brlock_tdb.c

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	} else {
		dbuf.dptr = (uint8_t *)locks;
	}
	locks[count] = lock;
	dbuf.dsize += sizeof(lock);

	status = rec->store(rec, dbuf, TDB_REPLACE);
	if (!NT_STATUS_IS_OK(status)) {
		goto fail;
	}

	talloc_free(rec);

	/* the caller needs to know if the real lock was granted. If
	   we have reached here then it must be a pending lock that
	   was granted, so tell them the lock failed */
	if (lock_type >= PENDING_READ_LOCK) {
		return NT_STATUS_LOCK_NOT_GRANTED;
	}

	return NT_STATUS_OK;

 fail:
	talloc_free(rec);
	return status;
}


/*
  we are removing a lock that might be holding up a pending lock. Scan for pending
  locks that cover this range and if we find any then notify the server that it should
  retry the lock
*/
static void brl_tdb_notify_unlock(struct brl_context *brl,
			      struct lock_struct *locks, int count, 
			      struct lock_struct *removed_lock)
{
	int i, last_notice;

	/* the last_notice logic is to prevent stampeding on a lock
	   range. It prevents us sending hundreds of notifies on the
	   same range of bytes. It doesn't prevent all possible
	   stampedes, but it does prevent the most common problem */
	last_notice = -1;

	for (i=0;i<count;i++) {
		if (locks[i].lock_type >= PENDING_READ_LOCK &&
		    brl_tdb_overlap(&locks[i], removed_lock)) {
			if (last_notice != -1 && brl_tdb_overlap(&locks[i], &locks[last_notice])) {
				continue;
			}
			if (locks[i].lock_type == PENDING_WRITE_LOCK) {
				last_notice = i;
			}
			messaging_send_ptr(brl->messaging_ctx, locks[i].context.server, 
					   MSG_BRL_RETRY, locks[i].notify_ptr);
		}
	}
}


/*
  send notifications for all pending locks - the file is being closed by this
  user
*/
static void brl_tdb_notify_all(struct brl_context *brl,
			   struct lock_struct *locks, int count)
{
	int i;
	for (i=0;i<count;i++) {
		if (locks->lock_type >= PENDING_READ_LOCK) {
			brl_tdb_notify_unlock(brl, locks, count, &locks[i]);
		}
	}
}



/*
 Unlock a range of bytes.
*/
static NTSTATUS brl_tdb_unlock(struct brl_context *brl,
			   struct brl_handle *brlh, 
			   uint16_t smbpid,
			   uint64_t start, uint64_t size)
{
	TDB_DATA kbuf, dbuf;
	int count, i;
	struct lock_struct *locks, *lock;
	struct lock_context context;
	NTSTATUS status;
	struct db_record *rec = NULL;

	kbuf.dptr = brlh->key.data;
	kbuf.dsize = brlh->key.length;

	rec = brl->db->fetch_locked(brl->db, brl, kbuf);
	if (rec == NULL) {
		return NT_STATUS_INTERNAL_DB_CORRUPTION;
	}

	if (!rec->value.dptr) {
		talloc_free(rec);
		return NT_STATUS_RANGE_NOT_LOCKED;
	}

	dbuf = rec->value;

	context.smbpid = smbpid;
	context.server = brl->server;
	context.ctx = brl;

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

	for (i=0; i<count; i++) {
		lock = &locks[i];
		if (brl_tdb_same_context(&lock->context, &context) &&
		    lock->ntvfs == brlh->ntvfs &&
		    lock->start == start &&
		    lock->size == size &&
		    lock->lock_type == WRITE_LOCK) {
			break;
		}
	}
	if (i < count) goto found;

	for (i=0; i<count; i++) {
		lock = &locks[i];
		if (brl_tdb_same_context(&lock->context, &context) &&
		    lock->ntvfs == brlh->ntvfs &&
		    lock->start == start &&
		    lock->size == size &&
		    lock->lock_type < PENDING_READ_LOCK) {
			break;
		}
	}

found:
	if (i == count) {
		status = NT_STATUS_RANGE_NOT_LOCKED;
	} else if (count == 1) {
		status = rec->delete_rec(rec);
	} else {
		struct lock_struct removed_lock = *lock;
		if (i < count-1) {
			memmove(&locks[i], &locks[i+1], 
				sizeof(*locks)*((count-1) - i));
		}
		count--;
		
		/* send notifications for any relevant pending locks */
		brl_tdb_notify_unlock(brl, locks, count, &removed_lock);
		
		dbuf.dsize = count * sizeof(*locks);
		
		status = rec->store(rec, dbuf, TDB_REPLACE);
	}

 	talloc_free(rec);
	return status;
}


/*
  remove a pending lock. This is called when the caller has either
  given up trying to establish a lock or when they have succeeded in
  getting it. In either case they no longer need to be notified.
*/
static NTSTATUS brl_tdb_remove_pending(struct brl_context *brl,
				   struct brl_handle *brlh, 
				   void *notify_ptr)
{
	TDB_DATA kbuf, dbuf;
	int count, i;
	struct lock_struct *locks;
	NTSTATUS status;
	struct db_record *rec = NULL;

	kbuf.dptr = brlh->key.data;
	kbuf.dsize = brlh->key.length;

	rec = brl->db->fetch_locked(brl->db, brl, kbuf);
	if (rec == NULL) {
		return NT_STATUS_INTERNAL_DB_CORRUPTION;
	}

	dbuf = rec->value;

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

	status = NT_STATUS_RANGE_NOT_LOCKED;

	for (i=0; i<count; i++) {
		struct lock_struct *lock = &locks[i];
		
		if (lock->lock_type >= PENDING_READ_LOCK &&
		    lock->notify_ptr == notify_ptr &&
		    cluster_id_equal(&lock->context.server, &brl->server)) {
			/* found it - delete it */
			if (count == 1) {
				status = rec->delete_rec(rec);
			} else {
				if (i < count-1) {
					memmove(&locks[i], &locks[i+1], 
						sizeof(*locks)*((count-1) - i));
				}
				count--;
				dbuf.dsize = count * sizeof(*locks);
				status = rec->store(rec, dbuf, TDB_REPLACE);
			}			
			break;
		}
	}

	talloc_free(rec);
	return status;
}


/*
  Test if we are allowed to perform IO on a region of an open file
*/
static NTSTATUS brl_tdb_locktest(struct brl_context *brl,
			     struct brl_handle *brlh,
			     uint16_t smbpid, 
			     uint64_t start, uint64_t size, 
			     enum brl_type lock_type)
{
	TDB_DATA kbuf, dbuf;
	int count, i;
	struct lock_struct lock, *locks;
	NTSTATUS status;

	kbuf.dptr = brlh->key.data;
	kbuf.dsize = brlh->key.length;

	if (brl->db->fetch(brl->db, brl, kbuf, &dbuf) != 0) {
		return NT_STATUS_OK;
	}

	lock.context.smbpid = smbpid;
	lock.context.server = brl->server;
	lock.context.ctx = brl;
	lock.ntvfs = brlh->ntvfs;
	lock.start = start;
	lock.size = size;
	lock.lock_type = lock_type;

	/* there are existing locks - make sure they don't conflict */
	locks = (struct lock_struct *)dbuf.dptr;
	count = dbuf.dsize / sizeof(*locks);

	status = NT_STATUS_OK;

	for (i=0; i<count; i++) {
		if (brl_tdb_conflict_other(&locks[i], &lock)) {
			status = NT_STATUS_FILE_LOCK_CONFLICT;
			break;
		}
	}

	talloc_free(dbuf.dptr);
	return status;
}


/*
 Remove any locks associated with a open file.
*/
static NTSTATUS brl_tdb_close(struct brl_context *brl,
			  struct brl_handle *brlh)
{
	TDB_DATA kbuf, dbuf;
	int count, i, dcount=0;
	struct lock_struct *locks;
	NTSTATUS status;
	struct db_record *rec = NULL;

	kbuf.dptr = brlh->key.data;
	kbuf.dsize = brlh->key.length;

	rec = brl->db->fetch_locked(brl->db, brl, kbuf);
	if (rec == NULL) {
		return NT_STATUS_INTERNAL_DB_CORRUPTION;
	}

	dbuf = rec->value;
	if (!dbuf.dptr) {
		talloc_free(rec);
		return NT_STATUS_OK;
	}

	/* there are existing locks - remove any for this fnum */
	locks = (struct lock_struct *)dbuf.dptr;
	count = dbuf.dsize / sizeof(*locks);

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

		if (lock->context.ctx == brl &&
		    cluster_id_equal(&lock->context.server, &brl->server) &&
		    lock->ntvfs == brlh->ntvfs) {
			/* found it - delete it */
			if (count > 1 && i < count-1) {
				memmove(&locks[i], &locks[i+1], 
					sizeof(*locks)*((count-1) - i));
			}
			count--;
			i--;
			dcount++;
		}
	}

	status = NT_STATUS_OK;

	if (count == 0) {
		status = rec->delete_rec(rec);
	} else if (dcount != 0) {
		/* tell all pending lock holders for this file that
		   they have a chance now. This is a bit indiscriminant,
		   but works OK */
		brl_tdb_notify_all(brl, locks, count);

		dbuf.dsize = count * sizeof(*locks);

		status = rec->store(rec, dbuf, TDB_REPLACE);
	}

	talloc_free(rec);

	return status;
}


static const struct brlock_ops brlock_tdb_ops = {
	.brl_init           = brl_tdb_init,
	.brl_create_handle  = brl_tdb_create_handle,
	.brl_lock           = brl_tdb_lock,
	.brl_unlock         = brl_tdb_unlock,
	.brl_remove_pending = brl_tdb_remove_pending,
	.brl_locktest       = brl_tdb_locktest,
	.brl_close          = brl_tdb_close
};


void brl_tdb_init_ops(void)
{
	brl_set_ops(&brlock_tdb_ops);
}