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Subject[PATCH v4 3/4] mm/khugepaged: unify collapse pmd clear, flush and free
Date
Unify the code that flushes, clears pmd entry, and frees the PTE table
level into a new function collapse_and_free_pmd().

This clean-up is useful as in the next patch we will add another call to
this function to iterate through PTE prior to freeing the level for page
table check.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: David Rientjes <rientjes@google.com>
---
mm/khugepaged.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 35f14d0a00a6..30e59e4af272 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1416,6 +1416,19 @@ static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
return 0;
}

+static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr, pmd_t *pmdp)
+{
+ spinlock_t *ptl;
+ pmd_t pmd;
+
+ ptl = pmd_lock(vma->vm_mm, pmdp);
+ pmd = pmdp_collapse_flush(vma, addr, pmdp);
+ spin_unlock(ptl);
+ mm_dec_nr_ptes(mm);
+ pte_free(mm, pmd_pgtable(pmd));
+}
+
/**
* collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at
* address haddr.
@@ -1433,7 +1446,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
struct vm_area_struct *vma = find_vma(mm, haddr);
struct page *hpage;
pte_t *start_pte, *pte;
- pmd_t *pmd, _pmd;
+ pmd_t *pmd;
spinlock_t *ptl;
int count = 0;
int i;
@@ -1509,12 +1522,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
}

/* step 4: collapse pmd */
- ptl = pmd_lock(vma->vm_mm, pmd);
- _pmd = pmdp_collapse_flush(vma, haddr, pmd);
- spin_unlock(ptl);
- mm_dec_nr_ptes(mm);
- pte_free(mm, pmd_pgtable(_pmd));
-
+ collapse_and_free_pmd(mm, vma, haddr, pmd);
drop_hpage:
unlock_page(hpage);
put_page(hpage);
@@ -1552,7 +1560,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
struct vm_area_struct *vma;
struct mm_struct *mm;
unsigned long addr;
- pmd_t *pmd, _pmd;
+ pmd_t *pmd;

i_mmap_lock_write(mapping);
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
@@ -1591,14 +1599,8 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
* reverse order. Trylock is a way to avoid deadlock.
*/
if (mmap_write_trylock(mm)) {
- if (!khugepaged_test_exit(mm)) {
- spinlock_t *ptl = pmd_lock(mm, pmd);
- /* assume page table is clear */
- _pmd = pmdp_collapse_flush(vma, addr, pmd);
- spin_unlock(ptl);
- mm_dec_nr_ptes(mm);
- pte_free(mm, pmd_pgtable(_pmd));
- }
+ if (!khugepaged_test_exit(mm))
+ collapse_and_free_pmd(mm, vma, addr, pmd);
mmap_write_unlock(mm);
} else {
/* Try again later */
--
2.35.0.rc0.227.g00780c9af4-goog
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