Re: [PATCH 7/7] Add /proc/sys/vm/compact_node for the explicitcompaction of a node

From: Christoph Lameter
Date: Wed May 30 2007 - 00:14:35 EST


On Tue, 29 May 2007, Mel Gorman wrote:

> + if (nodeid < 0)
> + return -EINVAL;
> +
> + pgdat = NODE_DATA(nodeid);
> + if (!pgdat || pgdat->node_id != nodeid)
> + return -EINVAL;

You cannot pass an arbitrary number to node data since NODE_DATA may do a
simple array lookup.

Check for node < nr_node_ids first.

pgdat->node_id != nodeid? Sounds like something you should BUG() on.

IA64's NODE_DATA is

struct ia64_node_data {
short active_cpu_count;
short node;
struct pglist_data *pg_data_ptrs[MAX_NUMNODES];
};

/*
* Given a node id, return a pointer to the pg_data_t for the node.
*
* NODE_DATA - should be used in all code not related to system
* initialization. It uses pernode data structures to minimize
* offnode memory references. However, these structure are not
* present during boot. This macro can be used once cpu_init
* completes.
*/
#define NODE_DATA(nid) (local_node_data->pg_data_ptrs[nid])

x86_64 also does

#define NODE_DATA(nid) (node_data[nid])

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