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brlock.c

/* 
   Unix SMB/CIFS implementation.
   byte range locking code
   Updated to handle range splits/merges.

   Copyright (C) Andrew Tridgell 1992-2000
   Copyright (C) Jeremy Allison 1992-2000
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program 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 General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/* This module implements a tdb based byte range locking service,
   replacing the fcntl() based byte range locking previously
   used. This allows us to provide the same semantics as NT */

#include "includes.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_LOCKING

#define ZERO_ZERO 0

/* The open brlock.tdb database. */

static struct db_context *brlock_db;

/****************************************************************************
 Debug info at level 10 for lock struct.
****************************************************************************/

static void print_lock_struct(unsigned int i, struct lock_struct *pls)
{
      DEBUG(10,("[%u]: smbpid = %u, tid = %u, pid = %u, ",
                  i,
                  (unsigned int)pls->context.smbpid,
                  (unsigned int)pls->context.tid,
                  (unsigned int)procid_to_pid(&pls->context.pid) ));
      
      DEBUG(10,("start = %.0f, size = %.0f, fnum = %d, %s %s\n",
            (double)pls->start,
            (double)pls->size,
            pls->fnum,
            lock_type_name(pls->lock_type),
            lock_flav_name(pls->lock_flav) ));
}

/****************************************************************************
 See if two locking contexts are equal.
****************************************************************************/

bool brl_same_context(const struct lock_context *ctx1, 
                       const struct lock_context *ctx2)
{
      return (procid_equal(&ctx1->pid, &ctx2->pid) &&
            (ctx1->smbpid == ctx2->smbpid) &&
            (ctx1->tid == ctx2->tid));
}

/****************************************************************************
 See if lck1 and lck2 overlap.
****************************************************************************/

static bool brl_overlap(const struct lock_struct *lck1,
                        const struct lock_struct *lck2)
{
      /* this extra check is not redundent - it copes with locks
         that go beyond the end of 64 bit file space */
      if (lck1->size != 0 &&
          lck1->start == lck2->start &&
          lck1->size == lck2->size) {
            return True;
      }

      if (lck1->start >= (lck2->start+lck2->size) ||
          lck2->start >= (lck1->start+lck1->size)) {
            return False;
      }
      return True;
}

/****************************************************************************
 See if lock2 can be added when lock1 is in place.
****************************************************************************/

static bool brl_conflict(const struct lock_struct *lck1, 
                   const struct lock_struct *lck2)
{
      /* Ignore PENDING locks. */
      if (IS_PENDING_LOCK(lck1->lock_type) || IS_PENDING_LOCK(lck2->lock_type))
            return False;

      /* Read locks never conflict. */
      if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) {
            return False;
      }

      if (brl_same_context(&lck1->context, &lck2->context) &&
          lck2->lock_type == READ_LOCK && lck1->fnum == lck2->fnum) {
            return False;
      }

      return brl_overlap(lck1, lck2);
} 

/****************************************************************************
 See if lock2 can be added when lock1 is in place - when both locks are POSIX
 flavour. POSIX locks ignore fnum - they only care about dev/ino which we
 know already match.
****************************************************************************/

static bool brl_conflict_posix(const struct lock_struct *lck1, 
                        const struct lock_struct *lck2)
{
#if defined(DEVELOPER)
      SMB_ASSERT(lck1->lock_flav == POSIX_LOCK);
      SMB_ASSERT(lck2->lock_flav == POSIX_LOCK);
#endif

      /* Ignore PENDING locks. */
      if (IS_PENDING_LOCK(lck1->lock_type) || IS_PENDING_LOCK(lck2->lock_type))
            return False;

      /* Read locks never conflict. */
      if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) {
            return False;
      }

      /* Locks on the same context con't conflict. Ignore fnum. */
      if (brl_same_context(&lck1->context, &lck2->context)) {
            return False;
      }

      /* One is read, the other write, or the context is different,
         do they overlap ? */
      return brl_overlap(lck1, lck2);
} 

#if ZERO_ZERO
static bool brl_conflict1(const struct lock_struct *lck1, 
                   const struct lock_struct *lck2)
{
      if (IS_PENDING_LOCK(lck1->lock_type) || IS_PENDING_LOCK(lck2->lock_type))
            return False;

      if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) {
            return False;
      }

      if (brl_same_context(&lck1->context, &lck2->context) &&
          lck2->lock_type == READ_LOCK && lck1->fnum == lck2->fnum) {
            return False;
      }

      if (lck2->start == 0 && lck2->size == 0 && lck1->size != 0) {
            return True;
      }

      if (lck1->start >= (lck2->start + lck2->size) ||
          lck2->start >= (lck1->start + lck1->size)) {
            return False;
      }
          
      return True;
} 
#endif

/****************************************************************************
 Check to see if this lock conflicts, but ignore our own locks on the
 same fnum only. This is the read/write lock check code path.
 This is never used in the POSIX lock case.
****************************************************************************/

static bool brl_conflict_other(const struct lock_struct *lck1, const struct lock_struct *lck2)
{
      if (IS_PENDING_LOCK(lck1->lock_type) || IS_PENDING_LOCK(lck2->lock_type))
            return False;

      if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) 
            return False;

      /* POSIX flavour locks never conflict here - this is only called
         in the read/write path. */

      if (lck1->lock_flav == POSIX_LOCK && lck2->lock_flav == POSIX_LOCK)
            return False;

      /*
       * Incoming WRITE locks conflict with existing READ locks even
       * if the context is the same. JRA. See LOCKTEST7 in smbtorture.
       */

      if (!(lck2->lock_type == WRITE_LOCK && lck1->lock_type == READ_LOCK)) {
            if (brl_same_context(&lck1->context, &lck2->context) &&
                              lck1->fnum == lck2->fnum)
                  return False;
      }

      return brl_overlap(lck1, lck2);
} 

/****************************************************************************
 Check if an unlock overlaps a pending lock.
****************************************************************************/

static bool brl_pending_overlap(const struct lock_struct *lock, const struct lock_struct *pend_lock)
{
      if ((lock->start <= pend_lock->start) && (lock->start + lock->size > pend_lock->start))
            return True;
      if ((lock->start >= pend_lock->start) && (lock->start <= pend_lock->start + pend_lock->size))
            return True;
      return False;
}

/****************************************************************************
 Amazingly enough, w2k3 "remembers" whether the last lock failure on a fnum
 is the same as this one and changes its error code. I wonder if any
 app depends on this ?
****************************************************************************/

static NTSTATUS brl_lock_failed(files_struct *fsp, const struct lock_struct *lock, bool blocking_lock)
{
      if (lock->start >= 0xEF000000 && (lock->start >> 63) == 0) {
            /* amazing the little things you learn with a test
               suite. Locks beyond this offset (as a 64 bit
               number!) always generate the conflict error code,
               unless the top bit is set */
            if (!blocking_lock) {
                  fsp->last_lock_failure = *lock;
            }
            return NT_STATUS_FILE_LOCK_CONFLICT;
      }

      if (procid_equal(&lock->context.pid, &fsp->last_lock_failure.context.pid) &&
                  lock->context.tid == fsp->last_lock_failure.context.tid &&
                  lock->fnum == fsp->last_lock_failure.fnum &&
                  lock->start == fsp->last_lock_failure.start) {
            return NT_STATUS_FILE_LOCK_CONFLICT;
      }

      if (!blocking_lock) {
            fsp->last_lock_failure = *lock;
      }
      return NT_STATUS_LOCK_NOT_GRANTED;
}

/****************************************************************************
 Open up the brlock.tdb database.
****************************************************************************/

void brl_init(bool read_only)
{
      if (brlock_db) {
            return;
      }
      brlock_db = db_open(NULL, lock_path("brlock.tdb"),
                      lp_open_files_db_hash_size(),
                      TDB_DEFAULT | TDB_CLEAR_IF_FIRST,
                      read_only?O_RDONLY:(O_RDWR|O_CREAT), 0644 );
      if (!brlock_db) {
            DEBUG(0,("Failed to open byte range locking database %s\n",
                  lock_path("brlock.tdb")));
            return;
      }
}

/****************************************************************************
 Close down the brlock.tdb database.
****************************************************************************/

void brl_shutdown(void)
{
      TALLOC_FREE(brlock_db);
}

#if ZERO_ZERO
/****************************************************************************
 Compare two locks for sorting.
****************************************************************************/

static int lock_compare(const struct lock_struct *lck1, 
                   const struct lock_struct *lck2)
{
      if (lck1->start != lck2->start) {
            return (lck1->start - lck2->start);
      }
      if (lck2->size != lck1->size) {
            return ((int)lck1->size - (int)lck2->size);
      }
      return 0;
}
#endif

/****************************************************************************
 Lock a range of bytes - Windows lock semantics.
****************************************************************************/

static NTSTATUS brl_lock_windows(struct byte_range_lock *br_lck,
                  struct lock_struct *plock, bool blocking_lock)
{
      unsigned int i;
      files_struct *fsp = br_lck->fsp;
      struct lock_struct *locks = br_lck->lock_data;

      for (i=0; i < br_lck->num_locks; i++) {
            /* Do any Windows or POSIX locks conflict ? */
            if (brl_conflict(&locks[i], plock)) {
                  /* Remember who blocked us. */
                  plock->context.smbpid = locks[i].context.smbpid;
                  return brl_lock_failed(fsp,plock,blocking_lock);
            }
#if ZERO_ZERO
            if (plock->start == 0 && plock->size == 0 && 
                        locks[i].size == 0) {
                  break;
            }
#endif
      }

      /* We can get the Windows lock, now see if it needs to
         be mapped into a lower level POSIX one, and if so can
         we get it ? */

      if (!IS_PENDING_LOCK(plock->lock_type) && lp_posix_locking(fsp->conn->params)) {
            int errno_ret;
            if (!set_posix_lock_windows_flavour(fsp,
                        plock->start,
                        plock->size,
                        plock->lock_type,
                        &plock->context,
                        locks,
                        br_lck->num_locks,
                        &errno_ret)) {

                  /* We don't know who blocked us. */
                  plock->context.smbpid = 0xFFFFFFFF;

                  if (errno_ret == EACCES || errno_ret == EAGAIN) {
                        return NT_STATUS_FILE_LOCK_CONFLICT;
                  } else {
                        return map_nt_error_from_unix(errno);
                  }
            }
      }

      /* no conflicts - add it to the list of locks */
      locks = (struct lock_struct *)SMB_REALLOC(locks, (br_lck->num_locks + 1) * sizeof(*locks));
      if (!locks) {
            return NT_STATUS_NO_MEMORY;
      }

      memcpy(&locks[br_lck->num_locks], plock, sizeof(struct lock_struct));
      br_lck->num_locks += 1;
      br_lck->lock_data = locks;
      br_lck->modified = True;

      return NT_STATUS_OK;
}

/****************************************************************************
 Cope with POSIX range splits and merges.
****************************************************************************/

static unsigned int brlock_posix_split_merge(struct lock_struct *lck_arr,           /* Output array. */
                                    const struct lock_struct *ex,       /* existing lock. */
                                    const struct lock_struct *plock,    /* proposed lock. */
                                    bool *lock_was_added)
{
      bool lock_types_differ = (ex->lock_type != plock->lock_type);

      /* We can't merge non-conflicting locks on different context - ignore fnum. */

      if (!brl_same_context(&ex->context, &plock->context)) {
            /* Just copy. */
            memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
            return 1;
      }

      /* We now know we have the same context. */

      /* Did we overlap ? */

/*********************************************
                                             +---------+
                                             | ex      |
                                             +---------+
                              +-------+
                              | plock |
                              +-------+
OR....
             +---------+
             |  ex     |
             +---------+
**********************************************/

      if ( (ex->start > (plock->start + plock->size)) ||
                  (plock->start > (ex->start + ex->size))) {
            /* No overlap with this lock - copy existing. */
            memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
            return 1;
      }

/*********************************************
        +---------------------------+
        |          ex               |
        +---------------------------+
        +---------------------------+
        |       plock               | -> replace with plock.
        +---------------------------+
**********************************************/

      if ( (ex->start >= plock->start) &&
                  (ex->start + ex->size <= plock->start + plock->size) ) {
            memcpy(&lck_arr[0], plock, sizeof(struct lock_struct));
            *lock_was_added = True;
            return 1;
      }

/*********************************************
        +-----------------------+
        |          ex           |
        +-----------------------+
        +---------------+
        |   plock       |
        +---------------+
OR....
                        +-------+
                        |  ex   |
                        +-------+
        +---------------+
        |   plock       |
        +---------------+

BECOMES....
        +---------------+-------+
        |   plock       | ex    | - different lock types.
        +---------------+-------+
OR.... (merge)
        +-----------------------+
        |   ex                  | - same lock type.
        +-----------------------+
**********************************************/

      if ( (ex->start >= plock->start) &&
                        (ex->start <= plock->start + plock->size) &&
                        (ex->start + ex->size > plock->start + plock->size) ) {

            *lock_was_added = True;

            /* If the lock types are the same, we merge, if different, we
               add the new lock before the old. */

            if (lock_types_differ) {
                  /* Add new. */
                  memcpy(&lck_arr[0], plock, sizeof(struct lock_struct));
                  memcpy(&lck_arr[1], ex, sizeof(struct lock_struct));
                  /* Adjust existing start and size. */
                  lck_arr[1].start = plock->start + plock->size;
                  lck_arr[1].size = (ex->start + ex->size) - (plock->start + plock->size);
                  return 2;
            } else {
                  /* Merge. */
                  memcpy(&lck_arr[0], plock, sizeof(struct lock_struct));
                  /* Set new start and size. */
                  lck_arr[0].start = plock->start;
                  lck_arr[0].size = (ex->start + ex->size) - plock->start;
                  return 1;
            }
      }

/*********************************************
   +-----------------------+
   |  ex                   |
   +-----------------------+
           +---------------+
           |   plock       |
           +---------------+
OR....
   +-------+        
   |  ex   |
   +-------+
           +---------------+
           |   plock       |
           +---------------+
BECOMES....
   +-------+---------------+
   | ex    |   plock       | - different lock types
   +-------+---------------+

OR.... (merge)
   +-----------------------+
   | ex                    | - same lock type.
   +-----------------------+

**********************************************/

      if ( (ex->start < plock->start) &&
                  (ex->start + ex->size >= plock->start) &&
                  (ex->start + ex->size <= plock->start + plock->size) ) {

            *lock_was_added = True;

            /* If the lock types are the same, we merge, if different, we
               add the new lock after the old. */

            if (lock_types_differ) {
                  memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                  memcpy(&lck_arr[1], plock, sizeof(struct lock_struct));
                  /* Adjust existing size. */
                  lck_arr[0].size = plock->start - ex->start;
                  return 2;
            } else {
                  /* Merge. */
                  memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                  /* Adjust existing size. */
                  lck_arr[0].size = (plock->start + plock->size) - ex->start;
                  return 1;
            }
      }

/*********************************************
        +---------------------------+
        |        ex                 |
        +---------------------------+
                +---------+
                |  plock  |
                +---------+
BECOMES.....
        +-------+---------+---------+
        | ex    |  plock  | ex      | - different lock types.
        +-------+---------+---------+
OR
        +---------------------------+
        |        ex                 | - same lock type.
        +---------------------------+
**********************************************/

      if ( (ex->start < plock->start) && (ex->start + ex->size > plock->start + plock->size) ) {
            *lock_was_added = True;

            if (lock_types_differ) {

                  /* We have to split ex into two locks here. */

                  memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                  memcpy(&lck_arr[1], plock, sizeof(struct lock_struct));
                  memcpy(&lck_arr[2], ex, sizeof(struct lock_struct));

                  /* Adjust first existing size. */
                  lck_arr[0].size = plock->start - ex->start;

                  /* Adjust second existing start and size. */
                  lck_arr[2].start = plock->start + plock->size;
                  lck_arr[2].size = (ex->start + ex->size) - (plock->start + plock->size);
                  return 3;
            } else {
                  /* Just eat plock. */
                  memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                  return 1;
            }
      }

      /* Never get here. */
      smb_panic("brlock_posix_split_merge");
      /* Notreached. */

      /* Keep some compilers happy. */
      return 0;
}

/****************************************************************************
 Lock a range of bytes - POSIX lock semantics.
 We must cope with range splits and merges.
****************************************************************************/

static NTSTATUS brl_lock_posix(struct messaging_context *msg_ctx,
                         struct byte_range_lock *br_lck,
                         struct lock_struct *plock)
{
      unsigned int i, count;
      struct lock_struct *locks = br_lck->lock_data;
      struct lock_struct *tp;
      bool lock_was_added = False;
      bool signal_pending_read = False;

      /* No zero-zero locks for POSIX. */
      if (plock->start == 0 && plock->size == 0) {
            return NT_STATUS_INVALID_PARAMETER;
      }

      /* Don't allow 64-bit lock wrap. */
      if (plock->start + plock->size < plock->start ||
                  plock->start + plock->size < plock->size) {
            return NT_STATUS_INVALID_PARAMETER;
      }

      /* The worst case scenario here is we have to split an
         existing POSIX lock range into two, and add our lock,
         so we need at most 2 more entries. */

      tp = SMB_MALLOC_ARRAY(struct lock_struct, (br_lck->num_locks + 2));
      if (!tp) {
            return NT_STATUS_NO_MEMORY;
      }
      
      count = 0;
      for (i=0; i < br_lck->num_locks; i++) {
            struct lock_struct *curr_lock = &locks[i];

            /* If we have a pending read lock, a lock downgrade should
               trigger a lock re-evaluation. */
            if (curr_lock->lock_type == PENDING_READ_LOCK &&
                        brl_pending_overlap(plock, curr_lock)) {
                  signal_pending_read = True;
            }

            if (curr_lock->lock_flav == WINDOWS_LOCK) {
                  /* Do any Windows flavour locks conflict ? */
                  if (brl_conflict(curr_lock, plock)) {
                        /* No games with error messages. */
                        SAFE_FREE(tp);
                        /* Remember who blocked us. */
                        plock->context.smbpid = curr_lock->context.smbpid;
                        return NT_STATUS_FILE_LOCK_CONFLICT;
                  }
                  /* Just copy the Windows lock into the new array. */
                  memcpy(&tp[count], curr_lock, sizeof(struct lock_struct));
                  count++;
            } else {
                  /* POSIX conflict semantics are different. */
                  if (brl_conflict_posix(curr_lock, plock)) {
                        /* Can't block ourselves with POSIX locks. */
                        /* No games with error messages. */
                        SAFE_FREE(tp);
                        /* Remember who blocked us. */
                        plock->context.smbpid = curr_lock->context.smbpid;
                        return NT_STATUS_FILE_LOCK_CONFLICT;
                  }

                  /* Work out overlaps. */
                  count += brlock_posix_split_merge(&tp[count], curr_lock, plock, &lock_was_added);
            }
      }

      if (!lock_was_added) {
            memcpy(&tp[count], plock, sizeof(struct lock_struct));
            count++;
      }

      /* We can get the POSIX lock, now see if it needs to
         be mapped into a lower level POSIX one, and if so can
         we get it ? */

      if (!IS_PENDING_LOCK(plock->lock_type) && lp_posix_locking(br_lck->fsp->conn->params)) {
            int errno_ret;

            /* The lower layer just needs to attempt to
               get the system POSIX lock. We've weeded out
               any conflicts above. */

            if (!set_posix_lock_posix_flavour(br_lck->fsp,
                        plock->start,
                        plock->size,
                        plock->lock_type,
                        &errno_ret)) {

                  /* We don't know who blocked us. */
                  plock->context.smbpid = 0xFFFFFFFF;

                  if (errno_ret == EACCES || errno_ret == EAGAIN) {
                        SAFE_FREE(tp);
                        return NT_STATUS_FILE_LOCK_CONFLICT;
                  } else {
                        SAFE_FREE(tp);
                        return map_nt_error_from_unix(errno);
                  }
            }
      }

      /* Realloc so we don't leak entries per lock call. */
      tp = (struct lock_struct *)SMB_REALLOC(tp, count * sizeof(*locks));
      if (!tp) {
            return NT_STATUS_NO_MEMORY;
      }
      br_lck->num_locks = count;
      SAFE_FREE(br_lck->lock_data);
      br_lck->lock_data = tp;
      locks = tp;
      br_lck->modified = True;

      /* A successful downgrade from write to read lock can trigger a lock
         re-evalutation where waiting readers can now proceed. */

      if (signal_pending_read) {
            /* Send unlock messages to any pending read waiters that overlap. */
            for (i=0; i < br_lck->num_locks; i++) {
                  struct lock_struct *pend_lock = &locks[i];

                  /* Ignore non-pending locks. */
                  if (!IS_PENDING_LOCK(pend_lock->lock_type)) {
                        continue;
                  }

                  if (pend_lock->lock_type == PENDING_READ_LOCK &&
                              brl_pending_overlap(plock, pend_lock)) {
                        DEBUG(10,("brl_lock_posix: sending unlock message to pid %s\n",
                              procid_str_static(&pend_lock->context.pid )));

                        messaging_send(msg_ctx, pend_lock->context.pid,
                                     MSG_SMB_UNLOCK, &data_blob_null);
                  }
            }
      }

      return NT_STATUS_OK;
}

/****************************************************************************
 Lock a range of bytes.
****************************************************************************/

NTSTATUS brl_lock(struct messaging_context *msg_ctx,
            struct byte_range_lock *br_lck,
            uint32 smbpid,
            struct server_id pid,
            br_off start,
            br_off size, 
            enum brl_type lock_type,
            enum brl_flavour lock_flav,
            bool blocking_lock,
            uint32 *psmbpid)
{
      NTSTATUS ret;
      struct lock_struct lock;

#if !ZERO_ZERO
      if (start == 0 && size == 0) {
            DEBUG(0,("client sent 0/0 lock - please report this\n"));
      }
#endif

      lock.context.smbpid = smbpid;
      lock.context.pid = pid;
      lock.context.tid = br_lck->fsp->conn->cnum;
      lock.start = start;
      lock.size = size;
      lock.fnum = br_lck->fsp->fnum;
      lock.lock_type = lock_type;
      lock.lock_flav = lock_flav;

      if (lock_flav == WINDOWS_LOCK) {
            ret = brl_lock_windows(br_lck, &lock, blocking_lock);
      } else {
            ret = brl_lock_posix(msg_ctx, br_lck, &lock);
      }

#if ZERO_ZERO
      /* sort the lock list */
      qsort(br_lck->lock_data, (size_t)br_lck->num_locks, sizeof(lock), lock_compare);
#endif

      /* If we're returning an error, return who blocked us. */
      if (!NT_STATUS_IS_OK(ret) && psmbpid) {
            *psmbpid = lock.context.smbpid;
      }
      return ret;
}

/****************************************************************************
 Unlock a range of bytes - Windows semantics.
****************************************************************************/

static bool brl_unlock_windows(struct messaging_context *msg_ctx,
                         struct byte_range_lock *br_lck,
                         const struct lock_struct *plock)
{
      unsigned int i, j;
      struct lock_struct *locks = br_lck->lock_data;
      enum brl_type deleted_lock_type = READ_LOCK; /* shut the compiler up.... */

#if ZERO_ZERO
      /* Delete write locks by preference... The lock list
         is sorted in the zero zero case. */

      for (i = 0; i < br_lck->num_locks; i++) {
            struct lock_struct *lock = &locks[i];

            if (lock->lock_type == WRITE_LOCK &&
                brl_same_context(&lock->context, &plock->context) &&
                lock->fnum == plock->fnum &&
                lock->lock_flav == WINDOWS_LOCK &&
                lock->start == plock->start &&
                lock->size == plock->size) {

                  /* found it - delete it */
                  deleted_lock_type = lock->lock_type;
                  break;
            }
      }

      if (i != br_lck->num_locks) {
            /* We found it - don't search again. */
            goto unlock_continue;
      }
#endif

      for (i = 0; i < br_lck->num_locks; i++) {
            struct lock_struct *lock = &locks[i];

            /* Only remove our own locks that match in start, size, and flavour. */
            if (brl_same_context(&lock->context, &plock->context) &&
                              lock->fnum == plock->fnum &&
                              lock->lock_flav == WINDOWS_LOCK &&
                              lock->start == plock->start &&
                              lock->size == plock->size ) {
                  deleted_lock_type = lock->lock_type;
                  break;
            }
      }

      if (i == br_lck->num_locks) {
            /* we didn't find it */
            return False;
      }

#if ZERO_ZERO
  unlock_continue:
#endif

      /* Actually delete the lock. */
      if (i < br_lck->num_locks - 1) {
            memmove(&locks[i], &locks[i+1], 
                  sizeof(*locks)*((br_lck->num_locks-1) - i));
      }

      br_lck->num_locks -= 1;
      br_lck->modified = True;

      /* Unlock the underlying POSIX regions. */
      if(lp_posix_locking(br_lck->fsp->conn->params)) {
            release_posix_lock_windows_flavour(br_lck->fsp,
                        plock->start,
                        plock->size,
                        deleted_lock_type,
                        &plock->context,
                        locks,
                        br_lck->num_locks);
      }

      /* Send unlock messages to any pending waiters that overlap. */
      for (j=0; j < br_lck->num_locks; j++) {
            struct lock_struct *pend_lock = &locks[j];

            /* Ignore non-pending locks. */
            if (!IS_PENDING_LOCK(pend_lock->lock_type)) {
                  continue;
            }

            /* We could send specific lock info here... */
            if (brl_pending_overlap(plock, pend_lock)) {
                  DEBUG(10,("brl_unlock: sending unlock message to pid %s\n",
                        procid_str_static(&pend_lock->context.pid )));

                  messaging_send(msg_ctx, pend_lock->context.pid,
                               MSG_SMB_UNLOCK, &data_blob_null);
            }
      }

      return True;
}

/****************************************************************************
 Unlock a range of bytes - POSIX semantics.
****************************************************************************/

static bool brl_unlock_posix(struct messaging_context *msg_ctx,
                       struct byte_range_lock *br_lck,
                       const struct lock_struct *plock)
{
      unsigned int i, j, count;
      struct lock_struct *tp;
      struct lock_struct *locks = br_lck->lock_data;
      bool overlap_found = False;

      /* No zero-zero locks for POSIX. */
      if (plock->start == 0 && plock->size == 0) {
            return False;
      }

      /* Don't allow 64-bit lock wrap. */
      if (plock->start + plock->size < plock->start ||
                  plock->start + plock->size < plock->size) {
            DEBUG(10,("brl_unlock_posix: lock wrap\n"));
            return False;
      }

      /* The worst case scenario here is we have to split an
         existing POSIX lock range into two, so we need at most
         1 more entry. */

      tp = SMB_MALLOC_ARRAY(struct lock_struct, (br_lck->num_locks + 1));
      if (!tp) {
            DEBUG(10,("brl_unlock_posix: malloc fail\n"));
            return False;
      }

      count = 0;
      for (i = 0; i < br_lck->num_locks; i++) {
            struct lock_struct *lock = &locks[i];
            struct lock_struct tmp_lock[3];
            bool lock_was_added = False;
            unsigned int tmp_count;

            /* Only remove our own locks - ignore fnum. */
            if (IS_PENDING_LOCK(lock->lock_type) ||
                        !brl_same_context(&lock->context, &plock->context)) {
                  memcpy(&tp[count], lock, sizeof(struct lock_struct));
                  count++;
                  continue;
            }

            /* Work out overlaps. */
            tmp_count = brlock_posix_split_merge(&tmp_lock[0], &locks[i], plock, &lock_was_added);

            if (tmp_count == 1) {
                  /* Ether the locks didn't overlap, or the unlock completely
                     overlapped this lock. If it didn't overlap, then there's
                     no change in the locks. */
                  if (tmp_lock[0].lock_type != UNLOCK_LOCK) {
                        SMB_ASSERT(tmp_lock[0].lock_type == locks[i].lock_type);
                        /* No change in this lock. */
                        memcpy(&tp[count], &tmp_lock[0], sizeof(struct lock_struct));
                        count++;
                  } else {
                        SMB_ASSERT(tmp_lock[0].lock_type == UNLOCK_LOCK);
                        overlap_found = True;
                  }
                  continue;
            } else if (tmp_count == 2) {
                  /* The unlock overlapped an existing lock. Copy the truncated
                     lock into the lock array. */
                  if (tmp_lock[0].lock_type != UNLOCK_LOCK) {
                        SMB_ASSERT(tmp_lock[0].lock_type == locks[i].lock_type);
                        SMB_ASSERT(tmp_lock[1].lock_type == UNLOCK_LOCK);
                        memcpy(&tp[count], &tmp_lock[0], sizeof(struct lock_struct));
                        if (tmp_lock[0].size != locks[i].size) {
                              overlap_found = True;
                        }
                  } else {
                        SMB_ASSERT(tmp_lock[0].lock_type == UNLOCK_LOCK);
                        SMB_ASSERT(tmp_lock[1].lock_type == locks[i].lock_type);
                        memcpy(&tp[count], &tmp_lock[1], sizeof(struct lock_struct));
                        if (tmp_lock[1].start != locks[i].start) {
                              overlap_found = True;
                        }
                  }
                  count++;
                  continue;
            } else {
                  /* tmp_count == 3 - (we split a lock range in two). */
                  SMB_ASSERT(tmp_lock[0].lock_type == locks[i].lock_type);
                  SMB_ASSERT(tmp_lock[1].lock_type == UNLOCK_LOCK);
                  SMB_ASSERT(tmp_lock[2].lock_type == locks[i].lock_type);

                  memcpy(&tp[count], &tmp_lock[0], sizeof(struct lock_struct));
                  count++;
                  memcpy(&tp[count], &tmp_lock[2], sizeof(struct lock_struct));
                  count++;
                  overlap_found = True;
                  /* Optimisation... */
                  /* We know we're finished here as we can't overlap any
                     more POSIX locks. Copy the rest of the lock array. */
                  if (i < br_lck->num_locks - 1) {
                        memcpy(&tp[count], &locks[i+1], 
                              sizeof(*locks)*((br_lck->num_locks-1) - i));
                        count += ((br_lck->num_locks-1) - i);
                  }
                  break;
            }
      }

      if (!overlap_found) {
            /* Just ignore - no change. */
            SAFE_FREE(tp);
            DEBUG(10,("brl_unlock_posix: No overlap - unlocked.\n"));
            return True;
      }

      /* Unlock any POSIX regions. */
      if(lp_posix_locking(br_lck->fsp->conn->params)) {
            release_posix_lock_posix_flavour(br_lck->fsp,
                                    plock->start,
                                    plock->size,
                                    &plock->context,
                                    tp,
                                    count);
      }

      /* Realloc so we don't leak entries per unlock call. */
      if (count) {
            tp = (struct lock_struct *)SMB_REALLOC(tp, count * sizeof(*locks));
            if (!tp) {
                  DEBUG(10,("brl_unlock_posix: realloc fail\n"));
                  return False;
            }
      } else {
            /* We deleted the last lock. */
            SAFE_FREE(tp);
            tp = NULL;
      }

      br_lck->num_locks = count;
      SAFE_FREE(br_lck->lock_data);
      locks = tp;
      br_lck->lock_data = tp;
      br_lck->modified = True;

      /* Send unlock messages to any pending waiters that overlap. */

      for (j=0; j < br_lck->num_locks; j++) {
            struct lock_struct *pend_lock = &locks[j];

            /* Ignore non-pending locks. */
            if (!IS_PENDING_LOCK(pend_lock->lock_type)) {
                  continue;
            }

            /* We could send specific lock info here... */
            if (brl_pending_overlap(plock, pend_lock)) {
                  DEBUG(10,("brl_unlock: sending unlock message to pid %s\n",
                        procid_str_static(&pend_lock->context.pid )));

                  messaging_send(msg_ctx, pend_lock->context.pid,
                               MSG_SMB_UNLOCK, &data_blob_null);
            }
      }

      return True;
}

/****************************************************************************
 Unlock a range of bytes.
****************************************************************************/

bool brl_unlock(struct messaging_context *msg_ctx,
            struct byte_range_lock *br_lck,
            uint32 smbpid,
            struct server_id pid,
            br_off start,
            br_off size,
            enum brl_flavour lock_flav)
{
      struct lock_struct lock;

      lock.context.smbpid = smbpid;
      lock.context.pid = pid;
      lock.context.tid = br_lck->fsp->conn->cnum;
      lock.start = start;
      lock.size = size;
      lock.fnum = br_lck->fsp->fnum;
      lock.lock_type = UNLOCK_LOCK;
      lock.lock_flav = lock_flav;

      if (lock_flav == WINDOWS_LOCK) {
            return brl_unlock_windows(msg_ctx, br_lck, &lock);
      } else {
            return brl_unlock_posix(msg_ctx, br_lck, &lock);
      }
}

/****************************************************************************
 Test if we could add a lock if we wanted to.
 Returns True if the region required is currently unlocked, False if locked.
****************************************************************************/

bool brl_locktest(struct byte_range_lock *br_lck,
            uint32 smbpid,
            struct server_id pid,
            br_off start,
            br_off size, 
            enum brl_type lock_type,
            enum brl_flavour lock_flav)
{
      bool ret = True;
      unsigned int i;
      struct lock_struct lock;
      const struct lock_struct *locks = br_lck->lock_data;
      files_struct *fsp = br_lck->fsp;

      lock.context.smbpid = smbpid;
      lock.context.pid = pid;
      lock.context.tid = br_lck->fsp->conn->cnum;
      lock.start = start;
      lock.size = size;
      lock.fnum = fsp->fnum;
      lock.lock_type = lock_type;
      lock.lock_flav = lock_flav;

      /* Make sure existing locks don't conflict */
      for (i=0; i < br_lck->num_locks; i++) {
            /*
             * Our own locks don't conflict.
             */
            if (brl_conflict_other(&locks[i], &lock)) {
                  return False;
            }
      }

      /*
       * There is no lock held by an SMB daemon, check to
       * see if there is a POSIX lock from a UNIX or NFS process.
       * This only conflicts with Windows locks, not POSIX locks.
       */

      if(lp_posix_locking(fsp->conn->params) && (lock_flav == WINDOWS_LOCK)) {
            ret = is_posix_locked(fsp, &start, &size, &lock_type, WINDOWS_LOCK);

            DEBUG(10,("brl_locktest: posix start=%.0f len=%.0f %s for fnum %d file %s\n",
                  (double)start, (double)size, ret ? "locked" : "unlocked",
                  fsp->fnum, fsp->fsp_name ));

            /* We need to return the inverse of is_posix_locked. */
            ret = !ret;
        }

      /* no conflicts - we could have added it */
      return ret;
}

/****************************************************************************
 Query for existing locks.
****************************************************************************/

NTSTATUS brl_lockquery(struct byte_range_lock *br_lck,
            uint32 *psmbpid,
            struct server_id pid,
            br_off *pstart,
            br_off *psize, 
            enum brl_type *plock_type,
            enum brl_flavour lock_flav)
{
      unsigned int i;
      struct lock_struct lock;
      const struct lock_struct *locks = br_lck->lock_data;
      files_struct *fsp = br_lck->fsp;

      lock.context.smbpid = *psmbpid;
      lock.context.pid = pid;
      lock.context.tid = br_lck->fsp->conn->cnum;
      lock.start = *pstart;
      lock.size = *psize;
      lock.fnum = fsp->fnum;
      lock.lock_type = *plock_type;
      lock.lock_flav = lock_flav;

      /* Make sure existing locks don't conflict */
      for (i=0; i < br_lck->num_locks; i++) {
            const struct lock_struct *exlock = &locks[i];
            bool conflict = False;

            if (exlock->lock_flav == WINDOWS_LOCK) {
                  conflict = brl_conflict(exlock, &lock);
            } else {    
                  conflict = brl_conflict_posix(exlock, &lock);
            }

            if (conflict) {
                  *psmbpid = exlock->context.smbpid;
                  *pstart = exlock->start;
                    *psize = exlock->size;
                  *plock_type = exlock->lock_type;
                  return NT_STATUS_LOCK_NOT_GRANTED;
            }
      }

      /*
       * There is no lock held by an SMB daemon, check to
       * see if there is a POSIX lock from a UNIX or NFS process.
       */

      if(lp_posix_locking(fsp->conn->params)) {
            bool ret = is_posix_locked(fsp, pstart, psize, plock_type, POSIX_LOCK);

            DEBUG(10,("brl_lockquery: posix start=%.0f len=%.0f %s for fnum %d file %s\n",
                  (double)*pstart, (double)*psize, ret ? "locked" : "unlocked",
                  fsp->fnum, fsp->fsp_name ));

            if (ret) {
                  /* Hmmm. No clue what to set smbpid to - use -1. */
                  *psmbpid = 0xFFFF;
                  return NT_STATUS_LOCK_NOT_GRANTED;
            }
        }

      return NT_STATUS_OK;
}

/****************************************************************************
 Remove a particular pending lock.
****************************************************************************/

bool brl_lock_cancel(struct byte_range_lock *br_lck,
            uint32 smbpid,
            struct server_id pid,
            br_off start,
            br_off size,
            enum brl_flavour lock_flav)
{
      unsigned int i;
      struct lock_struct *locks = br_lck->lock_data;
      struct lock_context context;

      context.smbpid = smbpid;
      context.pid = pid;
      context.tid = br_lck->fsp->conn->cnum;

      for (i = 0; i < br_lck->num_locks; i++) {
            struct lock_struct *lock = &locks[i];

            /* For pending locks we *always* care about the fnum. */
            if (brl_same_context(&lock->context, &context) &&
                        lock->fnum == br_lck->fsp->fnum &&
                        IS_PENDING_LOCK(lock->lock_type) &&
                        lock->lock_flav == lock_flav &&
                        lock->start == start &&
                        lock->size == size) {
                  break;
            }
      }

      if (i == br_lck->num_locks) {
            /* Didn't find it. */
            return False;
      }

      if (i < br_lck->num_locks - 1) {
            /* Found this particular pending lock - delete it */
            memmove(&locks[i], &locks[i+1], 
                  sizeof(*locks)*((br_lck->num_locks-1) - i));
      }

      br_lck->num_locks -= 1;
      br_lck->modified = True;
      return True;
}

/****************************************************************************
 Remove any locks associated with a open file.
 We return True if this process owns any other Windows locks on this
 fd and so we should not immediately close the fd.
****************************************************************************/

void brl_close_fnum(struct messaging_context *msg_ctx,
                struct byte_range_lock *br_lck)
{
      files_struct *fsp = br_lck->fsp;
      uint16 tid = fsp->conn->cnum;
      int fnum = fsp->fnum;
      unsigned int i, j, dcount=0;
      int num_deleted_windows_locks = 0;
      struct lock_struct *locks = br_lck->lock_data;
      struct server_id pid = procid_self();
      bool unlock_individually = False;

      if(lp_posix_locking(fsp->conn->params)) {

            /* Check if there are any Windows locks associated with this dev/ino
               pair that are not this fnum. If so we need to call unlock on each
               one in order to release the system POSIX locks correctly. */

            for (i=0; i < br_lck->num_locks; i++) {
                  struct lock_struct *lock = &locks[i];

                  if (!procid_equal(&lock->context.pid, &pid)) {
                        continue;
                  }

                  if (lock->lock_type != READ_LOCK && lock->lock_type != WRITE_LOCK) {
                        continue; /* Ignore pending. */
                  }

                  if (lock->context.tid != tid || lock->fnum != fnum) {
                        unlock_individually = True;
                        break;
                  }
            }

            if (unlock_individually) {
                  struct lock_struct *locks_copy;
                  unsigned int num_locks_copy;

                  /* Copy the current lock array. */
                  if (br_lck->num_locks) {
                        locks_copy = (struct lock_struct *)TALLOC_MEMDUP(br_lck, locks, br_lck->num_locks * sizeof(struct lock_struct));
                        if (!locks_copy) {
                              smb_panic("brl_close_fnum: talloc failed");
                        }
                  } else {    
                        locks_copy = NULL;
                  }

                  num_locks_copy = br_lck->num_locks;

                  for (i=0; i < num_locks_copy; i++) {
                        struct lock_struct *lock = &locks_copy[i];

                        if (lock->context.tid == tid && procid_equal(&lock->context.pid, &pid) &&
                                    (lock->fnum == fnum)) {
                              brl_unlock(msg_ctx,
                                    br_lck,
                                    lock->context.smbpid,
                                    pid,
                                    lock->start,
                                    lock->size,
                                    lock->lock_flav);
                        }
                  }
                  return;
            }
      }

      /* We can bulk delete - any POSIX locks will be removed when the fd closes. */

      /* Remove any existing locks for this fnum (or any fnum if they're POSIX). */

      for (i=0; i < br_lck->num_locks; i++) {
            struct lock_struct *lock = &locks[i];
            bool del_this_lock = False;

            if (lock->context.tid == tid && procid_equal(&lock->context.pid, &pid)) {
                  if ((lock->lock_flav == WINDOWS_LOCK) && (lock->fnum == fnum)) {
                        del_this_lock = True;
                        num_deleted_windows_locks++;
                  } else if (lock->lock_flav == POSIX_LOCK) {
                        del_this_lock = True;
                  }
            }

            if (del_this_lock) {
                  /* Send unlock messages to any pending waiters that overlap. */
                  for (j=0; j < br_lck->num_locks; j++) {
                        struct lock_struct *pend_lock = &locks[j];

                        /* Ignore our own or non-pending locks. */
                        if (!IS_PENDING_LOCK(pend_lock->lock_type)) {
                              continue;
                        }

                        /* Optimisation - don't send to this fnum as we're
                           closing it. */
                        if (pend_lock->context.tid == tid &&
                            procid_equal(&pend_lock->context.pid, &pid) &&
                            pend_lock->fnum == fnum) {
                              continue;
                        }

                        /* We could send specific lock info here... */
                        if (brl_pending_overlap(lock, pend_lock)) {
                              messaging_send(msg_ctx, pend_lock->context.pid,
                                           MSG_SMB_UNLOCK, &data_blob_null);
                        }
                  }

                  /* found it - delete it */
                  if (br_lck->num_locks > 1 && i < br_lck->num_locks - 1) {
                        memmove(&locks[i], &locks[i+1], 
                              sizeof(*locks)*((br_lck->num_locks-1) - i));
                  }
                  br_lck->num_locks--;
                  br_lck->modified = True;
                  i--;
                  dcount++;
            }
      }

      if(lp_posix_locking(fsp->conn->params) && num_deleted_windows_locks) {
            /* Reduce the Windows lock POSIX reference count on this dev/ino pair. */
            reduce_windows_lock_ref_count(fsp, num_deleted_windows_locks);
      }
}

/****************************************************************************
 Ensure this set of lock entries is valid.
****************************************************************************/

static bool validate_lock_entries(unsigned int *pnum_entries, struct lock_struct **pplocks)
{
      unsigned int i;
      unsigned int num_valid_entries = 0;
      struct lock_struct *locks = *pplocks;

      for (i = 0; i < *pnum_entries; i++) {
            struct lock_struct *lock_data = &locks[i];
            if (!process_exists(lock_data->context.pid)) {
                  /* This process no longer exists - mark this
                     entry as invalid by zeroing it. */
                  ZERO_STRUCTP(lock_data);
            } else {
                  num_valid_entries++;
            }
      }

      if (num_valid_entries != *pnum_entries) {
            struct lock_struct *new_lock_data = NULL;

            if (num_valid_entries) {
                  new_lock_data = SMB_MALLOC_ARRAY(struct lock_struct, num_valid_entries);
                  if (!new_lock_data) {
                        DEBUG(3, ("malloc fail\n"));
                        return False;
                  }

                  num_valid_entries = 0;
                  for (i = 0; i < *pnum_entries; i++) {
                        struct lock_struct *lock_data = &locks[i];
                        if (lock_data->context.smbpid &&
                                    lock_data->context.tid) {
                              /* Valid (nonzero) entry - copy it. */
                              memcpy(&new_lock_data[num_valid_entries],
                                    lock_data, sizeof(struct lock_struct));
                              num_valid_entries++;
                        }
                  }
            }

            SAFE_FREE(*pplocks);
            *pplocks = new_lock_data;
            *pnum_entries = num_valid_entries;
      }

      return True;
}

struct brl_forall_cb {
      void (*fn)(struct file_id id, struct server_id pid,
               enum brl_type lock_type,
               enum brl_flavour lock_flav,
               br_off start, br_off size,
               void *private_data);
      void *private_data;
};

/****************************************************************************
 Traverse the whole database with this function, calling traverse_callback
 on each lock.
****************************************************************************/

static int traverse_fn(struct db_record *rec, void *state)
{
      struct brl_forall_cb *cb = (struct brl_forall_cb *)state;
      struct lock_struct *locks;
      struct file_id *key;
      unsigned int i;
      unsigned int num_locks = 0;
      unsigned int orig_num_locks = 0;

      /* In a traverse function we must make a copy of
         dbuf before modifying it. */

      locks = (struct lock_struct *)memdup(rec->value.dptr,
                                   rec->value.dsize);
      if (!locks) {
            return -1; /* Terminate traversal. */
      }

      key = (struct file_id *)rec->key.dptr;
      orig_num_locks = num_locks = rec->value.dsize/sizeof(*locks);

      /* Ensure the lock db is clean of entries from invalid processes. */

      if (!validate_lock_entries(&num_locks, &locks)) {
            SAFE_FREE(locks);
            return -1; /* Terminate traversal */
      }

      if (orig_num_locks != num_locks) {
            if (num_locks) {
                  TDB_DATA data;
                  data.dptr = (uint8_t *)locks;
                  data.dsize = num_locks*sizeof(struct lock_struct);
                  rec->store(rec, data, TDB_REPLACE);
            } else {
                  rec->delete_rec(rec);
            }
      }

      if (cb->fn) {
            for ( i=0; i<num_locks; i++) {
                  cb->fn(*key,
                        locks[i].context.pid,
                        locks[i].lock_type,
                        locks[i].lock_flav,
                        locks[i].start,
                        locks[i].size,
                        cb->private_data);
            }
      }

      SAFE_FREE(locks);
      return 0;
}

/*******************************************************************
 Call the specified function on each lock in the database.
********************************************************************/

int brl_forall(void (*fn)(struct file_id id, struct server_id pid,
                    enum brl_type lock_type,
                    enum brl_flavour lock_flav,
                    br_off start, br_off size,
                    void *private_data),
             void *private_data)
{
      struct brl_forall_cb cb;

      if (!brlock_db) {
            return 0;
      }
      cb.fn = fn;
      cb.private_data = private_data;
      return brlock_db->traverse(brlock_db, traverse_fn, &cb);
}

/*******************************************************************
 Store a potentially modified set of byte range lock data back into
 the database.
 Unlock the record.
********************************************************************/

static int byte_range_lock_destructor(struct byte_range_lock *br_lck)
{
      if (br_lck->read_only) {
            SMB_ASSERT(!br_lck->modified);
      }

      if (!br_lck->modified) {
            goto done;
      }

      if (br_lck->num_locks == 0) {
            /* No locks - delete this entry. */
            NTSTATUS status = br_lck->record->delete_rec(br_lck->record);
            if (!NT_STATUS_IS_OK(status)) {
                  DEBUG(0, ("delete_rec returned %s\n",
                          nt_errstr(status)));
                  smb_panic("Could not delete byte range lock entry");
            }
      } else {
            TDB_DATA data;
            NTSTATUS status;

            data.dptr = (uint8 *)br_lck->lock_data;
            data.dsize = br_lck->num_locks * sizeof(struct lock_struct);

            status = br_lck->record->store(br_lck->record, data,
                                     TDB_REPLACE);
            if (!NT_STATUS_IS_OK(status)) {
                  DEBUG(0, ("store returned %s\n", nt_errstr(status)));
                  smb_panic("Could not store byte range mode entry");
            }
      }

 done:

      SAFE_FREE(br_lck->lock_data);
      TALLOC_FREE(br_lck->record);
      return 0;
}

/*******************************************************************
 Fetch a set of byte range lock data from the database.
 Leave the record locked.
 TALLOC_FREE(brl) will release the lock in the destructor.
********************************************************************/

static struct byte_range_lock *brl_get_locks_internal(TALLOC_CTX *mem_ctx,
                              files_struct *fsp, bool read_only)
{
      TDB_DATA key, data;
      struct byte_range_lock *br_lck = TALLOC_P(mem_ctx, struct byte_range_lock);

      if (br_lck == NULL) {
            return NULL;
      }

      br_lck->fsp = fsp;
      br_lck->num_locks = 0;
      br_lck->modified = False;
      memset(&br_lck->key, '\0', sizeof(struct file_id));
      br_lck->key = fsp->file_id;

      key.dptr = (uint8 *)&br_lck->key;
      key.dsize = sizeof(struct file_id);

      if (!fsp->lockdb_clean) {
            /* We must be read/write to clean
               the dead entries. */
            read_only = False;
      }

      if (read_only) {
            if (brlock_db->fetch(brlock_db, br_lck, key, &data) == -1) {
                  DEBUG(3, ("Could not fetch byte range lock record\n"));
                  TALLOC_FREE(br_lck);
                  return NULL;
            }
            br_lck->record = NULL;
      }
      else {
            br_lck->record = brlock_db->fetch_locked(brlock_db, br_lck, key);

            if (br_lck->record == NULL) {
                  DEBUG(3, ("Could not lock byte range lock entry\n"));
                  TALLOC_FREE(br_lck);
                  return NULL;
            }

            data = br_lck->record->value;
      }

      br_lck->read_only = read_only;
      br_lck->lock_data = NULL;

      talloc_set_destructor(br_lck, byte_range_lock_destructor);

      br_lck->num_locks = data.dsize / sizeof(struct lock_struct);

      if (br_lck->num_locks != 0) {
            br_lck->lock_data = SMB_MALLOC_ARRAY(struct lock_struct,
                                         br_lck->num_locks);
            if (br_lck->lock_data == NULL) {
                  DEBUG(0, ("malloc failed\n"));
                  TALLOC_FREE(br_lck);
                  return NULL;
            }

            memcpy(br_lck->lock_data, data.dptr, data.dsize);
      }
      
      if (!fsp->lockdb_clean) {
            int orig_num_locks = br_lck->num_locks;

            /* This is the first time we've accessed this. */
            /* Go through and ensure all entries exist - remove any that don't. */
            /* Makes the lockdb self cleaning at low cost. */

            if (!validate_lock_entries(&br_lck->num_locks,
                                 &br_lck->lock_data)) {
                  SAFE_FREE(br_lck->lock_data);
                  TALLOC_FREE(br_lck);
                  return NULL;
            }

            /* Ensure invalid locks are cleaned up in the destructor. */
            if (orig_num_locks != br_lck->num_locks) {
                  br_lck->modified = True;
            }

            /* Mark the lockdb as "clean" as seen from this open file. */
            fsp->lockdb_clean = True;
      }

      if (DEBUGLEVEL >= 10) {
            unsigned int i;
            struct lock_struct *locks = br_lck->lock_data;
            DEBUG(10,("brl_get_locks_internal: %u current locks on file_id %s\n",
                  br_lck->num_locks,
                    file_id_string_tos(&fsp->file_id)));
            for( i = 0; i < br_lck->num_locks; i++) {
                  print_lock_struct(i, &locks[i]);
            }
      }
      return br_lck;
}

struct byte_range_lock *brl_get_locks(TALLOC_CTX *mem_ctx,
                              files_struct *fsp)
{
      return brl_get_locks_internal(mem_ctx, fsp, False);
}

struct byte_range_lock *brl_get_locks_readonly(TALLOC_CTX *mem_ctx,
                              files_struct *fsp)
{
      return brl_get_locks_internal(mem_ctx, fsp, True);
}

struct brl_revalidate_state {
      ssize_t array_size;
      uint32 num_pids;
      struct server_id *pids;
};

/*
 * Collect PIDs of all processes with pending entries
 */

static void brl_revalidate_collect(struct file_id id, struct server_id pid,
                           enum brl_type lock_type,
                           enum brl_flavour lock_flav,
                           br_off start, br_off size,
                           void *private_data)
{
      struct brl_revalidate_state *state =
            (struct brl_revalidate_state *)private_data;

      if (!IS_PENDING_LOCK(lock_type)) {
            return;
      }

      add_to_large_array(state, sizeof(pid), (void *)&pid,
                     &state->pids, &state->num_pids,
                     &state->array_size);
}

/*
 * qsort callback to sort the processes
 */

static int compare_procids(const void *p1, const void *p2)
{
      const struct server_id *i1 = (struct server_id *)p1;
      const struct server_id *i2 = (struct server_id *)p2;

      if (i1->pid < i2->pid) return -1;
      if (i2->pid > i2->pid) return 1;
      return 0;
}

/*
 * Send a MSG_SMB_UNLOCK message to all processes with pending byte range
 * locks so that they retry. Mainly used in the cluster code after a node has
 * died.
 *
 * Done in two steps to avoid double-sends: First we collect all entries in an
 * array, then qsort that array and only send to non-dupes.
 */

static void brl_revalidate(struct messaging_context *msg_ctx,
                     void *private_data,
                     uint32_t msg_type,
                     struct server_id server_id,
                     DATA_BLOB *data)
{
      struct brl_revalidate_state *state;
      uint32 i;
      struct server_id last_pid;

      if (!(state = TALLOC_ZERO_P(NULL, struct brl_revalidate_state))) {
            DEBUG(0, ("talloc failed\n"));
            return;
      }

      brl_forall(brl_revalidate_collect, state);

      if (state->array_size == -1) {
            DEBUG(0, ("talloc failed\n"));
            goto done;
      }

      if (state->num_pids == 0) {
            goto done;
      }

      qsort(state->pids, state->num_pids, sizeof(state->pids[0]),
            compare_procids);

      ZERO_STRUCT(last_pid);

      for (i=0; i<state->num_pids; i++) {
            if (procid_equal(&last_pid, &state->pids[i])) {
                  /*
                   * We've seen that one already
                   */
                  continue;
            }

            messaging_send(msg_ctx, state->pids[i], MSG_SMB_UNLOCK,
                         &data_blob_null);
            last_pid = state->pids[i];
      }

 done:
      TALLOC_FREE(state);
      return;
}

void brl_register_msgs(struct messaging_context *msg_ctx)
{
      messaging_register(msg_ctx, NULL, MSG_SMB_BRL_VALIDATE,
                     brl_revalidate);
}

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