linux-kernel - Re: [PATCH 1/2] Add vzalloc shortcut

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Date:	Tue, 19 Oct 2010 09:27:47 +0800
From:	Dave Young <hidave.darkstar@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH 1/2] Add vzalloc shortcut

On Tue, Oct 19, 2010 at 7:46 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Sat, 16 Oct 2010 12:33:31 +0800
> Dave Young <hidave.darkstar@...il.com> wrote:
>
>> Add vzalloc for convinience of vmalloc-then-memset-zero case
>>
>> Use __GFP_ZERO in vzalloc to zero fill the allocated memory.
>>
>> Signed-off-by: Dave Young <hidave.darkstar@...il.com>
>> ---
>>  include/linux/vmalloc.h |    1 +
>>  mm/vmalloc.c            |   13 +++++++++++++
>>  2 files changed, 14 insertions(+)
>>
>> --- linux-2.6.orig/include/linux/vmalloc.h    2010-08-22 15:31:38.000000000 +0800
>> +++ linux-2.6/include/linux/vmalloc.h 2010-10-16 10:50:54.739996121 +0800
>> @@ -53,6 +53,7 @@ static inline void vmalloc_init(void)
>>  #endif
>>
>>  extern void *vmalloc(unsigned long size);
>> +extern void *vzalloc(unsigned long size);
>>  extern void *vmalloc_user(unsigned long size);
>>  extern void *vmalloc_node(unsigned long size, int node);
>>  extern void *vmalloc_exec(unsigned long size);
>> --- linux-2.6.orig/mm/vmalloc.c       2010-08-22 15:31:39.000000000 +0800
>> +++ linux-2.6/mm/vmalloc.c    2010-10-16 10:51:57.126665918 +0800
>> @@ -1604,6 +1604,19 @@ void *vmalloc(unsigned long size)
>>  EXPORT_SYMBOL(vmalloc);
>>
>>  /**
>> + *   vzalloc  -  allocate virtually contiguous memory with zero filled
>
> s/filled/fill/

Thanks, Will fix

>
>> + *   @size:          allocation size
>> + *   Allocate enough pages to cover @size from the page level
>> + *   allocator and map them into contiguous kernel virtual space.
>> + */
>> +void *vzalloc(unsigned long size)
>> +{
>> +     return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
>> +                             PAGE_KERNEL, -1, __builtin_return_address(0));
>> +}
>> +EXPORT_SYMBOL(vzalloc);
>
> We'd need to add the same interface to nommu, please.

Ok, will do

Minchan kim, thanks as well. I missed your comments about nommu before.

>
> Also, a slightly better implementation would be
>
> static inline void *__vmalloc_node_flags(unsigned long size, gfp_t flags)
> {
>        return __vmalloc_node(size, 1, flags, PAGE_KERNEL, -1,
>                                __builtin_return_address(0));
> }
>
> void *vzalloc(unsigned long size)
> {
>        return __vmalloc_node_flags(size,
>                                GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
> }
>
> void *vmalloc(unsigned long size)
> {
>        return __vmalloc_node_flags(size, GFP_KERNEL | __GFP_HIGHMEM);
> }
>
> just to avoid code duplication (and possible later errors derived from it).
>
> Perhaps it should be always_inline, so the __builtin_return_address()
> can't get broken.
>
> Or just leave it the way you had it :)

Andrew, your suggestion is cleaner and better. I will do as yours.

-- 
Regards
dave
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