2021-05-03 18:04:36

by Chen Li

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

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 <[email protected]>
---
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

2021-05-03 18:07:32

by Matthew Wilcox

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

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) <[email protected]>

> Signed-off-by: Chen Li <[email protected]>
> ---
> 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
>
>
>
>

2021-05-05 11:16:19

by David Hildenbrand

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

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 <[email protected]>
> ---
> 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 <[email protected]>

--
Thanks,

David / dhildenb