[Devel] [PATCH RHEL7 COMMIT] mm/memcg: fix crashes on migrating THP

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-514.26.1.vz7.35.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-514.26.1.vz7.35.4
------>
commit a7140eca2d73e219e7fc51822c57f3a163b8eb4d
Author: Andrey Ryabinin <aryabinin at virtuozzo.com>
Date:   Mon Aug 14 20:28:22 2017 +0400

    mm/memcg: fix crashes on migrating THP
    
    memcg_numa_isolate_pages() calls list_del() inside list_for_each_entry()
    causing crashes. Use list_for_each_entry_safe() instead as it's safe
    against removal of list entries.
    
    https://jira.sw.ru/browse/PSBM-69999
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 mm/memcontrol.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2dd4833..97824e2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4925,7 +4925,7 @@ static long memcg_numa_isolate_pages(struct lruvec *lruvec, enum lru_list lru,
 {
 	struct list_head *src = &lruvec->lists[lru];
 	struct zone *zone = lruvec_zone(lruvec);
-	struct page *page;
+	struct page *page, *tmp;
 	long scanned = 0, taken = 0;
 
 	spin_lock_irq(&zone->lru_lock);
@@ -4955,7 +4955,7 @@ static long memcg_numa_isolate_pages(struct lruvec *lruvec, enum lru_list lru,
 	__mod_zone_page_state(zone, NR_ISOLATED_ANON + is_file_lru(lru), taken);
 	spin_unlock_irq(&zone->lru_lock);
 
-	list_for_each_entry(page, dst, lru) {
+	list_for_each_entry_safe(page, tmp, dst, lru) {
 		if (PageTransHuge(page) && split_huge_page_to_list(page, dst)) {
 			list_del(&page->lru);
 			mod_zone_page_state(zone, NR_ISOLATED_ANON,