--- /dev/null
+From zhongjiang@huawei.com Tue Nov 19 05:55:06 2019
+From: zhong jiang <zhongjiang@huawei.com>
+Date: Mon, 18 Nov 2019 11:26:07 +0800
+Subject: memfd: Use radix_tree_deref_slot_protected to avoid the warning.
+To: <sashal@kernel.org>, <gregkh@linuxfoundation.org>, <stable@vger.kernel.org>, <willy@infradead.org>
+Cc: <linux-mm@kvack.org>, <yangyingliang@huawei.com>
+Message-ID: <20191118032610.182862-1-zhongjiang@huawei.com>
+
+From: zhong jiang <zhongjiang@huawei.com>
+
+The commit 391d4ee568b5 ("memfd: Fix locking when tagging pins")
+introduces the following warning messages.
+
+*WARNING: suspicious RCU usage in memfd_wait_for_pins*
+
+It is because we still use radix_tree_deref_slot without read_rcu_lock.
+We should use radix_tree_deref_slot_protected instead in the case.
+
+Cc: stable@vger.kernel.org
+Fixes: 391d4ee568b5 ("memfd: Fix locking when tagging pins")
+Signed-off-by: zhong jiang <zhongjiang@huawei.com>
+Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ mm/shmem.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/mm/shmem.c
++++ b/mm/shmem.c
+@@ -2664,7 +2664,7 @@ static void shmem_tag_pins(struct addres
+
+ spin_lock_irq(&mapping->tree_lock);
+ radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
+- page = radix_tree_deref_slot(slot);
++ page = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
+ if (!page || radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);