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-manipul... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-grab-the-lock-before-manipul...

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------------------------------------------------------ From: Wei Yang richardw.yang@linux.intel.com 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@linux.intel.co... Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") Signed-off-by: Wei Yang richardw.yang@linux.intel.com Acked-by: David Rientjes rientjes@google.com Acked-by: Michal Hocko mhocko@suse.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: stable@vger.kernel.org [5.4+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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@linux.intel.com are

mm-thp-grab-the-lock-before-manipulation-defer-list.patch mm-remove-dead-code-totalram_pages_set.patch