[PATCH v3 2/3] mm: unify checks in alloc_pages_node() and __alloc_pages_node()

Vlastimil Babka vbabka at suse.cz
Fri Jul 31 02:34:30 AEST 2015

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

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: Vlastimil Babka <vbabka at suse.cz>
Acked-by: David Rientjes <rientjes at google.com>
v3: I think this is enough for what patch 4/4 in v2 tried to provide on top,
    so there's no patch 4/4 anymore. The DEBUG_VM-only fixup didn't seem
    justified to me.

 include/linux/gfp.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index d2c142b..4a12cae2 100644
--- a/include/linux/gfp.h
+++ b/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);

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