It can only be upgradable if you have some
 * other way of guaranteeing exclusivity (ie. transaction write lock).
 * We do the locking gradually to avoid being starved by smaller locks. */
int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
           enum tdb_lock_flags flags, bool upgradable)
{
  int ret;

  switch (tdb_allrecord_check(tdb, ltype, flags, upgradable)) {
  case -1:
    return -1;
  case 0:
    return 0;
  }

  /* We cover two kinds of locks:
   * 1) Normal chain locks.  Taken for almost all operations.
   * 2) Individual records locks.  Taken after normal or free
   *    chain locks.
   *
   * It is (1) which cause the starvation problem, so we're only
   * gradual for that. */

  if (tdb_have_mutexes(tdb)) {
    ret = tdb_mutex_allrecord_lock(tdb, ltype, flags);
  } else {
    ret = tdb_chainlock_gradual(tdb, ltype, flags, FREELIST_TOP,
              tdb->hash_size * 4);
  }

  if (ret == -1) {
    return -1;
  }

  /* Grab individual record locks. */
  if (tdb_brlock(tdb, ltype, lock_offset(tdb->hash_size), 0,
           flags) == -1) {
    if (tdb_have_mutexes(tdb)) {
      tdb_mutex_allrecord_unlock(tdb);
    } else {
      tdb_brunlock(tdb, ltype, FREELIST_TOP,
             tdb->hash_size * 4);
    }
    return -1;
  }

  tdb->allrecord_lock.count = 1;
  /* If it's upgradable, it's actually exclusive so we can treat
   * it as a write lock. */
  tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
  tdb->allrecord_lock.off = upgradable;

  if (tdb_needs_recovery(tdb)) {
    bool mark = flags & TDB_LOCK_MARK_ONLY;
    tdb_allrecord_unlock(tdb, ltype, mark);
    if (mark) {
      tdb->ecode = TDB_ERR_LOCK;
      TDB_LOG((tdb, TDB_DEBUG_ERROR,
         "tdb_lockall_mark cannot do recovery\n"));
      return -1;
    }
    if (tdb_lock_and_recover(tdb) == -1) {
      return -1;
    }
    return tdb_allrecord_lock(tdb, ltype, flags, upgradable);
  }

  return 0;
}



/* unlock entire db */
int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype, bool mark_lock)
{
  /* There are no locks on read-only dbs */
  if (tdb->read_only || tdb->traverse_read) {
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (tdb->allrecord_lock.count == 0) {
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  /* Upgradable locks are marked as write locks. */
  if (tdb->allrecord_lock.ltype != (uint32_t)ltype
      && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
    tdb->ecode = TDB_ERR_LOCK;
    return -1;
  }

  if (tdb->allrecord_lock.count > 1) {
    tdb->allrecord_lock.count--;
    return 0;
  }

  if (!mark_lock) {
    int ret;

    if (tdb_have_mutexes(tdb)) {
      ret = tdb_mutex_allrecord_unlock(tdb);
      if (ret == 0) {
        ret = tdb_brunlock(tdb, ltype,
               lock_offset(tdb->hash_size),
               0);
      }
    } else {
      ret = tdb_brunlock(tdb, ltype, FREELIST_TOP, 0);
    }

    if (ret != 0) {
      TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed "
         "(%s)\n", strerror(errno)));
      return -1;
    }
  }

  tdb->allrecord_lock.count = 0;
  tdb->allrecord_lock.ltype = 0;

  return 0;
}

/* lock entire database with write lock */
_PUBLIC_ int tdb_lockall(struct tdb_context *tdb)
{
  tdb_trace(tdb, "tdb_lockall");
  return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false);
}

/* lock entire database with write lock - mark only */
_PUBLIC_ int tdb_lockall_mark(struct tdb_context *tdb)
{
  tdb_trace(tdb, "tdb_lockall_mark");
  return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY, false);
}

/* unlock entire database with write lock - unmark only */
_PUBLIC_ int tdb_lockall_unmark(struct tdb_context *tdb)
{
  tdb_trace(tdb, "tdb_lockall_unmark");
  return tdb_allrecord_unlock(tdb, F_WRLCK, true);
}

/* lock entire database with write lock - nonblocking variant */
_PUBLIC_ int tdb_lockall_nonblock(struct tdb_context *tdb)
{
  int ret = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_NOWAIT, false);
  tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret);
  return ret;
}

/* unlock entire database with write lock */
_PUBLIC_ int tdb_unlockall(struct tdb_context *tdb)
{
  tdb_trace(tdb, "tdb_unlockall");
  return tdb_allrecord_unlock(tdb, F_WRLCK, false);
}

/* lock entire database with read lock */
_PUBLIC_ int tdb_lockall_read(struct tdb_context *tdb)
{
  tdb_trace(tdb, "tdb_lockall_read");
  return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false);
}

/* lock entire database with read lock - nonblock variant */
_PUBLIC_ int tdb_lockall_read_nonblock(struct tdb_context *tdb)
{
  int ret = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_NOWAIT, false);
  tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret);
  return ret;
}

/* unlock entire database with read lock */
_PUBLIC_ int tdb_unlockall_read(struct tdb_context *tdb)
{
  tdb_trace(tdb, "tdb_unlockall_read");
  return tdb_allrecord_unlock(tdb, F_RDLCK, false);
}

/* lock/unlock one hash chain. This is meant to be used to reduce
   contention - it cannot guarantee how many records will be locked */
_PUBLIC_ int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
{
  int ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
  tdb_trace_1rec(tdb, "tdb_chainlock", key);
  return ret;
}

/* lock/unlock one hash chain, non-blocking. This is meant to be used
   to reduce contention - it cannot guarantee how many records will be
   locked */
_PUBLIC_ int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
{
  int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
  tdb_trace_1rec_ret(tdb, "tdb_chainlock_nonblock", key, ret);
  return ret;
}

/* mark a chain as locked without actually locking it. Warning! use with great caution! */
_PUBLIC_ int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
{
  int ret = tdb_nest_lock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),
        F_WRLCK, TDB_LOCK_MARK_ONLY);
  tdb_trace_1rec(tdb, "tdb_chainlock_mark", key);
  return ret;
}

/* unmark a chain as locked without actually locking it. Warning! use with great caution! */
_PUBLIC_ int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
{
  tdb_trace_1rec(tdb, "tdb_chainlock_unmark", key);
  return tdb_nest_unlock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),
             F_WRLCK, true);
}

_PUBLIC_ int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
{
  tdb_trace_1rec(tdb, "tdb_chainunlock", key);
  return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
}

_PUBLIC_ int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
{
  int ret;
  ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
  tdb_trace_1rec(tdb, "tdb_chainlock_read", key);
  return ret;
}

_PUBLIC_ int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
{
  tdb_trace_1rec(tdb, "tdb_chainunlock_read", key);
  return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
}

_PUBLIC_ int tdb_chainlock_read_nonblock(struct tdb_context *tdb, TDB_DATA key)
{
  int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
  tdb_trace_1rec_ret(tdb, "tdb_chainlock_read_nonblock", key, ret);
  return ret;
}

/* record lock stops delete underneath */
int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
{
  if (tdb->allrecord_lock.count) {
    return 0;
  }
  return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0;
}

/*
  Write locks override our own fcntl readlocks, so check it here.
  Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
  an error to fail to get the lock here.
*/
int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
{
  struct tdb_traverse_lock *i;
  if (tdb == NULL) {
    return -1;
  }
  for (i = &tdb->travlocks; i; i = i->next)
    if (i->off == off)
      return -1;
  if (tdb->allrecord_lock.count) {
    if (tdb->allrecord_lock.ltype == F_WRLCK) {
      return 0;
    }
    return -1;
  }
  return tdb_brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
}

int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
{
  if (tdb->allrecord_lock.count) {
    return 0;
  }
  return tdb_brunlock(tdb, F_WRLCK, off, 1);
}

/* fcntl locks don't stack: avoid unlocking someone else's */
int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
{
  struct tdb_traverse_lock *i;
  uint32_t count = 0;

  if (tdb->allrecord_lock.count) {
    return 0;
  }

  if (off == 0)
    return 0;
  for (i = &tdb->travlocks; i; i = i->next)
    if (i->off == off)
      count++;
  return (count == 1 ? tdb_brunlock(tdb, F_RDLCK, off, 1) : 0);
}

bool tdb_have_extra_locks(struct tdb_context *tdb)
{
  unsigned int extra = tdb->num_lockrecs;

  /* A transaction holds the lock for all records. */
  if (!tdb->transaction && tdb->allrecord_lock.count) {
    return true;
  }

  /* We always hold the active lock if CLEAR_IF_FIRST. */
  if (find_nestlock(tdb, ACTIVE_LOCK)) {
    extra--;
  }

  /* In a transaction, we expect to hold the transaction lock */
  if (tdb->transaction && find_nestlock(tdb, TRANSACTION_LOCK)) {
    extra--;
  }

  return extra;
}

/* The transaction code uses this to remove all locks. */
void tdb_release_transaction_locks(struct tdb_context *tdb)
{
  int i;
  unsigned int active = 0;

  if (tdb->allrecord_lock.count != 0) {
    tdb_allrecord_unlock(tdb, tdb->allrecord_lock.ltype, false);
    tdb->allrecord_lock.count = 0;
  }

  for (i=0;i<tdb->num_lockrecs;i++) {
    struct tdb_lock_type *lck = &tdb->lockrecs[i];

    /* Don't release the active lock!  Copy it to first entry. */
    if (lck->off == ACTIVE_LOCK) {
      tdb->lockrecs[active++] = *lck;
    } else {
      tdb_brunlock(tdb, lck->ltype, lck->off, 1);
    }
  }
  tdb->num_lockrecs = active;
}

/* Following functions are added specifically to support CTDB. */

/* Don't do actual fcntl locking, just mark tdb locked */
_PUBLIC_ int tdb_transaction_write_lock_mark(struct tdb_context *tdb);
_PUBLIC_ int tdb_transaction_write_lock_mark(struct tdb_context *tdb)
{
  return tdb_transaction_lock(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY);
}

/* Don't do actual fcntl unlocking, just mark tdb unlocked */
_PUBLIC_ int tdb_transaction_write_lock_unmark(struct tdb_context *tdb);
_PUBLIC_ int tdb_transaction_write_lock_unmark(struct tdb_context *tdb)
{
  return tdb_nest_unlock(tdb, TRANSACTION_LOCK, F_WRLCK, true);
}

Coverage Report

Created: 2025-12-31 06:20