[PATCH 1/2] hugetlb.h: flatten logic in arch_hugetlb_migration_supported

[PATCH 1/2] hugetlb.h: flatten logic in arch_hugetlb_migration_supported

[Gregory Price]

Simplify if-true-return-true-else-false logic.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
 include/linux/hugetlb.h | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 526d27e88b3b..b030850975ef 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -876,12 +876,9 @@ static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
 #ifndef arch_hugetlb_migration_supported
 static inline bool arch_hugetlb_migration_supported(struct hstate *h)
 {
-	if ((huge_page_shift(h) == PMD_SHIFT) ||
+	return ((huge_page_shift(h) == PMD_SHIFT) ||
 		(huge_page_shift(h) == PUD_SHIFT) ||
-			(huge_page_shift(h) == PGDIR_SHIFT))
-		return true;
-	else
-		return false;
+		(huge_page_shift(h) == PGDIR_SHIFT));
 }
 #endif
 #else
-- 
2.51.0

[PATCH 2/2] hugetlb: add __read_mostly to sysctl_hugetlb_shm_group

[Gregory Price]

sysctl bits are mostly-read values.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
 include/linux/hugetlb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index b030850975ef..7ea667d4ad5e 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -172,7 +172,7 @@ bool hugetlbfs_pagecache_present(struct hstate *h,
 
 struct address_space *hugetlb_folio_mapping_lock_write(struct folio *folio);
 
-extern int sysctl_hugetlb_shm_group;
+extern int sysctl_hugetlb_shm_group __read_mostly;
 extern struct list_head huge_boot_pages[MAX_NUMNODES];
 
 void hugetlb_bootmem_alloc(void);
-- 
2.51.0

Re: [PATCH 2/2] hugetlb: add __read_mostly to sysctl_hugetlb_shm_group

[Oscar Salvador]

On Wed, Oct 08, 2025 at 05:26:14PM -0400, Gregory Price wrote:
> sysctl bits are mostly-read values.
> 
> Signed-off-by: Gregory Price <gourry@gourry.net>

Acked-by: Oscar Salvador <osalvador@suse.de>


-- 
Oscar Salvador
SUSE Labs

Re: [PATCH 1/2] hugetlb.h: flatten logic in arch_hugetlb_migration_supported

[Oscar Salvador]

On Wed, Oct 08, 2025 at 05:26:13PM -0400, Gregory Price wrote:
> Simplify if-true-return-true-else-false logic.
> 
> Signed-off-by: Gregory Price <gourry@gourry.net>

Acked-by: Oscar Salvador <osalvador@suse.de>

 

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH 1/2] hugetlb.h: flatten logic in arch_hugetlb_migration_supported

[David Hildenbrand]

On 08.10.25 23:26, Gregory Price wrote:
> Simplify if-true-return-true-else-false logic.
> 
> Signed-off-by: Gregory Price <gourry@gourry.net>
> ---
>   include/linux/hugetlb.h | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 526d27e88b3b..b030850975ef 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -876,12 +876,9 @@ static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
>   #ifndef arch_hugetlb_migration_supported
>   static inline bool arch_hugetlb_migration_supported(struct hstate *h)
>   {
> -	if ((huge_page_shift(h) == PMD_SHIFT) ||
> +	return ((huge_page_shift(h) == PMD_SHIFT) ||
>   		(huge_page_shift(h) == PUD_SHIFT) ||
> -			(huge_page_shift(h) == PGDIR_SHIFT))
> -		return true;
> -	else
> -		return false;
> +		(huge_page_shift(h) == PGDIR_SHIFT));

switch (huge_page_shift(h)) {
case PMD_SHIFT:
case PUD_SHIFT:
case PGDIR_SHIFT:
	return true;
default:
	return false;
}

-- 
Cheers

David / dhildenb

Re: [PATCH 1/2] hugetlb.h: flatten logic in arch_hugetlb_migration_supported

[Gregory Price]

On Mon, Oct 13, 2025 at 10:10:05AM +0200, David Hildenbrand wrote:
> On 08.10.25 23:26, Gregory Price wrote:
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 526d27e88b3b..b030850975ef 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -876,12 +876,9 @@ static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
> >   #ifndef arch_hugetlb_migration_supported
> >   static inline bool arch_hugetlb_migration_supported(struct hstate *h)
> >   {
> > -	if ((huge_page_shift(h) == PMD_SHIFT) ||
> > +	return ((huge_page_shift(h) == PMD_SHIFT) ||
> >   		(huge_page_shift(h) == PUD_SHIFT) ||
> > -			(huge_page_shift(h) == PGDIR_SHIFT))
> > -		return true;
> > -	else
> > -		return false;
> > +		(huge_page_shift(h) == PGDIR_SHIFT));
> 
> switch (huge_page_shift(h)) {
> case PMD_SHIFT:
> case PUD_SHIFT:
> case PGDIR_SHIFT:

PGDIR_SHIFT is not a constant on x86.

~Gregory

Re: [PATCH 1/2] hugetlb.h: flatten logic in arch_hugetlb_migration_supported

[David Hildenbrand]

On 20.10.25 18:14, Gregory Price wrote:
> On Mon, Oct 13, 2025 at 10:10:05AM +0200, David Hildenbrand wrote:
>> On 08.10.25 23:26, Gregory Price wrote:
>>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>>> index 526d27e88b3b..b030850975ef 100644
>>> --- a/include/linux/hugetlb.h
>>> +++ b/include/linux/hugetlb.h
>>> @@ -876,12 +876,9 @@ static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
>>>    #ifndef arch_hugetlb_migration_supported
>>>    static inline bool arch_hugetlb_migration_supported(struct hstate *h)
>>>    {
>>> -	if ((huge_page_shift(h) == PMD_SHIFT) ||
>>> +	return ((huge_page_shift(h) == PMD_SHIFT) ||
>>>    		(huge_page_shift(h) == PUD_SHIFT) ||
>>> -			(huge_page_shift(h) == PGDIR_SHIFT))
>>> -		return true;
>>> -	else
>>> -		return false;
>>> +		(huge_page_shift(h) == PGDIR_SHIFT));
>>
>> switch (huge_page_shift(h)) {
>> case PMD_SHIFT:
>> case PUD_SHIFT:
>> case PGDIR_SHIFT:
> 
> PGDIR_SHIFT is not a constant on x86.

Ah, probably because of 4 vs. 5 level page tables. On x86 the check 
doesn't even make any sense as we don't support PGD-sized pages.

If we could rule that out at compile time, it would be nice. But I don't 
think we have a way to test that support at compile time.

But anyhow, nothing against what we have in this patch here

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

-- 
Cheers

David / dhildenb