mm: Allow only __GFP_CMA allocations from Movable zone

Ensure that only allocations which include __GFP_CMA can be satisfied from
zone Movable. This restriction helps reduces the likelihood of a page in
the movable zone being pinned which would prevent memory from being
offlined.

Change-Id: I570970ff848d4a7147f3ccda2b294f08bcdf88d8
Signed-off-by: Liam Mark <lmark@codeaurora.org>

include/linux/gfp.h

@@ -420,7 +420,14 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
 static inline enum zone_type gfp_zone(gfp_t flags)
 {
 	enum zone_type z;
-	int bit = (__force int) (flags & GFP_ZONEMASK);
+	int bit;
+
+	if (!IS_ENABLED(CONFIG_HIGHMEM)) {
+		if ((flags & __GFP_MOVABLE) && !(flags & __GFP_CMA))
+			flags &= ~__GFP_HIGHMEM;
+	}
+
+	bit = (__force int) (flags & GFP_ZONEMASK);
 
 	z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) &
 					 ((1 << GFP_ZONES_SHIFT) - 1);