Re: Uninline kcalloc

[Xi Wang <xi.wang@gmail.com>]

On Feb 14, 2012, at 5:08 PM, Christoph Lameter wrote:
> kcalloc is still there. Certainly useful for legacy purposes. But I'd feel
> better if I had fine grained control over the size of my allocation rather
> than rely on the slab allocators to check up on my multiplication.
> 
> With these patches both is possible. And if you want the check of an
> allocation that is not zeroed then you can do so because you have a
> function that will perform the size check for you without calling into the
> slab allocator.

In the code you proposed, where calculate_array_size() returns 0
for overflow, one has to write:

        size_t s = calculate_array_size(n, size);
        if (s)
                p = kmalloc(s, ...);

This "if" thing is just too verbose --- you need three lines to
allocate an array.

We could change calculate_array_size() to return ULONG_MAX or some
large number with which kmalloc() would fail.  Then one would write:

        p = kmalloc(calculate_array_size(n, size), ...);

This looks better to me.  The advantage is that we don't need another
allocator (and avoid this name picking game).  The disadvantage is
that the semantics of calculate_array_size(), returning ULONG_MAX
on overflow, sounds sort of strange.

- xi