[PATCH] Make GFP_DMA allocations w/o ZONE_DMA emit a warning instead of failing

[Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>]

Please be more polite to other people. After a197b59ae6 all allocations
with GFP_DMA set on nodes without ZONE_DMA fail nearly silently (only
one warning during bootup is emited, no matter how many things fail).
This is a very crude change on behaviour. To be more civil, instead of
failing emit noisy warnings each time smbd. tries to allocate a GFP_DMA
memory on non-ZONE_DMA node.

This change should be reverted after one or two major releases, but
we should be more accurate rather than hoping for the best.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 mm/page_alloc.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a4e1db3..e22dd4e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2248,8 +2248,9 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	if (should_fail_alloc_page(gfp_mask, order))
 		return NULL;
 #ifndef CONFIG_ZONE_DMA
-	if (WARN_ON_ONCE(gfp_mask & __GFP_DMA))
-		return NULL;
+	/* Change this back to hard failure after 3.0 or 3.1. For now give
+	 * drivers people a chance to fix their drivers w/o causing breakage. */
+	WARN_ON(gfp_mask & __GFP_DMA);
 #endif
 
 	/*
-- 
1.7.4.4