From: zhong jiang zhongjiang@huawei.com
The commit eb4058d8daf8 ("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: eb4058d8daf8 ("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 @@ -1862,7 +1862,7 @@ static void shmem_tag_pins(struct addres spin_lock_irq(&mapping->tree_lock); restart: 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)) goto restart;