void *ctl_ms_borrow_sector_cache_memory(int n);
ctl_ms_borrow_sector_cache_memory borrows n contiguous sector cache entries and prevents ctl_ms_read_lock_sector and ctl_ms_write_lock_sector from using those buffers. ctl_ms_borrow_sector_cache_memory returns zero if n contiguous entries cannot be found.
You can borrow as much as you like from the sector cache but in doing so you may starve the file system of buffers that it requires to manage files and folders on the mounted volume. If the file system is starved, it will fail gracefully without damaging the volume.