mlocked_vma_newpage() is only called in fault path by
page_add_new_anon_rmap(), which is called on a *new* page.
And such page is initially only visible via the pagetables, and the
pte is locked while calling page_add_new_anon_rmap(), so we need not
use an irq-safe mod_zone_page_state() here, using a light-weight version
__mod_zone_page_state() would be OK.
And as suggested by Andrew, to reduce the risks that new call sites
incorrectly using mlocked_vma_newpage() without knowing they are adding
racing, this patch also moves it from internal.h to right before its only
call site page_add_new_anon_rmap() in rmap.c, with detailed document added.
Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jianyu Zhan <nasa4836@xxxxxxxxx>
---
mm/internal.h | 22 ++--------------------
mm/rmap.c | 24 ++++++++++++++++++++++++
2 files changed, 26 insertions(+), 20 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 07b6736..20abafb 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -183,26 +183,8 @@ static inline void munlock_vma_pages_all(struct vm_area_struct *vma)
munlock_vma_pages_range(vma, vma->vm_start, vma->vm_end);
}
-/*
- * Called only in fault path, to determine if a new page is being
- * mapped into a LOCKED vma. If it is, mark page as mlocked.
- */
-static inline int mlocked_vma_newpage(struct vm_area_struct *vma,
- struct page *page)
-{
- VM_BUG_ON_PAGE(PageLRU(page), page);
-
- if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
- return 0;
-
- if (!TestSetPageMlocked(page)) {
- mod_zone_page_state(page_zone(page), NR_MLOCK,
- hpage_nr_pages(page));
- count_vm_event(UNEVICTABLE_PGMLOCKED);
- }
- return 1;
-}
-
+extern int mlocked_vma_newpage(struct vm_area_struct *vma,
+ struct page *page);
/*
* must be called with vma's mmap_sem held for read or write, and page locked.
*/
diff --git a/mm/rmap.c b/mm/rmap.c
index 6078a30..a9d02ef 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1005,6 +1005,30 @@ void do_page_add_anon_rmap(struct page *page,
__page_check_anon_rmap(page, vma, address);
}
+/*
+ * Called only in fault path, to determine if a new page is being
+ * mapped into a LOCKED vma. If it is, mark page as mlocked.
+ * This function is only called in fault path by
+ * page_add_new_anon_rmap(), which is called on a *new* page.
+ * And such page is initially only visible via the pagetables, and the
+ * pte is locked while calling page_add_new_anon_rmap(), so using a
+ * light-weight version __mod_zone_page_state() would be OK.
+ */
+int mlocked_vma_newpage(struct vm_area_struct *vma,
+ struct page *page)
+{
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
+ return 0;
+
+ if (!TestSetPageMlocked(page)) {
+ __mod_zone_page_state(page_zone(page), NR_MLOCK,
+ hpage_nr_pages(page));
+ count_vm_event(UNEVICTABLE_PGMLOCKED);
+ }
+ return 1;
+}
+
/**
* page_add_new_anon_rmap - add pte mapping to a new anonymous page
* @page: the page to add the mapping to
--
2.0.0-rc1
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