Set file attributes
In the 'attr' argument only members indicated by the 'to_set' bitmask contain valid values. Other members contain undefined values.
If the setattr was invoked from the ftruncate() system call under Linux kernel versions 2.6.15 or later, the fi->fh will contain the value set by the open method or will be undefined if the open method didn't set any value. Otherwise (not ftruncate call, or kernel version earlier than 2.6.15) the fi parameter will be NULL.
Valid replies: fuse_reply_attr() fuse_reply_err()