[PATCH] ksm: set anon_vma of first rmap_item of ksm page to page's anon_vma other than vma's anon_vma
From: zhouxianrong
Date: Thu Jun 23 2016 - 09:37:12 EST
From: z00281421 <z00281421@xxxxxxxxxxxxxxxxxxxx>
set anon_vma of first rmap_item of ksm page to page's anon_vma
other than vma's anon_vma so that we can lookup all the forked
vma of kpage via reserve map. thus we can try_to_unmap ksm page
completely and reclaim or migrate the ksm page successfully and
need not to merg other forked vma addresses of ksm page with
building a rmap_item for it ever after.
a forked more mapcount ksm page with partially merged vma addresses and
a ksm page mapped into non-VM_MERGEABLE vma due to setting MADV_MERGEABLE
on one of the forked vma can be unmapped completely by try_to_unmap.
Signed-off-by: z00281421 <z00281421@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index 4786b41..6bacc08 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -971,11 +971,13 @@ out:
* @page: the PageAnon page that we want to replace with kpage
* @kpage: the PageKsm page that we want to map instead of page,
* or NULL the first time when we want to use page as kpage.
+ * @anon_vma: output the anon_vma of page used as kpage
*
* This function returns 0 if the pages were merged, -EFAULT otherwise.
*/
static int try_to_merge_one_page(struct vm_area_struct *vma,
- struct page *page, struct page *kpage)
+ struct page *page, struct page *kpage,
+ struct anon_vma **anon_vma)
{
pte_t orig_pte = __pte(0);
int err = -EFAULT;
@@ -1015,6 +1017,8 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
* PageAnon+anon_vma to PageKsm+NULL stable_node:
* stable_tree_insert() will update stable_node.
*/
+ if (anon_vma != NULL)
+ *anon_vma = page_anon_vma(page);
set_page_stable_node(page, NULL);
mark_page_accessed(page);
/*
@@ -1055,6 +1059,7 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
{
struct mm_struct *mm = rmap_item->mm;
struct vm_area_struct *vma;
+ struct anon_vma *anon_vma = NULL;
int err = -EFAULT;
down_read(&mm->mmap_sem);
@@ -1062,7 +1067,7 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
if (!vma)
goto out;
- err = try_to_merge_one_page(vma, page, kpage);
+ err = try_to_merge_one_page(vma, page, kpage, &anon_vma);
if (err)
goto out;
@@ -1070,7 +1075,10 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
remove_rmap_item_from_tree(rmap_item);
/* Must get reference to anon_vma while still holding mmap_sem */
- rmap_item->anon_vma = vma->anon_vma;
+ if (anon_vma != NULL)
+ rmap_item->anon_vma = anon_vma;
+ else
+ rmap_item->anon_vma = vma->anon_vma;
get_anon_vma(vma->anon_vma);
out:
up_read(&mm->mmap_sem);
@@ -1435,6 +1443,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
remove_rmap_item_from_tree(rmap_item);
+ if (kpage == page) {
+ put_page(kpage);
+ return;
+ }
+
if (kpage) {
err = try_to_merge_with_ksm_page(rmap_item, page, kpage);
if (!err) {
--
1.7.9.5