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From ea0c9d768bade0bc87046841a3e667f477d90668 Mon Sep 17 00:00:00 2001
From: Oleksandr Natalenko <oleksandr@natalenko.name>
Date: Mon, 6 May 2019 22:02:49 +0200
Subject: [PATCH] uksm-5.1: apply 52d1e606ee733
Signed-off-by: Oleksandr Natalenko <oleksandr@natalenko.name>
---
mm/uksm.c | 36 +++++++++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 5 deletions(-)
diff --git a/mm/uksm.c b/mm/uksm.c
index 174e1921eade..2531599038b8 100644
--- a/mm/uksm.c
+++ b/mm/uksm.c
@@ -875,8 +875,8 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node,
* to keep the page_count protocol described with page_cache_get_speculative.
*
* Note: it is possible that get_uksm_page() will return NULL one moment,
- * then page the next, if the page is in between page_freeze_refs() and
- * page_unfreeze_refs(): this shouldn't be a problem anywhere, the page
+ * then page the next, if the page is in between page_ref_freeze() and
+ * page_ref_unfreeze(): this shouldn't be a problem anywhere, the page
* is on its way to being freed; but it is an anomaly to bear in mind.
*
* @unlink_rb: if the removal of this node will firstly unlink from
@@ -914,10 +914,11 @@ static struct page *get_uksm_page(struct stable_node *stable_node,
* We cannot do anything with the page while its refcount is 0.
* Usually 0 means free, or tail of a higher-order page: in which
* case this node is no longer referenced, and should be freed;
- * however, it might mean that the page is under page_freeze_refs().
+ * however, it might mean that the page is under page_ref_freeze().
* The __remove_mapping() case is easy, again the node is now stale;
- * but if page is swapcache in migrate_page_move_mapping(), it might
- * still be our page, in which case it's essential to keep the node.
+ * the same is in reuse_ksm_page() case; but if page is swapcache
+ * in migrate_page_move_mapping(), it might still be our page,
+ * in which case it's essential to keep the node.
*/
while (!get_page_unless_zero(page)) {
/*
@@ -4749,6 +4750,31 @@ void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
goto again;
}
+bool reuse_ksm_page(struct page *page,
+ struct vm_area_struct *vma,
+ unsigned long address)
+{
+#ifdef CONFIG_DEBUG_VM
+ if (WARN_ON(is_zero_pfn(page_to_pfn(page))) ||
+ WARN_ON(!page_mapped(page)) ||
+ WARN_ON(!PageLocked(page))) {
+ dump_page(page, "reuse_ksm_page");
+ return false;
+ }
+#endif
+
+ if (PageSwapCache(page) || !page_stable_node(page))
+ return false;
+ /* Prohibit parallel get_ksm_page() */
+ if (!page_ref_freeze(page, 1))
+ return false;
+
+ page_move_anon_rmap(page, vma);
+ page->index = linear_page_index(vma, address);
+ page_ref_unfreeze(page, 1);
+
+ return true;
+}
#ifdef CONFIG_MIGRATION
/* Common ksm interface but may be specific to uksm */
void ksm_migrate_page(struct page *newpage, struct page *oldpage)
--
2.21.0.777.g83232e3864
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