[bacula/bacula] / bacula / src / stored / reserve.c

/*
   Bacula® - The Network Backup Solution

   Copyright (C) 2000-2007 Free Software Foundation Europe e.V.

   The main author of Bacula is Kern Sibbald, with contributions from
   many others, a complete list can be found in the file AUTHORS.
   This program is Free Software; you can redistribute it and/or
   modify it under the terms of version two of the GNU General Public
   License as published by the Free Software Foundation plus additions
   that are listed in the file LICENSE.

   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, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301, USA.

   Bacula® is a registered trademark of John Walker.
   The licensor of Bacula is the Free Software Foundation Europe
   (FSFE), Fiduciary Program, Sumatrastrasse 25, 8006 Zürich,
   Switzerland, email:ftf@fsfeurope.org.
*/
/*
 *   Drive reservation functions for Storage Daemon
 *
 *   Kern Sibbald, MM
 *
 *   Split from job.c and acquire.c June 2005
 *
 *   Version $Id$
 *
 */

#include "bacula.h"
#include "stored.h"

static dlist *vol_list = NULL;
static pthread_mutex_t vol_list_lock = PTHREAD_MUTEX_INITIALIZER;

/* Forward referenced functions */
static int can_reserve_drive(DCR *dcr, RCTX &rctx);
static int reserve_device(RCTX &rctx);
static bool reserve_device_for_read(DCR *dcr);
static bool reserve_device_for_append(DCR *dcr, RCTX &rctx);
static bool use_storage_cmd(JCR *jcr);
static void queue_reserve_message(JCR *jcr);

/* Requests from the Director daemon */
static char use_storage[]  = "use storage=%127s media_type=%127s "
   "pool_name=%127s pool_type=%127s append=%d copy=%d stripe=%d\n";
static char use_device[]  = "use device=%127s\n";

/* Responses sent to Director daemon */
static char OK_device[] = "3000 OK use device device=%s\n";
static char NO_device[] = "3924 Device \"%s\" not in SD Device resources.\n";
static char BAD_use[]   = "3913 Bad use command: %s\n";

bool use_cmd(JCR *jcr) 
{
   /*
    * Get the device, media, and pool information
    */
   if (!use_storage_cmd(jcr)) {
      set_jcr_job_status(jcr, JS_ErrorTerminated);
      memset(jcr->sd_auth_key, 0, strlen(jcr->sd_auth_key));
      return false;
   }
   return true;
}

static int my_compare(void *item1, void *item2)
{
   return strcmp(((VOLRES *)item1)->vol_name, ((VOLRES *)item2)->vol_name);
}

static brwlock_t reservation_lock;

void init_reservations_lock()
{
   int errstat;
   if ((errstat=rwl_init(&reservation_lock)) != 0) {
      berrno be;
      Emsg1(M_ABORT, 0, _("Unable to initialize reservation lock. ERR=%s\n"),
            be.strerror(errstat));
   }

}

void term_reservations_lock()
{
   rwl_destroy(&reservation_lock);
}

int reservations_lock_count = 0;

/* This applies to a drive and to Volumes */
void _lock_reservations()
{
   int errstat;
   reservations_lock_count++;
   if ((errstat=rwl_writelock(&reservation_lock)) != 0) {
      berrno be;
      Emsg2(M_ABORT, 0, "rwl_writelock failure. stat=%d: ERR=%s\n",
           errstat, be.strerror(errstat));
   }
}

void _unlock_reservations()
{
   int errstat;
   reservations_lock_count--;
   if ((errstat=rwl_writeunlock(&reservation_lock)) != 0) {
      berrno be;
      Emsg2(M_ABORT, 0, "rwl_writeunlock failure. stat=%d: ERR=%s\n",
           errstat, be.strerror(errstat));
   }
}

/*
 * List Volumes -- this should be moved to status.c
 */
enum {
   debug_lock = true,
   debug_nolock = false
};

static void debug_list_volumes(const char *imsg, bool do_lock)
{
   VOLRES *vol;
   POOL_MEM msg(PM_MESSAGE);
   int count = 0;
   DEVICE *dev = NULL;

   if (do_lock) P(vol_list_lock);
   for (vol=(VOLRES *)vol_list->first(); vol; vol=(VOLRES *)vol_list->next(vol)) {
      if (vol->dev) {
         Mmsg(msg, "List from %s: %s at %p on device %s\n", imsg, 
              vol->vol_name, vol->vol_name, vol->dev->print_name());
      } else {
         Mmsg(msg, "List from %s: %s at %p no dev\n", imsg, vol->vol_name, vol->vol_name);
      }
      Dmsg1(100, "%s", msg.c_str());
      count++;
   }

   for (vol=(VOLRES *)vol_list->first(); vol; vol=(VOLRES *)vol_list->next(vol)) {
      if (vol->dev == dev) {
         Dmsg0(000, "Two Volumes on same device.\n");
         ASSERT(0);
         dev = vol->dev;
      }
   }

   Dmsg2(100, "List from %s: %d volumes\n", imsg, count);
   if (do_lock) V(vol_list_lock);
}


/*
 * List Volumes -- this should be moved to status.c
 */
void list_volumes(void sendit(const char *msg, int len, void *sarg), void *arg)
{
   VOLRES *vol;
   POOL_MEM msg(PM_MESSAGE);
   int len;

   P(vol_list_lock);
   for (vol=(VOLRES *)vol_list->first(); vol; vol=(VOLRES *)vol_list->next(vol)) {
      if (vol->dev) {
         len = Mmsg(msg, "%s on device %s\n", vol->vol_name, vol->dev->print_name());
         sendit(msg.c_str(), len, arg);
      } else {
         len = Mmsg(msg, "%s no dev\n", vol->vol_name);
         sendit(msg.c_str(), len, arg);
      }
   }
   V(vol_list_lock);
}

/*
 * Create a Volume item to put in the Volume list
 *   Ensure that the device points to it.
 */
static VOLRES *new_vol_item(DCR *dcr, const char *VolumeName)
{
   VOLRES *vol;
   vol = (VOLRES *)malloc(sizeof(VOLRES));
   memset(vol, 0, sizeof(VOLRES));
   vol->vol_name = bstrdup(VolumeName);
   vol->dev = dcr->dev;
   Dmsg4(100, "New Vol=%s at %p dev=%s JobId=%u\n", VolumeName, vol->vol_name,
         vol->dev->print_name(), (int)dcr->jcr->JobId);
   return vol;
}

static void free_vol_item(VOLRES *vol)
{
   free(vol->vol_name);
   if (vol->dev) {
      vol->dev->vol = NULL;
   }
   free(vol);
}


/*
 * Put a new Volume entry in the Volume list. This
 *  effectively reserves the volume so that it will
 *  not be mounted again.
 *
 * If the device has any current volume associated with it,
 *  and it is a different Volume, and the device is not busy,
 *  we release the old Volume item and insert the new one.
 * 
 * It is assumed that the device is free and locked so that
 *  we can change the device structure.
 *
 * Some details of the Volume list handling:
 *
 *  1. The Volume list entry must be attached to the drive (rather than 
 *       attached to a job as it currently is. I.e. the drive that "owns" 
 *       the volume (reserved, in use, mounted)
 *       must point to the volume (still to be maintained in a list).
 *
 *  2. The Volume is entered in the list when a drive is reserved.  
 *
 *  3. When a drive is in use, the device code must appropriately update the
 *      volume name as it changes (currently the list is static -- an entry is
 *      removed when the Volume is no longer reserved, in use or mounted).  
 *      The new code must keep the same list entry as long as the drive
 *       has any volume associated with it but the volume name in the list
 *       must be updated when the drive has a different volume mounted.
 *
 *  4. A job that has reserved a volume, can un-reserve the volume, and if the 
 *      volume is not mounted, and not reserved, and not in use, it will be
 *      removed from the list.
 *
 *  5. If a job wants to reserve a drive with a different Volume from the one on
 *      the drive, it can re-use the drive for the new Volume.
 *
 *  6. If a job wants a Volume that is in a different drive, it can either use the
 *      other drive or take the volume, only if the other drive is not in use or
 *      not reserved.
 *
 *  One nice aspect of this is that the reserve use count and the writer use count 
 *  already exist and are correctly programmed and will need no changes -- use 
 *  counts are always very tricky.
 *
 *  The old code had a concept of "reserving" a Volume, but it needs to be changed 
 *  to reserving and using a drive.  A volume is must be attached to (owned by) a 
 *  drive and can move from drive to drive or be unused given certain specific 
 *  conditions of the drive.  The key is that the drive must "own" the Volume.  
 *  The old code has the job (dcr) owning the volume (more or less).  The job is 
 *  to change the insertion and removal of the volumes from the list to be based 
 *  on the drive rather than the job.  The new logic described above needs to be 
 *  reviewed a couple more times for completeness and correctness.  Then I can 
 *  program it.

 *
 *  Return: VOLRES entry on success
 *          NULL volume busy on another drive
 */
VOLRES *reserve_volume(DCR *dcr, const char *VolumeName)
{
   VOLRES *vol, *nvol;
   DEVICE *dev = dcr->dev;

   ASSERT(dev != NULL);

   Dmsg1(100, "reserve_volume %s\n", VolumeName);
   /* 
    * We lock the reservations system here to ensure
    *  when adding a new volume that no newly scheduled
    *  job can reserve it.
    */
   P(vol_list_lock);
   debug_list_volumes("begin reserve_volume", debug_nolock);
   /* 
    * First, remove any old volume attached to this device as it
    *  is no longer used.
    */
   if (dev->vol) {
      vol = dev->vol;
      /*
       * Make sure we don't remove the current volume we are inserting
       *  because it was probably inserted by another job.
       */
      if (strcmp(vol->vol_name, VolumeName) == 0) {
         goto get_out;                  /* Volume already on this device */
      } else {
         Dmsg3(100, "reserve_vol free vol=%s at %p JobId=%u\n", vol->vol_name,
               vol->vol_name, (int)dcr->jcr->JobId);
         debug_list_volumes("reserve_vol free", debug_nolock);
         vol_list->remove(vol);
         free_vol_item(vol);
      }
   }

   /* Create a new Volume entry */
   nvol = new_vol_item(dcr, VolumeName);

   /*
    * Now try to insert the new Volume
    */
   vol = (VOLRES *)vol_list->binary_insert(nvol, my_compare);
   if (vol != nvol) {
      Dmsg2(100, "Found vol=%s dev-same=%d\n", vol->vol_name, dev==vol->dev);
      /*
       * At this point, a Volume with this name already is in the list,
       *   so we simply release our new Volume entry. Note, this should
       *   only happen if we are moving the volume from one drive to another.
       */
      Dmsg3(100, "reserve_vol free-tmp vol=%s at %p JobId=%u\n", vol->vol_name,
            vol->vol_name, (int)dcr->jcr->JobId);
      /*
       * Clear dev pointer so that free_vol_item() doesn't 
       *  take away our volume. 
       */
      nvol->dev = NULL;                   /* don't zap dev entry */
      free_vol_item(nvol);

      /* Check if we are trying to use the Volume on a different drive */
      if (dev != vol->dev) {
         /* Caller wants to switch Volume to another device */
         if (!vol->dev->is_busy()) {
            /* OK to move it -- I'm not sure this will work */
            Dmsg3(100, "==== Swap vol=%s from dev=%s to %s\n", VolumeName,
               vol->dev->print_name(), dev->print_name());
            vol->dev->vol = NULL;         /* take vol from old drive */
            vol->dev->VolHdr.VolumeName[0] = 0;
            vol->dev = dev;               /* point vol at new drive */
            dev->vol = vol;               /* point dev at vol */
            dev->VolHdr.VolumeName[0] = 0;
         } else {
            Dmsg3(100, "Volume busy could not swap vol=%s from dev=%s to %s\n", VolumeName,
               vol->dev->print_name(), dev->print_name());
            vol = NULL;                /* device busy */
         }
      }
   }
   dev->vol = vol;

get_out:
   debug_list_volumes("end new volume", debug_nolock);
   V(vol_list_lock);
   return vol;
}

/*
 * Search for a Volume name in the Volume list.
 *
 *  Returns: VOLRES entry on success
 *           NULL if the Volume is not in the list
 */
VOLRES *find_volume(const char *VolumeName)
{
   VOLRES vol, *fvol;
   /* Do not lock reservations here */
   P(vol_list_lock);
   vol.vol_name = bstrdup(VolumeName);
   fvol = (VOLRES *)vol_list->binary_search(&vol, my_compare);
   free(vol.vol_name);
   Dmsg2(100, "find_vol=%s found=%d\n", VolumeName, fvol!=NULL);
   debug_list_volumes("find_volume", debug_nolock);
   V(vol_list_lock);
   return fvol;
}

/* 
 * Remove any reservation from a drive and tell the system
 *  that the volume is unused at least by us.
 */
void unreserve_device(DCR *dcr)
{
   DEVICE *dev = dcr->dev;
   dev->dlock();
   if (dcr->reserved_device) {
      dcr->reserved_device = false;
      dev->reserved_device--;
      Dmsg2(100, "Dec reserve=%d dev=%s\n", dev->reserved_device, dev->print_name());
      dcr->reserved_device = false;
      /* If we set read mode in reserving, remove it */
      if (dev->can_read()) {
         dev->clear_read();
      }
      if (dev->num_writers < 0) {
         Jmsg1(dcr->jcr, M_ERROR, 0, _("Hey! num_writers=%d!!!!\n"), dev->num_writers);
         dev->num_writers = 0;
      }
   }

   volume_unused(dcr);
   dev->dunlock();
}

/*  
 * Free a Volume from the Volume list if it is no longer used
 *
 *  Returns: true if the Volume found and removed from the list
 *           false if the Volume is not in the list or is in use
 */
bool volume_unused(DCR *dcr)
{
   DEVICE *dev = dcr->dev;

   if (dev->vol == NULL) {
      Dmsg1(100, " unreserve_volume: no vol on %s\n", dev->print_name());
      debug_list_volumes("null return unreserve_volume", debug_lock);
      return false;
   }

   if (dev->is_busy()) {
      Dmsg1(100, "unreserve_volume: dev is busy %s\n", dev->print_name());
      debug_list_volumes("dev busy return unreserve_volume", debug_lock);
      return false;
   }

   return free_volume(dev);
}

/*
 * Unconditionally release the volume
 */
bool free_volume(DEVICE *dev)
{
   VOLRES *vol;

   if (dev->vol == NULL) {
      Dmsg1(100, "No vol on dev %s\n", dev->print_name());
      return false;
   }
   P(vol_list_lock);
   vol = dev->vol;
   dev->vol = NULL;
   Dmsg1(100, "free_volume %s\n", vol->vol_name);
   vol_list->remove(vol);
   Dmsg3(100, "free_volume %s at %p dev=%s\n", vol->vol_name, vol->vol_name,
         dev->print_name());
   free_vol_item(vol);
   debug_list_volumes("free_volume", debug_nolock);
   V(vol_list_lock);
   return vol != NULL;
}

      
/* Create the Volume list */
void create_volume_list()
{
   VOLRES *dummy = NULL;
   if (vol_list == NULL) {
      vol_list = New(dlist(dummy, &dummy->link));
   }
}

/* Release all Volumes from the list */
void free_volume_list()
{
   VOLRES *vol;
   if (!vol_list) {
      return;
   }
   P(vol_list_lock);
   for (vol=(VOLRES *)vol_list->first(); vol; vol=(VOLRES *)vol_list->next(vol)) {
      Dmsg2(100, "Unreleased Volume=%s dev=%p\n", vol->vol_name, vol->dev);
      free(vol->vol_name);
      vol->vol_name = NULL;
   }
   delete vol_list;
   vol_list = NULL;
   V(vol_list_lock);
}

bool is_volume_in_use(DCR *dcr)
{
   VOLRES *vol = find_volume(dcr->VolumeName);
   if (!vol) {
      Dmsg1(100, "Vol=%s not in use.\n", dcr->VolumeName);
      return false;                   /* vol not in list */
   }
   ASSERT(vol->dev != NULL);

   if (dcr->dev == vol->dev) {        /* same device OK */
      Dmsg1(100, "Vol=%s on same dev.\n", dcr->VolumeName);
      return false;
   }
   if (!vol->dev->is_busy()) {
      Dmsg2(100, "Vol=%s dev=%s not busy.\n", dcr->VolumeName, vol->dev->print_name());
      return false;
   }
   Dmsg2(100, "Vol=%s used by %s.\n", dcr->VolumeName, vol->dev->print_name());
   return true;
}


/*
 * We get the following type of information:
 *
 * use storage=xxx media_type=yyy pool_name=xxx pool_type=yyy append=1 copy=0 strip=0
 *  use device=zzz
 *  use device=aaa
 *  use device=bbb
 * use storage=xxx media_type=yyy pool_name=xxx pool_type=yyy append=0 copy=0 strip=0
 *  use device=bbb
 *
 */
static bool use_storage_cmd(JCR *jcr)
{
   POOL_MEM store_name, dev_name, media_type, pool_name, pool_type;
   BSOCK *dir = jcr->dir_bsock;
   int append;
   bool ok;       
   int Copy, Stripe;
   DIRSTORE *store;
   RCTX rctx;
   char *msg;
   alist *msgs;
   alist *dirstore;

   memset(&rctx, 0, sizeof(RCTX));
   rctx.jcr = jcr;
   /*
    * If there are multiple devices, the director sends us
    *   use_device for each device that it wants to use.
    */
   dirstore = New(alist(10, not_owned_by_alist));
// Dmsg2(000, "dirstore=%p JobId=%u\n", dirstore, jcr->JobId);
   msgs = jcr->reserve_msgs = New(alist(10, not_owned_by_alist));  
   do {
      Dmsg1(100, "<dird: %s", dir->msg);
      ok = sscanf(dir->msg, use_storage, store_name.c_str(), 
                  media_type.c_str(), pool_name.c_str(), 
                  pool_type.c_str(), &append, &Copy, &Stripe) == 7;
      if (!ok) {
         break;
      }
      if (append) {
         jcr->write_store = dirstore;
      } else {
         jcr->read_store = dirstore;
      }
      rctx.append = append;
      unbash_spaces(store_name);
      unbash_spaces(media_type);
      unbash_spaces(pool_name);
      unbash_spaces(pool_type);
      store = new DIRSTORE;
      dirstore->append(store);
      memset(store, 0, sizeof(DIRSTORE));
      store->device = New(alist(10));
      bstrncpy(store->name, store_name, sizeof(store->name));
      bstrncpy(store->media_type, media_type, sizeof(store->media_type));
      bstrncpy(store->pool_name, pool_name, sizeof(store->pool_name));
      bstrncpy(store->pool_type, pool_type, sizeof(store->pool_type));
      store->append = append;

      /* Now get all devices */
      while (dir->recv() >= 0) {
         Dmsg1(100, "<dird device: %s", dir->msg);
         ok = sscanf(dir->msg, use_device, dev_name.c_str()) == 1;
         if (!ok) {
            break;
         }
         unbash_spaces(dev_name);
         store->device->append(bstrdup(dev_name.c_str()));
      }
   }  while (ok && dir->recv() >= 0);

#ifdef DEVELOPER
   /* This loop is debug code and can be removed */
   /* ***FIXME**** remove after 1.38 release */
   char *device_name;
   foreach_alist(store, dirstore) {
      Dmsg5(110, "Storage=%s media_type=%s pool=%s pool_type=%s append=%d\n", 
         store->name, store->media_type, store->pool_name, 
         store->pool_type, store->append);
      foreach_alist(device_name, store->device) {
         Dmsg1(110, "   Device=%s\n", device_name);
      }
   }
#endif

   init_jcr_device_wait_timers(jcr);
   /*                    
    * At this point, we have a list of all the Director's Storage
    *  resources indicated for this Job, which include Pool, PoolType,
    *  storage name, and Media type.     
    * Then for each of the Storage resources, we have a list of
    *  device names that were given.
    *
    * Wiffle through them and find one that can do the backup.
    */
   if (ok) {
      bool first = true;           /* print wait message once */
      bool fail = false;
      rctx.notify_dir = true;
      lock_reservations();
      for ( ; !fail && !job_canceled(jcr); ) {
         while ((msg = (char *)msgs->pop())) {
            free(msg);
         }
         rctx.suitable_device = false;
         rctx.have_volume = false;
         rctx.VolumeName[0] = 0;
         rctx.any_drive = false;
         if (!jcr->PreferMountedVols) {
            /* Look for unused drives in autochangers */
            rctx.num_writers = 20000000;   /* start with impossible number */
            rctx.low_use_drive = NULL;
            rctx.PreferMountedVols = false;                
            rctx.exact_match = false;
            rctx.autochanger_only = true;
            Dmsg5(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d any=%d\n",
               rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
               rctx.autochanger_only, rctx.any_drive);
            if ((ok = find_suitable_device_for_job(jcr, rctx))) {
               break;
            }
            /* Look through all drives possibly for low_use drive */
            if (rctx.low_use_drive) {
               rctx.try_low_use_drive = true;
               if ((ok = find_suitable_device_for_job(jcr, rctx))) {
                  break;
               }
               rctx.try_low_use_drive = false;
            }
            rctx.autochanger_only = false;
            Dmsg5(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d any=%d\n",
               rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
               rctx.autochanger_only, rctx.any_drive);
            if ((ok = find_suitable_device_for_job(jcr, rctx))) {
               break;
            }
         }
         /* Look for an exact match all drives */
         rctx.PreferMountedVols = true;
         rctx.exact_match = true;
         rctx.autochanger_only = false;
         Dmsg5(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d any=%d\n",
            rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
            rctx.autochanger_only, rctx.any_drive);
         if ((ok = find_suitable_device_for_job(jcr, rctx))) {
            break;
         }
         /* Look for any mounted drive */
         rctx.exact_match = false;
         Dmsg5(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d any=%d\n",
            rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
            rctx.autochanger_only, rctx.any_drive);
         if ((ok = find_suitable_device_for_job(jcr, rctx))) {
            break;
         }
         /* Try any drive */
         rctx.any_drive = true;
         Dmsg5(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d any=%d\n",
            rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
            rctx.autochanger_only, rctx.any_drive);
         if ((ok = find_suitable_device_for_job(jcr, rctx))) {
            break;
         }
         /* Keep reservations locked *except* during wait_for_device() */
         unlock_reservations();
         if (!rctx.suitable_device || !wait_for_device(jcr, first)) {
            Dmsg0(100, "Fail. !suitable_device || !wait_for_device\n");
            fail = true;
         }   
         lock_reservations();
         first = false;
         bnet_sig(dir, BNET_HEARTBEAT);  /* Inform Dir that we are alive */
      }
      unlock_reservations();
      if (!ok) {
         /*
          * If we get here, there are no suitable devices available, which
          *  means nothing configured.  If a device is suitable but busy
          *  with another Volume, we will not come here.
          */
         unbash_spaces(dir->msg);
         pm_strcpy(jcr->errmsg, dir->msg);
         Jmsg(jcr, M_INFO, 0, _("Failed command: %s\n"), jcr->errmsg);
         Jmsg(jcr, M_FATAL, 0, _("\n"
            "     Device \"%s\" with MediaType \"%s\" requested by DIR not found in SD Device resources.\n"),
              dev_name.c_str(), media_type.c_str());
         bnet_fsend(dir, NO_device, dev_name.c_str());

         Dmsg1(100, ">dird: %s", dir->msg);
      }
   } else {
      unbash_spaces(dir->msg);
      pm_strcpy(jcr->errmsg, dir->msg);
      Jmsg(jcr, M_FATAL, 0, _("Failed command: %s\n"), jcr->errmsg);
      bnet_fsend(dir, BAD_use, jcr->errmsg);
      Dmsg1(100, ">dird: %s", dir->msg);
   }

   release_msgs(jcr);
   return ok;
}

void release_msgs(JCR *jcr)
{
   alist *msgs = jcr->reserve_msgs;
   char *msg;

   if (!msgs) {
      return;
   }
   lock_reservations();
   while ((msg = (char *)msgs->pop())) {
      free(msg);
   }
   delete msgs;
   jcr->reserve_msgs = NULL;
   unlock_reservations();
}

/*
 * Search for a device suitable for this job.
 */
bool find_suitable_device_for_job(JCR *jcr, RCTX &rctx)
{
   bool ok;
   DIRSTORE *store;
   char *device_name;
   alist *dirstore;

   if (rctx.append) {
      dirstore = jcr->write_store;
   } else {
      dirstore = jcr->read_store;
   }
   /* 
    * For each storage device that the user specified, we
    *  search and see if there is a resource for that device.
    */
   Dmsg4(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d\n",
      rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
      rctx.autochanger_only);
   ok = false;
   foreach_alist(store, dirstore) {
      rctx.store = store;
      foreach_alist(device_name, store->device) {
         int stat;
         rctx.device_name = device_name;
         stat = search_res_for_device(rctx); 
         if (stat == 1) {             /* found available device */
            Dmsg1(100, "Suitable device found=%s\n", device_name);
            ok = true;
            break;
         } else if (stat == 0) {      /* device busy */
            Dmsg1(110, "Suitable device=%s, busy: not use\n", device_name);
         } else {
            /* otherwise error */
            Dmsg0(110, "No suitable device found.\n");
         }
      }
      if (ok) {
         break;
      }
   }
   return ok;
}

/*
 * Search for a particular storage device with particular storage
 *  characteristics (MediaType).
 */
int search_res_for_device(RCTX &rctx) 
{
   AUTOCHANGER *changer;
   BSOCK *dir = rctx.jcr->dir_bsock;
   bool ok;
   int stat;

   Dmsg1(110, "Search res for %s\n", rctx.device_name);
   /* Look through Autochangers first */
   foreach_res(changer, R_AUTOCHANGER) {
      Dmsg1(150, "Try match changer res=%s\n", changer->hdr.name);
      /* Find resource, and make sure we were able to open it */
      if (fnmatch(rctx.device_name, changer->hdr.name, 0) == 0) {
         /* Try each device in this AutoChanger */
         foreach_alist(rctx.device, changer->device) {
            Dmsg1(110, "Try changer device %s\n", rctx.device->hdr.name);
            stat = reserve_device(rctx);
            if (stat != 1) {             /* try another device */
               continue;
            }
            POOL_MEM dev_name;
            if (rctx.store->append == SD_APPEND) {
               Dmsg2(100, "Device %s reserved=%d for append.\n", rctx.device->hdr.name,
                  rctx.jcr->dcr->dev->reserved_device);
            } else {
               Dmsg2(100, "Device %s reserved=%d for read.\n", rctx.device->hdr.name,
                  rctx.jcr->read_dcr->dev->reserved_device);
            }
            if (rctx.notify_dir) {
               pm_strcpy(dev_name, rctx.device->hdr.name);
               bash_spaces(dev_name);
               ok = bnet_fsend(dir, OK_device, dev_name.c_str());  /* Return real device name */
               Dmsg1(100, ">dird changer: %s", dir->msg);
            } else {
               ok = true;
            }
            return ok ? 1 : -1;
         }
      }
   }

   /* Now if requested look through regular devices */
   if (!rctx.autochanger_only) {
      foreach_res(rctx.device, R_DEVICE) {
         Dmsg1(150, "Try match res=%s\n", rctx.device->hdr.name);
         /* Find resource, and make sure we were able to open it */
         if (fnmatch(rctx.device_name, rctx.device->hdr.name, 0) == 0) {
            stat = reserve_device(rctx);
            if (stat != 1) {
               return stat;
            }
            if (rctx.notify_dir) {
               bash_spaces(rctx.device_name);
               ok = bnet_fsend(dir, OK_device, rctx.device_name);
               Dmsg1(100, ">dird dev: %s", dir->msg);
            } else {
               ok = true;
            }
            return ok ? 1 : -1;
         }
      }
   }
   return -1;                    /* nothing found */
}

/*
 *  Try to reserve a specific device.
 *
 *  Returns: 1 -- OK, have DCR
 *           0 -- must wait
 *          -1 -- fatal error
 */
static int reserve_device(RCTX &rctx)
{
   bool ok;
   DCR *dcr;
   const int name_len = MAX_NAME_LENGTH;

   /* Make sure MediaType is OK */
   Dmsg2(110, "MediaType device=%s request=%s\n",
         rctx.device->media_type, rctx.store->media_type);
   if (strcmp(rctx.device->media_type, rctx.store->media_type) != 0) {
      return -1;
   }

   /* Make sure device exists -- i.e. we can stat() it */
   if (!rctx.device->dev) {
      rctx.device->dev = init_dev(rctx.jcr, rctx.device);
   }
   if (!rctx.device->dev) {
      if (rctx.device->changer_res) {
        Jmsg(rctx.jcr, M_WARNING, 0, _("\n"
           "     Device \"%s\" in changer \"%s\" requested by DIR could not be opened or does not exist.\n"),
             rctx.device->hdr.name, rctx.device_name);
      } else {
         Jmsg(rctx.jcr, M_WARNING, 0, _("\n"
            "     Device \"%s\" requested by DIR could not be opened or does not exist.\n"),
              rctx.device_name);
      }
      return -1;  /* no use waiting */
   }  

   rctx.suitable_device = true;
   Dmsg2(110, "Try reserve %s JobId=%u\n", rctx.device->hdr.name,
         rctx.jcr->JobId);
   dcr = new_dcr(rctx.jcr, rctx.device->dev);
   if (!dcr) {
      BSOCK *dir = rctx.jcr->dir_bsock;
      bnet_fsend(dir, _("3926 Could not get dcr for device: %s\n"), rctx.device_name);
      Dmsg1(100, ">dird: %s", dir->msg);
      return -1;
   }
   bstrncpy(dcr->pool_name, rctx.store->pool_name, name_len);
   bstrncpy(dcr->pool_type, rctx.store->pool_type, name_len);
   bstrncpy(dcr->media_type, rctx.store->media_type, name_len);
   bstrncpy(dcr->dev_name, rctx.device_name, name_len);
   if (rctx.store->append == SD_APPEND) {
      Dmsg2(100, "have_vol=%d vol=%s\n", rctx.have_volume, rctx.VolumeName);
      if (!rctx.have_volume) {
         dcr->any_volume = true;
         if (dir_find_next_appendable_volume(dcr)) {
            bstrncpy(rctx.VolumeName, dcr->VolumeName, sizeof(rctx.VolumeName));
            Dmsg2(100, "JobId=%u looking for Volume=%s\n", (int)rctx.jcr->JobId, rctx.VolumeName);
            rctx.have_volume = true;
         } else {
            Dmsg0(100, "No next volume found\n");
            rctx.have_volume = false;
            rctx.VolumeName[0] = 0;
        }
      }
      ok = reserve_device_for_append(dcr, rctx);
      if (ok) {
         rctx.jcr->dcr = dcr;
         Dmsg5(100, "Reserved=%d dev_name=%s mediatype=%s pool=%s ok=%d\n",
               dcr->dev->reserved_device,
               dcr->dev_name, dcr->media_type, dcr->pool_name, ok);
      }
   } else {
      ok = reserve_device_for_read(dcr);
      if (ok) {
         rctx.jcr->read_dcr = dcr;
         Dmsg5(100, "Read reserved=%d dev_name=%s mediatype=%s pool=%s ok=%d\n",
               dcr->dev->reserved_device,
               dcr->dev_name, dcr->media_type, dcr->pool_name, ok);
      }
   }
   if (!ok) {
      rctx.have_volume = false;
      free_dcr(dcr);
      Dmsg0(110, "Not OK.\n");
      return 0;
   }
   return 1;
}

/*
 * We "reserve" the drive by setting the ST_READ bit. No one else
 *  should touch the drive until that is cleared.
 *  This allows the DIR to "reserve" the device before actually
 *  starting the job. 
 */
static bool reserve_device_for_read(DCR *dcr)
{
   DEVICE *dev = dcr->dev;
   JCR *jcr = dcr->jcr;
   bool ok = false;

   ASSERT(dcr);

   dev->dlock();  

   if (is_device_unmounted(dev)) {             
      Dmsg1(200, "Device %s is BLOCKED due to user unmount.\n", dev->print_name());
      Mmsg(jcr->errmsg, _("3601 JobId=%u device %s is BLOCKED due to user unmount.\n"),
           jcr->JobId, dev->print_name());
      queue_reserve_message(jcr);
      goto bail_out;
   }

   if (dev->is_busy()) {
      Dmsg4(200, "Device %s is busy ST_READ=%d num_writers=%d reserved=%d.\n", dev->print_name(),
         dev->state & ST_READ?1:0, dev->num_writers, dev->reserved_device);
      Mmsg(jcr->errmsg, _("3602 JobId=%u device %s is busy (already reading/writing).\n"),
            jcr->JobId, dev->print_name());
      queue_reserve_message(jcr);
      goto bail_out;
   }

   dev->clear_append();
   dev->set_read();
   ok = true;
   dev->reserved_device++;
   Dmsg3(100, "Inc reserve=%d dev=%s %p\n", dev->reserved_device, 
      dev->print_name(), dev);
   dcr->reserved_device = true;

bail_out:
   dev->dunlock();
   return ok;
}


/*
 * We reserve the device for appending by incrementing the 
 *  reserved_device. We do virtually all the same work that
 *  is done in acquire_device_for_append(), but we do
 *  not attempt to mount the device. This routine allows
 *  the DIR to reserve multiple devices before *really* 
 *  starting the job. It also permits the SD to refuse 
 *  certain devices (not up, ...).
 *
 * Note, in reserving a device, if the device is for the
 *  same pool and the same pool type, then it is acceptable.
 *  The Media Type has already been checked. If we are
 *  the first tor reserve the device, we put the pool
 *  name and pool type in the device record.
 */
static bool reserve_device_for_append(DCR *dcr, RCTX &rctx)
{
   JCR *jcr = dcr->jcr;
   DEVICE *dev = dcr->dev;
   bool ok = false;

   ASSERT(dcr);

   dev->dlock();

   /* If device is being read, we cannot write it */
   if (dev->can_read()) {
      Mmsg(jcr->errmsg, _("3603 JobId=%u device %s is busy reading.\n"), 
         jcr->JobId, dev->print_name());
      Dmsg1(110, "%s", jcr->errmsg);
      queue_reserve_message(jcr);
      goto bail_out;
   }

   /* If device is unmounted, we are out of luck */
   if (is_device_unmounted(dev)) {
      Mmsg(jcr->errmsg, _("3604 JobId=%u device %s is BLOCKED due to user unmount.\n"), 
         jcr->JobId, dev->print_name());
      Dmsg1(110, "%s", jcr->errmsg);
      queue_reserve_message(jcr);
      goto bail_out;
   }

   Dmsg1(110, "reserve_append device is %s\n", dev->is_tape()?"tape":"disk");

   /* Now do detailed tests ... */
   if (can_reserve_drive(dcr, rctx) != 1) {
      Dmsg0(110, "can_reserve_drive!=1\n");
      goto bail_out;
   }

   dev->reserved_device++;
   Dmsg3(100, "Inc reserve=%d dev=%s %p\n", dev->reserved_device, 
      dev->print_name(), dev);
   dcr->reserved_device = true;
   ok = true;

bail_out:
   dev->dunlock();
   return ok;
}

/*
 * Returns: 1 if drive can be reserved
 *          0 if we should wait
 *         -1 on error or impossibility
 */
static int can_reserve_drive(DCR *dcr, RCTX &rctx) 
{
   DEVICE *dev = dcr->dev;
   JCR *jcr = dcr->jcr;

   Dmsg5(110, "PrefMnt=%d exact=%d suitable=%d chgronly=%d any=%d\n",
         rctx.PreferMountedVols, rctx.exact_match, rctx.suitable_device,
         rctx.autochanger_only, rctx.any_drive);

   /* setting any_drive overrides PreferMountedVols flag */
   if (!rctx.any_drive) {
      /*
       * When PreferMountedVols is set, we keep track of the 
       *  drive in use that has the least number of writers, then if
       *  no unmounted drive is found, we try that drive. This   
       *  helps spread the load to the least used drives.  
       */
      if (rctx.try_low_use_drive && dev == rctx.low_use_drive) {
         Dmsg3(110, "OK dev=%s == low_drive=%s. JobId=%u\n",
            dev->print_name(), rctx.low_use_drive->print_name(), jcr->JobId);
         return 1;
      }
      /* If he wants a free drive, but this one is busy, no go */
      if (!rctx.PreferMountedVols && dev->is_busy()) {
         /* Save least used drive */
         if ((dev->num_writers + dev->reserved_device) < rctx.num_writers) {
            rctx.num_writers = dev->num_writers + dev->reserved_device;
            rctx.low_use_drive = dev;
            Dmsg2(110, "set low use drive=%s num_writers=%d\n", dev->print_name(),
               rctx.num_writers);
         } else {
            Dmsg1(110, "not low use num_writers=%d\n", dev->num_writers+ 
               dev->reserved_device);
         }
         Dmsg1(110, "failed: !prefMnt && busy. JobId=%u\n", jcr->JobId);
         Mmsg(jcr->errmsg, _("3605 JobId=%u wants free drive but device %s is busy.\n"), 
            jcr->JobId, dev->print_name());
         queue_reserve_message(jcr);
         return 0;
      }

      /* Check for prefer mounted volumes */
      if (rctx.PreferMountedVols && !dev->VolHdr.VolumeName[0] && dev->is_tape()) {
         Mmsg(jcr->errmsg, _("3606 JobId=%u prefers mounted drives, but drive %s has no Volume.\n"), 
            jcr->JobId, dev->print_name());
         queue_reserve_message(jcr);
         Dmsg1(110, "failed: want mounted -- no vol JobId=%u\n", jcr->JobId);
         return 0;                 /* No volume mounted */
      }

      /* Check for exact Volume name match */
      if (rctx.exact_match && rctx.have_volume &&
          strcmp(dev->VolHdr.VolumeName, rctx.VolumeName) != 0) {
         Mmsg(jcr->errmsg, _("3607 JobId=%u wants Vol=\"%s\" drive has Vol=\"%s\" on drive %s.\n"), 
            jcr->JobId, rctx.VolumeName, dev->VolHdr.VolumeName, 
            dev->print_name());
         queue_reserve_message(jcr);
         Dmsg2(110, "failed: Not exact match have=%s want=%s\n",
               dev->VolHdr.VolumeName, rctx.VolumeName);
         return 0;
      }
   }

   /* Check for unused autochanger drive */
   if (rctx.autochanger_only && dev->num_writers == 0 &&
       dev->VolHdr.VolumeName[0] == 0) {
      /* Device is available but not yet reserved, reserve it for us */
      Dmsg2(100, "OK Res Unused autochanger %s JobId=%u.\n",
         dev->print_name(), jcr->JobId);
      bstrncpy(dev->pool_name, dcr->pool_name, sizeof(dev->pool_name));
      bstrncpy(dev->pool_type, dcr->pool_type, sizeof(dev->pool_type));
      return 1;                       /* reserve drive */
   }

   /*
    * Handle the case that there are no writers
    */
   if (dev->num_writers == 0) {
      /* Now check if there are any reservations on the drive */
      if (dev->reserved_device) {           
         /* Now check if we want the same Pool and pool type */
         if (strcmp(dev->pool_name, dcr->pool_name) == 0 &&
             strcmp(dev->pool_type, dcr->pool_type) == 0) {
            /* OK, compatible device */
            Dmsg2(100, "OK dev: %s num_writers=0, reserved, pool matches JobId=%u\n",
               dev->print_name(), jcr->JobId);
            return 1;
         } else {
            /* Drive Pool not suitable for us */
            Mmsg(jcr->errmsg, _(
"3608 JobId=%u wants Pool=\"%s\" but have Pool=\"%s\" nreserve=%d on drive %s.\n"), 
                  jcr->JobId, dcr->pool_name, dev->pool_name,
                  dev->reserved_device, dev->print_name());
            queue_reserve_message(jcr);
            Dmsg2(110, "failed: busy num_writers=0, reserved, pool=%s wanted=%s\n",
               dev->pool_name, dcr->pool_name);
            return 0;                 /* wait */
         }
      } else if (dev->can_append()) {
         /* Device in append mode, check if changing pool */
         if (strcmp(dev->pool_name, dcr->pool_name) == 0 &&
             strcmp(dev->pool_type, dcr->pool_type) == 0) {
            Dmsg2(100, "OK dev: %s num_writers=0, can_append, pool matches. JobId=%u\n",
               dev->print_name(), jcr->JobId);
            /* OK, compatible device */
            return 1;
         } else {
            /* Changing pool, unload old tape if any in drive */
            Dmsg0(100, "OK dev: num_writers=0, not reserved, pool change, unload changer\n");
            unload_autochanger(dcr, 0);
         }
      }
      /* Device is available but not yet reserved, reserve it for us */
      Dmsg2(100, "OK Dev avail reserved %s JobId=%u\n", dev->print_name(),
         jcr->JobId);
      bstrncpy(dev->pool_name, dcr->pool_name, sizeof(dev->pool_name));
      bstrncpy(dev->pool_type, dcr->pool_type, sizeof(dev->pool_type));
      return 1;                       /* reserve drive */
   }

   /*
    * Check if the device is in append mode with writers (i.e.
    *  available if pool is the same).
    */
   if (dev->can_append() || dev->num_writers > 0) {
      /* Yes, now check if we want the same Pool and pool type */
      if (strcmp(dev->pool_name, dcr->pool_name) == 0 &&
          strcmp(dev->pool_type, dcr->pool_type) == 0) {
         Dmsg2(100, "OK dev: %s num_writers>=0, can_append, pool matches. JobId=%u\n",
            dev->print_name(), jcr->JobId);
         /* OK, compatible device */
         return 1;
      } else {
         /* Drive Pool not suitable for us */
         Mmsg(jcr->errmsg, _("3609 JobId=%u wants Pool=\"%s\" but has Pool=\"%s\" on drive %s.\n"), 
               jcr->JobId, dcr->pool_name, dev->pool_name, dev->print_name());
         queue_reserve_message(jcr);
         Dmsg2(110, "failed: busy num_writers>0, can_append, pool=%s wanted=%s\n",
            dev->pool_name, dcr->pool_name);
         return 0;                    /* wait */
      }
   } else {
      Pmsg0(000, _("Logic error!!!! Should not get here.\n"));
      Mmsg(jcr->errmsg, _("3910 JobId=%u Logic error!!!! drive %s Should not get here.\n"),
            jcr->JobId, dev->print_name());
      queue_reserve_message(jcr);
      Jmsg0(jcr, M_FATAL, 0, _("Logic error!!!! Should not get here.\n"));
      return -1;                      /* error, should not get here */
   }
   Mmsg(jcr->errmsg, _("3911 JobId=%u failed reserve drive %s.\n"), 
         jcr->JobId, dev->print_name());
   queue_reserve_message(jcr);
   Dmsg2(110, "failed: No reserve %s JobId=%u\n", dev->print_name(), jcr->JobId);
   return 0;
}

/*
 * search_lock is already set on entering this routine 
 */
static void queue_reserve_message(JCR *jcr)
{
   int i;   
   alist *msgs = jcr->reserve_msgs;
   char *msg;

   if (!msgs) {
      return;
   }
   /*
    * Look for duplicate message.  If found, do
    * not insert
    */
   for (i=msgs->size()-1; i >= 0; i--) {
      msg = (char *)msgs->get(i);
      if (!msg) {
         return;
      }
      /* Comparison based on 4 digit message number */
      if (strncmp(msg, jcr->errmsg, 4) == 0) {
         return;
      }
   }      
   /* Message unique, so insert it */
   jcr->reserve_msgs->push(bstrdup(jcr->errmsg));
}

/*
 * Send any reservation messages queued for this jcr
 */
void send_drive_reserve_messages(JCR *jcr, void sendit(const char *msg, int len, void *sarg), void *arg)
{
   int i;
   alist *msgs;
   char *msg;

   lock_reservations();
   msgs = jcr->reserve_msgs;
   if (!msgs || msgs->size() == 0) {
      unlock_reservations();
      return;
   }
   for (i=msgs->size()-1; i >= 0; i--) {
      msg = (char *)msgs->get(i);
      if (msg) {
         sendit("   ", 3, arg);
         sendit(msg, strlen(msg), arg);
      } else {
         break;
      }
   }
   unlock_reservations();
}