The patch titled
Subject: mm: thp: grab the lock before manipulation defer list
has been added to the -mm tree. Its filename is
mm-thp-grab-the-lock-before-manipulation-defer-list.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-grab-the-lock-before-manipulation-defer-list.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-grab-the-lock-before-manipulation-defer-list.patch
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------------------------------------------------------
From: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Subject: mm: thp: grab the lock before manipulation defer list
As in all the other places, we grab the lock before manipulating the defer
list. Current implementation may face a race condition.
For example, the potential race would be:
CPU1 CPU2
mem_cgroup_move_account split_huge_page_to_list
!list_empty
lock
!list_empty
list_del
unlock
lock
# !list_empty might not hold anymore
list_del_init
unlock
When this sequence happens, the list_del_init() in
mem_cgroup_move_account() would crash if CONFIG_DEBUG_LIST since the page
is already been removed by list_del in split_huge_page_to_list().
Link: http://lkml.kernel.org/r/20200109143054.13203-1-richardw.yang@xxxxxxxxxxxxxxx
Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware")
Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.4+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
--- a/mm/memcontrol.c~mm-thp-grab-the-lock-before-manipulation-defer-list
+++ a/mm/memcontrol.c
@@ -5341,10 +5341,12 @@ static int mem_cgroup_move_account(struc
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- if (compound && !list_empty(page_deferred_list(page))) {
+ if (compound) {
spin_lock(&from->deferred_split_queue.split_queue_lock);
- list_del_init(page_deferred_list(page));
- from->deferred_split_queue.split_queue_len--;
+ if (!list_empty(page_deferred_list(page))) {
+ list_del_init(page_deferred_list(page));
+ from->deferred_split_queue.split_queue_len--;
+ }
spin_unlock(&from->deferred_split_queue.split_queue_lock);
}
#endif
@@ -5358,11 +5360,13 @@ static int mem_cgroup_move_account(struc
page->mem_cgroup = to;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- if (compound && list_empty(page_deferred_list(page))) {
+ if (compound) {
spin_lock(&to->deferred_split_queue.split_queue_lock);
- list_add_tail(page_deferred_list(page),
- &to->deferred_split_queue.split_queue);
- to->deferred_split_queue.split_queue_len++;
+ if (list_empty(page_deferred_list(page))) {
+ list_add_tail(page_deferred_list(page),
+ &to->deferred_split_queue.split_queue);
+ to->deferred_split_queue.split_queue_len++;
+ }
spin_unlock(&to->deferred_split_queue.split_queue_lock);
}
#endif
_
Patches currently in -mm which might be from richardw.yang@xxxxxxxxxxxxxxx are
mm-thp-grab-the-lock-before-manipulation-defer-list.patch
mm-remove-dead-code-totalram_pages_set.patch
