The ff_mutex_take function is for mutal exclusion control of file system object. It is called on the control enters file API to lock the volume.
int ff_mutex_take ( int vol /* [IN] Volume ID */ );
A non-zero value is returned if the mutex has successfully been taken. If the mutex could not be taken within a time defined by FF_TIMEOUT, a zero is returned and the file function will abort with FR_TIMEOUT.
This function is required when FF_FS_REENTRANT = 1.