Oliver O'Halloran <oohall@xxxxxxxxx> writes:
> Although all architectures use a deposited page table for THP on anonymous VMAs
> some architectures (s390 and powerpc) require the deposited storage even for
> file backed VMAs due to quirks of their MMUs. This patch adds support for
> depositing a table in DAX PMD fault handling path for archs that require it.
> Other architectures should see no functional changes.
>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Signed-off-by: Oliver O'Halloran <oohall@xxxxxxxxx>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
> mm/huge_memory.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index aa01dd47cc65..a84909cf20d3 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -715,7 +715,8 @@ int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
> }
>
> static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> - pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
> + pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
> + pgtable_t pgtable)
> {
> struct mm_struct *mm = vma->vm_mm;
> pmd_t entry;
> @@ -729,6 +730,12 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> entry = pmd_mkyoung(pmd_mkdirty(entry));
> entry = maybe_pmd_mkwrite(entry, vma);
> }
> +
> + if (pgtable) {
> + pgtable_trans_huge_deposit(mm, pmd, pgtable);
> + atomic_long_inc(&mm->nr_ptes);
> + }
> +
> set_pmd_at(mm, addr, pmd, entry);
> update_mmu_cache_pmd(vma, addr, pmd);
> spin_unlock(ptl);
> @@ -738,6 +745,7 @@ int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> pmd_t *pmd, pfn_t pfn, bool write)
> {
> pgprot_t pgprot = vma->vm_page_prot;
> + pgtable_t pgtable = NULL;
> /*
> * If we had pmd_special, we could avoid all these restrictions,
> * but we need to be consistent with PTEs and architectures that
> @@ -752,9 +760,15 @@ int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> if (addr < vma->vm_start || addr >= vma->vm_end)
> return VM_FAULT_SIGBUS;
>
> + if (arch_needs_pgtable_deposit()) {
> + pgtable = pte_alloc_one(vma->vm_mm, addr);
> + if (!pgtable)
> + return VM_FAULT_OOM;
> + }
> +
> track_pfn_insert(vma, &pgprot, pfn);
>
> - insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
> + insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
> return VM_FAULT_NOPAGE;
> }
> EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
> @@ -1611,6 +1625,8 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> tlb->fullmm);
> tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
> if (vma_is_dax(vma)) {
> + if (arch_needs_pgtable_deposit())
> + zap_deposited_table(tlb->mm, pmd);
> spin_unlock(ptl);
> if (is_huge_zero_pmd(orig_pmd))
> tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
> --
> 2.9.3
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