linux-kernel - Re: [PATCH] mm/vmalloc: don't use vmalloc

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Message-ID: <4B1D9EF2.4010406@kernel.org>
Date:	Tue, 08 Dec 2009 09:33:54 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Jan Beulich <JBeulich@...ell.com>, linux-kernel@...r.kernel.org,
	tony.luck@...el.com, linux-mm@...ck.org,
	linux-ia64@...r.kernel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] mm/vmalloc: don't use vmalloc_end

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@...ell.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@...nel.org>
    Acked-by: Tony Luck <tony.luck@...el.com>
    Cc: Fenghua Yu <fenghua.yu@...el.com>
    Cc: linux-ia64 <linux-ia64@...r.kernel.org>
    Cc: Christoph Lameter <cl@...ux-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
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