* [PATCH] mm: add gfp mask checking for __get_free_pages()
@ 2009-07-04 2:09 Akinobu Mita
2009-07-18 0:41 ` Andrew Morton
0 siblings, 1 reply; 5+ messages in thread
From: Akinobu Mita @ 2009-07-04 2:09 UTC (permalink / raw)
To: linux-kernel; +Cc: akpm
__get_free_pages() with __GFP_HIGHMEM is not safe because the return
address cannot represent a highmem page. get_zeroed_page() already has
such a debug checking.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
mm/page_alloc.c | 24 +++++++++---------------
1 files changed, 9 insertions(+), 15 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e0f2cdf..4a1a374 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1903,31 +1903,25 @@ EXPORT_SYMBOL(__alloc_pages_nodemask);
*/
unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
{
- struct page * page;
+ struct page *page;
+
+ /*
+ * __get_free_pages() returns a 32-bit address, which cannot represent
+ * a highmem page
+ */
+ VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
+
page = alloc_pages(gfp_mask, order);
if (!page)
return 0;
return (unsigned long) page_address(page);
}
-
EXPORT_SYMBOL(__get_free_pages);
unsigned long get_zeroed_page(gfp_t gfp_mask)
{
- struct page * page;
-
- /*
- * get_zeroed_page() returns a 32-bit address, which cannot represent
- * a highmem page
- */
- VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
-
- page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
- if (page)
- return (unsigned long) page_address(page);
- return 0;
+ return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
}
-
EXPORT_SYMBOL(get_zeroed_page);
void __pagevec_free(struct pagevec *pvec)
--
1.6.0.6
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] mm: add gfp mask checking for __get_free_pages()
2009-07-04 2:09 [PATCH] mm: add gfp mask checking for __get_free_pages() Akinobu Mita
@ 2009-07-18 0:41 ` Andrew Morton
0 siblings, 0 replies; 5+ messages in thread
From: Andrew Morton @ 2009-07-18 0:41 UTC (permalink / raw)
To: Akinobu Mita; +Cc: linux-kernel, linux-mm
On Sat, 4 Jul 2009 11:09:50 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:
> __get_free_pages() with __GFP_HIGHMEM is not safe because the return
> address cannot represent a highmem page. get_zeroed_page() already has
> such a debug checking.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> ---
> mm/page_alloc.c | 24 +++++++++---------------
> 1 files changed, 9 insertions(+), 15 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e0f2cdf..4a1a374 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1903,31 +1903,25 @@ EXPORT_SYMBOL(__alloc_pages_nodemask);
> */
> unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
> {
> - struct page * page;
> + struct page *page;
> +
> + /*
> + * __get_free_pages() returns a 32-bit address, which cannot represent
> + * a highmem page
> + */
> + VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
> +
> page = alloc_pages(gfp_mask, order);
> if (!page)
> return 0;
> return (unsigned long) page_address(page);
> }
> -
> EXPORT_SYMBOL(__get_free_pages);
>
> unsigned long get_zeroed_page(gfp_t gfp_mask)
> {
> - struct page * page;
> -
> - /*
> - * get_zeroed_page() returns a 32-bit address, which cannot represent
> - * a highmem page
> - */
> - VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
> -
> - page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
> - if (page)
> - return (unsigned long) page_address(page);
> - return 0;
> + return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
> }
> -
> EXPORT_SYMBOL(get_zeroed_page);
>
> void __pagevec_free(struct pagevec *pvec)
Fair enough.
I suspect we could just delete that VM_BUG_ON() - we can't go and do
runtime checking for every darn programmer error, and this would be a
pretty dumb one.
Your patch turns get_zeroed_page() into a simple one-liner wrapper
around __get_free_pages(). We could perhaps save some .text, some
kernel stack and some CPU cycles by inlining get_zeroed_page().
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] mm: add gfp mask checking for __get_free_pages()
@ 2009-07-18 0:41 ` Andrew Morton
0 siblings, 0 replies; 5+ messages in thread
From: Andrew Morton @ 2009-07-18 0:41 UTC (permalink / raw)
To: Akinobu Mita; +Cc: linux-kernel, linux-mm
On Sat, 4 Jul 2009 11:09:50 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:
> __get_free_pages() with __GFP_HIGHMEM is not safe because the return
> address cannot represent a highmem page. get_zeroed_page() already has
> such a debug checking.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> ---
> mm/page_alloc.c | 24 +++++++++---------------
> 1 files changed, 9 insertions(+), 15 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e0f2cdf..4a1a374 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1903,31 +1903,25 @@ EXPORT_SYMBOL(__alloc_pages_nodemask);
> */
> unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
> {
> - struct page * page;
> + struct page *page;
> +
> + /*
> + * __get_free_pages() returns a 32-bit address, which cannot represent
> + * a highmem page
> + */
> + VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
> +
> page = alloc_pages(gfp_mask, order);
> if (!page)
> return 0;
> return (unsigned long) page_address(page);
> }
> -
> EXPORT_SYMBOL(__get_free_pages);
>
> unsigned long get_zeroed_page(gfp_t gfp_mask)
> {
> - struct page * page;
> -
> - /*
> - * get_zeroed_page() returns a 32-bit address, which cannot represent
> - * a highmem page
> - */
> - VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
> -
> - page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
> - if (page)
> - return (unsigned long) page_address(page);
> - return 0;
> + return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
> }
> -
> EXPORT_SYMBOL(get_zeroed_page);
>
> void __pagevec_free(struct pagevec *pvec)
Fair enough.
I suspect we could just delete that VM_BUG_ON() - we can't go and do
runtime checking for every darn programmer error, and this would be a
pretty dumb one.
Your patch turns get_zeroed_page() into a simple one-liner wrapper
around __get_free_pages(). We could perhaps save some .text, some
kernel stack and some CPU cycles by inlining get_zeroed_page().
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] mm: add gfp mask checking for __get_free_pages()
2009-07-18 0:41 ` Andrew Morton
@ 2009-07-18 1:29 ` Akinobu Mita
-1 siblings, 0 replies; 5+ messages in thread
From: Akinobu Mita @ 2009-07-18 1:29 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-kernel, linux-mm
2009/7/18 Andrew Morton <akpm@linux-foundation.org>:
> On Sat, 4 Jul 2009 11:09:50 +0900
> Akinobu Mita <akinobu.mita@gmail.com> wrote:
>
>> __get_free_pages() with __GFP_HIGHMEM is not safe because the return
>> address cannot represent a highmem page. get_zeroed_page() already has
>> such a debug checking.
>>
>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
>> ---
>> mm/page_alloc.c | 24 +++++++++---------------
>> 1 files changed, 9 insertions(+), 15 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e0f2cdf..4a1a374 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -1903,31 +1903,25 @@ EXPORT_SYMBOL(__alloc_pages_nodemask);
>> */
>> unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
>> {
>> - struct page * page;
>> + struct page *page;
>> +
>> + /*
>> + * __get_free_pages() returns a 32-bit address, which cannot represent
>> + * a highmem page
>> + */
>> + VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
>> +
>> page = alloc_pages(gfp_mask, order);
>> if (!page)
>> return 0;
>> return (unsigned long) page_address(page);
>> }
>> -
>> EXPORT_SYMBOL(__get_free_pages);
>>
>> unsigned long get_zeroed_page(gfp_t gfp_mask)
>> {
>> - struct page * page;
>> -
>> - /*
>> - * get_zeroed_page() returns a 32-bit address, which cannot represent
>> - * a highmem page
>> - */
>> - VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
>> -
>> - page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
>> - if (page)
>> - return (unsigned long) page_address(page);
>> - return 0;
>> + return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
>> }
>> -
>> EXPORT_SYMBOL(get_zeroed_page);
>>
>> void __pagevec_free(struct pagevec *pvec)
>
> Fair enough.
>
> I suspect we could just delete that VM_BUG_ON() - we can't go and do
> runtime checking for every darn programmer error, and this would be a
> pretty dumb one.
Maybe. But we had such a bug in c51b1a160b63304720d49479986915e4c475a2cf
(xip: fix get_zeroed_page with __GFP_HIGHME). Even the VM code
had it and did not fixed for a long time.
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] mm: add gfp mask checking for __get_free_pages()
@ 2009-07-18 1:29 ` Akinobu Mita
0 siblings, 0 replies; 5+ messages in thread
From: Akinobu Mita @ 2009-07-18 1:29 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-kernel, linux-mm
2009/7/18 Andrew Morton <akpm@linux-foundation.org>:
> On Sat, 4 Jul 2009 11:09:50 +0900
> Akinobu Mita <akinobu.mita@gmail.com> wrote:
>
>> __get_free_pages() with __GFP_HIGHMEM is not safe because the return
>> address cannot represent a highmem page. get_zeroed_page() already has
>> such a debug checking.
>>
>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
>> ---
>> mm/page_alloc.c | 24 +++++++++---------------
>> 1 files changed, 9 insertions(+), 15 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e0f2cdf..4a1a374 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -1903,31 +1903,25 @@ EXPORT_SYMBOL(__alloc_pages_nodemask);
>> */
>> unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
>> {
>> - struct page * page;
>> + struct page *page;
>> +
>> + /*
>> + * __get_free_pages() returns a 32-bit address, which cannot represent
>> + * a highmem page
>> + */
>> + VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
>> +
>> page = alloc_pages(gfp_mask, order);
>> if (!page)
>> return 0;
>> return (unsigned long) page_address(page);
>> }
>> -
>> EXPORT_SYMBOL(__get_free_pages);
>>
>> unsigned long get_zeroed_page(gfp_t gfp_mask)
>> {
>> - struct page * page;
>> -
>> - /*
>> - * get_zeroed_page() returns a 32-bit address, which cannot represent
>> - * a highmem page
>> - */
>> - VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
>> -
>> - page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
>> - if (page)
>> - return (unsigned long) page_address(page);
>> - return 0;
>> + return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
>> }
>> -
>> EXPORT_SYMBOL(get_zeroed_page);
>>
>> void __pagevec_free(struct pagevec *pvec)
>
> Fair enough.
>
> I suspect we could just delete that VM_BUG_ON() - we can't go and do
> runtime checking for every darn programmer error, and this would be a
> pretty dumb one.
Maybe. But we had such a bug in c51b1a160b63304720d49479986915e4c475a2cf
(xip: fix get_zeroed_page with __GFP_HIGHME). Even the VM code
had it and did not fixed for a long time.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2009-07-04 2:09 [PATCH] mm: add gfp mask checking for __get_free_pages() Akinobu Mita
2009-07-18 0:41 ` Andrew Morton
2009-07-18 0:41 ` Andrew Morton
2009-07-18 1:29 ` Akinobu Mita
2009-07-18 1:29 ` Akinobu Mita
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