r26492: Some hosts have a define called ifa_dstaddr.

[Samba.git] / source / locking / 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);
}