+Called to synchronize any changes to a directory's contents. If flag is
+non-zero, only synchronize user data, otherwise synchronize user data and
+metadata.
+
+=head3 init
+
+Arguments: None.
+
+Returns (optionally) an SV to be passed as private_data via fuse_get_context().
+
+=head3 destroy
+
+Arguments: (optional) private data SV returned from init(), if any.
+
+Returns nothing.
+
+=head3 access
+
+Arguments: Pathname, access mode flags
+
+Returns an errno or 0 on success.
+
+Determine if the user attempting to access the indicated file has access to
+perform the requested actions. The user ID can be determined by calling
+fuse_get_context(). See access(2) for more information.
+
+=head3 create
+
+Arguments: Pathname, create mask, open mode flags
+
+Returns errno or 0 on success, and (optional) file handle.
+
+Create a file with the path indicated, then open a handle for reading and/or
+writing with the supplied mode flags. Can also return a file handle like
+open() as part of the call.
+
+=head3 ftruncate
+
+Arguments: Pathname, numeric offset, (optional) file handle
+
+Returns errno or 0 on success
+
+Like truncate(), but on an opened file.
+
+=head3 fgetattr
+
+Arguments: Pathname, (optional) file handle
+
+Returns a list, very similar to the 'stat' function (see
+perlfunc). On error, simply return a single numeric scalar
+value (e.g. "return -ENOENT();").
+
+Like getattr(), but on an opened file.
+
+=head3 lock
+
+Arguments: Pathname, numeric command code, hashref containing lock parameters, (optional) file handle
+
+Returns errno or 0 on success
+
+Used to lock or unlock regions of a file. Locking is handled locally, but this
+allows (especially for networked file systems) for protocol-level locking
+semantics to also be employed, if any are available.
+
+See the Fuse documentation for more explanation of lock(). The needed symbols
+for the lock constants can be obtained by importing Fcntl.
+
+=head3 utimens
+
+Arguments: Pathname, last accessed time, last modified time
+
+Returns errno or 0 on success
+
+Like utime(), but allows time resolution down to the nanosecond. By default,
+times are passed as "numeric" (internally these are typically represented
+as "double"), so the sub-second portion is represented as fractions of a
+second. If you want times passed as arrays instead of floating point
+values, for higher precision, you should pass the C<utimens_as_array> option
+to C<Fuse::main>.
+
+Note that if this call is implemented, it overrides utime() ALWAYS.
+
+=head3 bmap
+
+Arguments: Pathname, numeric blocksize, numeric block number
+
+Returns errno or 0 on success, and physical block number if successful
+
+Used to map a block number offset in a file to the physical block offset
+on the block device backing the file system. This is intended for
+filesystems that are stored on an actual block device, with the 'blkdev'
+option passed.
+
+=head3 ioctl
+
+Arguments: Pathname, ioctl command code, flags, data if ioctl op is a write, (optional) file handle
+
+Returns errno or 0 on success, and data if ioctl op is a read
+
+Used to handle ioctl() operations on files. See ioctl(2) for more
+information on the fine details of ioctl operation numbers. May need to
+h2ph system headers to get the necessary macros; keep in mind the macros
+are highly OS-dependent.
+
+Keep in mind that read and write are from the client perspective, so
+read from our end means data is going *out*, and write means data is
+coming *in*. It can be slightly confusing.
+
+=head3 poll
+
+Arguments: Pathname, poll handle ID (or undef if none), event mask, (optional) file handle
+
+Returns errno or 0 on success, and updated event mask on success
+
+Used to handle poll() operations on files. See poll(2) to learn more about
+event polling. Use IO::Poll to get the POLLIN, POLLOUT, and other symbols
+to describe the events which can happen on the filehandle. Save the poll
+handle ID to be passed to C<notify_poll> and C<pollhandle_destroy>
+functions, if it is not undef. Threading will likely be necessary for this
+operation to work.
+
+There is not an "out of band" data transfer channel provided as part of
+FUSE, so POLLPRI/POLLRDBAND/POLLWRBAND won't work.
+
+Poll handle is currently a read-only scalar; we are investigating a way
+to make this an object instead.
+