linux-hardening - [RFC PATCH v2 02/19] list: Support list head not in object for list

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Message-Id: <20210830235927.6443-3-rick.p.edgecombe@intel.com>
Date:   Mon, 30 Aug 2021 16:59:10 -0700
From:   Rick Edgecombe <rick.p.edgecombe@...el.com>
To:     dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org,
        x86@...nel.org, akpm@...ux-foundation.org, keescook@...omium.org,
        shakeelb@...gle.com, vbabka@...e.cz, rppt@...nel.org
Cc:     Rick Edgecombe <rick.p.edgecombe@...el.com>, linux-mm@...ck.org,
        linux-hardening@...r.kernel.org,
        kernel-hardening@...ts.openwall.com, ira.weiny@...el.com,
        dan.j.williams@...el.com, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2 02/19] list: Support list head not in object for list_lru

In future patches, there will be a need to keep track of objects with
list_lru where the list_head is not in the object (will be in struct
page). Since list_lru automatically determines the node id from the
list_head, this will fail when using struct page.

So create a new function in list_lru, list_lru_add_node(), that allows
the node id of the item to be passed in. Otherwise it behaves exactly
like list_lru_add().

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
 include/linux/list_lru.h | 13 +++++++++++++
 mm/list_lru.c            | 10 ++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 08e07c19fd13..42c22322058b 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -90,6 +90,19 @@ void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg);
  */
 bool list_lru_add(struct list_lru *lru, struct list_head *item);
 
+/**
+ * list_lru_add_node: add an element to the lru list's tail
+ * @list_lru: the lru pointer
+ * @item: the item to be added.
+ * @nid: the node id of the item
+ *
+ * Like list_lru_add, but takes the node id as parameter instead of
+ * calculating it from the list_head passed in.
+ *
+ * Return value: true if the list was updated, false otherwise
+ */
+bool list_lru_add_node(struct list_lru *lru, struct list_head *item, int nid);
+
 /**
  * list_lru_del: delete an element to the lru list
  * @list_lru: the lru pointer
diff --git a/mm/list_lru.c b/mm/list_lru.c
index c1bec58168e1..f35f11ada8a1 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -112,9 +112,8 @@ list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
-bool list_lru_add(struct list_lru *lru, struct list_head *item)
+bool list_lru_add_node(struct list_lru *lru, struct list_head *item, int nid)
 {
-	int nid = page_to_nid(virt_to_page(item));
 	struct list_lru_node *nlru = &lru->node[nid];
 	struct mem_cgroup *memcg;
 	struct list_lru_one *l;
@@ -134,6 +133,13 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
 	spin_unlock(&nlru->lock);
 	return false;
 }
+
+bool list_lru_add(struct list_lru *lru, struct list_head *item)
+{
+	int nid = page_to_nid(virt_to_page(item));
+
+	return list_lru_add_node(lru, item, nid);
+}
 EXPORT_SYMBOL_GPL(list_lru_add);
 
 bool list_lru_del(struct list_lru *lru, struct list_head *item)
-- 
2.17.1