From: Wei Yang richardw.yang@linux.intel.com Subject: mm: thp: don't need care deferred split queue in memcg charge move path

If compound is true, this means it is a PMD mapped THP. Which implies the page is not linked to any defer list. So the first code chunk will not be executed.

Also with this reason, it would not be proper to add this page to a defer list. So the second code chunk is not correct.

Based on this, we should remove the defer list related code.

[yang.shi@linux.alibaba.com: better patch title] Link: http://lkml.kernel.org/r/20200117233836.3434-1-richardw.yang@linux.intel.com Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") Signed-off-by: Wei Yang richardw.yang@linux.intel.com Suggested-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Acked-by: Yang Shi yang.shi@linux.alibaba.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, 18 deletions(-)

--- a/mm/memcontrol.c~mm-thp-remove-the-defer-list-related-code-since-this-will-not-happen +++ a/mm/memcontrol.c @@ -5340,14 +5340,6 @@ static int mem_cgroup_move_account(struc __mod_lruvec_state(to_vec, NR_WRITEBACK, nr_pages); }

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (compound && !list_empty(page_deferred_list(page))) { - spin_lock(&from->deferred_split_queue.split_queue_lock); - list_del_init(page_deferred_list(page)); - from->deferred_split_queue.split_queue_len--; - spin_unlock(&from->deferred_split_queue.split_queue_lock); - } -#endif /* * It is safe to change page->mem_cgroup here because the page * is referenced, charged, and isolated - we can't race with @@ -5357,16 +5349,6 @@ static int mem_cgroup_move_account(struc /* caller should have done css_get */ page->mem_cgroup = to;

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (compound && list_empty(page_deferred_list(page))) { - 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++; - spin_unlock(&to->deferred_split_queue.split_queue_lock); - } -#endif - spin_unlock_irqrestore(&from->move_lock, flags);

ret = 0; _