mm, page_alloc: use masks and shifts when converting GFP flags to migrate 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 <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index f92cbd2..440fca3 100644 (file)
--- 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
index e326843..38bed71 100644 (file)
--- 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