Re: [patch 04/15] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

[Vlastimil Babka <vbabka@suse.cz>]

On 11/30/2017 11:15 PM, akpm@linux-foundation.org wrote:
> From: Yisheng Xie <xieyisheng1@huawei.com>
> Subject: mm/mempolicy: add nodes_empty check in SYSC_migrate_pages
> 
> As in manpage of migrate_pages, the errno should be set to EINVAL when
> 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.  However, when test by following case:
> 
> 	new_nodes = 0;
> 	old_nodes = 0xf;
> 	ret = migrate_pages(pid, old_nodes, new_nodes, MAX);
> 
> The ret will be 0 and no errno is set.  As the new_nodes is empty, we
> should expect EINVAL as documented.
> 
> To fix the case like above, this patch check whether target nodes AND
> current task_nodes is empty, and then check whether AND
> node_states[N_MEMORY] is empty.
> 
> Link: http://lkml.kernel.org/r/1510882624-44342-4-git-send-email-xieyisheng1@huawei.com
> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Chris Salls <salls@cs.ucsb.edu>
> Cc: Christopher Lameter <cl@linux.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Tan Xiaojun <tanxiaojun@huawei.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

My previous concerns here were a mistake as I explained in my reply to
v4. So you can add

Acked-by: Vlastimil Babka <vbabka@suse.cz>

and proceed with the series. Thanks.

> ---
> 
>  mm/mempolicy.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff -puN mm/mempolicy.c~mm-mempolicy-add-nodes_empty-check-in-sysc_migrate_pages mm/mempolicy.c
> --- a/mm/mempolicy.c~mm-mempolicy-add-nodes_empty-check-in-sysc_migrate_pages
> +++ a/mm/mempolicy.c
> @@ -1433,10 +1433,14 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pi
>  		goto out_put;
>  	}
>  
> -	if (!nodes_subset(*new, node_states[N_MEMORY])) {
> -		err = -EINVAL;
> +	task_nodes = cpuset_mems_allowed(current);
> +	nodes_and(*new, *new, task_nodes);
> +	if (nodes_empty(*new))
> +		goto out_put;
> +
> +	nodes_and(*new, *new, node_states[N_MEMORY]);
> +	if (nodes_empty(*new))
>  		goto out_put;
> -	}
>  
>  	err = security_task_movememory(task);
>  	if (err)
> _
> 

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