mm: update alloc_flags after oom killer has been called

It is possible for the oom killer to select current as the task to kill.
When this happens, alloc_flags needs to be updated accordingly to set
ALLOC_NO_WATERMARKS so the subsequent allocation attempt may use memory
reserves as the result of its thread having TIF_MEMDIE set if the
allocation is not __GFP_NOMEMALLOC.

Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -1771,6 +1771,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 
 	wake_all_kswapd(order, zonelist, high_zoneidx);
 
+restart:
 	/*
 	 * OK, we're below the kswapd watermark and have kicked background
 	 * reclaim. Now things get more complex, so set up alloc_flags according
@@ -1778,7 +1779,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 	 */
 	alloc_flags = gfp_to_alloc_flags(gfp_mask);
 
-restart:
 	/* This is the last chance, in general, before the goto nopage. */
 	page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
 			high_zoneidx, alloc_flags & ~ALLOC_NO_WATERMARKS,