From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935800AbdJRHyJ (ORCPT ); Wed, 18 Oct 2017 03:54:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:54323 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932533AbdJRHyH (ORCPT ); Wed, 18 Oct 2017 03:54:07 -0400 Subject: Re: [PATCH] mm/mempolicy: add node_empty check in SYSC_migrate_pages To: Yisheng Xie , akpm@linux-foundation.org, mhocko@suse.com, mingo@kernel.org, rientjes@google.com, n-horiguchi@ah.jp.nec.com, salls@cs.ucsb.edu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, will.deacon@arm.com, tanxiaojun@huawei.com, Linux API References: <1508290660-60619-1-git-send-email-xieyisheng1@huawei.com> From: Vlastimil Babka Message-ID: <7086c6ea-b721-684e-fe3d-ff59ae1d78ed@suse.cz> Date: Wed, 18 Oct 2017 09:54:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1508290660-60619-1-git-send-email-xieyisheng1@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +CC linux-api On 10/18/2017 03:37 AM, Yisheng Xie wrote: > As Xiaojun reported the ltp of migrate_pages01 will failed on ARCH arm64 > system whoes has 4 nodes[0...3], all have memory and CONFIG_NODES_SHIFT=2: > > migrate_pages01 0 TINFO : test_invalid_nodes > migrate_pages01 14 TFAIL : migrate_pages_common.c:45: unexpected failure - returned value = 0, expected: -1 > migrate_pages01 15 TFAIL : migrate_pages_common.c:55: call succeeded unexpectedly > > In this case the test_invalid_nodes of migrate_pages01 will call: > SYSC_migrate_pages as: > > migrate_pages(0, , {0x0000000000000001}, 64, , {0x0000000000000010}, 64) = 0 is 64 here the maxnode parameter of migrate_pages() ? > For MAX_NUMNODES is 4, so 0x10 nodemask will tread as empty set which makes > nodes_subset(*new, node_states[N_MEMORY]) According to manpage of migrate_pages: EINVAL The value specified by maxnode exceeds a kernel-imposed limit. Or, old_nodes or new_nodes specifies one or more node IDs that are greater than the maximum supported node ID. Or, none of the node IDs specified by new_nodes are on-line and allowed by the process's current cpuset context, or none of the specified nodes contain memory. if maxnode parameter is 64, but MAX_NUMNODES ("kernel-imposed limit") is 4, we should get EINVAL just because of that. I don't see such check in the migrate_pages implementation though. But then at least the "new_nodes specifies one or more node IDs that are greater than the maximum supported node ID" part should trigger here, because you have node number 8 set in the new_nodes nodemask, right? get_nodes() should be checking this according to comment: /* When the user specified more nodes than supported just check if the non supported part is all zero. */ Somehow that doesn't seem to work then? I think we should look into this. Your patch may still be needed, or not, after that is resolved. > return true, as empty set is subset of any set. > > So this is a common issue which also can happens in X86_64 system eg. 8 nodes[0..7], > all with memory and CONFIG_NODES_SHIFT=3. Fix it by adding node_empty check in > SYSC_migrate_pages. > > Reported-by: Tan Xiaojun > Signed-off-by: Yisheng Xie > --- > mm/mempolicy.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index a2af6d5..1dfd3cc 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1388,6 +1388,11 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode, > if (err) > goto out; > > + if (nodes_empty(*new)) { > + err = -EINVAL; > + goto out; > + } > + > /* Find the mm_struct */ > rcu_read_lock(); > task = pid ? find_task_by_vpid(pid) : current; >