[patch -mmotm] mm: invoke oom killer for __GFP_NOFAIL

[David Rientjes]

The oom killer must be invoked regardless of the order if the allocation
is __GFP_NOFAIL, otherwise it will loop forever when reclaim fails to
free some memory.

Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
 mm/page_alloc.c |   16 ++++++----------
 1 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1547,7 +1547,7 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 		goto out;
 
 	/* The OOM killer will not help higher order allocs */
-	if (order > PAGE_ALLOC_COSTLY_ORDER)
+	if (order > PAGE_ALLOC_COSTLY_ORDER && !(gfp_mask & __GFP_NOFAIL))
 		goto out;
 
 	/* Exhausted what can be done so it's blamo time */
@@ -1763,16 +1763,12 @@ rebalance:
 					migratetype);
 			if (page)
 				goto got_pg;
+			if ((gfp_mask & __GFP_NOFAIL) ||
+					order <= PAGE_ALLOC_COSTLY_ORDER)
+				goto restart;
 
-			/*
-			 * The OOM killer does not trigger for high-order allocations
-			 * but if no progress is being made, there are no other
-			 * options and retrying is unlikely to help
-			 */
-			if (order > PAGE_ALLOC_COSTLY_ORDER)
-				goto nopage;
-
-			goto restart;
+			/* No freeing is possible so just fail */
+			goto nopage;
 		}
 	}
 
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