ksm: cond_resched in unstable tree

KSM needs a cond_resched() for CONFIG_PREEMPT_NONE, in its unbounded
search of the unstable tree.  The stable tree cases already have one,
and originally there was one down inside get_user_pages();
but I missed it when I converted to follow_page() instead.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index bef1af4f77e3..5575f8628fef 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1012,6 +1012,7 @@ static struct rmap_item *unstable_tree_search_insert(struct page *page,
                 struct rmap_item *tree_rmap_item;
                 int ret;
 
+                cond_resched();
                 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
                 page2[0] = get_mergeable_page(tree_rmap_item);
                 if (!page2[0])