From: Ben Widawsky <ben.widawsky@xxxxxxxxx> Subject: mm: add comments on pglist_data zones While making other modifications it was easy to confuse the two struct members node_zones and node_zonelists. For those already familiar with the code, this might seem to be a silly patch, but it's quite helpful to disambiguate the similar-sounding fields While here, add a small comment on why nr_zones isn't simply MAX_NR_ZONES Link: http://lkml.kernel.org/r/20200520205443.2757414-1-ben.widawsky@xxxxxxxxx Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mmzone.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/include/linux/mmzone.h~mm-add-comments-on-pglist_data-zones +++ a/include/linux/mmzone.h @@ -660,9 +660,21 @@ struct deferred_split { * per-zone basis. */ typedef struct pglist_data { + /* + * node_zones contains just the zones for THIS node. Not all of the + * zones may be populated, but it is the full list. It is referenced by + * this node's node_zonelists as well as other node's node_zonelists. + */ struct zone node_zones[MAX_NR_ZONES]; + + /* + * node_zonelists contains references to all zones in all nodes. + * Generally the first zones will be references to this node's + * node_zones. + */ struct zonelist node_zonelists[MAX_ZONELISTS]; - int nr_zones; + + int nr_zones; /* number of populated zones in this node */ #ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */ struct page *node_mem_map; #ifdef CONFIG_PAGE_EXTENSION _
