From: Balbir Singh <bsingharora@gmail.com>
To: Anshuman Khandual <khandual@linux.vnet.ibm.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org
Cc: hughd@google.com, kirill@shutemov.name,
n-horiguchi@ah.jp.nec.com, akpm@linux-foundation.org,
mgorman@techsingularity.net, dave.hansen@intel.com,
aneesh.kumar@linux.vnet.ibm.com, mpe@ellerman.id.au
Subject: Re: [PATCH 02/10] mm/hugetlb: Add PGD based implementation awareness
Date: Thu, 7 Apr 2016 19:04:52 +1000 [thread overview]
Message-ID: <570622B4.5020407@gmail.com> (raw)
In-Reply-To: <1460007464-26726-3-git-send-email-khandual@linux.vnet.ibm.com>
On 07/04/16 15:37, Anshuman Khandual wrote:
> Currently the config ARCH_WANT_GENERAL_HUGETLB enabled functions like
> 'huge_pte_alloc' and 'huge_pte_offset' dont take into account HugeTLB
> page implementation at the PGD level. This is also true for functions
> like 'follow_page_mask' which is called from move_pages() system call.
> This lack of PGD level huge page support prohibits some architectures
> to use these generic HugeTLB functions.
>
>From what I know of move_pages(), it will always call follow_page_mask()
with FOLL_GET (I could be wrong here) and the implementation below
returns NULL for follow_huge_pgd().
> This change adds the required PGD based implementation awareness and
> with that, more architectures like POWER which implements 16GB pages
> at the PGD level along with the 16MB pages at the PMD level can now
> use ARCH_WANT_GENERAL_HUGETLB config option.
>
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> include/linux/hugetlb.h | 3 +++
> mm/gup.c | 6 ++++++
> mm/hugetlb.c | 20 ++++++++++++++++++++
> 3 files changed, 29 insertions(+)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 7d953c2..71832e1 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -115,6 +115,8 @@ struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
> pmd_t *pmd, int flags);
> struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
> pud_t *pud, int flags);
> +struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
> + pgd_t *pgd, int flags);
> int pmd_huge(pmd_t pmd);
> int pud_huge(pud_t pmd);
> unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
> @@ -143,6 +145,7 @@ static inline void hugetlb_show_meminfo(void)
> }
> #define follow_huge_pmd(mm, addr, pmd, flags) NULL
> #define follow_huge_pud(mm, addr, pud, flags) NULL
> +#define follow_huge_pgd(mm, addr, pgd, flags) NULL
> #define prepare_hugepage_range(file, addr, len) (-EINVAL)
> #define pmd_huge(x) 0
> #define pud_huge(x) 0
> diff --git a/mm/gup.c b/mm/gup.c
> index fb87aea..9bac78c 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -234,6 +234,12 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
> pgd = pgd_offset(mm, address);
> if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
> return no_page_table(vma, flags);
> + if (pgd_huge(*pgd) && vma->vm_flags & VM_HUGETLB) {
> + page = follow_huge_pgd(mm, address, pgd, flags);
> + if (page)
> + return page;
> + return no_page_table(vma, flags);
This will return NULL as well?
> + }
>
> pud = pud_offset(pgd, address);
> if (pud_none(*pud))
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 19d0d08..5ea3158 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4250,6 +4250,11 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte_t *pte = NULL;
>
> pgd = pgd_offset(mm, addr);
> + if (sz == PGDIR_SIZE) {
> + pte = (pte_t *)pgd;
> + goto huge_pgd;
> + }
> +
No allocation for a pgd slot - right?
> pud = pud_alloc(mm, pgd, addr);
> if (pud) {
> if (sz == PUD_SIZE) {
> @@ -4262,6 +4267,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte = (pte_t *)pmd_alloc(mm, pud, addr);
> }
> }
> +
> +huge_pgd:
> BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
>
> return pte;
> @@ -4275,6 +4282,8 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
>
> pgd = pgd_offset(mm, addr);
> if (pgd_present(*pgd)) {
> + if (pgd_huge(*pgd))
> + return (pte_t *)pgd;
> pud = pud_offset(pgd, addr);
> if (pud_present(*pud)) {
> if (pud_huge(*pud))
> @@ -4343,6 +4352,17 @@ follow_huge_pud(struct mm_struct *mm, unsigned long address,
> return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
> }
>
> +struct page * __weak
> +follow_huge_pgd(struct mm_struct *mm, unsigned long address,
> + pgd_t *pgd, int flags)
> +{
> + if (flags & FOLL_GET)
> + return NULL;
> +
> + return pte_page(*(pte_t *)pgd) +
> + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);
> +}
> +
> #ifdef CONFIG_MEMORY_FAILURE
>
> /*
>
next prev parent reply other threads:[~2016-04-07 9:05 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-07 5:37 [PATCH 00/10] Enable HugeTLB page migration on POWER Anshuman Khandual
2016-04-07 5:37 ` [PATCH 01/10] mm/mmap: Replace SHM_HUGE_MASK with MAP_HUGE_MASK inside mmap_pgoff Anshuman Khandual
2016-04-07 8:28 ` Balbir Singh
2016-04-13 7:54 ` Michal Hocko
2016-04-07 5:37 ` [PATCH 02/10] mm/hugetlb: Add PGD based implementation awareness Anshuman Khandual
2016-04-07 9:04 ` Balbir Singh [this message]
2016-04-11 5:25 ` Anshuman Khandual
2016-04-11 6:10 ` Anshuman Khandual
2016-04-07 5:37 ` [PATCH 03/10] mm/hugetlb: Protect follow_huge_(pud|pgd) functions from race Anshuman Khandual
2016-04-07 9:16 ` kbuild test robot
2016-04-18 8:44 ` Anshuman Khandual
2016-04-07 9:26 ` Balbir Singh
2016-04-11 5:39 ` Anshuman Khandual
2016-04-11 12:46 ` Balbir Singh
2016-04-07 9:34 ` kbuild test robot
2016-04-11 6:04 ` Anshuman Khandual
2016-04-18 8:42 ` Anshuman Khandual
2016-04-07 5:37 ` [PATCH 04/10] powerpc/hugetlb: Add ABI defines for MAP_HUGE_16MB and MAP_HUGE_16GB Anshuman Khandual
2016-04-07 5:37 ` [PATCH 05/10] powerpc/hugetlb: Split the function 'huge_pte_alloc' Anshuman Khandual
2016-04-11 13:51 ` Balbir Singh
2016-04-13 11:08 ` Anshuman Khandual
2016-04-07 5:37 ` [PATCH 06/10] powerpc/hugetlb: Split the function 'huge_pte_offset' Anshuman Khandual
2016-04-07 5:37 ` [PATCH 07/10] powerpc/hugetlb: Prepare arch functions for ARCH_WANT_GENERAL_HUGETLB Anshuman Khandual
2016-04-07 5:37 ` [PATCH 08/10] powerpc/hugetlb: Selectively enable ARCH_WANT_GENERAL_HUGETLB Anshuman Khandual
2016-04-07 5:37 ` [PATCH 09/10] powerpc/hugetlb: Selectively enable ARCH_ENABLE_HUGEPAGE_MIGRATION Anshuman Khandual
2016-04-07 5:37 ` [PATCH 10/10] selfttest/powerpc: Add memory page migration tests Anshuman Khandual
2016-04-18 8:52 ` [PATCH 00/10] Enable HugeTLB page migration on POWER Anshuman Khandual
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