mm, page_alloc: use masks and shifts when converting GFP flags to mig…

…rate types This patch redefines which GFP bits are used for specifying mobility and the order of the migrate types. Once redefined it's possible to convert GFP flags to a migrate type with a simple mask and shift. The only downside is that readers of OOM kill messages and allocation failures may have been used to the existing values but scripts/gfp-translate will help. Signed-off-by: Mel Gorman <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: David Rientjes <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Vitaly Wool <[email protected]> Cc: Rik van Riel <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
cluon · Nov 7, 2015 · 016c13d · 016c13d
1 parent 46e700a
commit 016c13d
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Showing 2 changed files with 8 additions and 6 deletions.
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
@@ -14,7 +14,7 @@ struct vm_area_struct;
 #define ___GFP_HIGHMEM		0x02u
 #define ___GFP_DMA32		0x04u
 #define ___GFP_MOVABLE		0x08u
-#define ___GFP_WAIT		0x10u
+#define ___GFP_RECLAIMABLE	0x10u
 #define ___GFP_HIGH		0x20u
 #define ___GFP_IO		0x40u
 #define ___GFP_FS		0x80u
@@ -29,7 +29,7 @@ struct vm_area_struct;
 #define ___GFP_NOMEMALLOC	0x10000u
 #define ___GFP_HARDWALL		0x20000u
 #define ___GFP_THISNODE		0x40000u
-#define ___GFP_RECLAIMABLE	0x80000u
+#define ___GFP_WAIT		0x80000u
 #define ___GFP_NOACCOUNT	0x100000u
 #define ___GFP_NOTRACK		0x200000u
 #define ___GFP_NO_KSWAPD	0x400000u
@@ -126,6 +126,7 @@ struct vm_area_struct;
 
 /* This mask makes up all the page movable related flags */
 #define GFP_MOVABLE_MASK (__GFP_RECLAIMABLE|__GFP_MOVABLE)
+#define GFP_MOVABLE_SHIFT 3
 
 /* Control page allocator reclaim behavior */
 #define GFP_RECLAIM_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS|\
@@ -152,14 +153,15 @@ struct vm_area_struct;
 /* Convert GFP flags to their corresponding migrate type */
 static inline int gfpflags_to_migratetype(const gfp_t gfp_flags)
 {
-	WARN_ON((gfp_flags & GFP_MOVABLE_MASK) == GFP_MOVABLE_MASK);
+	VM_WARN_ON((gfp_flags & GFP_MOVABLE_MASK) == GFP_MOVABLE_MASK);
+	BUILD_BUG_ON((1UL << GFP_MOVABLE_SHIFT) != ___GFP_MOVABLE);
+	BUILD_BUG_ON((___GFP_MOVABLE >> GFP_MOVABLE_SHIFT) != MIGRATE_MOVABLE);
 
 	if (unlikely(page_group_by_mobility_disabled))
 		return MIGRATE_UNMOVABLE;
 
 	/* Group based on mobility */
-	return (((gfp_flags & __GFP_MOVABLE) != 0) << 1) |
-		((gfp_flags & __GFP_RECLAIMABLE) != 0);
+	return (gfp_flags & GFP_MOVABLE_MASK) >> GFP_MOVABLE_SHIFT;
 }
 
 #ifdef CONFIG_HIGHMEM

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
@@ -37,8 +37,8 @@
 
 enum {
 	MIGRATE_UNMOVABLE,
-	MIGRATE_RECLAIMABLE,
 	MIGRATE_MOVABLE,
+	MIGRATE_RECLAIMABLE,
 	MIGRATE_PCPTYPES,	/* the number of types on the pcp lists */
 	MIGRATE_RESERVE = MIGRATE_PCPTYPES,
 #ifdef CONFIG_CMA