Page allocation: GFP_THISNODE must not perform reclaim

The intent of GFP_THISNODE is to make sure that an allocation occurs on a
particular node. If this is not possible then NULL needs to be returned
so that the caller can pick another way of allocating the memory (the
slab allocator depends on that).

However GFP_THISNODE currently triggers reclaim before returning a failure
(GFP_THISNODE means GFP_NORETRY is set). If we have overallocated a node
then we will currently do some reclaim before returning NULL. The caller
may want memory from other nodes before reclaim should be triggered.
(If the caller wants reclaim then he can directly use __GFP_THISNODE instead).

There is no flag for avoiding reclaim in the page allocator and adding yet
another GFP_xx flag would be difficult given that we are out of available
flags.

So just compare and see if all bits for GFP_THISNODE (__GFP_THISNODE,
__GFP_NORETRY and __GFP_NOWARN) are set. If so then we return NULL
before waking up kswapd.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc6-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.19-rc6-mm1.orig/mm/page_alloc.c	2006-11-29 16:10:30.257282914 -0600
+++ linux-2.6.19-rc6-mm1/mm/page_alloc.c	2006-11-29 16:10:56.697054927 -0600
@@ -1307,6 +1307,17 @@ restart:
 	if (page)
 		goto got_pg;
 
+	/*
+	 * GFP_THISNODE (meaning __GFP_THISNODE, __GFP_NORETRY and
+	 * __GFP_NOWARN set) should not cause reclaim since the subsystem
+	 * (f.e. slab) using GFP_THISNODE may choose to trigger reclaim
+	 * using a larger set of nodes after it has established that the
+	 * allowed per node queues are empty and that nodes are
+	 * overallocated.
+	 */
+	if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
+		goto nopage;
+
 	for (z = zonelist->zones; *z; z++)
 		wakeup_kswapd(*z, order);