The patch titled
Subject: mm: allocate THP on hugezeropage wp-fault
has been added to the -mm mm-unstable branch. Its filename is
mm-allocate-thp-on-hugezeropage-wp-fault.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-allocate-thp-on-hugezeropage-wp-fault.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Dev Jain <dev.jain@xxxxxxx>
Subject: mm: allocate THP on hugezeropage wp-fault
Date: Tue, 8 Oct 2024 11:47:46 +0530
Introduce do_huge_zero_wp_pmd() to handle wp-fault on a hugezeropage and
replace it with a PMD-mapped THP. Remember to flush TLB entry
corresponding to the hugezeropage. In case of failure, fallback to
splitting the PMD.
Link: https://lkml.kernel.org/r/20241008061746.285961-3-dev.jain@xxxxxxx
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Barry Song <baohua@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dev Jain <dev.jain@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lance Yang <ioworker0@xxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 41 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)
--- a/mm/huge_memory.c~mm-allocate-thp-on-hugezeropage-wp-fault
+++ a/mm/huge_memory.c
@@ -1792,6 +1792,38 @@ unlock:
spin_unlock(vmf->ptl);
}
+static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf)
+{
+ unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+ struct vm_area_struct *vma = vmf->vma;
+ struct mmu_notifier_range range;
+ struct folio *folio;
+ vm_fault_t ret = 0;
+
+ folio = vma_alloc_anon_folio_pmd(vma, vmf->address);
+ if (unlikely(!folio))
+ return VM_FAULT_FALLBACK;
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, haddr,
+ haddr + HPAGE_PMD_SIZE);
+ mmu_notifier_invalidate_range_start(&range);
+ vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+ if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd)))
+ goto release;
+ ret = check_stable_address_space(vma->vm_mm);
+ if (ret)
+ goto release;
+ (void)pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
+ map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
+ goto unlock;
+release:
+ folio_put(folio);
+unlock:
+ spin_unlock(vmf->ptl);
+ mmu_notifier_invalidate_range_end(&range);
+ return ret;
+}
+
vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
@@ -1804,8 +1836,15 @@ vm_fault_t do_huge_pmd_wp_page(struct vm
vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
VM_BUG_ON_VMA(!vma->anon_vma, vma);
- if (is_huge_zero_pmd(orig_pmd))
+ if (is_huge_zero_pmd(orig_pmd)) {
+ vm_fault_t ret = do_huge_zero_wp_pmd(vmf);
+
+ if (!(ret & VM_FAULT_FALLBACK))
+ return ret;
+
+ /* Fallback to splitting PMD if THP cannot be allocated */
goto fallback;
+ }
spin_lock(vmf->ptl);
_
Patches currently in -mm which might be from dev.jain@xxxxxxx are
mm-abstract-thp-allocation.patch
mm-allocate-thp-on-hugezeropage-wp-fault.patch
