The patch titled
Subject: ksm: fix potential missing rmap_item for stable_node
has been removed from the -mm tree. Its filename was
ksm-fix-potential-missing-rmap_item-for-stable_node.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: ksm: fix potential missing rmap_item for stable_node
When removing rmap_item from stable tree, STABLE_FLAG of rmap_item is
cleared with head reserved. So the following scenario might happen: For
ksm page with rmap_item1:
cmp_and_merge_page
stable_node->head = &migrate_nodes;
remove_rmap_item_from_tree, but head still equal to stable_node;
try_to_merge_with_ksm_page failed;
return;
For the same ksm page with rmap_item2, stable node migration succeed this
time. The stable_node->head does not equal to migrate_nodes now. For ksm
page with rmap_item1 again:
cmp_and_merge_page
stable_node->head != &migrate_nodes && rmap_item->head == stable_node
return;
We would miss the rmap_item for stable_node and might result in failed
rmap_walk_ksm(). Fix this by set rmap_item->head to NULL when rmap_item
is removed from stable tree.
Link: https://lkml.kernel.org/r/20210330140228.45635-5-linmiaohe@xxxxxxxxxx
Fixes: 4146d2d673e8 ("ksm: make !merge_across_nodes migration safe")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/ksm.c~ksm-fix-potential-missing-rmap_item-for-stable_node
+++ a/mm/ksm.c
@@ -791,6 +791,7 @@ static void remove_rmap_item_from_tree(s
stable_node->rmap_hlist_len--;
put_anon_vma(rmap_item->anon_vma);
+ rmap_item->head = NULL;
rmap_item->address &= PAGE_MASK;
} else if (rmap_item->address & UNSTABLE_FLAG) {
_
Patches currently in -mm which might be from linmiaohe@xxxxxxxxxx are
