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

On Thu, Jul 30, 2015 at 06:34:30PM +0200, Vlastimil Babka wrote:

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: Vlastimil Babka <redacted>
Acked-by: David Rientjes <rientjes@google.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>