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    SubjectRe: [PATCH] mm/alloc: fallback to first node if the wanted node offline
    On Tue, Dec 4, 2018 at 3:16 PM Pingfan Liu <kernelfans@gmail.com> wrote:
    >
    > On Tue, Dec 4, 2018 at 11:53 AM David Rientjes <rientjes@google.com> wrote:
    > >
    > > On Tue, 4 Dec 2018, Pingfan Liu wrote:
    > >
    > > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
    > > > index 76f8db0..8324953 100644
    > > > --- a/include/linux/gfp.h
    > > > +++ b/include/linux/gfp.h
    > > > @@ -453,6 +453,8 @@ static inline int gfp_zonelist(gfp_t flags)
    > > > */
    > > > static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
    > > > {
    > > > + if (unlikely(!node_online(nid)))
    > > > + nid = first_online_node;
    > > > return NODE_DATA(nid)->node_zonelists + gfp_zonelist(flags);
    > > > }
    > > >
    > >
    > > So we're passing the node id from dev_to_node() to kmalloc which
    > > interprets that as the preferred node and then does node_zonelist() to
    > > find the zonelist at allocation time.
    > >
    > > What happens if we fix this in alloc_dr()? Does anything else cause
    > > problems?
    > >
    > I think it is better to fix it mm, since it can protect any new
    > similar bug in future. While fixing in alloc_dr() just work at present
    >
    > > And rather than using first_online_node, would next_online_node() work?
    > >
    > What is the gain? Is it for memory pressure on node0?
    >
    Maybe I got your point now. Do you try to give a cheap assumption on
    nearest neigh of this node?

    Thanks,
    Pingfan

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