[v3 PATCH 4/7] mm: khugepaged: use transhuge_vma_suitable replace open-code

[Yang Shi <shy828301@gmail.com>]

The hugepage_vma_revalidate() needs to check if the address is still in
the aligned HPAGE_PMD_SIZE area of the vma when reacquiring mmap_lock,
but it was open-coded, use transhuge_vma_suitable() to do the job.  And
add proper comments for transhuge_vma_suitable().

Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 include/linux/huge_mm.h | 6 ++++++
 mm/khugepaged.c         | 5 +----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a8f61db47f2a..79d5919beb83 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -128,6 +128,12 @@ static inline bool transhuge_vma_size_ok(struct vm_area_struct *vma)
 	return false;
 }
 
+/*
+ * Do the below checks:
+ *   - For non-anon vma, check if the vm_pgoff is HPAGE_PMD_NR aligned.
+ *   - For all vmas, check if the haddr is in an aligned HPAGE_PMD_SIZE
+ *     area.
+ */
 static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
 		unsigned long addr)
 {
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 7a5d1c1a1833..ca1754d3a827 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -951,7 +951,6 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
 		struct vm_area_struct **vmap)
 {
 	struct vm_area_struct *vma;
-	unsigned long hstart, hend;
 
 	if (unlikely(khugepaged_test_exit(mm)))
 		return SCAN_ANY_PROCESS;
@@ -960,9 +959,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
 	if (!vma)
 		return SCAN_VMA_NULL;
 
-	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
-	hend = vma->vm_end & HPAGE_PMD_MASK;
-	if (address < hstart || address + HPAGE_PMD_SIZE > hend)
+	if (!transhuge_vma_suitable(vma, address))
 		return SCAN_ADDRESS_RANGE;
 	if (!hugepage_vma_check(vma, vma->vm_flags))
 		return SCAN_VMA_CHECK;
-- 
2.26.3