posix.c

samba-3.0.22.tar.gz 编译smb服务器的源码

		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(struct posix_lock));

	/*
	 * 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->fh->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(struct posix_lock)*((count-1) - i));
				}
				dbuf.dsize -= sizeof(struct posix_lock);
				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->fh->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;
	}
#if 0
	/* We no longer open files write-only. */
	 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;
	}
#endif

	/*
	 * 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;

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

	ret = SMB_VFS_LOCK(fsp,fsp->fh->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 = SMB_VFS_LOCK(fsp,fsp->fh->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_DATA kbuf = locking_key_fsp(fsp);
	TDB_DATA dbuf;
	struct posix_lock *locks;
	size_t num_locks, i;

	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(struct posix_lock));

	/*
	 * 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;