WHATSNEW: Start release notes for 3.5.9.

[Samba.git] / source3 / smbd / oplock.c

/* 
   Unix SMB/CIFS implementation.
   oplock processing
   Copyright (C) Andrew Tridgell 1992-1998
   Copyright (C) Jeremy Allison 1998 - 2001
   Copyright (C) Volker Lendecke 2005
   
   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/>.
*/

#define DBGC_CLASS DBGC_LOCKING
#include "includes.h"
#include "smbd/globals.h"

/****************************************************************************
 Get the number of current exclusive oplocks.
****************************************************************************/

int32 get_number_of_exclusive_open_oplocks(void)
{
  return exclusive_oplocks_open;
}

/*
 * helper function used by the kernel oplock backends to post the break message
 */
void break_kernel_oplock(struct messaging_context *msg_ctx, files_struct *fsp)
{
        uint8_t msg[MSG_SMB_KERNEL_BREAK_SIZE];

        /* Put the kernel break info into the message. */
        push_file_id_24((char *)msg, &fsp->file_id);
        SIVAL(msg,24,fsp->fh->gen_id);

        /* Don't need to be root here as we're only ever
           sending to ourselves. */

        messaging_send_buf(msg_ctx, procid_self(),
                           MSG_SMB_KERNEL_BREAK,
                           msg, MSG_SMB_KERNEL_BREAK_SIZE);
}

/****************************************************************************
 Attempt to set an oplock on a file. Always succeeds if kernel oplocks are
 disabled (just sets flags). Returns True if oplock set.
****************************************************************************/

bool set_file_oplock(files_struct *fsp, int oplock_type)
{
        if ((fsp->oplock_type == LEVEL_II_OPLOCK)
            && koplocks && !(koplocks->flags & KOPLOCKS_LEVEL2_SUPPORTED)) {
                DEBUG(10, ("Refusing level2 oplock, kernel oplocks don't "
                           "support them\n"));
                return false;
        }
        if ((fsp->oplock_type != NO_OPLOCK) &&
            (fsp->oplock_type != FAKE_LEVEL_II_OPLOCK) &&
            koplocks &&
            !koplocks->ops->set_oplock(koplocks, fsp, oplock_type)) {
                return False;
        }

        fsp->oplock_type = oplock_type;
        fsp->sent_oplock_break = NO_BREAK_SENT;
        if (oplock_type == LEVEL_II_OPLOCK) {
                level_II_oplocks_open++;
        } else if (EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type)) {
                exclusive_oplocks_open++;
        }

        DEBUG(5,("set_file_oplock: granted oplock on file %s, %s/%lu, "
                    "tv_sec = %x, tv_usec = %x\n",
                 fsp_str_dbg(fsp), file_id_string_tos(&fsp->file_id),
                 fsp->fh->gen_id, (int)fsp->open_time.tv_sec,
                 (int)fsp->open_time.tv_usec ));

        return True;
}

/****************************************************************************
 Attempt to release an oplock on a file. Decrements oplock count.
****************************************************************************/

void release_file_oplock(files_struct *fsp)
{
        if ((fsp->oplock_type != NO_OPLOCK) &&
            (fsp->oplock_type != FAKE_LEVEL_II_OPLOCK) &&
            koplocks) {
                koplocks->ops->release_oplock(koplocks, fsp, NO_OPLOCK);
        }

        if (fsp->oplock_type == LEVEL_II_OPLOCK) {
                level_II_oplocks_open--;
        } else if (EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type)) {
                exclusive_oplocks_open--;
        }

        SMB_ASSERT(exclusive_oplocks_open>=0);
        SMB_ASSERT(level_II_oplocks_open>=0);

        if (EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type)) {
                /* This doesn't matter for close. */
                fsp->oplock_type = FAKE_LEVEL_II_OPLOCK;
        } else {
                fsp->oplock_type = NO_OPLOCK;
        }
        fsp->sent_oplock_break = NO_BREAK_SENT;

        flush_write_cache(fsp, OPLOCK_RELEASE_FLUSH);
        delete_write_cache(fsp);

        TALLOC_FREE(fsp->oplock_timeout);
}

/****************************************************************************
 Attempt to downgrade an oplock on a file. Doesn't decrement oplock count.
****************************************************************************/

static void downgrade_file_oplock(files_struct *fsp)
{
        if (!EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type)) {
                DEBUG(0, ("trying to downgrade an already-downgraded oplock!\n"));
                return;
        }

        if (koplocks) {
                koplocks->ops->release_oplock(koplocks, fsp, LEVEL_II_OPLOCK);
        }
        fsp->oplock_type = LEVEL_II_OPLOCK;
        exclusive_oplocks_open--;
        level_II_oplocks_open++;
        fsp->sent_oplock_break = NO_BREAK_SENT;
}

/****************************************************************************
 Remove a file oplock. Copes with level II and exclusive.
 Locks then unlocks the share mode lock. Client can decide to go directly
 to none even if a "break-to-level II" was sent.
****************************************************************************/

bool remove_oplock(files_struct *fsp)
{
        bool ret;
        struct share_mode_lock *lck;

        /* Remove the oplock flag from the sharemode. */
        lck = get_share_mode_lock(talloc_tos(), fsp->file_id, NULL, NULL,
                                  NULL);
        if (lck == NULL) {
                DEBUG(0,("remove_oplock: failed to lock share entry for "
                         "file %s\n", fsp_str_dbg(fsp)));
                return False;
        }
        ret = remove_share_oplock(lck, fsp);
        if (!ret) {
                DEBUG(0,("remove_oplock: failed to remove share oplock for "
                         "file %s fnum %d, %s\n",
                         fsp_str_dbg(fsp), fsp->fnum,
                         file_id_string_tos(&fsp->file_id)));
        }
        release_file_oplock(fsp);
        TALLOC_FREE(lck);
        return ret;
}

/*
 * Deal with a reply when a break-to-level II was sent.
 */
bool downgrade_oplock(files_struct *fsp)
{
        bool ret;
        struct share_mode_lock *lck;

        lck = get_share_mode_lock(talloc_tos(), fsp->file_id, NULL, NULL,
                                  NULL);
        if (lck == NULL) {
                DEBUG(0,("downgrade_oplock: failed to lock share entry for "
                         "file %s\n", fsp_str_dbg(fsp)));
                return False;
        }
        ret = downgrade_share_oplock(lck, fsp);
        if (!ret) {
                DEBUG(0,("downgrade_oplock: failed to downgrade share oplock "
                         "for file %s fnum %d, file_id %s\n",
                         fsp_str_dbg(fsp), fsp->fnum,
                         file_id_string_tos(&fsp->file_id)));
        }

        downgrade_file_oplock(fsp);
        TALLOC_FREE(lck);
        return ret;
}

/*
 * Some kernel oplock implementations handle the notification themselves.
 */
bool should_notify_deferred_opens()
{
        return !(koplocks &&
                (koplocks->flags & KOPLOCKS_DEFERRED_OPEN_NOTIFICATION));
}

/****************************************************************************
 Set up an oplock break message.
****************************************************************************/

static char *new_break_smb_message(TALLOC_CTX *mem_ctx,
                                   files_struct *fsp, uint8 cmd)
{
        char *result = TALLOC_ARRAY(mem_ctx, char, smb_size + 8*2 + 0);

        if (result == NULL) {
                DEBUG(0, ("talloc failed\n"));
                return NULL;
        }

        memset(result,'\0',smb_size);
        srv_set_message(result,8,0,true);
        SCVAL(result,smb_com,SMBlockingX);
        SSVAL(result,smb_tid,fsp->conn->cnum);
        SSVAL(result,smb_pid,0xFFFF);
        SSVAL(result,smb_uid,0);
        SSVAL(result,smb_mid,0xFFFF);
        SCVAL(result,smb_vwv0,0xFF);
        SSVAL(result,smb_vwv2,fsp->fnum);
        SCVAL(result,smb_vwv3,LOCKING_ANDX_OPLOCK_RELEASE);
        SCVAL(result,smb_vwv3+1,cmd);
        return result;
}

/****************************************************************************
 Function to do the waiting before sending a local break.
****************************************************************************/

static void wait_before_sending_break(void)
{
        long wait_time = (long)lp_oplock_break_wait_time();

        if (wait_time) {
                smb_msleep(wait_time);
        }
}

/****************************************************************************
 Ensure that we have a valid oplock.
****************************************************************************/

static files_struct *initial_break_processing(struct file_id id, unsigned long file_id)
{
        files_struct *fsp = NULL;

        if( DEBUGLVL( 3 ) ) {
                dbgtext( "initial_break_processing: called for %s/%u\n",
                         file_id_string_tos(&id), (int)file_id);
                dbgtext( "Current oplocks_open (exclusive = %d, levelII = %d)\n",
                        exclusive_oplocks_open, level_II_oplocks_open );
        }

        /*
         * We need to search the file open table for the
         * entry containing this dev and inode, and ensure
         * we have an oplock on it.
         */

        fsp = file_find_dif(id, file_id);

        if(fsp == NULL) {
                /* The file could have been closed in the meantime - return success. */
                if( DEBUGLVL( 3 ) ) {
                        dbgtext( "initial_break_processing: cannot find open file with " );
                        dbgtext( "file_id %s gen_id = %lu", file_id_string_tos(&id), file_id);
                        dbgtext( "allowing break to succeed.\n" );
                }
                return NULL;
        }

        /* Ensure we have an oplock on the file */

        /*
         * There is a potential race condition in that an oplock could
         * have been broken due to another udp request, and yet there are
         * still oplock break messages being sent in the udp message
         * queue for this file. So return true if we don't have an oplock,
         * as we may have just freed it.
         */

        if(fsp->oplock_type == NO_OPLOCK) {
                if( DEBUGLVL( 3 ) ) {
                        dbgtext( "initial_break_processing: file %s ",
                                 fsp_str_dbg(fsp));
                        dbgtext( "(file_id = %s gen_id = %lu) has no oplock.\n",
                                 file_id_string_tos(&id), fsp->fh->gen_id );
                        dbgtext( "Allowing break to succeed regardless.\n" );
                }
                return NULL;
        }

        return fsp;
}

static void oplock_timeout_handler(struct event_context *ctx,
                                   struct timed_event *te,
                                   struct timeval now,
                                   void *private_data)
{
        files_struct *fsp = (files_struct *)private_data;

        /* Remove the timed event handler. */
        TALLOC_FREE(fsp->oplock_timeout);
        DEBUG(0, ("Oplock break failed for file %s -- replying anyway\n",
                  fsp_str_dbg(fsp)));
        global_client_failed_oplock_break = True;
        remove_oplock(fsp);
        reply_to_oplock_break_requests(fsp);
}

/*******************************************************************
 Add a timeout handler waiting for the client reply.
*******************************************************************/

static void add_oplock_timeout_handler(files_struct *fsp)
{
        /*
         * If kernel oplocks already notifies smbds when an oplock break times
         * out, just return.
         */
        if (koplocks &&
            (koplocks->flags & KOPLOCKS_TIMEOUT_NOTIFICATION)) {
                return;
        }

        if (fsp->oplock_timeout != NULL) {
                DEBUG(0, ("Logic problem -- have an oplock event hanging "
                          "around\n"));
        }

        fsp->oplock_timeout =
                event_add_timed(smbd_event_context(), NULL,
                                timeval_current_ofs(OPLOCK_BREAK_TIMEOUT, 0),
                                oplock_timeout_handler, fsp);

        if (fsp->oplock_timeout == NULL) {
                DEBUG(0, ("Could not add oplock timeout handler\n"));
        }
}

void break_level2_to_none_async(files_struct *fsp)
{
        char *break_msg;

        if (fsp->oplock_type == NO_OPLOCK) {
                /* We already got a "break to none" message and we've handled
                 * it.  just ignore. */
                DEBUG(3, ("process_oplock_async_level2_break_message: already "
                          "broken to none, ignoring.\n"));
                return;
        }

        if (fsp->oplock_type == FAKE_LEVEL_II_OPLOCK) {
                /* Don't tell the client, just downgrade. */
                DEBUG(3, ("process_oplock_async_level2_break_message: "
                          "downgrading fake level 2 oplock.\n"));
                remove_oplock(fsp);
                return;
        }

        /* Ensure we're really at level2 state. */
        SMB_ASSERT(fsp->oplock_type == LEVEL_II_OPLOCK);

        DEBUG(10,("process_oplock_async_level2_break_message: sending break "
                  "to none message for fid %d, file %s\n", fsp->fnum,
                  fsp_str_dbg(fsp)));

        /* Now send a break to none message to our client. */
        break_msg = new_break_smb_message(NULL, fsp, OPLOCKLEVEL_NONE);
        if (break_msg == NULL) {
                exit_server("Could not talloc break_msg\n");
        }

        show_msg(break_msg);
        if (!srv_send_smb(smbd_server_fd(),
                        break_msg, false, 0,
                        IS_CONN_ENCRYPTED(fsp->conn),
                        NULL)) {
                exit_server_cleanly("oplock_break: srv_send_smb failed.");
        }

        TALLOC_FREE(break_msg);

        /* Async level2 request, don't send a reply, just remove the oplock. */
        remove_oplock(fsp);

}

/*******************************************************************
 This handles the case of a write triggering a break to none
 message on a level2 oplock.
 When we get this message we may be in any of three states :
 NO_OPLOCK, LEVEL_II, FAKE_LEVEL2. We only send a message to
 the client for LEVEL2.
*******************************************************************/

void process_oplock_async_level2_break_message(struct messaging_context *msg_ctx,
                                                      void *private_data,
                                                      uint32_t msg_type,
                                                      struct server_id src,
                                                      DATA_BLOB *data)
{
        struct share_mode_entry msg;
        files_struct *fsp;

        if (data->data == NULL) {
                DEBUG(0, ("Got NULL buffer\n"));
                return;
        }

        if (data->length != MSG_SMB_SHARE_MODE_ENTRY_SIZE) {
                DEBUG(0, ("Got invalid msg len %d\n", (int)data->length));
                return;
        }

        /* De-linearize incoming message. */
        message_to_share_mode_entry(&msg, (char *)data->data);

        DEBUG(10, ("Got oplock async level 2 break message from pid %s: "
                   "%s/%lu\n", procid_str(talloc_tos(), &src),
                   file_id_string_tos(&msg.id), msg.share_file_id));

        fsp = initial_break_processing(msg.id, msg.share_file_id);

        if (fsp == NULL) {
                /* We hit a race here. Break messages are sent, and before we
                 * get to process this message, we have closed the file. 
                 * No need to reply as this is an async message. */
                DEBUG(3, ("process_oplock_async_level2_break_message: Did not find fsp, ignoring\n"));
                return;
        }

        break_level2_to_none_async(fsp);
}

/*******************************************************************
 This handles the generic oplock break message from another smbd.
*******************************************************************/

static void process_oplock_break_message(struct messaging_context *msg_ctx,
                                         void *private_data,
                                         uint32_t msg_type,
                                         struct server_id src,
                                         DATA_BLOB *data)
{
        struct share_mode_entry msg;
        files_struct *fsp;
        char *break_msg;
        bool break_to_level2 = False;

        if (data->data == NULL) {
                DEBUG(0, ("Got NULL buffer\n"));
                return;
        }

        if (data->length != MSG_SMB_SHARE_MODE_ENTRY_SIZE) {
                DEBUG(0, ("Got invalid msg len %d\n", (int)data->length));
                return;
        }

        /* De-linearize incoming message. */
        message_to_share_mode_entry(&msg, (char *)data->data);

        DEBUG(10, ("Got oplock break message from pid %s: %s/%lu\n",
                   procid_str(talloc_tos(), &src), file_id_string_tos(&msg.id),
                   msg.share_file_id));

        fsp = initial_break_processing(msg.id, msg.share_file_id);

        if (fsp == NULL) {
                /* a We hit race here. Break messages are sent, and before we
                 * get to process this message, we have closed the file. Reply
                 * with 'ok, oplock broken' */
                DEBUG(3, ("Did not find fsp\n"));

                /* We just send the same message back. */
                messaging_send_buf(msg_ctx, src, MSG_SMB_BREAK_RESPONSE,
                                   (uint8 *)data->data,
                                   MSG_SMB_SHARE_MODE_ENTRY_SIZE);
                return;
        }

        if (fsp->sent_oplock_break != NO_BREAK_SENT) {
                /* Remember we have to inform the requesting PID when the
                 * client replies */
                msg.pid = src;
                ADD_TO_ARRAY(NULL, struct share_mode_entry, msg,
                             &fsp->pending_break_messages,
                             &fsp->num_pending_break_messages);
                return;
        }

        if (EXCLUSIVE_OPLOCK_TYPE(msg.op_type) &&
            !EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type)) {
                DEBUG(3, ("Already downgraded oplock on %s: %s\n",
                          file_id_string_tos(&fsp->file_id),
                          fsp_str_dbg(fsp)));
                /* We just send the same message back. */
                messaging_send_buf(msg_ctx, src, MSG_SMB_BREAK_RESPONSE,
                                   (uint8 *)data->data,
                                   MSG_SMB_SHARE_MODE_ENTRY_SIZE);
                return;
        }

        if ((global_client_caps & CAP_LEVEL_II_OPLOCKS) && 
            !(msg.op_type & FORCE_OPLOCK_BREAK_TO_NONE) &&
            !(koplocks && !(koplocks->flags & KOPLOCKS_LEVEL2_SUPPORTED)) &&
            lp_level2_oplocks(SNUM(fsp->conn))) {
                break_to_level2 = True;
        }

        break_msg = new_break_smb_message(NULL, fsp, break_to_level2 ?
                                          OPLOCKLEVEL_II : OPLOCKLEVEL_NONE);
        if (break_msg == NULL) {
                exit_server("Could not talloc break_msg\n");
        }

        /* Need to wait before sending a break message if we sent ourselves this message. */
        if (procid_is_me(&src)) {
                wait_before_sending_break();
        }

        show_msg(break_msg);
        if (!srv_send_smb(smbd_server_fd(),
                        break_msg, false, 0,
                        IS_CONN_ENCRYPTED(fsp->conn),
                        NULL)) {
                exit_server_cleanly("oplock_break: srv_send_smb failed.");
        }

        TALLOC_FREE(break_msg);

        fsp->sent_oplock_break = break_to_level2 ? LEVEL_II_BREAK_SENT:BREAK_TO_NONE_SENT;

        msg.pid = src;
        ADD_TO_ARRAY(NULL, struct share_mode_entry, msg,
                     &fsp->pending_break_messages,
                     &fsp->num_pending_break_messages);

        add_oplock_timeout_handler(fsp);
}

/*******************************************************************
 This handles the kernel oplock break message.
*******************************************************************/

static void process_kernel_oplock_break(struct messaging_context *msg_ctx,
                                        void *private_data,
                                        uint32_t msg_type,
                                        struct server_id src,
                                        DATA_BLOB *data)
{
        struct file_id id;
        unsigned long file_id;
        files_struct *fsp;
        char *break_msg;

        if (data->data == NULL) {
                DEBUG(0, ("Got NULL buffer\n"));
                return;
        }

        if (data->length != MSG_SMB_KERNEL_BREAK_SIZE) {
                DEBUG(0, ("Got invalid msg len %d\n", (int)data->length));
                return;
        }

        /* Pull the data from the message. */
        pull_file_id_24((char *)data->data, &id);
        file_id = (unsigned long)IVAL(data->data, 24);

        DEBUG(10, ("Got kernel oplock break message from pid %s: %s/%u\n",
                   procid_str(talloc_tos(), &src), file_id_string_tos(&id),
                   (unsigned int)file_id));

        fsp = initial_break_processing(id, file_id);

        if (fsp == NULL) {
                DEBUG(3, ("Got a kernel oplock break message for a file "
                          "I don't know about\n"));
                return;
        }

        if (fsp->sent_oplock_break != NO_BREAK_SENT) {
                /* This is ok, kernel oplocks come in completely async */
                DEBUG(3, ("Got a kernel oplock request while waiting for a "
                          "break reply\n"));
                return;
        }

        break_msg = new_break_smb_message(NULL, fsp, OPLOCKLEVEL_NONE);
        if (break_msg == NULL) {
                exit_server("Could not talloc break_msg\n");
        }

        show_msg(break_msg);
        if (!srv_send_smb(smbd_server_fd(),
                        break_msg, false, 0,
                        IS_CONN_ENCRYPTED(fsp->conn),
                        NULL)) {
                exit_server_cleanly("oplock_break: srv_send_smb failed.");
        }

        TALLOC_FREE(break_msg);

        fsp->sent_oplock_break = BREAK_TO_NONE_SENT;

        add_oplock_timeout_handler(fsp);
}

void reply_to_oplock_break_requests(files_struct *fsp)
{
        int i;

        /*
         * If kernel oplocks already notifies smbds when oplocks are
         * broken/removed, just return.
         */
        if (koplocks &&
            (koplocks->flags & KOPLOCKS_OPLOCK_BROKEN_NOTIFICATION)) {
                return;
        }

        for (i=0; i<fsp->num_pending_break_messages; i++) {
                struct share_mode_entry *e = &fsp->pending_break_messages[i];
                char msg[MSG_SMB_SHARE_MODE_ENTRY_SIZE];

                share_mode_entry_to_message(msg, e);

                messaging_send_buf(smbd_messaging_context(), e->pid,
                                   MSG_SMB_BREAK_RESPONSE,
                                   (uint8 *)msg,
                                   MSG_SMB_SHARE_MODE_ENTRY_SIZE);
        }

        SAFE_FREE(fsp->pending_break_messages);
        fsp->num_pending_break_messages = 0;
        if (fsp->oplock_timeout != NULL) {
                /* Remove the timed event handler. */
                TALLOC_FREE(fsp->oplock_timeout);
                fsp->oplock_timeout = NULL;
        }
        return;
}

static void process_oplock_break_response(struct messaging_context *msg_ctx,
                                          void *private_data,
                                          uint32_t msg_type,
                                          struct server_id src,
                                          DATA_BLOB *data)
{
        struct share_mode_entry msg;

        if (data->data == NULL) {
                DEBUG(0, ("Got NULL buffer\n"));
                return;
        }

        if (data->length != MSG_SMB_SHARE_MODE_ENTRY_SIZE) {
                DEBUG(0, ("Got invalid msg len %u\n",
                          (unsigned int)data->length));
                return;
        }

        /* De-linearize incoming message. */
        message_to_share_mode_entry(&msg, (char *)data->data);

        DEBUG(10, ("Got oplock break response from pid %s: %s/%lu mid %u\n",
                   procid_str(talloc_tos(), &src), file_id_string_tos(&msg.id),
                   msg.share_file_id, (unsigned int)msg.op_mid));

        /* Here's the hack from open.c, store the mid in the 'port' field */
        schedule_deferred_open_smb_message(msg.op_mid);
}

static void process_open_retry_message(struct messaging_context *msg_ctx,
                                       void *private_data,
                                       uint32_t msg_type,
                                       struct server_id src,
                                       DATA_BLOB *data)
{
        struct share_mode_entry msg;
        
        if (data->data == NULL) {
                DEBUG(0, ("Got NULL buffer\n"));
                return;
        }

        if (data->length != MSG_SMB_SHARE_MODE_ENTRY_SIZE) {
                DEBUG(0, ("Got invalid msg len %d\n", (int)data->length));
                return;
        }

        /* De-linearize incoming message. */
        message_to_share_mode_entry(&msg, (char *)data->data);

        DEBUG(10, ("Got open retry msg from pid %s: %s mid %u\n",
                   procid_str(talloc_tos(), &src), file_id_string_tos(&msg.id),
                   (unsigned int)msg.op_mid));

        schedule_deferred_open_smb_message(msg.op_mid);
}

/****************************************************************************
 This function is called on any file modification or lock request. If a file
 is level 2 oplocked then it must tell all other level 2 holders to break to
 none.
****************************************************************************/

static void contend_level2_oplocks_begin_default(files_struct *fsp,
                                              enum level2_contention_type type)
{
        int i;
        struct share_mode_lock *lck;

        /*
         * If this file is level II oplocked then we need
         * to grab the shared memory lock and inform all
         * other files with a level II lock that they need
         * to flush their read caches. We keep the lock over
         * the shared memory area whilst doing this.
         */

        if (!LEVEL_II_OPLOCK_TYPE(fsp->oplock_type))
                return;

        lck = get_share_mode_lock(talloc_tos(), fsp->file_id, NULL, NULL,
                                  NULL);
        if (lck == NULL) {
                DEBUG(0,("release_level_2_oplocks_on_change: failed to lock "
                         "share mode entry for file %s.\n", fsp_str_dbg(fsp)));
                return;
        }

        DEBUG(10,("release_level_2_oplocks_on_change: num_share_modes = %d\n", 
                  lck->num_share_modes ));

        for(i = 0; i < lck->num_share_modes; i++) {
                struct share_mode_entry *share_entry = &lck->share_modes[i];
                char msg[MSG_SMB_SHARE_MODE_ENTRY_SIZE];

                if (!is_valid_share_mode_entry(share_entry)) {
                        continue;
                }

                /*
                 * As there could have been multiple writes waiting at the
                 * lock_share_entry gate we may not be the first to
                 * enter. Hence the state of the op_types in the share mode
                 * entries may be partly NO_OPLOCK and partly LEVEL_II or FAKE_LEVEL_II
                 * oplock. It will do no harm to re-send break messages to
                 * those smbd's that are still waiting their turn to remove
                 * their LEVEL_II state, and also no harm to ignore existing
                 * NO_OPLOCK states. JRA.
                 */

                DEBUG(10,("release_level_2_oplocks_on_change: "
                          "share_entry[%i]->op_type == %d\n",
                          i, share_entry->op_type ));

                if (share_entry->op_type == NO_OPLOCK) {
                        continue;
                }

                /* Paranoia .... */
                if (EXCLUSIVE_OPLOCK_TYPE(share_entry->op_type)) {
                        DEBUG(0,("release_level_2_oplocks_on_change: PANIC. "
                                 "share mode entry %d is an exlusive "
                                 "oplock !\n", i ));
                        TALLOC_FREE(lck);
                        abort();
                }

                share_mode_entry_to_message(msg, share_entry);

                /*
                 * Deal with a race condition when breaking level2
                 * oplocks. Don't send all the messages and release
                 * the lock, this allows someone else to come in and
                 * get a level2 lock before any of the messages are
                 * processed, and thus miss getting a break message.
                 * Ensure at least one entry (the one we're breaking)
                 * is processed immediately under the lock and becomes
                 * set as NO_OPLOCK to stop any waiter getting a level2.
                 * Bugid #5980.
                 */

                if (procid_is_me(&share_entry->pid)) {
                        wait_before_sending_break();
                        break_level2_to_none_async(fsp);
                } else {
                        messaging_send_buf(smbd_messaging_context(),
                                        share_entry->pid,
                                        MSG_SMB_ASYNC_LEVEL2_BREAK,
                                        (uint8 *)msg,
                                        MSG_SMB_SHARE_MODE_ENTRY_SIZE);
                }
        }

        /* We let the message receivers handle removing the oplock state
           in the share mode lock db. */

        TALLOC_FREE(lck);
}

void contend_level2_oplocks_begin(files_struct *fsp,
                                  enum level2_contention_type type)
{
        if (koplocks && koplocks->ops->contend_level2_oplocks_begin) {
                koplocks->ops->contend_level2_oplocks_begin(fsp, type);
                return;
        }

        contend_level2_oplocks_begin_default(fsp, type);
}

void contend_level2_oplocks_end(files_struct *fsp,
                                enum level2_contention_type type)
{
        /* Only kernel oplocks implement this so far */
        if (koplocks && koplocks->ops->contend_level2_oplocks_end) {
                koplocks->ops->contend_level2_oplocks_end(fsp, type);
        }
}

/****************************************************************************
 Linearize a share mode entry struct to an internal oplock break message.
****************************************************************************/

void share_mode_entry_to_message(char *msg, const struct share_mode_entry *e)
{
        SIVAL(msg,0,(uint32)e->pid.pid);
        SSVAL(msg,4,e->op_mid);
        SSVAL(msg,6,e->op_type);
        SIVAL(msg,8,e->access_mask);
        SIVAL(msg,12,e->share_access);
        SIVAL(msg,16,e->private_options);
        SIVAL(msg,20,(uint32)e->time.tv_sec);
        SIVAL(msg,24,(uint32)e->time.tv_usec);
        push_file_id_24(msg+28, &e->id);
        SIVAL(msg,52,e->share_file_id);
        SIVAL(msg,56,e->uid);
        SSVAL(msg,60,e->flags);
#ifdef CLUSTER_SUPPORT
        SIVAL(msg,62,e->pid.vnn);
#endif
}

/****************************************************************************
 De-linearize an internal oplock break message to a share mode entry struct.
****************************************************************************/

void message_to_share_mode_entry(struct share_mode_entry *e, char *msg)
{
        e->pid.pid = (pid_t)IVAL(msg,0);
        e->op_mid = SVAL(msg,4);
        e->op_type = SVAL(msg,6);
        e->access_mask = IVAL(msg,8);
        e->share_access = IVAL(msg,12);
        e->private_options = IVAL(msg,16);
        e->time.tv_sec = (time_t)IVAL(msg,20);
        e->time.tv_usec = (int)IVAL(msg,24);
        pull_file_id_24(msg+28, &e->id);
        e->share_file_id = (unsigned long)IVAL(msg,52);
        e->uid = (uint32)IVAL(msg,56);
        e->flags = (uint16)SVAL(msg,60);
#ifdef CLUSTER_SUPPORT
        e->pid.vnn = IVAL(msg,62);
#endif
}

/****************************************************************************
 Setup oplocks for this process.
****************************************************************************/

bool init_oplocks(struct messaging_context *msg_ctx)
{
        DEBUG(3,("init_oplocks: initializing messages.\n"));

        messaging_register(msg_ctx, NULL, MSG_SMB_BREAK_REQUEST,
                           process_oplock_break_message);
        messaging_register(msg_ctx, NULL, MSG_SMB_ASYNC_LEVEL2_BREAK,
                           process_oplock_async_level2_break_message);
        messaging_register(msg_ctx, NULL, MSG_SMB_BREAK_RESPONSE,
                           process_oplock_break_response);
        messaging_register(msg_ctx, NULL, MSG_SMB_KERNEL_BREAK,
                           process_kernel_oplock_break);
        messaging_register(msg_ctx, NULL, MSG_SMB_OPEN_RETRY,
                           process_open_retry_message);

        if (lp_kernel_oplocks()) {
#if HAVE_KERNEL_OPLOCKS_IRIX
                koplocks = irix_init_kernel_oplocks(talloc_autofree_context());
#elif HAVE_KERNEL_OPLOCKS_LINUX
                koplocks = linux_init_kernel_oplocks(talloc_autofree_context());
#elif HAVE_ONEFS
                koplocks = onefs_init_kernel_oplocks(talloc_autofree_context());
#endif
        }

        return True;
}