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posix.c

/* 
   Unix SMB/Netbios implementation.
   Version 3.0
   Locking functions
   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   Revision History:

   POSIX locking support. Jeremy Allison (jeremy@valinux.com), Apr. 2000.
*/

#include "includes.h"

/*
 * The POSIX locking database handle.
 */

static TDB_CONTEXT *posix_lock_tdb;

/*
 * The pending close database handle.
 */

static TDB_CONTEXT *posix_pending_close_tdb;

/*
 * The data in POSIX lock records is an unsorted linear array of these
 * records.  It is unnecessary to store the count as tdb provides the
 * size of the record.
 */

struct posix_lock {
      int fd;
      SMB_OFF_T start;
      SMB_OFF_T size;
      int lock_type;
};

/*
 * The data in POSIX pending close records is an unsorted linear array of int
 * records.  It is unnecessary to store the count as tdb provides the
 * size of the record.
 */

/* The key used in both the POSIX databases. */

struct posix_lock_key {
      SMB_DEV_T device;
      SMB_INO_T inode;
}; 

/*******************************************************************
 Form a static locking key for a dev/inode pair.
******************************************************************/

static TDB_KEY locking_key(SMB_DEV_T dev, SMB_INO_T inode)
{
      static struct posix_lock_key key;
      TDB_KEY kbuf;

      memset(&key, '\0', sizeof(key));
      key.device = dev;
      key.inode = inode;
      kbuf.dptr = (char *)&key;
      kbuf.dsize = sizeof(key);
      return kbuf;
}

/*******************************************************************
 Convenience function to get a key from an fsp.
******************************************************************/

static TDB_KEY locking_key_fsp(files_struct *fsp)
{
      return locking_key(fsp->dev, fsp->inode);
}

/****************************************************************************
 Add an fd to the pending close tdb.
****************************************************************************/

static BOOL add_fd_to_close_entry(files_struct *fsp)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      char *tp;

      kbuf = locking_key_fsp(fsp);
      dbuf.dptr = NULL;

      dbuf = tdb_fetch(posix_pending_close_tdb, kbuf);

      tp = Realloc(dbuf.dptr, dbuf.dsize + sizeof(int));
      if (!tp) {
            DEBUG(0,("add_fd_to_close_entry: Realloc fail !\n"));
            SAFE_FREE(dbuf.dptr);
            return False;
      } else
            dbuf.dptr = tp;

      memcpy(dbuf.dptr + dbuf.dsize, &fsp->fd, sizeof(int));
      dbuf.dsize += sizeof(int);

      if (tdb_store(posix_pending_close_tdb, kbuf, dbuf, TDB_REPLACE) == -1) {
            DEBUG(0,("add_fd_to_close_entry: tdb_store fail !\n"));
      }

      SAFE_FREE(dbuf.dptr);
      return True;
}

/****************************************************************************
 Remove all fd entries for a specific dev/inode pair from the tdb.
****************************************************************************/

static void delete_close_entries(files_struct *fsp)
{
      TDB_KEY kbuf;

      kbuf = locking_key_fsp(fsp);
      if (tdb_delete(posix_pending_close_tdb, kbuf) == -1)
            DEBUG(0,("delete_close_entries: tdb_delete fail !\n"));
}

/****************************************************************************
 Get the array of POSIX pending close records for an open fsp. Caller must
 free. Returns number of entries.
****************************************************************************/

static size_t get_posix_pending_close_entries(files_struct *fsp, int **entries)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      size_t count = 0;

      kbuf = locking_key_fsp(fsp);
      *entries = NULL;
      dbuf.dptr = NULL;

      dbuf = tdb_fetch(posix_pending_close_tdb, kbuf);

      if (!dbuf.dptr)
            return 0;

      *entries = (int *)dbuf.dptr;
      count = (size_t)(dbuf.dsize / sizeof(int));

      return count;
}

/****************************************************************************
 Get the array of POSIX locks for an fsp. Caller must free. Returns
 number of entries.
****************************************************************************/

static size_t get_posix_lock_entries(files_struct *fsp, struct posix_lock **entries)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      size_t count = 0;

      kbuf = locking_key_fsp(fsp);
      *entries = NULL;

      dbuf.dptr = NULL;

      dbuf = tdb_fetch(posix_lock_tdb, kbuf);

      if (!dbuf.dptr)
            return 0;

      *entries = (struct posix_lock *)dbuf.dptr;
      count = (size_t)(dbuf.dsize / sizeof(struct posix_lock));

      return count;
}

/****************************************************************************
 Deal with pending closes needed by POSIX locking support.
 Note that posix_locking_close_file() is expected to have been called
 to delete all locks on this fsp before this function is called.
****************************************************************************/

int fd_close_posix(struct connection_struct *conn, files_struct *fsp)
{
      int saved_errno = 0;
      int ret;
      size_t count, i;
      struct posix_lock *entries = NULL;
      int *fd_array = NULL;
      BOOL locks_on_other_fds = False;

      if (!lp_posix_locking(SNUM(conn))) {
            /*
             * No POSIX to worry about, just close.
             */
            ret = conn->vfs_ops.close(fsp,fsp->fd);
            fsp->fd = -1;
            return ret;
      }

      /*
       * Get the number of outstanding POSIX locks on this dev/inode pair.
       */

      count = get_posix_lock_entries(fsp, &entries);

      /*
       * Check if there are any outstanding locks belonging to
       * other fd's. This should never be the case if posix_locking_close_file()
       * has been called first, but it never hurts to be *sure*.
       */

      for (i = 0; i < count; i++) {
            if (entries[i].fd != fsp->fd) {
                  locks_on_other_fds = True;
                  break;
            }
      }

      if (locks_on_other_fds) {

            /*
             * There are outstanding locks on this dev/inode pair on other fds.
             * Add our fd to the pending close tdb and set fsp->fd to -1.
             */

            if (!add_fd_to_close_entry(fsp)) {
                  SAFE_FREE(entries);
                  return False;
            }

            SAFE_FREE(entries);
            fsp->fd = -1;
            return 0;
      }

      SAFE_FREE(entries);

      /*
       * No outstanding POSIX locks. Get the pending close fd's
       * from the tdb and close them all.
       */

      count = get_posix_pending_close_entries(fsp, &fd_array);

      if (count) {
            DEBUG(10,("fd_close_posix: doing close on %u fd's.\n", (unsigned int)count ));

            for(i = 0; i < count; i++) {
                  if (conn->vfs_ops.close(fsp,fd_array[i]) == -1) {
                        saved_errno = errno;
                  }
            }

            /*
             * Delete all fd's stored in the tdb
             * for this dev/inode pair.
             */

            delete_close_entries(fsp);
      }

      SAFE_FREE(fd_array);

      /*
       * Finally close the fd associated with this fsp.
       */

      ret = conn->vfs_ops.close(fsp,fsp->fd);

      if (saved_errno != 0) {
            errno = saved_errno;
            ret = -1;
      } 

      fsp->fd = -1;

      return ret;
}

/****************************************************************************
 Debugging aid :-).
****************************************************************************/

static const char *posix_lock_type_name(int lock_type)
{
      return (lock_type == F_RDLCK) ? "READ" : "WRITE";
}

/****************************************************************************
 Delete a POSIX lock entry by index number. Used if the tdb add succeeds, but
 then the POSIX fcntl lock fails.
****************************************************************************/

static BOOL delete_posix_lock_entry_by_index(files_struct *fsp, size_t entry)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      struct posix_lock *locks;
      size_t count;

      kbuf = locking_key_fsp(fsp);
      dbuf.dptr = NULL;
      
      dbuf = tdb_fetch(posix_lock_tdb, kbuf);

      if (!dbuf.dptr) {
            DEBUG(10,("delete_posix_lock_entry_by_index: tdb_fetch failed !\n"));
            goto fail;
      }

      count = (size_t)(dbuf.dsize / sizeof(struct posix_lock));
      locks = (struct posix_lock *)dbuf.dptr;

      if (count == 1) {
            tdb_delete(posix_lock_tdb, kbuf);
      } else {
            if (entry < count-1) {
                  memmove(&locks[entry], &locks[entry+1], sizeof(*locks)*((count-1) - entry));
            }
            dbuf.dsize -= sizeof(*locks);
            tdb_store(posix_lock_tdb, kbuf, dbuf, TDB_REPLACE);
      }

      SAFE_FREE(dbuf.dptr);

      return True;

 fail:

      SAFE_FREE(dbuf.dptr);
      return False;
}

/****************************************************************************
 Add an entry into the POSIX locking tdb. We return the index number of the
 added lock (used in case we need to delete *exactly* this entry). Returns
 False on fail, True on success.
****************************************************************************/

static BOOL add_posix_lock_entry(files_struct *fsp, SMB_OFF_T start, SMB_OFF_T size, int lock_type, size_t *pentry_num)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      struct posix_lock pl;
      char *tp;

      kbuf = locking_key_fsp(fsp);
      dbuf.dptr = NULL;

      dbuf = tdb_fetch(posix_lock_tdb, kbuf);

      *pentry_num = (size_t)(dbuf.dsize / sizeof(pl));

      /*
       * Add new record.
       */

      pl.fd = fsp->fd;
      pl.start = start;
      pl.size = size;
      pl.lock_type = lock_type;

      tp = Realloc(dbuf.dptr, dbuf.dsize + sizeof(pl));
      if (!tp) {
            DEBUG(0,("add_posix_lock_entry: Realloc fail !\n"));
            goto fail;
      } else
            dbuf.dptr = tp;

      memcpy(dbuf.dptr + dbuf.dsize, &pl, sizeof(pl));
      dbuf.dsize += sizeof(pl);

      if (tdb_store(posix_lock_tdb, kbuf, dbuf, TDB_REPLACE) == -1) {
            DEBUG(0,("add_posix_lock: Failed to add lock entry on file %s\n", fsp->fsp_name));
            goto fail;
      }

      SAFE_FREE(dbuf.dptr);

      DEBUG(10,("add_posix_lock: File %s: type = %s: start=%.0f size=%.0f: dev=%.0f inode=%.0f\n",
                  fsp->fsp_name, posix_lock_type_name(lock_type), (double)start, (double)size,
                  (double)fsp->dev, (double)fsp->inode ));

      return True;

 fail:

      SAFE_FREE(dbuf.dptr);
      return False;
}

/****************************************************************************
 Calculate if locks have any overlap at all.
****************************************************************************/

static BOOL does_lock_overlap(SMB_OFF_T start1, SMB_OFF_T size1, SMB_OFF_T start2, SMB_OFF_T size2)
{
      if (start1 >= start2 && start1 <= start2 + size2)
            return True;

      if (start1 < start2 && start1 + size1 > start2)
            return True;

      return False;
}

/****************************************************************************
 Delete an entry from the POSIX locking tdb. Returns a copy of the entry being
 deleted and the number of records that are overlapped by this one, or -1 on error.
****************************************************************************/

static int delete_posix_lock_entry(files_struct *fsp, SMB_OFF_T start, SMB_OFF_T size, struct posix_lock *pl)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      struct posix_lock *locks;
      size_t i, count;
      BOOL found = False;
      int num_overlapping_records = 0;

      kbuf = locking_key_fsp(fsp);
      dbuf.dptr = NULL;
      
      dbuf = tdb_fetch(posix_lock_tdb, kbuf);

      if (!dbuf.dptr) {
            DEBUG(10,("delete_posix_lock_entry: tdb_fetch failed !\n"));
            goto fail;
      }

      /* There are existing locks - find a match. */
      locks = (struct posix_lock *)dbuf.dptr;
      count = (size_t)(dbuf.dsize / sizeof(*locks));

      /*
       * Search for and delete the first record that matches the
       * unlock criteria.
       */

      for (i=0; i<count; i++) { 
            struct posix_lock *entry = &locks[i];

            if (entry->fd == fsp->fd &&
                  entry->start == start &&
                  entry->size == size) {

                  /* Make a copy if requested. */
                  if (pl)
                        *pl = *entry;

                  /* Found it - delete it. */
                  if (count == 1) {
                        tdb_delete(posix_lock_tdb, kbuf);
                  } else {
                        if (i < count-1) {
                              memmove(&locks[i], &locks[i+1], sizeof(*locks)*((count-1) - i));
                        }
                        dbuf.dsize -= sizeof(*locks);
                        tdb_store(posix_lock_tdb, kbuf, dbuf, TDB_REPLACE);
                  }
                  count--;
                  found = True;
                  break;
            }
      }

      if (!found)
            goto fail;

      /*
       * Count the number of entries that are
       * overlapped by this unlock request.
       */

      for (i = 0; i < count; i++) {
            struct posix_lock *entry = &locks[i];

            if (fsp->fd == entry->fd &&
                  does_lock_overlap( start, size, entry->start, entry->size))
                        num_overlapping_records++;
      }

      DEBUG(10,("delete_posix_lock_entry: type = %s: start=%.0f size=%.0f, num_records = %d\n",
                  posix_lock_type_name(pl->lock_type), (double)pl->start, (double)pl->size,
                        (unsigned int)num_overlapping_records ));

      SAFE_FREE(dbuf.dptr);

      return num_overlapping_records;

 fail:

      SAFE_FREE(dbuf.dptr);
      return -1;
}

/****************************************************************************
 Utility function to map a lock type correctly depending on the open
 mode of a file.
****************************************************************************/

static int map_posix_lock_type( files_struct *fsp, enum brl_type lock_type)
{
      if((lock_type == WRITE_LOCK) && !fsp->can_write) {
            /*
             * Many UNIX's cannot get a write lock on a file opened read-only.
             * Win32 locking semantics allow this.
             * Do the best we can and attempt a read-only lock.
             */
            DEBUG(10,("map_posix_lock_type: Downgrading write lock to read due to read-only file.\n"));
            return F_RDLCK;
      } else if((lock_type == READ_LOCK) && !fsp->can_read) {
            /*
             * Ditto for read locks on write only files.
             */
            DEBUG(10,("map_posix_lock_type: Changing read lock to write due to write-only file.\n"));
            return F_WRLCK;
      }

      /*
       * This return should be the most normal, as we attempt
       * to always open files read/write.
       */

      return (lock_type == READ_LOCK) ? F_RDLCK : F_WRLCK;
}

/****************************************************************************
 Check to see if the given unsigned lock range is within the possible POSIX
 range. Modifies the given args to be in range if possible, just returns
 False if not.
****************************************************************************/

static BOOL posix_lock_in_range(SMB_OFF_T *offset_out, SMB_OFF_T *count_out,
                                                SMB_BIG_UINT u_offset, SMB_BIG_UINT u_count)
{
      SMB_OFF_T offset = (SMB_OFF_T)u_offset;
      SMB_OFF_T count = (SMB_OFF_T)u_count;

      /*
       * For the type of system we are, attempt to
       * find the maximum positive lock offset as an SMB_OFF_T.
       */

#if defined(MAX_POSITIVE_LOCK_OFFSET) /* Some systems have arbitrary limits. */

      SMB_OFF_T max_positive_lock_offset = (MAX_POSITIVE_LOCK_OFFSET);

#elif defined(LARGE_SMB_OFF_T) && !defined(HAVE_BROKEN_FCNTL64_LOCKS)

      /*
       * In this case SMB_OFF_T is 64 bits,
       * and the underlying system can handle 64 bit signed locks.
       */

      SMB_OFF_T mask2 = ((SMB_OFF_T)0x4) << (SMB_OFF_T_BITS-4);
      SMB_OFF_T mask = (mask2<<1);
      SMB_OFF_T max_positive_lock_offset = ~mask;

#else /* !LARGE_SMB_OFF_T || HAVE_BROKEN_FCNTL64_LOCKS */

      /*
       * In this case either SMB_OFF_T is 32 bits,
       * or the underlying system cannot handle 64 bit signed locks.
       * All offsets & counts must be 2^31 or less.
       */

      SMB_OFF_T max_positive_lock_offset = 0x7FFFFFFF;

#endif /* !LARGE_SMB_OFF_T || HAVE_BROKEN_FCNTL64_LOCKS */

      /*
       * POSIX locks of length zero mean lock to end-of-file.
       * Win32 locks of length zero are point probes. Ignore
       * any Win32 locks of length zero. JRA.
       */

      if (count == (SMB_OFF_T)0) {
            DEBUG(10,("posix_lock_in_range: count = 0, ignoring.\n"));
            return False;
      }

      /*
       * If the given offset was > max_positive_lock_offset then we cannot map this at all
       * ignore this lock.
       */

      if (u_offset & ~((SMB_BIG_UINT)max_positive_lock_offset)) {
            DEBUG(10,("posix_lock_in_range: (offset = %.0f) offset > %.0f and we cannot handle this. Ignoring lock.\n",
                        (double)u_offset, (double)((SMB_BIG_UINT)max_positive_lock_offset) ));
            return False;
      }

      /*
       * We must truncate the count to less than max_positive_lock_offset.
       */

      if (u_count & ~((SMB_BIG_UINT)max_positive_lock_offset))
            count = max_positive_lock_offset;

      /*
       * Truncate count to end at max lock offset.
       */

      if (offset + count < 0 || offset + count > max_positive_lock_offset)
            count = max_positive_lock_offset - offset;

      /*
       * If we ate all the count, ignore this lock.
       */

      if (count == 0) {
            DEBUG(10,("posix_lock_in_range: Count = 0. Ignoring lock u_offset = %.0f, u_count = %.0f\n",
                        (double)u_offset, (double)u_count ));
            return False;
      }

      /*
       * The mapping was successful.
       */

      DEBUG(10,("posix_lock_in_range: offset_out = %.0f, count_out = %.0f\n",
                  (double)offset, (double)count ));

      *offset_out = offset;
      *count_out = count;
      
      return True;
}

/****************************************************************************
 Actual function that does POSIX locks. Copes with 64 -> 32 bit cruft and
 broken NFS implementations.
****************************************************************************/

static BOOL posix_fcntl_lock(files_struct *fsp, int op, SMB_OFF_T offset, SMB_OFF_T count, int type)
{
      int ret;
      struct connection_struct *conn = fsp->conn;

      DEBUG(8,("posix_fcntl_lock %d %d %.0f %.0f %d\n",fsp->fd,op,(double)offset,(double)count,type));

      ret = conn->vfs_ops.lock(fsp,fsp->fd,op,offset,count,type);

      if (!ret && ((errno == EFBIG) || (errno == ENOLCK) || (errno ==  EINVAL))) {

            DEBUG(0,("posix_fcntl_lock: WARNING: lock request at offset %.0f, length %.0f returned\n",
                              (double)offset,(double)count));
            DEBUG(0,("an %s error. This can happen when using 64 bit lock offsets\n", strerror(errno)));
            DEBUG(0,("on 32 bit NFS mounted file systems.\n"));

            /*
             * If the offset is > 0x7FFFFFFF then this will cause problems on
             * 32 bit NFS mounted filesystems. Just ignore it.
             */

            if (offset & ~((SMB_OFF_T)0x7fffffff)) {
                  DEBUG(0,("Offset greater than 31 bits. Returning success.\n"));
                  return True;
            }

            if (count & ~((SMB_OFF_T)0x7fffffff)) {
                  /* 32 bit NFS file system, retry with smaller offset */
                  DEBUG(0,("Count greater than 31 bits - retrying with 31 bit truncated length.\n"));
                  errno = 0;
                  count &= 0x7fffffff;
                  ret = conn->vfs_ops.lock(fsp,fsp->fd,op,offset,count,type);
            }
      }

      DEBUG(8,("posix_fcntl_lock: Lock call %s\n", ret ? "successful" : "failed"));

      return ret;
}

/****************************************************************************
 POSIX function to see if a file region is locked. Returns True if the
 region is locked, False otherwise.
****************************************************************************/

BOOL is_posix_locked(files_struct *fsp, SMB_BIG_UINT u_offset, SMB_BIG_UINT u_count, enum brl_type lock_type)
{
      SMB_OFF_T offset;
      SMB_OFF_T count;
      int posix_lock_type = map_posix_lock_type(fsp,lock_type);

      DEBUG(10,("is_posix_locked: File %s, offset = %.0f, count = %.0f, type = %s\n",
                  fsp->fsp_name, (double)u_offset, (double)u_count, posix_lock_type_name(lock_type) ));

      /*
       * If the requested lock won't fit in the POSIX range, we will
       * never set it, so presume it is not locked.
       */

      if(!posix_lock_in_range(&offset, &count, u_offset, u_count))
            return False;

      /*
       * Note that most UNIX's can *test* for a write lock on
       * a read-only fd, just not *set* a write lock on a read-only
       * fd. So we don't need to use map_lock_type here.
       */ 

      return posix_fcntl_lock(fsp,SMB_F_GETLK,offset,count,posix_lock_type);
}

/*
 * Structure used when splitting a lock range
 * into a POSIX lock range. Doubly linked list.
 */

struct lock_list {
      struct lock_list *next;
      struct lock_list *prev;
      SMB_OFF_T start;
      SMB_OFF_T size;
};

/****************************************************************************
 Create a list of lock ranges that don't overlap a given range. Used in calculating
 POSIX locks and unlocks. This is a difficult function that requires ASCII art to
 understand it :-).
****************************************************************************/

static struct lock_list *posix_lock_list(TALLOC_CTX *ctx, struct lock_list *lhead, files_struct *fsp)
{
      TDB_KEY kbuf;
      TDB_DATA dbuf;
      struct posix_lock *locks;
      size_t num_locks, i;

      kbuf = locking_key_fsp(fsp);
      dbuf.dptr = NULL;

      dbuf = tdb_fetch(posix_lock_tdb, kbuf);

      if (!dbuf.dptr)
            return lhead;
      
      locks = (struct posix_lock *)dbuf.dptr;
      num_locks = (size_t)(dbuf.dsize / sizeof(*locks));

      /*
       * Check the current lock list on this dev/inode pair.
       * Quit if the list is deleted.
       */

      DEBUG(10,("posix_lock_list: curr: start=%.0f,size=%.0f\n",
            (double)lhead->start, (double)lhead->size ));

      for (i=0; i<num_locks && lhead; i++) {

            struct posix_lock *lock = &locks[i];
            struct lock_list *l_curr;

            /*
             * Walk the lock list, checking for overlaps. Note that
             * the lock list can expand within this loop if the current
             * range being examined needs to be split.
             */

            for (l_curr = lhead; l_curr;) {

                  DEBUG(10,("posix_lock_list: lock: fd=%d: start=%.0f,size=%.0f:type=%s", lock->fd,
                        (double)lock->start, (double)lock->size, posix_lock_type_name(lock->lock_type) ));

                  if ( (l_curr->start >= (lock->start + lock->size)) ||
                         (lock->start >= (l_curr->start + l_curr->size))) {

                        /* No overlap with this lock - leave this range alone. */
/*********************************************
                                             +---------+
                                             | l_curr  |
                                             +---------+
                                +-------+
                                | lock  |
                                +-------+
OR....
             +---------+
             |  l_curr |
             +---------+
**********************************************/

                        DEBUG(10,("no overlap case.\n" ));

                        l_curr = l_curr->next;

                  } else if ( (l_curr->start >= lock->start) &&
                                    (l_curr->start + l_curr->size <= lock->start + lock->size) ) {

                        /*
                         * This unlock is completely overlapped by this existing lock range
                         * and thus should have no effect (not be unlocked). Delete it from the list.
                         */
/*********************************************
                +---------+
                |  l_curr |
                +---------+
        +---------------------------+
        |       lock                |
        +---------------------------+
**********************************************/
                        /* Save the next pointer */
                        struct lock_list *ul_next = l_curr->next;

                        DEBUG(10,("delete case.\n" ));

                        DLIST_REMOVE(lhead, l_curr);
                        if(lhead == NULL)
                              break; /* No more list... */

                        l_curr = ul_next;
                        
                  } else if ( (l_curr->start >= lock->start) &&
                                    (l_curr->start < lock->start + lock->size) &&
                                    (l_curr->start + l_curr->size > lock->start + lock->size) ) {

                        /*
                         * This unlock overlaps the existing lock range at the high end.
                         * Truncate by moving start to existing range end and reducing size.
                         */
/*********************************************
                +---------------+
                |  l_curr       |
                +---------------+
        +---------------+
        |    lock       |
        +---------------+
BECOMES....
                        +-------+
                        | l_curr|
                        +-------+
**********************************************/

                        l_curr->size = (l_curr->start + l_curr->size) - (lock->start + lock->size);
                        l_curr->start = lock->start + lock->size;

                        DEBUG(10,("truncate high case: start=%.0f,size=%.0f\n",
                                                (double)l_curr->start, (double)l_curr->size ));

                        l_curr = l_curr->next;

                  } else if ( (l_curr->start < lock->start) &&
                                    (l_curr->start + l_curr->size > lock->start) &&
                                    (l_curr->start + l_curr->size <= lock->start + lock->size) ) {

                        /*
                         * This unlock overlaps the existing lock range at the low end.
                         * Truncate by reducing size.
                         */
/*********************************************
   +---------------+
   |  l_curr       |
   +---------------+
           +---------------+
           |    lock       |
           +---------------+
BECOMES....
   +-------+
   | l_curr|
   +-------+
**********************************************/

                        l_curr->size = lock->start - l_curr->start;

                        DEBUG(10,("truncate low case: start=%.0f,size=%.0f\n",
                                                (double)l_curr->start, (double)l_curr->size ));

                        l_curr = l_curr->next;
            
                  } else if ( (l_curr->start < lock->start) &&
                                    (l_curr->start + l_curr->size > lock->start + lock->size) ) {
                        /*
                         * Worst case scenario. Unlock request completely overlaps an existing
                         * lock range. Split the request into two, push the new (upper) request
                         * into the dlink list, and continue with the entry after ul_new (as we
                         * know that ul_new will not overlap with this lock).
                         */
/*********************************************
        +---------------------------+
        |        l_curr             |
        +---------------------------+
                +---------+
                | lock    |
                +---------+
BECOMES.....
        +-------+         +---------+
        | l_curr|         | l_new   |
        +-------+         +---------+
**********************************************/
                        struct lock_list *l_new = (struct lock_list *)talloc(ctx,
                                                                              sizeof(struct lock_list));

                        if(l_new == NULL) {
                              DEBUG(0,("posix_lock_list: talloc fail.\n"));
                              return NULL; /* The talloc_destroy takes care of cleanup. */
                        }

                        ZERO_STRUCTP(l_new);
                        l_new->start = lock->start + lock->size;
                        l_new->size = l_curr->start + l_curr->size - l_new->start;

                        /* Truncate the l_curr. */
                        l_curr->size = lock->start - l_curr->start;

                        DEBUG(10,("split case: curr: start=%.0f,size=%.0f \
new: start=%.0f,size=%.0f\n", (double)l_curr->start, (double)l_curr->size,
                                                (double)l_new->start, (double)l_new->size ));

                        /*
                         * Add into the dlink list after the l_curr point - NOT at lhead. 
                         * Note we can't use DLINK_ADD here as this inserts at the head of the given list.
                         */

                        l_new->prev = l_curr;
                        l_new->next = l_curr->next;
                        l_curr->next = l_new;

                        /* And move after the link we added. */
                        l_curr = l_new->next;

                  } else {

                        /*
                         * This logic case should never happen. Ensure this is the
                         * case by forcing an abort.... Remove in production.
                         */
                        pstring msg;

                        slprintf(msg, sizeof(msg)-1, "logic flaw in cases: l_curr: start = %.0f, size = %.0f : \
lock: start = %.0f, size = %.0f\n", (double)l_curr->start, (double)l_curr->size, (double)lock->start, (double)lock->size );

                        smb_panic(msg);
                  }
            } /* end for ( l_curr = lhead; l_curr;) */
      } /* end for (i=0; i<num_locks && ul_head; i++) */

      SAFE_FREE(dbuf.dptr);
      
      return lhead;
}

/****************************************************************************
 POSIX function to acquire a lock. Returns True if the
 lock could be granted, False if not.
****************************************************************************/

BOOL set_posix_lock(files_struct *fsp, SMB_BIG_UINT u_offset, SMB_BIG_UINT u_count, enum brl_type lock_type)
{
      SMB_OFF_T offset;
      SMB_OFF_T count;
      BOOL ret = True;
      size_t entry_num = 0;
      size_t lock_count;
      TALLOC_CTX *l_ctx = NULL;
      struct lock_list *llist = NULL;
      struct lock_list *ll = NULL;
      int posix_lock_type = map_posix_lock_type(fsp,lock_type);

      DEBUG(5,("set_posix_lock: File %s, offset = %.0f, count = %.0f, type = %s\n",
                  fsp->fsp_name, (double)u_offset, (double)u_count, posix_lock_type_name(lock_type) ));

      /*
       * If the requested lock won't fit in the POSIX range, we will
       * pretend it was successful.
       */

      if(!posix_lock_in_range(&offset, &count, u_offset, u_count))
            return True;

      /*
       * Windows is very strange. It allows read locks to be overlayed
       * (even over a write lock), but leaves the write lock in force until the first
       * unlock. It also reference counts the locks. This means the following sequence :
       *
       * process1                                      process2
       * ------------------------------------------------------------------------
       * WRITE LOCK : start = 2, len = 10
       *                                            READ LOCK: start =0, len = 10 - FAIL
       * READ LOCK : start = 0, len = 14 
       *                                            READ LOCK: start =0, len = 10 - FAIL
       * UNLOCK : start = 2, len = 10
       *                                            READ LOCK: start =0, len = 10 - OK
       *
       * Under POSIX, the same sequence in steps 1 and 2 would not be reference counted, but
       * would leave a single read lock over the 0-14 region. In order to
       * re-create Windows semantics mapped to POSIX locks, we create multiple TDB
       * entries, one for each overlayed lock request. We are guarenteed by the brlock
       * semantics that if a write lock is added, then it will be first in the array.
       */
      
      if ((l_ctx = talloc_init()) == NULL) {
            DEBUG(0,("set_posix_lock: unable to init talloc context.\n"));
            return True; /* Not a fatal error. */
      }

      if ((ll = (struct lock_list *)talloc(l_ctx, sizeof(struct lock_list))) == NULL) {
            DEBUG(0,("set_posix_lock: unable to talloc unlock list.\n"));
            talloc_destroy(l_ctx);
            return True; /* Not a fatal error. */
      }

      /*
       * Create the initial list entry containing the
       * lock we want to add.
       */

      ZERO_STRUCTP(ll);
      ll->start = offset;
      ll->size = count;

      DLIST_ADD(llist, ll);

      /*
       * The following call calculates if there are any
       * overlapping locks held by this process on
       * fd's open on the same file and splits this list
       * into a list of lock ranges that do not overlap with existing
       * POSIX locks.
       */

      llist = posix_lock_list(l_ctx, llist, fsp);

      /*
       * Now we have the list of ranges to lock it is safe to add the
       * entry into the POSIX lock tdb. We take note of the entry we
       * added here in case we have to remove it on POSIX lock fail.
       */

      if (!add_posix_lock_entry(fsp,offset,count,posix_lock_type,&entry_num)) {
            DEBUG(0,("set_posix_lock: Unable to create posix lock entry !\n"));
            talloc_destroy(l_ctx);
            return False;
      }

      /*
       * Add the POSIX locks on the list of ranges returned.
       * As the lock is supposed to be added atomically, we need to
       * back out all the locks if any one of these calls fail.
       */

      for (lock_count = 0, ll = llist; ll; ll = ll->next, lock_count++) {
            offset = ll->start;
            count = ll->size;

            DEBUG(5,("set_posix_lock: Real lock: Type = %s: offset = %.0f, count = %.0f\n",
                  posix_lock_type_name(posix_lock_type), (double)offset, (double)count ));

            if (!posix_fcntl_lock(fsp,SMB_F_SETLK,offset,count,posix_lock_type)) {
                  DEBUG(5,("set_posix_lock: Lock fail !: Type = %s: offset = %.0f, count = %.0f. Errno = %s\n",
                        posix_lock_type_name(posix_lock_type), (double)offset, (double)count, strerror(errno) ));
                  ret = False;
                  break;
            }
      }

      if (!ret) {

            /*
             * Back out all the POSIX locks we have on fail.
             */

            for (ll = llist; lock_count; ll = ll->next, lock_count--) {
                  offset = ll->start;
                  count = ll->size;

                  DEBUG(5,("set_posix_lock: Backing out locks: Type = %s: offset = %.0f, count = %.0f\n",
                        posix_lock_type_name(posix_lock_type), (double)offset, (double)count ));

                  posix_fcntl_lock(fsp,SMB_F_SETLK,offset,count,F_UNLCK);
            }

            /*
             * Remove the tdb entry for this lock.
             */

            delete_posix_lock_entry_by_index(fsp,entry_num);
      }

      talloc_destroy(l_ctx);
      return ret;
}

/****************************************************************************
 POSIX function to release a lock. Returns True if the
 lock could be released, False if not.
****************************************************************************/

BOOL release_posix_lock(files_struct *fsp, SMB_BIG_UINT u_offset, SMB_BIG_UINT u_count)
{
      SMB_OFF_T offset;
      SMB_OFF_T count;
      BOOL ret = True;
      TALLOC_CTX *ul_ctx = NULL;
      struct lock_list *ulist = NULL;
      struct lock_list *ul = NULL;
      struct posix_lock deleted_lock;
      int num_overlapped_entries;

      DEBUG(5,("release_posix_lock: File %s, offset = %.0f, count = %.0f\n",
            fsp->fsp_name, (double)u_offset, (double)u_count ));

      /*
       * If the requested lock won't fit in the POSIX range, we will
       * pretend it was successful.
       */

      if(!posix_lock_in_range(&offset, &count, u_offset, u_count))
            return True;

      /*
       * We treat this as one unlock request for POSIX accounting purposes even
       * if it may later be split into multiple smaller POSIX unlock ranges.
       * num_overlapped_entries is the number of existing locks that have any
       * overlap with this unlock request.
       */ 

      num_overlapped_entries = delete_posix_lock_entry(fsp, offset, count, &deleted_lock);

      if (num_overlapped_entries == -1) {
        smb_panic("release_posix_lock: unable find entry to delete !\n");
      }

      /*
       * If num_overlapped_entries is > 0, and the lock_type we just deleted from the tdb was
       * a POSIX write lock, then before doing the unlock we need to downgrade
       * the POSIX lock to a read lock. This allows any overlapping read locks
       * to be atomically maintained.
       */

      if (num_overlapped_entries > 0 && deleted_lock.lock_type == F_WRLCK) {
            if (!posix_fcntl_lock(fsp,SMB_F_SETLK,offset,count,F_RDLCK)) {
                  DEBUG(0,("release_posix_lock: downgrade of lock failed with error %s !\n", strerror(errno) ));
                  return False;
            }
      }

      if ((ul_ctx = talloc_init()) == NULL) {
            DEBUG(0,("release_posix_lock: unable to init talloc context.\n"));
            return True; /* Not a fatal error. */
      }

      if ((ul = (struct lock_list *)talloc(ul_ctx, sizeof(struct lock_list))) == NULL) {
            DEBUG(0,("release_posix_lock: unable to talloc unlock list.\n"));
            talloc_destroy(ul_ctx);
            return True; /* Not a fatal error. */
      }

      /*
       * Create the initial list entry containing the
       * lock we want to remove.
       */

      ZERO_STRUCTP(ul);
      ul->start = offset;
      ul->size = count;

      DLIST_ADD(ulist, ul);

      /*
       * The following call calculates if there are any
       * overlapping locks held by this process on
       * fd's open on the same file and creates a
       * list of unlock ranges that will allow
       * POSIX lock ranges to remain on the file whilst the
       * unlocks are performed.
       */

      ulist = posix_lock_list(ul_ctx, ulist, fsp);

      /*
       * Release the POSIX locks on the list of ranges returned.
       */

      for(; ulist; ulist = ulist->next) {
            offset = ulist->start;
            count = ulist->size;

            DEBUG(5,("release_posix_lock: Real unlock: offset = %.0f, count = %.0f\n",
                  (double)offset, (double)count ));

            if (!posix_fcntl_lock(fsp,SMB_F_SETLK,offset,count,F_UNLCK))
                  ret = False;
      }

      talloc_destroy(ul_ctx);

      return ret;
}

/****************************************************************************
 Remove all lock entries for a specific dev/inode pair from the tdb.
****************************************************************************/

static void delete_posix_lock_entries(files_struct *fsp)
{
      TDB_KEY kbuf;

      kbuf = locking_key_fsp(fsp);
      if (tdb_delete(posix_lock_tdb, kbuf) == -1)
            DEBUG(0,("delete_close_entries: tdb_delete fail !\n"));
}

/****************************************************************************
 Debug function.
****************************************************************************/

static void dump_entry(struct posix_lock *pl)
{
      DEBUG(10,("entry: start=%.0f, size=%.0f, type=%d, fd=%i\n",
            (double)pl->start, (double)pl->size, (int)pl->lock_type, pl->fd ));
}

/****************************************************************************
 Remove any locks on this fd. Called from file_close().
****************************************************************************/

void posix_locking_close_file(files_struct *fsp)
{
      struct posix_lock *entries = NULL;
      size_t count, i;

      /*
       * Optimization for the common case where we are the only
       * opener of a file. If all fd entries are our own, we don't
       * need to explicitly release all the locks via the POSIX functions,
       * we can just remove all the entries in the tdb and allow the
       * close to remove the real locks.
       */

      count = get_posix_lock_entries(fsp, &entries);

      if (count == 0) {
            DEBUG(10,("posix_locking_close_file: file %s has no outstanding locks.\n", fsp->fsp_name ));
            return;
      }

      for (i = 0; i < count; i++) {
            if (entries[i].fd != fsp->fd )
                  break;

            dump_entry(&entries[i]);
      }

      if (i == count) {
            /* All locks are ours. */
            DEBUG(10,("posix_locking_close_file: file %s has %u outstanding locks, but all on one fd.\n", 
                  fsp->fsp_name, (unsigned int)count ));
            SAFE_FREE(entries);
            delete_posix_lock_entries(fsp);
            return;
      }

      /*
       * Difficult case. We need to delete all our locks, whilst leaving
       * all other POSIX locks in place.
       */

      for (i = 0; i < count; i++) {
            struct posix_lock *pl = &entries[i];
            if (pl->fd == fsp->fd)
                  release_posix_lock(fsp, (SMB_BIG_UINT)pl->start, (SMB_BIG_UINT)pl->size );
      }
      SAFE_FREE(entries);
}

/*******************************************************************
 Create the in-memory POSIX lock databases.
********************************************************************/

BOOL posix_locking_init(int read_only)
{
      if (posix_lock_tdb && posix_pending_close_tdb)
            return True;
      
      if (!posix_lock_tdb)
            posix_lock_tdb = tdb_open_log(NULL, 0, TDB_INTERNAL,
                                read_only?O_RDONLY:(O_RDWR|O_CREAT), 0644);
      if (!posix_lock_tdb) {
            DEBUG(0,("Failed to open POSIX byte range locking database.\n"));
            return False;
      }
      if (!posix_pending_close_tdb)
            posix_pending_close_tdb = tdb_open_log(NULL, 0, TDB_INTERNAL,
                                       read_only?O_RDONLY:(O_RDWR|O_CREAT), 0644);
      if (!posix_pending_close_tdb) {
            DEBUG(0,("Failed to open POSIX pending close database.\n"));
            return False;
      }

      return True;
}

/*******************************************************************
 Delete the in-memory POSIX lock databases.
********************************************************************/

BOOL posix_locking_end(void)
{
    if (posix_lock_tdb && tdb_close(posix_lock_tdb) != 0)
            return False;
    if (posix_pending_close_tdb && tdb_close(posix_pending_close_tdb) != 0)
            return False;
      return True;
}

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