The patch titled Subject: mm: thp: grab the lock before manipulating defer list has been removed from the -mm tree. Its filename was mm-thp-grab-the-lock-before-manipulation-defer-list.patch

This patch was dropped because an updated version will be merged

------------------------------------------------------ From: Wei Yang richardw.yang@linux.intel.com Subject: mm: thp: grab the lock before manipulating defer list

As all the other places, we grab the lock before manipulate the defer list. Current implementation may face a race condition.

For example, the potential race would be:

CPU1 CPU2 mem_cgroup_move_account deferred_split_huge_page list_empty lock list_empty list_add_tail unlock lock # list_empty might not hold anymore list_add_tail unlock

When this sequence happens, the list_add_tail() in mem_cgroup_move_account() corrupt the list since which is already been added to some split_queue in split_huge_page_to_list().

Besides this, David Rientjes points out the split_queue_len would be in a wrong state, which would be a significant issue for shrinkers.

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 Cc: David Rientjes rientjes@google.com Cc: Michal Hocko mhocko@suse.com Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.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-remove-the-defer-list-related-code-since-this-will-not-happen.patch mm-gupc-use-is_vm_hugetlb_page-to-check-whether-to-follow-huge.patch mm-huge_memoryc-use-head-to-check-huge-zero-page.patch mm-huge_memoryc-use-head-to-emphasize-the-purpose-of-page.patch mm-huge_memoryc-reduce-critical-section-protected-by-split_queue_lock.patch mm-remove-dead-code-totalram_pages_set.patch