RE: Redundant memset in AIO read_events

[Luck, Tony]

> > OK, here is another one.  In the top level read_events() function in
> > fs/aio.c, a struct io_event is instantiated on the stack 
> (variable ent).
> > It calls aio_read_evt() function which will fill the entire io_event
> > structure into variable ent.  What's the point of zeroing when copy
> > covers the same memory area?  Possible a debug code left around?
> 
> Read the comment before that memset. The structure might contain some
> padding (bytes not belonging to any of its entries), these bytes are
> random and if you do not zero them, you copy random data into 
> userspace.

That is true, but here's the definition of the io_event strcuture:

struct io_event {
        __u64           data;
        __u64           obj;
        __s64           res;
        __s64           res2;
};

In the words of the comment, C may be "fun", but I've
having trouble envisioning an architecture where a structure
that consists of four equal sized objects has some padding!

Don't we usually call code that defends against impossible
problems "bloat"?

-Tony