From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yisheng Xie Subject: Re: [PATCH] mm/mempolicy: add node_empty check in SYSC_migrate_pages Date: Wed, 18 Oct 2017 17:34:15 +0800 Message-ID: <20aac66a-7252-947c-355b-6da4be671dcf@huawei.com> References: <1508290660-60619-1-git-send-email-xieyisheng1@huawei.com> <7086c6ea-b721-684e-fe3d-ff59ae1d78ed@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <7086c6ea-b721-684e-fe3d-ff59ae1d78ed-AlSwsSmVLrQ@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Vlastimil Babka , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, mhocko-IBi9RG/b67k@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, n-horiguchi-PaJj6Psr51x8UrSeD/g0lQ@public.gmane.org, salls-b3bnyZ7c9ISVc3sceRu5cw@public.gmane.org Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, tanxiaojun-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, Linux API List-Id: linux-api@vger.kernel.org Hi Vlastimil, Thanks for your comment! On 2017/10/18 15:54, Vlastimil Babka wrote: > +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() ? Yes, I have print it in the kernel. > >> 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. Yes, that is what manpage said, but I have a question about this: if user set maxnode exceeds a kernel-imposed and try to access node without enough privilege, which errors values we should return ? For I have seen that all of the ltp migrate_pages01 will set maxnode to 64 in my system. > 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. OK, I will check why get_nodes do not works as it comments. Thanks Yisheng Xie > >> 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; >> > > > . >