On Tue, 15 May 2007 16:45:22 -0700 (PDT)
Christoph Lameter <clameter@xxxxxxx> wrote:
> On Tue, 15 May 2007, Andrew Morton wrote:
>
> > On Mon, 14 May 2007 16:46:17 -0700 (PDT)
> > Christoph Lameter <clameter@xxxxxxx> wrote:
> >
> > > @@ -86,6 +87,9 @@ static inline int kmalloc_index(int size
> > > */
> > > WARN_ON_ONCE(size == 0);
> > >
> > > + if (size >= (1UL << KMALLOC_SHIFT_HIGH))
> > > + return -1;
> > > +
> >
> > I don't quite understand why we did this. The subsequent logic in
> > kmalloc_index() should return -1 for this `size' anyway. If it doesn't,
> > it's bust, isn't it?
>
> KMALLOC_SHIFT_HIGH is not a constant but may be less than 25.
It darn well better be a compile-time constant.
And look:
static inline int kmalloc_index(int size)
{
/*
* We should return 0 if size == 0 but we use the smallest object
* here for SLAB legacy reasons.
*/
WARN_ON_ONCE(size == 0);
if (size > (1 << KMALLOC_SHIFT_HIGH))
return -1;
if (size > 64 && size <= 96)
return 1;
if (size > 128 && size <= 192)
return 2;
if (size <= 8) return 3;
if (size <= 16) return 4;
if (size <= 32) return 5;
if (size <= 64) return 6;
if (size <= 128) return 7;
if (size <= 256) return 8;
if (size <= 512) return 9;
if (size <= 1024) return 10;
if (size <= 2 * 1024) return 11;
if (size <= 4 * 1024) return 12;
if (size <= 8 * 1024) return 13;
if (size <= 16 * 1024) return 14;
if (size <= 32 * 1024) return 15;
if (size <= 64 * 1024) return 16;
if (size <= 128 * 1024) return 17;
if (size <= 256 * 1024) return 18;
#if KMALLOC_SHIFT_HIGH > 18
if (size <= 512 * 1024) return 19;
if (size <= 1024 * 1024) return 20;
#endif
#if KMALLOC_SHIFT_HIGH > 20
if (size <= 2 * 1024 * 1024) return 21;
if (size <= 4 * 1024 * 1024) return 22;
if (size <= 8 * 1024 * 1024) return 23;
if (size <= 16 * 1024 * 1024) return 24;
if (size <= 32 * 1024 * 1024) return 25;
#endif
return -1;
/*
* What we really wanted to do and cannot do because of compiler issues is:
* int i;
* for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++)
* if (size <= (1 << i))
* return i;
*/
}
Either that newly-added test isn't needed, or those ifdefs aren't needed?
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