mm/page_alloc.c:__alloc_pages_nodemask(): don't alter arg gfp_mask

__alloc_pages_nodemask() strips __GFP_IO when retrying the page
allocation.  But it does this by altering the function-wide variable
gfp_mask.  This will cause subsequent allocation attempts to inadvertently
use the modified gfp_mask.

Also, pass the correct mask (the mask we actually used) into
trace_mm_page_alloc().

Cc: Ming Lei <ming.lei@canonical.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -2865,6 +2865,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	unsigned int cpuset_mems_cookie;
 	int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR;
 	int classzone_idx;
+	gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */
 
 	gfp_mask &= gfp_allowed_mask;
 
@@ -2898,22 +2899,24 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	classzone_idx = zonelist_zone_idx(preferred_zoneref);
 
 	/* First allocation attempt */
-	page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
-			zonelist, high_zoneidx, alloc_flags,
-			preferred_zone, classzone_idx, migratetype);
+	alloc_mask = gfp_mask|__GFP_HARDWALL;
+	page = get_page_from_freelist(alloc_mask, nodemask, order, zonelist,
+			high_zoneidx, alloc_flags, preferred_zone,
+			classzone_idx, migratetype);
 	if (unlikely(!page)) {
 		/*
 		 * Runtime PM, block IO and its error handling path
 		 * can deadlock because I/O on the device might not
 		 * complete.
 		 */
-		gfp_mask = memalloc_noio_flags(gfp_mask);
-		page = __alloc_pages_slowpath(gfp_mask, order,
+		alloc_mask = memalloc_noio_flags(gfp_mask);
+
+		page = __alloc_pages_slowpath(alloc_mask, order,
 				zonelist, high_zoneidx, nodemask,
 				preferred_zone, classzone_idx, migratetype);
 	}
 
-	trace_mm_page_alloc(page, order, gfp_mask, migratetype);
+	trace_mm_page_alloc(page, order, alloc_mask, migratetype);
 
 out:
 	/*