[PATCH] nommu: remove __GFP_HIGHMEM in vmalloc/vzalloc

[PATCH] nommu: remove __GFP_HIGHMEM in vmalloc/vzalloc

[Chen Li]

From mm/nommu.c:
void *__vmalloc(unsigned long size, gfp_t gfp_mask)
{
	/*
	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
	 * returns only a logical address.
	 */
	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
}

nommu's __vmalloc just uses kmalloc internally and elimitates __GFP_HIGHMEM,
so it makes no sense to add __GFP_HIGHMEM for nommu's vmalloc/vzalloc.

Signed-off-by: Chen Li <chenli@uniontech.com>
---
 mm/nommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 5c9ab799c0e6..339a2f2eb1aa 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -233,7 +233,7 @@ long vwrite(char *buf, char *addr, unsigned long count)
  */
 void *vmalloc(unsigned long size)
 {
-       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM);
+       return __vmalloc(size, GFP_KERNEL);
 }
 EXPORT_SYMBOL(vmalloc);
 
@@ -251,7 +251,7 @@ EXPORT_SYMBOL(vmalloc);
  */
 void *vzalloc(unsigned long size)
 {
-	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
+	return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
 }
 EXPORT_SYMBOL(vzalloc);
 
-- 
2.31.1

Re: [PATCH] nommu: remove __GFP_HIGHMEM in vmalloc/vzalloc

[Matthew Wilcox]

On Mon, May 03, 2021 at 08:44:51PM +0800, Chen Li wrote:
> 
> From mm/nommu.c:
> void *__vmalloc(unsigned long size, gfp_t gfp_mask)
> {
> 	/*
> 	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
> 	 * returns only a logical address.
> 	 */
> 	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
> }
> 
> nommu's __vmalloc just uses kmalloc internally and elimitates __GFP_HIGHMEM,
> so it makes no sense to add __GFP_HIGHMEM for nommu's vmalloc/vzalloc.

I think this was originally [1] a copy of vmalloc() from vmalloc.c,
but of course the two have drifted apart over time.  At the time,
vmalloc.c's vmalloc() looked like this:

+void * vmalloc (unsigned long size)
+{
+       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
+}

[1] And I do mean originally; this was present in Alan Cox's original
submission of mm/nommu.c in 2002.

This patch makes sense to me, although I don't imagine it makes
much difference.

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

> Signed-off-by: Chen Li <chenli@uniontech.com>
> ---
>  mm/nommu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 5c9ab799c0e6..339a2f2eb1aa 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -233,7 +233,7 @@ long vwrite(char *buf, char *addr, unsigned long count)
>   */
>  void *vmalloc(unsigned long size)
>  {
> -       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM);
> +       return __vmalloc(size, GFP_KERNEL);
>  }
>  EXPORT_SYMBOL(vmalloc);
>  
> @@ -251,7 +251,7 @@ EXPORT_SYMBOL(vmalloc);
>   */
>  void *vzalloc(unsigned long size)
>  {
> -	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
> +	return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
>  }
>  EXPORT_SYMBOL(vzalloc);
>  
> -- 
> 2.31.1
> 
> 
> 
> 

Re: [PATCH] nommu: remove __GFP_HIGHMEM in vmalloc/vzalloc

[David Hildenbrand]

On 03.05.21 14:44, Chen Li wrote:
> 
>  From mm/nommu.c:
> void *__vmalloc(unsigned long size, gfp_t gfp_mask)
> {
> 	/*
> 	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
> 	 * returns only a logical address.
> 	 */
> 	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
> }
> 
> nommu's __vmalloc just uses kmalloc internally and elimitates __GFP_HIGHMEM,
> so it makes no sense to add __GFP_HIGHMEM for nommu's vmalloc/vzalloc.
> 
> Signed-off-by: Chen Li <chenli@uniontech.com>
> ---
>   mm/nommu.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 5c9ab799c0e6..339a2f2eb1aa 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -233,7 +233,7 @@ long vwrite(char *buf, char *addr, unsigned long count)
>    */
>   void *vmalloc(unsigned long size)
>   {
> -       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM);
> +       return __vmalloc(size, GFP_KERNEL);
>   }
>   EXPORT_SYMBOL(vmalloc);
>   
> @@ -251,7 +251,7 @@ EXPORT_SYMBOL(vmalloc);
>    */
>   void *vzalloc(unsigned long size)
>   {
> -	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
> +	return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
>   }
>   EXPORT_SYMBOL(vzalloc);
>   
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb