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Subject[PATCHv2 17/28] thp: skip file huge pmd on copy_huge_pmd()
Date
File pmds can be safely skip on copy_huge_pmd(), we can re-fault them
later. COW for file mappings handled on pte level.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/huge_memory.c | 34 ++++++++++++++++------------------
1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4da4e915af61..00f10d323039 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1052,14 +1052,15 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
struct page *src_page;
pmd_t pmd;
pgtable_t pgtable = NULL;
- int ret;
+ int ret = -ENOMEM;

- if (!vma_is_dax(vma)) {
- ret = -ENOMEM;
- pgtable = pte_alloc_one(dst_mm, addr);
- if (unlikely(!pgtable))
- goto out;
- }
+ /* Skip if can be re-fill on fault */
+ if (!vma_is_anonymous(vma))
+ return 0;
+
+ pgtable = pte_alloc_one(dst_mm, addr);
+ if (unlikely(!pgtable))
+ goto out;

dst_ptl = pmd_lock(dst_mm, dst_pmd);
src_ptl = pmd_lockptr(src_mm, src_pmd);
@@ -1067,7 +1068,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,

ret = -EAGAIN;
pmd = *src_pmd;
- if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
+ if (unlikely(!pmd_trans_huge(pmd))) {
pte_free(dst_mm, pgtable);
goto out_unlock;
}
@@ -1090,16 +1091,13 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
goto out_unlock;
}

- if (!vma_is_dax(vma)) {
- /* thp accounting separate from pmd_devmap accounting */
- src_page = pmd_page(pmd);
- VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
- get_page(src_page);
- page_dup_rmap(src_page, true);
- add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
- atomic_long_inc(&dst_mm->nr_ptes);
- pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
- }
+ src_page = pmd_page(pmd);
+ VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
+ get_page(src_page);
+ page_dup_rmap(src_page, true);
+ add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ atomic_long_inc(&dst_mm->nr_ptes);
+ pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);

pmdp_set_wrprotect(src_mm, addr, src_pmd);
pmd = pmd_mkold(pmd_wrprotect(pmd));
--
2.7.0
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