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Subject[RFC PATCH v2 09/30] mm: thp: add PUD THP support to zap_huge_pud.
Date
From: Zi Yan <ziy@nvidia.com>

Preallocated 513 (1 PMD and 512 PTE) page table pages need to be freed
when PUD THP is removed. zap_pud_deposited_table is added to perform the
action.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
mm/huge_memory.c | 48 +++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 45 insertions(+), 3 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ea9fbedcda26..76069affebef 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2013,11 +2013,27 @@ spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
}

#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static inline void zap_pud_deposited_table(struct mm_struct *mm, pud_t *pud)
+{
+ pgtable_t pgtable;
+ int i;
+
+ pgtable = pgtable_trans_huge_pud_withdraw(mm, pud);
+ pmd_free_page_with_ptes(mm, (pmd_t *)page_address(pgtable));
+
+ mm_dec_nr_pmds(mm);
+ for (i = 0; i < (1<<(HPAGE_PUD_ORDER - HPAGE_PMD_ORDER)); i++)
+ mm_dec_nr_ptes(mm);
+}
+
int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
pud_t *pud, unsigned long addr)
{
+ pud_t orig_pud;
spinlock_t *ptl;

+ tlb_change_page_size(tlb, HPAGE_PUD_SIZE);
+
ptl = __pud_trans_huge_lock(pud, vma);
if (!ptl)
return 0;
@@ -2027,14 +2043,40 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
* pgtable_trans_huge_withdraw after finishing pudp related
* operations.
*/
- pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
+ orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
+ tlb->fullmm);
tlb_remove_pud_tlb_entry(tlb, pud, addr);
if (vma_is_special_huge(vma)) {
spin_unlock(ptl);
/* No zero page support yet */
+ } else if (is_huge_zero_pud(orig_pud)) {
+ zap_pud_deposited_table(tlb->mm, pud);
+ spin_unlock(ptl);
+ tlb_remove_page_size(tlb, pud_page(orig_pud), HPAGE_PUD_SIZE);
} else {
- /* No support for anonymous PUD pages yet */
- BUG();
+ struct page *page = NULL;
+ int flush_needed = 1;
+
+ if (pud_present(orig_pud)) {
+ page = pud_page(orig_pud);
+ page_remove_rmap(page, true);
+ VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+ } else
+ WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
+
+ if (PageAnon(page)) {
+ zap_pud_deposited_table(tlb->mm, pud);
+ add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PUD_NR);
+ } else {
+ if (arch_needs_pgtable_deposit())
+ zap_pud_deposited_table(tlb->mm, pud);
+ add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PUD_NR);
+ }
+
+ spin_unlock(ptl);
+ if (flush_needed)
+ tlb_remove_page_size(tlb, page, HPAGE_PUD_SIZE);
}
return 1;
}
--
2.28.0
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