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Message-ID: <CAHS8izMYp_Km_R1p7ruE8CyrYt8A=oA6DmKc+pei_Uw9JO+uXQ@mail.gmail.com>
Date: Wed, 7 Dec 2022 16:30:48 -0800
From: Mina Almasry <almasrymina@...gle.com>
To: James Houghton <jthoughton@...gle.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>,
Muchun Song <songmuchun@...edance.com>,
Peter Xu <peterx@...hat.com>,
David Hildenbrand <david@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
"Zach O'Keefe" <zokeefe@...gle.com>,
Manish Mishra <manish.mishra@...anix.com>,
Naoya Horiguchi <naoya.horiguchi@....com>,
"Dr . David Alan Gilbert" <dgilbert@...hat.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Yang Shi <shy828301@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 09/47] hugetlb: make huge_pte_lockptr take an
explicit shift argument.
On Fri, Oct 21, 2022 at 9:37 AM James Houghton <jthoughton@...gle.com> wrote:
>
> This is needed to handle PTL locking with high-granularity mapping. We
> won't always be using the PMD-level PTL even if we're using the 2M
> hugepage hstate. It's possible that we're dealing with 4K PTEs, in which
> case, we need to lock the PTL for the 4K PTE.
>
> Signed-off-by: James Houghton <jthoughton@...gle.com>
Reviewed-by: Mina Almasry <almasrymina@...gle.com>
> ---
> arch/powerpc/mm/pgtable.c | 3 ++-
> include/linux/hugetlb.h | 9 ++++-----
> mm/hugetlb.c | 7 ++++---
> mm/migrate.c | 3 ++-
> 4 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index cb2dcdb18f8e..035a0df47af0 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -261,7 +261,8 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma,
>
> psize = hstate_get_psize(h);
> #ifdef CONFIG_DEBUG_VM
> - assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep));
> + assert_spin_locked(huge_pte_lockptr(huge_page_shift(h),
> + vma->vm_mm, ptep));
> #endif
>
> #else
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 6e0c36b08a0c..db3ed6095b1c 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -934,12 +934,11 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
> return modified_mask;
> }
>
> -static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
> +static inline spinlock_t *huge_pte_lockptr(unsigned int shift,
> struct mm_struct *mm, pte_t *pte)
> {
> - if (huge_page_size(h) == PMD_SIZE)
> + if (shift == PMD_SHIFT)
> return pmd_lockptr(mm, (pmd_t *) pte);
> - VM_BUG_ON(huge_page_size(h) == PAGE_SIZE);
> return &mm->page_table_lock;
> }
>
> @@ -1144,7 +1143,7 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
> return 0;
> }
>
> -static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
> +static inline spinlock_t *huge_pte_lockptr(unsigned int shift,
> struct mm_struct *mm, pte_t *pte)
> {
> return &mm->page_table_lock;
> @@ -1206,7 +1205,7 @@ static inline spinlock_t *huge_pte_lock(struct hstate *h,
> {
> spinlock_t *ptl;
>
> - ptl = huge_pte_lockptr(h, mm, pte);
> + ptl = huge_pte_lockptr(huge_page_shift(h), mm, pte);
> spin_lock(ptl);
> return ptl;
> }
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index a18143add956..ef7662bd0068 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4847,7 +4847,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
> }
>
> dst_ptl = huge_pte_lock(h, dst, dst_pte);
> - src_ptl = huge_pte_lockptr(h, src, src_pte);
> + src_ptl = huge_pte_lockptr(huge_page_shift(h), src, src_pte);
> spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
> entry = huge_ptep_get(src_pte);
> again:
> @@ -4925,7 +4925,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>
> /* Install the new huge page if src pte stable */
> dst_ptl = huge_pte_lock(h, dst, dst_pte);
> - src_ptl = huge_pte_lockptr(h, src, src_pte);
> + src_ptl = huge_pte_lockptr(huge_page_shift(h),
> + src, src_pte);
> spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
> entry = huge_ptep_get(src_pte);
> if (!pte_same(src_pte_old, entry)) {
> @@ -4979,7 +4980,7 @@ static void move_huge_pte(struct vm_area_struct *vma, unsigned long old_addr,
> pte_t pte;
>
> dst_ptl = huge_pte_lock(h, mm, dst_pte);
> - src_ptl = huge_pte_lockptr(h, mm, src_pte);
> + src_ptl = huge_pte_lockptr(huge_page_shift(h), mm, src_pte);
>
> /*
> * We don't have to worry about the ordering of src and dst ptlocks
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 1457cdbb7828..a0105fa6e3b2 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -334,7 +334,8 @@ void __migration_entry_wait_huge(pte_t *ptep, spinlock_t *ptl)
>
> void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte)
> {
> - spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, pte);
> + spinlock_t *ptl = huge_pte_lockptr(huge_page_shift(hstate_vma(vma)),
> + vma->vm_mm, pte);
>
> __migration_entry_wait_huge(pte, ptl);
> }
> --
> 2.38.0.135.g90850a2211-goog
>
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