We allocate a pgtable but do not attach it to anything if the PMD is in
a DAX VMA, causing it to leak.
We certainly try to not free pgtables associated with the huge zero page
if the zero page is in a DAX VMA, so I think this is the right solution.
This needs to be properly audited.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
---
mm/huge_memory.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4b9f2cb..1632e02 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -889,7 +889,8 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
return false;
entry = mk_pmd(zero_page, vma->vm_page_prot);
entry = pmd_mkhuge(entry);
- pgtable_trans_huge_deposit(mm, pmd, pgtable);
+ if (pgtable)
+ pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
atomic_long_inc(&mm->nr_ptes);
return true;
@@ -1176,13 +1177,15 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
spinlock_t *dst_ptl, *src_ptl;
struct page *src_page;
pmd_t pmd;
- pgtable_t pgtable;
+ pgtable_t pgtable = NULL;
int ret;
- ret = -ENOMEM;
- pgtable = pte_alloc_one(dst_mm, addr);
- if (unlikely(!pgtable))
- goto out;
+ if (!vma_is_dax(vma)) {
+ ret = -ENOMEM;
+ 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);
@@ -1213,7 +1216,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
goto out_unlock;
}
- if (pmd_trans_huge(pmd)) {
+ 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);
--
2.7.0.rc3
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