linux-kernel - Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage

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Message-ID: <050B65EF-6A1E-44A8-87D5-152FA9A60641@nvidia.com>
Date: Fri, 13 Jun 2025 11:13:50 -0400
From: Zi Yan <ziy@...dia.com>
To: Peter Xu <peterx@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, kvm@...r.kernel.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Alex Williamson <alex.williamson@...hat.com>,
 Jason Gunthorpe <jgg@...dia.com>, Alex Mastro <amastro@...com>,
 David Hildenbrand <david@...hat.com>, Nico Pache <npache@...hat.com>,
 Huacai Chen <chenhuacai@...nel.org>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 Muchun Song <muchun.song@...ux.dev>, Oscar Salvador <osalvador@...e.de>,
 loongarch@...ts.linux.dev, linux-mips@...r.kernel.org
Subject: Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range()

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@...nel.org>
> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> Cc: Muchun Song <muchun.song@...ux.dev>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: loongarch@...ts.linux.dev
> Cc: linux-mips@...r.kernel.org
> Signed-off-by: Peter Xu <peterx@...hat.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@...dia.com>


Best Regards,
Yan, Zi