From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Now unstable_tree_search_insert() will return NULL if encounter a stale
tree_rmap_item, in which case get_mergeable_page() return NULL.
More reasonable handling is to remove stale rmap_item out of unstable
tree and re-search from root. That stale rmap_item will be reclaimed
when next time of scan.
So we can insert our rmap_item successfully instead of returning NULL.
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
---
mm/ksm.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index e1034bf1c937..66219983eb3a 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2196,12 +2196,14 @@ struct ksm_rmap_item *unstable_tree_search_insert(struct ksm_rmap_item *rmap_ite
{
struct rb_node **new;
struct rb_root *root;
- struct rb_node *parent = NULL;
+ struct rb_node *parent;
int nid;
nid = get_kpfn_nid(page_to_pfn(page));
root = root_unstable_tree + nid;
+again:
new = &root->rb_node;
+ parent = NULL;
while (*new) {
struct ksm_rmap_item *tree_rmap_item;
@@ -2211,8 +2213,10 @@ struct ksm_rmap_item *unstable_tree_search_insert(struct ksm_rmap_item *rmap_ite
cond_resched();
tree_rmap_item = rb_entry(*new, struct ksm_rmap_item, node);
tree_page = get_mergeable_page(tree_rmap_item);
- if (!tree_page)
- return NULL;
+ if (!tree_page) {
+ remove_rmap_item_from_tree(tree_rmap_item);
+ goto again;
+ }
/*
* Don't substitute a ksm page for a forked page.
--
2.45.0
