mm: unify checks in alloc_pages_node() and __alloc_pages_node()

Perform the same debug checks in alloc_pages_node() as are done in
__alloc_pages_node(), by making the former function a wrapper of the
latter one.

In addition to better diagnostics in DEBUG_VM builds for situations
which have been already fatal (e.g.  out-of-bounds node id), there are
two visible changes for potential existing buggy callers of
alloc_pages_node():

- calling alloc_pages_node() with any negative nid (e.g. due to arithmetic
  overflow) was treated as passing NUMA_NO_NODE and fallback to local node was
  applied. This will now be fatal.
- calling alloc_pages_node() with an offline node will now be checked for
  DEBUG_VM builds. Since it's not fatal if the node has been previously online,
  and this patch may expose some existing buggy callers, change the VM_BUG_ON
  in __alloc_pages_node() to VM_WARN_ON.
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NChristoph Lameter <cl@linux.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/gfp.h

@@ -310,23 +310,23 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
 static inline struct page *
 __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
 {
-	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES || !node_online(nid));
+	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
+	VM_WARN_ON(!node_online(nid));
 
 	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
 }
 
 /*
  * Allocate pages, preferring the node given as nid. When nid == NUMA_NO_NODE,
- * prefer the current CPU's node.
+ * prefer the current CPU's node. Otherwise node must be valid and online.
  */
 static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
 						unsigned int order)
 {
-	/* Unknown node is current node */
-	if (nid < 0)
+	if (nid == NUMA_NO_NODE)
 		nid = numa_node_id();
 
-	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
+	return __alloc_pages_node(nid, gfp_mask, order);
 }
 
 #ifdef CONFIG_NUMA