linux-kernel - Re: [PATCH v7 1/5] mm/mempolicy: Add MPOL_PREFERRED

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Message-ID: <YQ041Djm5GzjU3WR@dhcp22.suse.cz>
Date:   Fri, 6 Aug 2021 15:27:48 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Feng Tang <feng.tang@...el.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andi Kleen <ak@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>, ying.huang@...el.com,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v7 1/5] mm/mempolicy: Add MPOL_PREFERRED_MANY for
 multiple preferred nodes

On Tue 03-08-21 13:59:18, Feng Tang wrote:
[...]
> @@ -1936,7 +1969,9 @@ unsigned int mempolicy_slab_node(void)
>  	case MPOL_INTERLEAVE:
>  		return interleave_nodes(policy);
>  
> -	case MPOL_BIND: {
> +	case MPOL_BIND:
> +	case MPOL_PREFERRED_MANY:
> +	{
>  		struct zoneref *z;

I guess this is ok for now but it would be great if slab maintainers
could have a look here. I suspect this will need some more changes. E.g.
I find it highly suspicious how fallback_alloc uses mempolicy_slab_node.
Let's say that the local node is not a part of the nodemask.
mempolicy_slab_node will switch to the first node in the order list
which is ok but fallback_alloc then iterates over the whole zonelist
without any policy node mask constrains. get_any_partial looks very
similar.


-- 
Michal Hocko
SUSE Labs