powerpc/mm: Add better comment on careful_allocation()
The behavior in careful_allocation() really confused me
at first. Add a comment to hopefully make it easier
on the next doofus that looks at it.
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index cf81049..213664c 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -840,8 +840,16 @@
size, nid);
/*
- * If the memory came from a previously allocated node, we must
- * retry with the bootmem allocator.
+ * We initialize the nodes in numeric order: 0, 1, 2...
+ * and hand over control from the LMB allocator to the
+ * bootmem allocator. If this function is called for
+ * node 5, then we know that all nodes <5 are using the
+ * bootmem allocator instead of the LMB allocator.
+ *
+ * So, check the nid from which this allocation came
+ * and double check to see if we need to use bootmem
+ * instead of the LMB. We don't free the LMB memory
+ * since it would be useless.
*/
new_nid = early_pfn_to_nid(ret >> PAGE_SHIFT);
if (new_nid < nid) {
