smbd: Restructure brl_conflict_other

[Samba.git] / source3 / 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"
#include "system/filesys.h"
#include "locking/proto.h"
#include "smbd/globals.h"
#include "dbwrap/dbwrap.h"
#include "dbwrap/dbwrap_open.h"
#include "serverid.h"
#include "messages.h"
#include "util_tdb.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_LOCKING

#define ZERO_ZERO 0

/* The open brlock.tdb database. */

static struct db_context *brlock_db;

struct byte_range_lock {
        struct files_struct *fsp;
        unsigned int num_locks;
        bool modified;
        bool have_read_oplocks;
        struct lock_struct *lock_data;
        struct db_record *record;
};

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

static void print_lock_struct(unsigned int i, const struct lock_struct *pls)
{
        DEBUG(10,("[%u]: smblctx = %llu, tid = %u, pid = %s, ",
                        i,
                        (unsigned long long)pls->context.smblctx,
                        (unsigned int)pls->context.tid,
                        server_id_str(talloc_tos(), &pls->context.pid) ));

        DEBUG(10, ("start = %ju, size = %ju, fnum = %ju, %s %s\n",
                   (uintmax_t)pls->start,
                   (uintmax_t)pls->size,
                   (uintmax_t)pls->fnum,
                   lock_type_name(pls->lock_type),
                   lock_flav_name(pls->lock_flav)));
}

unsigned int brl_num_locks(const struct byte_range_lock *brl)
{
        return brl->num_locks;
}

struct files_struct *brl_fsp(struct byte_range_lock *brl)
{
        return brl->fsp;
}

bool brl_have_read_oplocks(const struct byte_range_lock *brl)
{
        return brl->have_read_oplocks;
}

void brl_set_have_read_oplocks(struct byte_range_lock *brl,
                               bool have_read_oplocks)
{
        DEBUG(10, ("Setting have_read_oplocks to %s\n",
                   have_read_oplocks ? "true" : "false"));
        SMB_ASSERT(brl->record != NULL); /* otherwise we're readonly */
        brl->have_read_oplocks = have_read_oplocks;
        brl->modified = true;
}

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

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

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

static bool brl_overlap(const struct lock_struct *lck1,
                        const struct lock_struct *lck2)
{
        /* XXX Remove for Win7 compatibility. */
        /* this extra check is not redundant - 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;
        }

        /* A READ lock can stack on top of a WRITE lock if they have the same
         * context & fnum. */
        if (lck1->lock_type == WRITE_LOCK && lck2->lock_type == READ_LOCK &&
            brl_same_context(&lck1->context, &lck2->context) &&
            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 don'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 *lock,
                               const struct lock_struct *rw_probe)
{
        if (IS_PENDING_LOCK(lock->lock_type) ||
            IS_PENDING_LOCK(rw_probe->lock_type)) {
                return False;
        }

        if (lock->lock_type == READ_LOCK && rw_probe->lock_type == READ_LOCK) {
                return False;
        }

        if (lock->lock_flav == POSIX_LOCK &&
            rw_probe->lock_flav == POSIX_LOCK) {
                /*
                 * POSIX flavour locks never conflict here - this is only called
                 * in the read/write path.
                 */
                return False;
        }

        if (!brl_overlap(lock, rw_probe)) {
                /*
                 * I/O can only conflict when overlapping a lock, thus let it
                 * pass
                 */
                return false;
        }

        if (!brl_same_context(&lock->context, &rw_probe->context)) {
                /*
                 * Different process, conflict
                 */
                return true;
        }

        if (lock->fnum != rw_probe->fnum) {
                /*
                 * Different file handle, conflict
                 */
                return true;
        }

        if ((lock->lock_type == READ_LOCK) &&
            (rw_probe->lock_type == WRITE_LOCK)) {
                /*
                 * Incoming WRITE locks conflict with existing READ locks even
                 * if the context is the same. JRA. See LOCKTEST7 in
                 * smbtorture.
                 */
                return true;
        }

        /*
         * I/O request compatible with existing lock, let it pass without
         * conflict
         */

        return false;
}

/****************************************************************************
 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 (serverid_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)
{
        int tdb_flags;

        if (brlock_db) {
                return;
        }

        tdb_flags = TDB_DEFAULT|TDB_VOLATILE|TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH;

        if (!lp_clustering()) {
                /*
                 * We can't use the SEQNUM trick to cache brlock
                 * entries in the clustering case because ctdb seqnum
                 * propagation has a delay.
                 */
                tdb_flags |= TDB_SEQNUM;
        }

        brlock_db = db_open(NULL, lock_path("brlock.tdb"),
                            SMB_OPEN_DATABASE_TDB_HASH_SIZE, tdb_flags,
                            read_only?O_RDONLY:(O_RDWR|O_CREAT), 0644,
                            DBWRAP_LOCK_ORDER_2, DBWRAP_FLAG_NONE);
        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.
****************************************************************************/

NTSTATUS brl_lock_windows_default(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;
        NTSTATUS status;

        SMB_ASSERT(plock->lock_type != UNLOCK_LOCK);

        if ((plock->start + plock->size - 1 < plock->start) &&
                        plock->size != 0) {
                return NT_STATUS_INVALID_LOCK_RANGE;
        }

        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.smblctx = locks[i].context.smblctx;
                        return brl_lock_failed(fsp,plock,blocking_lock);
                }
#if ZERO_ZERO
                if (plock->start == 0 && plock->size == 0 &&
                                locks[i].size == 0) {
                        break;
                }
#endif
        }

        if (!IS_PENDING_LOCK(plock->lock_type)) {
                contend_level2_oplocks_begin(fsp, LEVEL2_CONTEND_WINDOWS_BRL);
        }

        /* 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.smblctx = 0xFFFFFFFFFFFFFFFFLL;

                        if (errno_ret == EACCES || errno_ret == EAGAIN) {
                                status = NT_STATUS_FILE_LOCK_CONFLICT;
                                goto fail;
                        } else {
                                status = map_nt_error_from_unix(errno);
                                goto fail;
                        }
                }
        }

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

        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;
 fail:
        if (!IS_PENDING_LOCK(plock->lock_type)) {
                contend_level2_oplocks_end(fsp, LEVEL2_CONTEND_WINDOWS_BRL);
        }
        return status;
}

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

static unsigned int brlock_posix_split_merge(struct lock_struct *lck_arr,       /* Output array. */
                                                struct lock_struct *ex,         /* existing lock. */
                                                struct lock_struct *plock)      /* proposed lock. */
{
        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.
        +---------------------------+
OR
             +---------------+
             |       ex      |
             +---------------+
        +---------------------------+
        |       plock               | -> replace with plock.
        +---------------------------+

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

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

                /* Replace - discard existing lock. */

                return 0;
        }

/*********************************************
Adjacent after.
                        +-------+
                        |  ex   |
                        +-------+
        +---------------+
        |   plock       |
        +---------------+

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

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

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

                if (lock_types_differ) {
                        /* Add existing. */
                        memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                        return 1;
                } else {
                        /* Merge - adjust incoming lock as we may have more
                         * merging to come. */
                        plock->size += ex->size;
                        return 0;
                }
        }

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

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

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

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

                /* If the lock types are the same, we merge, if different, we
                   add the existing lock. */

                if (lock_types_differ) {
                        memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                        return 1;
                } else {
                        /* Merge - adjust incoming lock as we may have more
                         * merging to come. */
                        plock->start = ex->start;
                        plock->size += ex->size;
                        return 0;
                }
        }

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

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

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

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

                if (lock_types_differ) {
                        /* Add remaining existing. */
                        memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                        /* Adjust existing start and size. */
                        lck_arr[0].start = plock->start + plock->size;
                        lck_arr[0].size = (ex->start + ex->size) - (plock->start + plock->size);
                        return 1;
                } else {
                        /* Merge - adjust incoming lock as we may have more
                         * merging to come. */
                        plock->size += (ex->start + ex->size) - (plock->start + plock->size);
                        return 0;
                }
        }

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

BECOMES....
        +-------+---------------+
        | ex    |   plock       | - different lock types
        +-------+---------------+

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

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

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

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

                if (lock_types_differ) {
                        memcpy(&lck_arr[0], ex, sizeof(struct lock_struct));
                        /* Adjust existing size. */
                        lck_arr[0].size = plock->start - ex->start;
                        return 1;
                } else {
                        /* Merge - adjust incoming lock as we may have more
                         * merging to come. MUST ADJUST plock SIZE FIRST ! */
                        plock->size += (plock->start - ex->start);
                        plock->start = ex->start;
                        return 0;
                }
        }

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

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

                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], 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[1].start = plock->start + plock->size;
                        lck_arr[1].size = (ex->start + ex->size) - (plock->start + plock->size);
                        return 2;
                } else {
                        /* Just eat the existing locks, merge them into plock. */
                        plock->start = ex->start;
                        plock->size = ex->size;
                        return 0;
                }
        }

        /* 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, posix_count;
        struct lock_struct *locks = br_lck->lock_data;
        struct lock_struct *tp;
        bool signal_pending_read = False;
        bool break_oplocks = false;
        NTSTATUS status;

        /* 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 - 1 < plock->start) {
                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 = talloc_array(br_lck, struct lock_struct, br_lck->num_locks + 2);
        if (!tp) {
                return NT_STATUS_NO_MEMORY;
        }

        count = posix_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. */
                                TALLOC_FREE(tp);
                                /* Remember who blocked us. */
                                plock->context.smblctx = curr_lock->context.smblctx;
                                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 {
                        unsigned int tmp_count = 0;

                        /* POSIX conflict semantics are different. */
                        if (brl_conflict_posix(curr_lock, plock)) {
                                /* Can't block ourselves with POSIX locks. */
                                /* No games with error messages. */
                                TALLOC_FREE(tp);
                                /* Remember who blocked us. */
                                plock->context.smblctx = curr_lock->context.smblctx;
                                return NT_STATUS_FILE_LOCK_CONFLICT;
                        }

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

        /*
         * Break oplocks while we hold a brl. Since lock() and unlock() calls
         * are not symetric with POSIX semantics, we cannot guarantee our
         * contend_level2_oplocks_begin/end calls will be acquired and
         * released one-for-one as with Windows semantics. Therefore we only
         * call contend_level2_oplocks_begin if this is the first POSIX brl on
         * the file.
         */
        break_oplocks = (!IS_PENDING_LOCK(plock->lock_type) &&
                         posix_count == 0);
        if (break_oplocks) {
                contend_level2_oplocks_begin(br_lck->fsp,
                                             LEVEL2_CONTEND_POSIX_BRL);
        }

        /* Try and add the lock in order, sorted by lock start. */
        for (i=0; i < count; i++) {
                struct lock_struct *curr_lock = &tp[i];

                if (curr_lock->start <= plock->start) {
                        continue;
                }
        }

        if (i < count) {
                memmove(&tp[i+1], &tp[i],
                        (count - i)*sizeof(struct lock_struct));
        }
        memcpy(&tp[i], 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.smblctx = 0xFFFFFFFFFFFFFFFFLL;

                        if (errno_ret == EACCES || errno_ret == EAGAIN) {
                                TALLOC_FREE(tp);
                                status = NT_STATUS_FILE_LOCK_CONFLICT;
                                goto fail;
                        } else {
                                TALLOC_FREE(tp);
                                status = map_nt_error_from_unix(errno);
                                goto fail;
                        }
                }
        }

        /* If we didn't use all the allocated size,
         * Realloc so we don't leak entries per lock call. */
        if (count < br_lck->num_locks + 2) {
                tp = talloc_realloc(br_lck, tp, struct lock_struct, count);
                if (!tp) {
                        status = NT_STATUS_NO_MEMORY;
                        goto fail;
                }
        }

        br_lck->num_locks = count;
        TALLOC_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;
 fail:
        if (break_oplocks) {
                contend_level2_oplocks_end(br_lck->fsp,
                                           LEVEL2_CONTEND_POSIX_BRL);
        }
        return status;
}

NTSTATUS smb_vfs_call_brl_lock_windows(struct vfs_handle_struct *handle,
                                       struct byte_range_lock *br_lck,
                                       struct lock_struct *plock,
                                       bool blocking_lock)
{
        VFS_FIND(brl_lock_windows);
        return handle->fns->brl_lock_windows_fn(handle, br_lck, plock,
                                                blocking_lock);
}

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

NTSTATUS brl_lock(struct messaging_context *msg_ctx,
                struct byte_range_lock *br_lck,
                uint64_t smblctx,
                struct server_id pid,
                br_off start,
                br_off size,
                enum brl_type lock_type,
                enum brl_flavour lock_flav,
                bool blocking_lock,
                uint64_t *psmblctx)
{
        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 = (struct lock_struct) {
                .context.smblctx = smblctx,
                .context.pid = pid,
                .context.tid = br_lck->fsp->conn->cnum,
                .start = start,
                .size = size,
                .fnum = br_lck->fsp->fnum,
                .lock_type = lock_type,
                .lock_flav = lock_flav
        };

        if (lock_flav == WINDOWS_LOCK) {
                ret = SMB_VFS_BRL_LOCK_WINDOWS(br_lck->fsp->conn, br_lck,
                                               &lock, blocking_lock);
        } else {
                ret = brl_lock_posix(msg_ctx, br_lck, &lock);
        }

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

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

static void brl_delete_lock_struct(struct lock_struct *locks,
                                   unsigned num_locks,
                                   unsigned del_idx)
{
        if (del_idx >= num_locks) {
                return;
        }
        memmove(&locks[del_idx], &locks[del_idx+1],
                sizeof(*locks) * (num_locks - del_idx - 1));
}

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

bool brl_unlock_windows_default(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.... */

        SMB_ASSERT(plock->lock_type == UNLOCK_LOCK);

#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];

                if (IS_PENDING_LOCK(lock->lock_type)) {
                        continue;
                }

                /* 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

        brl_delete_lock_struct(locks, br_lck->num_locks, 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);
                }
        }

        contend_level2_oplocks_end(br_lck->fsp, LEVEL2_CONTEND_WINDOWS_BRL);
        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,
                             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 = talloc_array(br_lck, 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];
                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;
                }

                if (lock->lock_flav == WINDOWS_LOCK) {
                        /* Do any Windows flavour locks conflict ? */
                        if (brl_conflict(lock, plock)) {
                                TALLOC_FREE(tp);
                                return false;
                        }
                        /* Just copy the Windows lock into the new array. */
                        memcpy(&tp[count], lock, sizeof(struct lock_struct));
                        count++;
                        continue;
                }

                /* Work out overlaps. */
                tmp_count = brlock_posix_split_merge(&tp[count], lock, plock);

                if (tmp_count == 0) {
                        /* plock overlapped the existing lock completely,
                           or replaced it. Don't copy the existing lock. */
                        overlap_found = true;
                } else if (tmp_count == 1) {
                        /* Either no overlap, (simple copy of existing lock) or
                         * an overlap of an existing lock. */
                        /* If the lock changed size, we had an overlap. */
                        if (tp[count].size != lock->size) {
                                overlap_found = true;
                        }
                        count += tmp_count;
                } else if (tmp_count == 2) {
                        /* We split a lock range in two. */
                        overlap_found = true;
                        count += tmp_count;

                        /* 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. */
                TALLOC_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 = talloc_realloc(br_lck, tp, struct lock_struct, count);
                if (!tp) {
                        DEBUG(10,("brl_unlock_posix: realloc fail\n"));
                        return False;
                }
        } else {
                /* We deleted the last lock. */
                TALLOC_FREE(tp);
                tp = NULL;
        }

        contend_level2_oplocks_end(br_lck->fsp,
                                   LEVEL2_CONTEND_POSIX_BRL);

        br_lck->num_locks = count;
        TALLOC_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;
}

bool smb_vfs_call_brl_unlock_windows(struct vfs_handle_struct *handle,
                                     struct messaging_context *msg_ctx,
                                     struct byte_range_lock *br_lck,
                                     const struct lock_struct *plock)
{
        VFS_FIND(brl_unlock_windows);
        return handle->fns->brl_unlock_windows_fn(handle, msg_ctx, br_lck,
                                                  plock);
}

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

bool brl_unlock(struct messaging_context *msg_ctx,
                struct byte_range_lock *br_lck,
                uint64_t smblctx,
                struct server_id pid,
                br_off start,
                br_off size,
                enum brl_flavour lock_flav)
{
        struct lock_struct lock;

        lock.context.smblctx = smblctx;
        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 SMB_VFS_BRL_UNLOCK_WINDOWS(br_lck->fsp->conn, 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,
                uint64_t smblctx,
                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.smblctx = smblctx;
        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=%ju len=%ju %s for %s "
                           "file %s\n", (uintmax_t)start, (uintmax_t)size,
                           ret ? "locked" : "unlocked",
                           fsp_fnum_dbg(fsp), fsp_str_dbg(fsp)));

                /* 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,
                uint64_t *psmblctx,
                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.smblctx = *psmblctx;
        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) {
                        *psmblctx = exlock->context.smblctx;
                        *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=%ju len=%ju %s for %s "
                           "file %s\n", (uintmax_t)*pstart,
                           (uintmax_t)*psize, ret ? "locked" : "unlocked",
                           fsp_fnum_dbg(fsp), fsp_str_dbg(fsp)));

                if (ret) {
                        /* Hmmm. No clue what to set smblctx to - use -1. */
                        *psmblctx = 0xFFFFFFFFFFFFFFFFLL;
                        return NT_STATUS_LOCK_NOT_GRANTED;
                }
        }

        return NT_STATUS_OK;
}


bool smb_vfs_call_brl_cancel_windows(struct vfs_handle_struct *handle,
                                     struct byte_range_lock *br_lck,
                                     struct lock_struct *plock)
{
        VFS_FIND(brl_cancel_windows);
        return handle->fns->brl_cancel_windows_fn(handle, br_lck, plock);
}

/****************************************************************************
 Remove a particular pending lock.
****************************************************************************/
bool brl_lock_cancel(struct byte_range_lock *br_lck,
                uint64_t smblctx,
                struct server_id pid,
                br_off start,
                br_off size,
                enum brl_flavour lock_flav)
{
        bool ret;
        struct lock_struct lock;

        lock.context.smblctx = smblctx;
        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_flav = lock_flav;
        /* lock.lock_type doesn't matter */

        if (lock_flav == WINDOWS_LOCK) {
                ret = SMB_VFS_BRL_CANCEL_WINDOWS(br_lck->fsp->conn, br_lck,
                                                 &lock);
        } else {
                ret = brl_lock_cancel_default(br_lck, &lock);
        }

        return ret;
}

bool brl_lock_cancel_default(struct byte_range_lock *br_lck,
                struct lock_struct *plock)
{
        unsigned int i;
        struct lock_struct *locks = br_lck->lock_data;

        SMB_ASSERT(plock);

        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, &plock->context) &&
                                lock->fnum == plock->fnum &&
                                IS_PENDING_LOCK(lock->lock_type) &&
                                lock->lock_flav == plock->lock_flav &&
                                lock->start == plock->start &&
                                lock->size == plock->size) {
                        break;
                }
        }

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

        brl_delete_lock_struct(locks, br_lck->num_locks, 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;
        uint32_t tid = fsp->conn->cnum;
        uint64_t fnum = fsp->fnum;
        unsigned int i;
        struct lock_struct *locks = br_lck->lock_data;
        struct server_id pid = messaging_server_id(fsp->conn->sconn->msg_ctx);
        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 && serverid_equal(&lock->context.pid, &pid) &&
                                (lock->fnum == fnum)) {
                        brl_unlock(msg_ctx,
                                br_lck,
                                lock->context.smblctx,
                                pid,
                                lock->start,
                                lock->size,
                                lock->lock_flav);
                }
        }
}

bool brl_mark_disconnected(struct files_struct *fsp)
{
        uint32_t tid = fsp->conn->cnum;
        uint64_t smblctx;
        uint64_t fnum = fsp->fnum;
        unsigned int i;
        struct server_id self = messaging_server_id(fsp->conn->sconn->msg_ctx);
        struct byte_range_lock *br_lck = NULL;

        if (fsp->op == NULL) {
                return false;
        }

        smblctx = fsp->op->global->open_persistent_id;

        if (!fsp->op->global->durable) {
                return false;
        }

        if (fsp->current_lock_count == 0) {
                return true;
        }

        br_lck = brl_get_locks(talloc_tos(), fsp);
        if (br_lck == NULL) {
                return false;
        }

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

                /*
                 * as this is a durable handle, we only expect locks
                 * of the current file handle!
                 */

                if (lock->context.smblctx != smblctx) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                if (lock->context.tid != tid) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                if (!serverid_equal(&lock->context.pid, &self)) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                if (lock->fnum != fnum) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                server_id_set_disconnected(&lock->context.pid);
                lock->context.tid = TID_FIELD_INVALID;
                lock->fnum = FNUM_FIELD_INVALID;
        }

        br_lck->modified = true;
        TALLOC_FREE(br_lck);
        return true;
}

bool brl_reconnect_disconnected(struct files_struct *fsp)
{
        uint32_t tid = fsp->conn->cnum;
        uint64_t smblctx;
        uint64_t fnum = fsp->fnum;
        unsigned int i;
        struct server_id self = messaging_server_id(fsp->conn->sconn->msg_ctx);
        struct byte_range_lock *br_lck = NULL;

        if (fsp->op == NULL) {
                return false;
        }

        smblctx = fsp->op->global->open_persistent_id;

        if (!fsp->op->global->durable) {
                return false;
        }

        /*
         * When reconnecting, we do not want to validate the brlock entries
         * and thereby remove our own (disconnected) entries but reactivate
         * them instead.
         */
        fsp->lockdb_clean = true;

        br_lck = brl_get_locks(talloc_tos(), fsp);
        if (br_lck == NULL) {
                return false;
        }

        if (br_lck->num_locks == 0) {
                TALLOC_FREE(br_lck);
                return true;
        }

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

                /*
                 * as this is a durable handle we only expect locks
                 * of the current file handle!
                 */

                if (lock->context.smblctx != smblctx) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                if (lock->context.tid != TID_FIELD_INVALID) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                if (!server_id_is_disconnected(&lock->context.pid)) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                if (lock->fnum != FNUM_FIELD_INVALID) {
                        TALLOC_FREE(br_lck);
                        return false;
                }

                lock->context.pid = self;
                lock->context.tid = tid;
                lock->fnum = fnum;
        }

        fsp->current_lock_count = br_lck->num_locks;
        br_lck->modified = true;
        TALLOC_FREE(br_lck);
        return true;
}

/****************************************************************************
 Ensure this set of lock entries is valid.
****************************************************************************/
static bool validate_lock_entries(unsigned int *pnum_entries, struct lock_struct **pplocks,
                                  bool keep_disconnected)
{
        unsigned int i;
        struct lock_struct *locks = *pplocks;
        unsigned int num_entries = *pnum_entries;
        TALLOC_CTX *frame;
        struct server_id *ids;
        bool *exists;

        if (num_entries == 0) {
                return true;
        }

        frame = talloc_stackframe();

        ids = talloc_array(frame, struct server_id, num_entries);
        if (ids == NULL) {
                DEBUG(0, ("validate_lock_entries: "
                          "talloc_array(struct server_id, %u) failed\n",
                          num_entries));
                talloc_free(frame);
                return false;
        }

        exists = talloc_array(frame, bool, num_entries);
        if (exists == NULL) {
                DEBUG(0, ("validate_lock_entries: "
                          "talloc_array(bool, %u) failed\n",
                          num_entries));
                talloc_free(frame);
                return false;
        }

        for (i = 0; i < num_entries; i++) {
                ids[i] = locks[i].context.pid;
        }

        if (!serverids_exist(ids, num_entries, exists)) {
                DEBUG(3, ("validate_lock_entries: serverids_exists failed\n"));
                talloc_free(frame);
                return false;
        }

        i = 0;

        while (i < num_entries) {
                if (exists[i]) {
                        i++;
                        continue;
                }

                if (keep_disconnected &&
                    server_id_is_disconnected(&ids[i]))
                {
                        i++;
                        continue;
                }

                /* This process no longer exists */

                brl_delete_lock_struct(locks, num_entries, i);
                num_entries -= 1;
        }
        TALLOC_FREE(frame);

        *pnum_entries = num_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 brl_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;
        TDB_DATA dbkey;
        TDB_DATA value;

        dbkey = dbwrap_record_get_key(rec);
        value = dbwrap_record_get_value(rec);

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

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

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

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

        if (!validate_lock_entries(&num_locks, &locks, true)) {
                TALLOC_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);
                        dbwrap_record_store(rec, data, TDB_REPLACE);
                } else {
                        dbwrap_record_delete(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);
                }
        }

        TALLOC_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;
        NTSTATUS status;
        int count = 0;

        if (!brlock_db) {
                return 0;
        }
        cb.fn = fn;
        cb.private_data = private_data;
        status = dbwrap_traverse(brlock_db, brl_traverse_fn, &cb, &count);

        if (!NT_STATUS_IS_OK(status)) {
                return -1;
        } else {
                return count;
        }
}

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

static void byte_range_lock_flush(struct byte_range_lock *br_lck)
{
        size_t data_len;
        if (!br_lck->modified) {
                DEBUG(10, ("br_lck not modified\n"));
                goto done;
        }

        data_len = br_lck->num_locks * sizeof(struct lock_struct);

        if (br_lck->have_read_oplocks) {
                data_len += 1;
        }

        DEBUG(10, ("data_len=%d\n", (int)data_len));

        if (data_len == 0) {
                /* No locks - delete this entry. */
                NTSTATUS status = dbwrap_record_delete(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.dsize = data_len;
                data.dptr = talloc_array(talloc_tos(), uint8_t, data_len);
                SMB_ASSERT(data.dptr != NULL);

                memcpy(data.dptr, br_lck->lock_data,
                       br_lck->num_locks * sizeof(struct lock_struct));

                if (br_lck->have_read_oplocks) {
                        data.dptr[data_len-1] = 1;
                }

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

        DEBUG(10, ("seqnum=%d\n", dbwrap_get_seqnum(brlock_db)));

 done:
        br_lck->modified = false;
        TALLOC_FREE(br_lck->record);
}

static int byte_range_lock_destructor(struct byte_range_lock *br_lck)
{
        byte_range_lock_flush(br_lck);
        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.
********************************************************************/

struct byte_range_lock *brl_get_locks(TALLOC_CTX *mem_ctx, files_struct *fsp)
{
        TDB_DATA key, data;
        struct byte_range_lock *br_lck = talloc(mem_ctx, struct byte_range_lock);

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

        br_lck->fsp = fsp;
        br_lck->num_locks = 0;
        br_lck->have_read_oplocks = false;
        br_lck->modified = False;

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

        br_lck->record = dbwrap_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 = dbwrap_record_get_value(br_lck->record);

        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 = talloc_array(
                        br_lck, 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,
                       talloc_get_size(br_lck->lock_data));
        }

        DEBUG(10, ("data.dsize=%d\n", (int)data.dsize));

        if ((data.dsize % sizeof(struct lock_struct)) == 1) {
                br_lck->have_read_oplocks = (data.dptr[data.dsize-1] == 1);
        }

        if (!fsp->lockdb_clean) {
                int orig_num_locks = br_lck->num_locks;

                /*
                 * This is the first time we access the byte range lock
                 * record with this fsp. Go through and ensure all entries
                 * are valid - remove any that don't.
                 * This makes the lockdb self cleaning at low cost.
                 *
                 * Note: Disconnected entries belong to disconnected
                 * durable handles. So at this point, we have a new
                 * handle on the file and the disconnected durable has
                 * already been closed (we are not a durable reconnect).
                 * So we need to clean the disconnected brl entry.
                 */

                if (!validate_lock_entries(&br_lck->num_locks,
                                           &br_lck->lock_data, false)) {
                        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 brl_get_locks_readonly_state {
        TALLOC_CTX *mem_ctx;
        struct byte_range_lock **br_lock;
};

static void brl_get_locks_readonly_parser(TDB_DATA key, TDB_DATA data,
                                          void *private_data)
{
        struct brl_get_locks_readonly_state *state =
                (struct brl_get_locks_readonly_state *)private_data;
        struct byte_range_lock *br_lock;

        br_lock = talloc_pooled_object(
                state->mem_ctx, struct byte_range_lock, 1, data.dsize);
        if (br_lock == NULL) {
                *state->br_lock = NULL;
                return;
        }
        br_lock->lock_data = (struct lock_struct *)talloc_memdup(
                br_lock, data.dptr, data.dsize);
        br_lock->num_locks = data.dsize / sizeof(struct lock_struct);

        if ((data.dsize % sizeof(struct lock_struct)) == 1) {
                br_lock->have_read_oplocks = (data.dptr[data.dsize-1] == 1);
        } else {
                br_lock->have_read_oplocks = false;
        }

        DEBUG(10, ("Got %d bytes, have_read_oplocks: %s\n", (int)data.dsize,
                   br_lock->have_read_oplocks ? "true" : "false"));

        *state->br_lock = br_lock;
}

struct byte_range_lock *brl_get_locks_readonly(files_struct *fsp)
{
        struct byte_range_lock *br_lock = NULL;
        struct byte_range_lock *rw = NULL;

        DEBUG(10, ("seqnum=%d, fsp->brlock_seqnum=%d\n",
                   dbwrap_get_seqnum(brlock_db), fsp->brlock_seqnum));

        if ((fsp->brlock_rec != NULL)
            && (dbwrap_get_seqnum(brlock_db) == fsp->brlock_seqnum)) {
                /*
                 * We have cached the brlock_rec and the database did not
                 * change.
                 */
                return fsp->brlock_rec;
        }

        if (!fsp->lockdb_clean) {
                /*
                 * Fetch the record in R/W mode to give validate_lock_entries
                 * a chance to kick in once.
                 */
                rw = brl_get_locks(talloc_tos(), fsp);
                if (rw == NULL) {
                        return NULL;
                }
                fsp->lockdb_clean = true;
        }

        if (rw != NULL) {
                size_t lock_data_size;

                /*
                 * Make a copy of the already retrieved and sanitized rw record
                 */
                lock_data_size = rw->num_locks * sizeof(struct lock_struct);
                br_lock = talloc_pooled_object(
                        fsp, struct byte_range_lock, 1, lock_data_size);
                if (br_lock == NULL) {
                        goto fail;
                }
                br_lock->have_read_oplocks = rw->have_read_oplocks;
                br_lock->num_locks = rw->num_locks;
                br_lock->lock_data = (struct lock_struct *)talloc_memdup(
                        br_lock, rw->lock_data, lock_data_size);
        } else {
                struct brl_get_locks_readonly_state state;
                NTSTATUS status;

                /*
                 * Parse the record fresh from the database
                 */

                state.mem_ctx = fsp;
                state.br_lock = &br_lock;

                status = dbwrap_parse_record(
                        brlock_db,
                        make_tdb_data((uint8_t *)&fsp->file_id,
                                      sizeof(fsp->file_id)),
                        brl_get_locks_readonly_parser, &state);

                if (NT_STATUS_EQUAL(status,NT_STATUS_NOT_FOUND)) {
                        /*
                         * No locks on this file. Return an empty br_lock.
                         */
                        br_lock = talloc(fsp, struct byte_range_lock);
                        if (br_lock == NULL) {
                                goto fail;
                        }

                        br_lock->have_read_oplocks = false;
                        br_lock->num_locks = 0;
                        br_lock->lock_data = NULL;

                } else if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(3, ("Could not parse byte range lock record: "
                                  "%s\n", nt_errstr(status)));
                        goto fail;
                }
                if (br_lock == NULL) {
                        goto fail;
                }
        }

        br_lock->fsp = fsp;
        br_lock->modified = false;
        br_lock->record = NULL;

        if (lp_clustering()) {
                /*
                 * In the cluster case we can't cache the brlock struct
                 * because dbwrap_get_seqnum does not work reliably over
                 * ctdb. Thus we have to throw away the brlock struct soon.
                 */
                talloc_steal(talloc_tos(), br_lock);
        } else {
                /*
                 * Cache the brlock struct, invalidated when the dbwrap_seqnum
                 * changes. See beginning of this routine.
                 */
                TALLOC_FREE(fsp->brlock_rec);
                fsp->brlock_rec = br_lock;
                fsp->brlock_seqnum = dbwrap_get_seqnum(brlock_db);
        }

fail:
        TALLOC_FREE(rw);
        return br_lock;
}

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 = (const struct server_id *)p1;
        const struct server_id *i2 = (const struct server_id *)p2;

        if (i1->pid < i2->pid) return -1;
        if (i1->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.
 */

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(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;
        }

        TYPESAFE_QSORT(state->pids, state->num_pids, compare_procids);

        ZERO_STRUCT(last_pid);

        for (i=0; i<state->num_pids; i++) {
                if (serverid_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;
}

bool brl_cleanup_disconnected(struct file_id fid, uint64_t open_persistent_id)
{
        bool ret = false;
        TALLOC_CTX *frame = talloc_stackframe();
        TDB_DATA key, val;
        struct db_record *rec;
        struct lock_struct *lock;
        unsigned n, num;
        NTSTATUS status;

        key = make_tdb_data((void*)&fid, sizeof(fid));

        rec = dbwrap_fetch_locked(brlock_db, frame, key);
        if (rec == NULL) {
                DEBUG(5, ("brl_cleanup_disconnected: failed to fetch record "
                          "for file %s\n", file_id_string(frame, &fid)));
                goto done;
        }

        val = dbwrap_record_get_value(rec);
        lock = (struct lock_struct*)val.dptr;
        num = val.dsize / sizeof(struct lock_struct);
        if (lock == NULL) {
                DEBUG(10, ("brl_cleanup_disconnected: no byte range locks for "
                           "file %s\n", file_id_string(frame, &fid)));
                ret = true;
                goto done;
        }

        for (n=0; n<num; n++) {
                struct lock_context *ctx = &lock[n].context;

                if (!server_id_is_disconnected(&ctx->pid)) {
                        DEBUG(5, ("brl_cleanup_disconnected: byte range lock "
                                  "%s used by server %s, do not cleanup\n",
                                  file_id_string(frame, &fid),
                                  server_id_str(frame, &ctx->pid)));
                        goto done;
                }

                if (ctx->smblctx != open_persistent_id) {
                        DEBUG(5, ("brl_cleanup_disconnected: byte range lock "
                                  "%s expected smblctx %llu but found %llu"
                                  ", do not cleanup\n",
                                  file_id_string(frame, &fid),
                                  (unsigned long long)open_persistent_id,
                                  (unsigned long long)ctx->smblctx));
                        goto done;
                }
        }

        status = dbwrap_record_delete(rec);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(5, ("brl_cleanup_disconnected: failed to delete record "
                          "for file %s from %s, open %llu: %s\n",
                          file_id_string(frame, &fid), dbwrap_name(brlock_db),
                          (unsigned long long)open_persistent_id,
                          nt_errstr(status)));
                goto done;
        }

        DEBUG(10, ("brl_cleanup_disconnected: "
                   "file %s cleaned up %u entries from open %llu\n",
                   file_id_string(frame, &fid), num,
                   (unsigned long long)open_persistent_id));

        ret = true;
done:
        talloc_free(frame);
        return ret;
}