[Crash-utility] One more change for crash

[Dave Anderson]

Badari Pulavarty wrote:

> Hi Dave,
>
> I am playing with "crash" on my machine with it fails with
> CONFIG_SPARSE_MEM. It looks like "node_mem_map" doesn't
> exist for SPARSE_MEM :(
>
> crash: invalid structure member offset: pglist_data_node_mem_map
>        FILE: memory.c  LINE: 10053  FUNCTION: dump_memory_nodes()
>
> [./crash] error trace: 100afe98 => 100d12f4 => 100d01cc => 10142f64
>
>   10142f64: .OFFSET_verify+140
>   100d01cc: .dump_memory_nodes+520
>   100d12f4: .node_table_init+492
>   100afe98: .vm_init+7948
>
> Thanks,
> Badari
>
> typedef struct pglist_data {
>         struct zone node_zones[MAX_NR_ZONES];
>         struct zonelist node_zonelists[GFP_ZONETYPES];
>         int nr_zones;
> #ifdef CONFIG_FLAT_NODE_MEM_MAP
>         struct page *node_mem_map;
> #endif
>         struct bootmem_data *bdata;

Hmmm,, it kind of looks like the global "mem_map" array should be
used in that case, but if that were true, then there could never
be multiple pglist_data structures in that case?

Here's what I mean -- in vm_init() there's this:

        if (VALID_STRUCT(pglist_data)) {
                vt->flags |= ZONES;

                if (symbol_exists("pgdat_list"))
                        vt->flags |= NODES;

And later on in dump_memory_nodes(), which gathers the memory-related
information for each node, it looks at that "NODES" flag.

- If the NODES flag is *not* set, then it presumes that there is
  just one node, and uses the global "mem_map".

- If the NODES flag is set, then starting at the pgdat_list list head,
  it walks though each of the pglist_data structures (one per node),
  and then collects all of the individual node_mem_map pointers
  found in each node.

In this hybrid case, I don't know how exactly the mem_map
is found for each pglist_data node?  You could quickly try
not setting the vt->flags NODES bit, and seeing what happens.
But I get the feeling that there's going to more to be done
than that -- presuming that you can have more than one pglist_data
node.  In other words if the pglist_data list can have more
than one node when CONFIG_FLAT_NODE_MEM_MAP is turned off,
then we need to find out how to make the relationship between
each sparse node and its associated mem_map array.

Dave






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