mm: thp: don't need care deferred split queue in memcg charge move path

commit fac0516b5534897bf4c4a88daa06a8cfa5611b23 upstream

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: NWei Yang <richardw.yang@linux.intel.com>
Suggested-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NYang 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
[Fixed conflicts with our 4.19 kernel]
Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

mm/memcontrol.c

@@ -5601,7 +5601,6 @@ static int mem_cgroup_move_account(struct page *page,
 	unsigned int nr_pages = compound ? hpage_nr_pages(page) : 1;
 	int ret;
 	bool anon;
-	struct deferred_split *ds_queue;
 	int nid = page_to_nid(page);
 
 	VM_BUG_ON(from == to);
@@ -5648,15 +5647,6 @@ static int mem_cgroup_move_account(struct page *page,
 		__mod_memcg_state(to, NR_WRITEBACK, nr_pages);
 	}
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (compound && !list_empty(page_deferred_list(page))) {
-		ds_queue = &from->nodeinfo[nid]->deferred_split_queue;
-		spin_lock(&ds_queue->split_queue_lock);
-		list_del_init(page_deferred_list(page));
-		ds_queue->split_queue_len--;
-		spin_unlock(&ds_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
@@ -5666,17 +5656,6 @@ static int mem_cgroup_move_account(struct page *page,
 	/* caller should have done css_get */
 	page->mem_cgroup = to;
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (compound && list_empty(page_deferred_list(page))) {
-		ds_queue = &to->nodeinfo[nid]->deferred_split_queue;
-		spin_lock(&ds_queue->split_queue_lock);
-		list_add_tail(page_deferred_list(page),
-			      &ds_queue->split_queue);
-		ds_queue->split_queue_len++;
-		spin_unlock(&ds_queue->split_queue_lock);
-	}
-#endif
-
 	spin_unlock_irqrestore(&from->move_lock, flags);
 
 	ret = 0;