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 <tanxiaojun@xxxxxxxxxx>
>> Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx>
>> ---
>> 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;
>>
>
>
> .
>
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