[v2 PATCH 7/8] mm: khugepaged: introduce khugepaged_enter_file() helper

[Yang Shi <shy828301@gmail.com>]

The following patch will have filesystems code call khugepaged_enter()
to make readonly FS THP collapse more consistent.  Extract the current
implementation used by shmem in khugepaged_enter_file() helper so that
it could be reused by other filesystems and export the symbol for
modules.

Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 include/linux/khugepaged.h |  6 ++++++
 mm/khugepaged.c            | 11 +++++++++++
 mm/shmem.c                 | 14 ++++----------
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index 54e169116d49..06464e9a1f91 100644
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -21,6 +21,8 @@ extern void khugepaged_fork(struct mm_struct *mm,
 extern void khugepaged_exit(struct mm_struct *mm);
 extern void khugepaged_enter(struct vm_area_struct *vma,
 			     unsigned long vm_flags);
+extern void khugepaged_enter_file(struct vm_area_struct *vma,
+				  unsigned long vm_flags);
 
 extern void khugepaged_min_free_kbytes_update(void);
 #ifdef CONFIG_SHMEM
@@ -53,6 +55,10 @@ static inline void khugepaged_enter(struct vm_area_struct *vma,
 				    unsigned long vm_flags)
 {
 }
+static inline void khugepaged_enter_file(struct vm_area_struct *vma,
+					 unsigned long vm_flags)
+{
+}
 static inline void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
 					      unsigned long vm_flags)
 {
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4cb4379ecf25..93c9072983e2 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -577,6 +577,17 @@ void khugepaged_enter(struct vm_area_struct *vma, unsigned long vm_flags)
 			__khugepaged_enter(vma->vm_mm);
 }
 
+void khugepaged_enter_file(struct vm_area_struct *vma, unsigned long vm_flags)
+{
+	if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
+	    khugepaged_enabled() &&
+	    (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
+	     (vma->vm_end & HPAGE_PMD_MASK)))
+		if (hugepage_vma_check(vma, vm_flags))
+			__khugepaged_enter(vma->vm_mm);
+}
+EXPORT_SYMBOL_GPL(khugepaged_enter_file);
+
 static void release_pte_page(struct page *page)
 {
 	mod_node_page_state(page_pgdat(page),
diff --git a/mm/shmem.c b/mm/shmem.c
index a09b29ec2b45..c2346e5d2b24 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2233,11 +2233,9 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &shmem_vm_ops;
-	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
-			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
-			(vma->vm_end & HPAGE_PMD_MASK)) {
-		khugepaged_enter(vma, vma->vm_flags);
-	}
+
+	khugepaged_enter_file(vma, vma->vm_flags);
+
 	return 0;
 }
 
@@ -4132,11 +4130,7 @@ int shmem_zero_setup(struct vm_area_struct *vma)
 	vma->vm_file = file;
 	vma->vm_ops = &shmem_vm_ops;
 
-	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
-			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
-			(vma->vm_end & HPAGE_PMD_MASK)) {
-		khugepaged_enter(vma, vma->vm_flags);
-	}
+	khugepaged_enter_file(vma, vma->vm_flags);
 
 	return 0;
 }
-- 
2.26.3