Re: [PATCH] mm/vmalloc: don't use vmalloc_end

Tejun Heo
2009-12-08T00:33:54Z

On 12/08/2009 08:35 AM, Andrew Morton wrote:
> (cc linux-ia64)
>
> On Mon, 07 Dec 2009 16:24:03 +0000
> "Jan Beulich" <JBeulich@novell.com> wrote:
>
>> At least on ia64 vmalloc_end is a global variable that VMALLOC_END
>> expands to. Hence having a local variable named vmalloc_end and
>> initialized from VMALLOC_END won't work on such platforms. Rename
>> these variables, and for consistency also rename vmalloc_start.
>>
>
> erk. So does 2.6.32's vmalloc() actually work correctly on ia64?
>
> Perhaps vmalloc_end wasn't a well chosen name for an arch-specific
> global variable.
>
> arch/m68k/include/asm/pgtable_mm.h does the same thing. Did it break too?

Hmmm... ISTR writing a patch updating ia64 so that it doesn't use that
macro. Looking it up.... Yeap, 126b3fcdecd350cad9700908d0ad845084e26a31
in percpu#for-next.

ia64: don't alias VMALLOC_END to vmalloc_end

If CONFIG_VIRTUAL_MEM_MAP is enabled, ia64 defines macro VMALLOC_END
as unsigned long variable vmalloc_end which is adjusted to prepare
room for vmemmap. This becomes probnlematic if a local variables
vmalloc_end is defined in some function (not very unlikely) and
VMALLOC_END is used in the function - the function thinks its
referencing the global VMALLOC_END value but would be referencing its
own local vmalloc_end variable.

There's no reason VMALLOC_END should be a macro. Just define it as an
unsigned long variable if CONFIG_VIRTUAL_MEM_MAP is set to avoid nasty
surprises.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64 <linux-ia64@vger.kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>

2.6.32 doesn't use new allocator on ia64 yet and the above commit will
be sent to Linus soon which will also enable new allocator.

Thanks.

--
tejun