[PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()

Peter Xu posted 5 patches 3 months, 4 weeks ago
[PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Peter Xu 3 months, 4 weeks ago
Only mips and loongarch implemented this API, however what it does was
checking against stack overflow for either len or addr.  That's already
done in arch's arch_get_unmapped_area*() functions, hence not needed.

It means the whole API is pretty much obsolete at least now, remove it
completely.

Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: loongarch@lists.linux.dev
Cc: linux-mips@vger.kernel.org
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/loongarch/include/asm/hugetlb.h | 14 --------------
 arch/mips/include/asm/hugetlb.h      | 14 --------------
 fs/hugetlbfs/inode.c                 |  8 ++------
 include/asm-generic/hugetlb.h        |  8 --------
 include/linux/hugetlb.h              |  6 ------
 5 files changed, 2 insertions(+), 48 deletions(-)

diff --git a/arch/loongarch/include/asm/hugetlb.h b/arch/loongarch/include/asm/hugetlb.h
index 4dc4b3e04225..ab68b594f889 100644
--- a/arch/loongarch/include/asm/hugetlb.h
+++ b/arch/loongarch/include/asm/hugetlb.h
@@ -10,20 +10,6 @@
 
 uint64_t pmd_to_entrylo(unsigned long pmd_val);
 
-#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
-static inline int prepare_hugepage_range(struct file *file,
-					 unsigned long addr,
-					 unsigned long len)
-{
-	unsigned long task_size = STACK_TOP;
-
-	if (len > task_size)
-		return -ENOMEM;
-	if (task_size - len < addr)
-		return -EINVAL;
-	return 0;
-}
-
 #define __HAVE_ARCH_HUGE_PTE_CLEAR
 static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
 				  pte_t *ptep, unsigned long sz)
diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h
index fbc71ddcf0f6..8c460ce01ffe 100644
--- a/arch/mips/include/asm/hugetlb.h
+++ b/arch/mips/include/asm/hugetlb.h
@@ -11,20 +11,6 @@
 
 #include <asm/page.h>
 
-#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
-static inline int prepare_hugepage_range(struct file *file,
-					 unsigned long addr,
-					 unsigned long len)
-{
-	unsigned long task_size = STACK_TOP;
-
-	if (len > task_size)
-		return -ENOMEM;
-	if (task_size - len < addr)
-		return -EINVAL;
-	return 0;
-}
-
 #define __HAVE_ARCH_HUGE_PTEP_GET_AND_CLEAR
 static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 					    unsigned long addr, pte_t *ptep,
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index fc03dd541b4d..32dff13463d2 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -179,12 +179,8 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 
 	if (len & ~huge_page_mask(h))
 		return -EINVAL;
-	if (flags & MAP_FIXED) {
-		if (addr & ~huge_page_mask(h))
-			return -EINVAL;
-		if (prepare_hugepage_range(file, addr, len))
-			return -EINVAL;
-	}
+	if ((flags & MAP_FIXED) && (addr & ~huge_page_mask(h)))
+		return -EINVAL;
 	if (addr)
 		addr0 = ALIGN(addr, huge_page_size(h));
 
diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h
index 3e0a8fe9b108..4bce4f07f44f 100644
--- a/include/asm-generic/hugetlb.h
+++ b/include/asm-generic/hugetlb.h
@@ -114,14 +114,6 @@ static inline int huge_pte_none_mostly(pte_t pte)
 }
 #endif
 
-#ifndef __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
-static inline int prepare_hugepage_range(struct file *file,
-		unsigned long addr, unsigned long len)
-{
-	return 0;
-}
-#endif
-
 #ifndef __HAVE_ARCH_HUGE_PTEP_SET_WRPROTECT
 static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
 		unsigned long addr, pte_t *ptep)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 42f374e828a2..85acdfdbe9f0 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -359,12 +359,6 @@ static inline void hugetlb_show_meminfo_node(int nid)
 {
 }
 
-static inline int prepare_hugepage_range(struct file *file,
-				unsigned long addr, unsigned long len)
-{
-	return -EINVAL;
-}
-
 static inline void hugetlb_vma_lock_read(struct vm_area_struct *vma)
 {
 }
-- 
2.49.0
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Liam R. Howlett 3 months, 4 weeks ago
* Peter Xu <peterx@redhat.com> [691231 23:00]:
> Only mips and loongarch implemented this API, however what it does was
> checking against stack overflow for either len or addr.  That's already
> done in arch's arch_get_unmapped_area*() functions, hence not needed.

I'm not as confident..

> 
> It means the whole API is pretty much obsolete at least now, remove it
> completely.
> 
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Muchun Song <muchun.song@linux.dev>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: loongarch@lists.linux.dev
> Cc: linux-mips@vger.kernel.org
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  arch/loongarch/include/asm/hugetlb.h | 14 --------------
>  arch/mips/include/asm/hugetlb.h      | 14 --------------
>  fs/hugetlbfs/inode.c                 |  8 ++------
>  include/asm-generic/hugetlb.h        |  8 --------
>  include/linux/hugetlb.h              |  6 ------
>  5 files changed, 2 insertions(+), 48 deletions(-)
> 
> diff --git a/arch/loongarch/include/asm/hugetlb.h b/arch/loongarch/include/asm/hugetlb.h
> index 4dc4b3e04225..ab68b594f889 100644
> --- a/arch/loongarch/include/asm/hugetlb.h
> +++ b/arch/loongarch/include/asm/hugetlb.h
> @@ -10,20 +10,6 @@
>  
>  uint64_t pmd_to_entrylo(unsigned long pmd_val);
>  
> -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> -static inline int prepare_hugepage_range(struct file *file,
> -					 unsigned long addr,
> -					 unsigned long len)
> -{
> -	unsigned long task_size = STACK_TOP;
> -
> -	if (len > task_size)
> -		return -ENOMEM;
> -	if (task_size - len < addr)
> -		return -EINVAL;
> -	return 0;
> -}
> -
>  #define __HAVE_ARCH_HUGE_PTE_CLEAR
>  static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
>  				  pte_t *ptep, unsigned long sz)
> diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h
> index fbc71ddcf0f6..8c460ce01ffe 100644
> --- a/arch/mips/include/asm/hugetlb.h
> +++ b/arch/mips/include/asm/hugetlb.h
> @@ -11,20 +11,6 @@
>  
>  #include <asm/page.h>
>  
> -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> -static inline int prepare_hugepage_range(struct file *file,
> -					 unsigned long addr,
> -					 unsigned long len)
> -{
> -	unsigned long task_size = STACK_TOP;

arch/mips/include/asm/processor.h:#define STACK_TOP             mips_stack_top()


unsigned long mips_stack_top(void)                                                                                                                                                                                                             
{       
        unsigned long top = TASK_SIZE & PAGE_MASK;                                                                                                                                                                                             
        
        if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
                /* One page for branch delay slot "emulation" */                                                                                                                                                                               
                top -= PAGE_SIZE;                                                                                                                                                                                                              
        }                                                                                                                                                                                                                                      
        
        /* Space for the VDSO, data page & GIC user page */                                                                                                                                                                                    
        top -= PAGE_ALIGN(current->thread.abi->vdso->size);                                                                                                                                                                                    
        top -= PAGE_SIZE;
        top -= mips_gic_present() ? PAGE_SIZE : 0;                                                                                                                                                                                             
        
        /* Space for cache colour alignment */                                                                                                                                                                                                 
        if (cpu_has_dc_aliases)
                top -= shm_align_mask + 1;                                                                                                                                                                                                     
        
        /* Space to randomize the VDSO base */                                                                                                                                                                                                 
        if (current->flags & PF_RANDOMIZE)
                top -= VDSO_RANDOMIZE_SIZE;                                                                                                                                                                                                    
        
        return top;                                                                                                                                                                                                                            
}

This seems different than TASK_SIZE.

Code is from:
commit ea7e0480a4b695d0aa6b3fa99bd658a003122113
Author: Paul Burton <paulburton@kernel.org>
Date:   Tue Sep 25 15:51:26 2018 -0700


> -	if (len > task_size)
> -		return -ENOMEM;
> -	if (task_size - len < addr)
> -		return -EINVAL;
> -	return 0;
> -}
> -

Unfortunately, the commit message for the addition of this code are not
helpful.

commit 50a41ff292fafe1e937102be23464b54fed8b78c
Author: David Daney <ddaney@caviumnetworks.com>
Date:   Wed May 27 17:47:42 2009 -0700

... But the dates are helpful.  This code used to use:
#define STACK_TOP      ((TASK_SIZE & PAGE_MASK) - PAGE_SIZE)

It's not exactly task size either.

I don't think this is an issue to remove this check because the overflow
should be caught later (or trigger the opposite search).  But it's not
clear why STACK_TOP was done in the first place.. Maybe just because we
know the overflow here would be an issue later, but then we'd avoid the
opposite search - and maybe that's the point?

Either way, your comment about the same check existing doesn't seem
correct.

I haven't checked loong arch, but I'd be willing to wager this was just
cloned mips code... because this happens so much.

...

Thanks,
Liam
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Peter Xu 3 months, 3 weeks ago
On Sat, Jun 14, 2025 at 12:11:22AM -0400, Liam R. Howlett wrote:
> * Peter Xu <peterx@redhat.com> [691231 23:00]:
> > Only mips and loongarch implemented this API, however what it does was
> > checking against stack overflow for either len or addr.  That's already
> > done in arch's arch_get_unmapped_area*() functions, hence not needed.
> 
> I'm not as confident..
> 
> > 
> > It means the whole API is pretty much obsolete at least now, remove it
> > completely.
> > 
> > Cc: Huacai Chen <chenhuacai@kernel.org>
> > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > Cc: Muchun Song <muchun.song@linux.dev>
> > Cc: Oscar Salvador <osalvador@suse.de>
> > Cc: loongarch@lists.linux.dev
> > Cc: linux-mips@vger.kernel.org
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  arch/loongarch/include/asm/hugetlb.h | 14 --------------
> >  arch/mips/include/asm/hugetlb.h      | 14 --------------
> >  fs/hugetlbfs/inode.c                 |  8 ++------
> >  include/asm-generic/hugetlb.h        |  8 --------
> >  include/linux/hugetlb.h              |  6 ------
> >  5 files changed, 2 insertions(+), 48 deletions(-)
> > 
> > diff --git a/arch/loongarch/include/asm/hugetlb.h b/arch/loongarch/include/asm/hugetlb.h
> > index 4dc4b3e04225..ab68b594f889 100644
> > --- a/arch/loongarch/include/asm/hugetlb.h
> > +++ b/arch/loongarch/include/asm/hugetlb.h
> > @@ -10,20 +10,6 @@
> >  
> >  uint64_t pmd_to_entrylo(unsigned long pmd_val);
> >  
> > -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> > -static inline int prepare_hugepage_range(struct file *file,
> > -					 unsigned long addr,
> > -					 unsigned long len)
> > -{
> > -	unsigned long task_size = STACK_TOP;
> > -
> > -	if (len > task_size)
> > -		return -ENOMEM;
> > -	if (task_size - len < addr)
> > -		return -EINVAL;
> > -	return 0;
> > -}
> > -
> >  #define __HAVE_ARCH_HUGE_PTE_CLEAR
> >  static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
> >  				  pte_t *ptep, unsigned long sz)
> > diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h
> > index fbc71ddcf0f6..8c460ce01ffe 100644
> > --- a/arch/mips/include/asm/hugetlb.h
> > +++ b/arch/mips/include/asm/hugetlb.h
> > @@ -11,20 +11,6 @@
> >  
> >  #include <asm/page.h>
> >  
> > -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> > -static inline int prepare_hugepage_range(struct file *file,
> > -					 unsigned long addr,
> > -					 unsigned long len)
> > -{
> > -	unsigned long task_size = STACK_TOP;
> 
> arch/mips/include/asm/processor.h:#define STACK_TOP             mips_stack_top()
> 
> 
> unsigned long mips_stack_top(void)                                                                                                                                                                                                             
> {       
>         unsigned long top = TASK_SIZE & PAGE_MASK;                                                                                                                                                                                             
>         
>         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
>                 /* One page for branch delay slot "emulation" */                                                                                                                                                                               
>                 top -= PAGE_SIZE;                                                                                                                                                                                                              
>         }                                                                                                                                                                                                                                      
>         
>         /* Space for the VDSO, data page & GIC user page */                                                                                                                                                                                    
>         top -= PAGE_ALIGN(current->thread.abi->vdso->size);                                                                                                                                                                                    
>         top -= PAGE_SIZE;
>         top -= mips_gic_present() ? PAGE_SIZE : 0;                                                                                                                                                                                             
>         
>         /* Space for cache colour alignment */                                                                                                                                                                                                 
>         if (cpu_has_dc_aliases)
>                 top -= shm_align_mask + 1;                                                                                                                                                                                                     
>         
>         /* Space to randomize the VDSO base */                                                                                                                                                                                                 
>         if (current->flags & PF_RANDOMIZE)
>                 top -= VDSO_RANDOMIZE_SIZE;                                                                                                                                                                                                    
>         
>         return top;                                                                                                                                                                                                                            
> }
> 
> This seems different than TASK_SIZE.
> 
> Code is from:
> commit ea7e0480a4b695d0aa6b3fa99bd658a003122113
> Author: Paul Burton <paulburton@kernel.org>
> Date:   Tue Sep 25 15:51:26 2018 -0700
> 
> 
> > -	if (len > task_size)
> > -		return -ENOMEM;
> > -	if (task_size - len < addr)
> > -		return -EINVAL;
> > -	return 0;
> > -}
> > -
> 
> Unfortunately, the commit message for the addition of this code are not
> helpful.
> 
> commit 50a41ff292fafe1e937102be23464b54fed8b78c
> Author: David Daney <ddaney@caviumnetworks.com>
> Date:   Wed May 27 17:47:42 2009 -0700
> 
> ... But the dates are helpful.  This code used to use:
> #define STACK_TOP      ((TASK_SIZE & PAGE_MASK) - PAGE_SIZE)
> 
> It's not exactly task size either.
> 
> I don't think this is an issue to remove this check because the overflow
> should be caught later (or trigger the opposite search).  But it's not
> clear why STACK_TOP was done in the first place.. Maybe just because we
> know the overflow here would be an issue later, but then we'd avoid the
> opposite search - and maybe that's the point?
> 
> Either way, your comment about the same check existing doesn't seem
> correct.

I will fix up the commit message to mention both archs:

  Only mips and loongarch implemented this API, however what it does was
  checking against stack overflow for either len or addr.  That's already
  done in arch's arch_get_unmapped_area*() functions, even though it may not
  be 100% identical checks.

  For example, for both of the architectures, there will be a trivial
  difference on how stack top was defined.  The old code uses STACK_TOP which
  may be slightly smaller than TASK_SIZE on either of them, but the hope is
  that shouldn't be a problem.

  It means the whole API is pretty much obsolete at least now, remove it
  completely.

> 
> I haven't checked loong arch, but I'd be willing to wager this was just
> cloned mips code... because this happens so much.

They define STACK_TOP differently, but AFAIU there're some duplications in
pattern of the two archs.

Please let me know if the fixed commit message works for you above, thanks.

-- 
Peter Xu
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Zi Yan 3 months, 4 weeks ago
On 13 Jun 2025, at 9:41, Peter Xu wrote:

> Only mips and loongarch implemented this API, however what it does was
> checking against stack overflow for either len or addr.  That's already
> done in arch's arch_get_unmapped_area*() functions, hence not needed.
>
> It means the whole API is pretty much obsolete at least now, remove it
> completely.
>
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Muchun Song <muchun.song@linux.dev>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: loongarch@lists.linux.dev
> Cc: linux-mips@vger.kernel.org
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  arch/loongarch/include/asm/hugetlb.h | 14 --------------
>  arch/mips/include/asm/hugetlb.h      | 14 --------------
>  fs/hugetlbfs/inode.c                 |  8 ++------
>  include/asm-generic/hugetlb.h        |  8 --------
>  include/linux/hugetlb.h              |  6 ------
>  5 files changed, 2 insertions(+), 48 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/hugetlb.h b/arch/loongarch/include/asm/hugetlb.h
> index 4dc4b3e04225..ab68b594f889 100644
> --- a/arch/loongarch/include/asm/hugetlb.h
> +++ b/arch/loongarch/include/asm/hugetlb.h
> @@ -10,20 +10,6 @@
>
>  uint64_t pmd_to_entrylo(unsigned long pmd_val);
>
> -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> -static inline int prepare_hugepage_range(struct file *file,
> -					 unsigned long addr,
> -					 unsigned long len)
> -{
> -	unsigned long task_size = STACK_TOP;
> -
> -	if (len > task_size)
> -		return -ENOMEM;
> -	if (task_size - len < addr)
> -		return -EINVAL;
> -	return 0;
> -}
> -
>  #define __HAVE_ARCH_HUGE_PTE_CLEAR
>  static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
>  				  pte_t *ptep, unsigned long sz)
> diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h
> index fbc71ddcf0f6..8c460ce01ffe 100644
> --- a/arch/mips/include/asm/hugetlb.h
> +++ b/arch/mips/include/asm/hugetlb.h
> @@ -11,20 +11,6 @@
>
>  #include <asm/page.h>
>
> -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> -static inline int prepare_hugepage_range(struct file *file,
> -					 unsigned long addr,
> -					 unsigned long len)
> -{
> -	unsigned long task_size = STACK_TOP;
> -
> -	if (len > task_size)
> -		return -ENOMEM;

arch_get_unmapped_area_topdown() has this check.

> -	if (task_size - len < addr)
> -		return -EINVAL;

For this one, arch_get_unmapped_area_topdown() instead will try to
provide a different addr if the check fails.

So this patch changes the original code behavior, right?
If yes, it is worth spelling it out in the commit log.

Otherwise, Reviewed-by: Zi Yan <ziy@nvidia.com>


Best Regards,
Yan, Zi
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Peter Xu 3 months, 4 weeks ago
On Fri, Jun 13, 2025 at 11:13:50AM -0400, Zi Yan wrote:
> On 13 Jun 2025, at 9:41, Peter Xu wrote:
> 
> > Only mips and loongarch implemented this API, however what it does was
> > checking against stack overflow for either len or addr.  That's already
> > done in arch's arch_get_unmapped_area*() functions, hence not needed.
> >
> > It means the whole API is pretty much obsolete at least now, remove it
> > completely.
> >
> > Cc: Huacai Chen <chenhuacai@kernel.org>
> > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > Cc: Muchun Song <muchun.song@linux.dev>
> > Cc: Oscar Salvador <osalvador@suse.de>
> > Cc: loongarch@lists.linux.dev
> > Cc: linux-mips@vger.kernel.org
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  arch/loongarch/include/asm/hugetlb.h | 14 --------------
> >  arch/mips/include/asm/hugetlb.h      | 14 --------------
> >  fs/hugetlbfs/inode.c                 |  8 ++------
> >  include/asm-generic/hugetlb.h        |  8 --------
> >  include/linux/hugetlb.h              |  6 ------
> >  5 files changed, 2 insertions(+), 48 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/hugetlb.h b/arch/loongarch/include/asm/hugetlb.h
> > index 4dc4b3e04225..ab68b594f889 100644
> > --- a/arch/loongarch/include/asm/hugetlb.h
> > +++ b/arch/loongarch/include/asm/hugetlb.h
> > @@ -10,20 +10,6 @@
> >
> >  uint64_t pmd_to_entrylo(unsigned long pmd_val);
> >
> > -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> > -static inline int prepare_hugepage_range(struct file *file,
> > -					 unsigned long addr,
> > -					 unsigned long len)
> > -{
> > -	unsigned long task_size = STACK_TOP;
> > -
> > -	if (len > task_size)
> > -		return -ENOMEM;
> > -	if (task_size - len < addr)
> > -		return -EINVAL;
> > -	return 0;
> > -}
> > -
> >  #define __HAVE_ARCH_HUGE_PTE_CLEAR
> >  static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
> >  				  pte_t *ptep, unsigned long sz)
> > diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h
> > index fbc71ddcf0f6..8c460ce01ffe 100644
> > --- a/arch/mips/include/asm/hugetlb.h
> > +++ b/arch/mips/include/asm/hugetlb.h
> > @@ -11,20 +11,6 @@
> >
> >  #include <asm/page.h>
> >
> > -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE
> > -static inline int prepare_hugepage_range(struct file *file,
> > -					 unsigned long addr,
> > -					 unsigned long len)
> > -{
> > -	unsigned long task_size = STACK_TOP;
> > -
> > -	if (len > task_size)
> > -		return -ENOMEM;
> 
> arch_get_unmapped_area_topdown() has this check.
> 
> > -	if (task_size - len < addr)
> > -		return -EINVAL;
> 
> For this one, arch_get_unmapped_area_topdown() instead will try to
> provide a different addr if the check fails.
> 
> So this patch changes the original code behavior, right?

It almost shouldn't change.  Note that prepare_hugepage_range() is only
used for MAP_FIXED before this patch:

hugetlb_get_unmapped_area():
        if (flags & MAP_FIXED) {
                if (addr & ~huge_page_mask(h))
                        return -EINVAL;
                if (prepare_hugepage_range(file, addr, len))
                        return -EINVAL;
        }

Then for MAP_FIXED, on MIPS:

arch_get_unmapped_area_common():
        ...
	if (flags & MAP_FIXED) {
		/* Even MAP_FIXED mappings must reside within TASK_SIZE */
		if (TASK_SIZE - len < addr)
			return -EINVAL;
                ...
        }

But if we want to be super accurate, it's indeed different, in that the old
hugetlb code was checking stack top with STACK_TOP, which is
mips_stack_top() for MIPS: it's a value that might be slightly less than
TASK_SIZE..

So strictly speaking, there's indeed a trivial difference on the oddity of
defining stack top, but my guess is nothing will be affected.  I can add
some explanation into the commit message in that case.

Thanks,

-- 
Peter Xu
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by David Hildenbrand 3 months, 4 weeks ago
> 
> But if we want to be super accurate, it's indeed different, in that the old
> hugetlb code was checking stack top with STACK_TOP, which is
> mips_stack_top() for MIPS: it's a value that might be slightly less than
> TASK_SIZE..
> 
> So strictly speaking, there's indeed a trivial difference on the oddity of
> defining stack top, but my guess is nothing will be affected.  I can add
> some explanation into the commit message in that case.

Yeah, that would be good.

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

-- 
Cheers,

David / dhildenb
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Oscar Salvador 3 months, 4 weeks ago
On Fri, Jun 13, 2025 at 09:41:08AM -0400, Peter Xu wrote:
> Only mips and loongarch implemented this API, however what it does was
> checking against stack overflow for either len or addr.  That's already
> done in arch's arch_get_unmapped_area*() functions, hence not needed.
> 
> It means the whole API is pretty much obsolete at least now, remove it
> completely.
> 
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Muchun Song <muchun.song@linux.dev>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: loongarch@lists.linux.dev
> Cc: linux-mips@vger.kernel.org
> Signed-off-by: Peter Xu <peterx@redhat.com>

I think I forgot to clean these up when I unified the unmapped_area for
hugetlb.

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

Thanks Peter!
 

-- 
Oscar Salvador
SUSE Labs
Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()
Posted by Jason Gunthorpe 3 months, 4 weeks ago
On Fri, Jun 13, 2025 at 09:41:08AM -0400, Peter Xu wrote:
> Only mips and loongarch implemented this API, however what it does was
> checking against stack overflow for either len or addr.  That's already
> done in arch's arch_get_unmapped_area*() functions, hence not needed.
> 
> It means the whole API is pretty much obsolete at least now, remove it
> completely.
> 
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Muchun Song <muchun.song@linux.dev>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: loongarch@lists.linux.dev
> Cc: linux-mips@vger.kernel.org
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  arch/loongarch/include/asm/hugetlb.h | 14 --------------
>  arch/mips/include/asm/hugetlb.h      | 14 --------------
>  fs/hugetlbfs/inode.c                 |  8 ++------
>  include/asm-generic/hugetlb.h        |  8 --------
>  include/linux/hugetlb.h              |  6 ------
>  5 files changed, 2 insertions(+), 48 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason