On 07/20/2015 04:28 PM, Andrew Morton wrote:
On Mon, 20 Jul 2015 19:57:18 +0200 Rasmus Villemoes <[email protected]>
wrote:
On Mon, Jul 20 2015, Guenter Roeck <[email protected]> wrote:
So either case ~0l appears to be wrong; it should be ~0ul.
Yes, right-shifting -1 of any type is probably always wrong, as it will
always give -1 again.
Not for unsigned types.
The kernel uses "-1UL" and "-1ULL" quite a lot - it's a convenient way
of saying "all ones, regardless of size". Also, assigning plain old
"-1" to an unsigned variable will make that variable all-ones
regardless of size.
In this case I expect we could do
align_mask = -1UL >> (64 - align_order);
-1ul works, at least on x86 (32 and 64 bit).
but I don't know about that 64. Maybe it should be BITS_PER_LONG?
I think that is going to be in the next version of the patch.
Guenter
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