mm: exclude ZONE_DEVICE from GFP_ZONE_TABLE
ZONE_DEVICE (merged in 4.3) and ZONE_CMA (proposed) are examples of new
mm zones that are bumping up against the current maximum limit of 4
zones, i.e. 2 bits in page->flags for the GFP_ZONE_TABLE.
The GFP_ZONE_TABLE poses an interesting constraint since
include/linux/gfp.h gets included by the 32-bit portion of a 64-bit
build. We need to be careful to only build the table for zones that
have a corresponding gfp_t flag. GFP_ZONES_SHIFT is introduced for this
purpose. This patch does not attempt to solve the problem of adding a
new zone that also has a corresponding GFP_ flag.
Vlastimil points out that ZONE_DEVICE, by depending on x86_64 and
SPARSEMEM_VMEMMAP implies that SECTIONS_WIDTH is zero. In other words
even though ZONE_DEVICE does not fit in GFP_ZONE_TABLE it is free to
consume another bit in page->flags (expand ZONES_WIDTH) with room to
spare.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=110931
Fixes: 033fbae988fc ("mm: ZONE_DEVICE for "device memory"")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Mark <markk@clara.co.uk>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.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 11d56c6..570383a 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -331,22 +331,29 @@
* 0xe => BAD (MOVABLE+DMA32+HIGHMEM)
* 0xf => BAD (MOVABLE+DMA32+HIGHMEM+DMA)
*
- * ZONES_SHIFT must be <= 2 on 32 bit platforms.
+ * GFP_ZONES_SHIFT must be <= 2 on 32 bit platforms.
*/
-#if 16 * ZONES_SHIFT > BITS_PER_LONG
-#error ZONES_SHIFT too large to create GFP_ZONE_TABLE integer
+#if defined(CONFIG_ZONE_DEVICE) && (MAX_NR_ZONES-1) <= 4
+/* ZONE_DEVICE is not a valid GFP zone specifier */
+#define GFP_ZONES_SHIFT 2
+#else
+#define GFP_ZONES_SHIFT ZONES_SHIFT
+#endif
+
+#if 16 * GFP_ZONES_SHIFT > BITS_PER_LONG
+#error GFP_ZONES_SHIFT too large to create GFP_ZONE_TABLE integer
#endif
#define GFP_ZONE_TABLE ( \
- (ZONE_NORMAL << 0 * ZONES_SHIFT) \
- | (OPT_ZONE_DMA << ___GFP_DMA * ZONES_SHIFT) \
- | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * ZONES_SHIFT) \
- | (OPT_ZONE_DMA32 << ___GFP_DMA32 * ZONES_SHIFT) \
- | (ZONE_NORMAL << ___GFP_MOVABLE * ZONES_SHIFT) \
- | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * ZONES_SHIFT) \
- | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * ZONES_SHIFT) \
- | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * ZONES_SHIFT) \
+ (ZONE_NORMAL << 0 * GFP_ZONES_SHIFT) \
+ | (OPT_ZONE_DMA << ___GFP_DMA * GFP_ZONES_SHIFT) \
+ | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * GFP_ZONES_SHIFT) \
+ | (OPT_ZONE_DMA32 << ___GFP_DMA32 * GFP_ZONES_SHIFT) \
+ | (ZONE_NORMAL << ___GFP_MOVABLE * GFP_ZONES_SHIFT) \
+ | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * GFP_ZONES_SHIFT) \
+ | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * GFP_ZONES_SHIFT)\
+ | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * GFP_ZONES_SHIFT)\
)
/*
@@ -371,8 +378,8 @@
enum zone_type z;
int bit = (__force int) (flags & GFP_ZONEMASK);
- z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) &
- ((1 << ZONES_SHIFT) - 1);
+ z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) &
+ ((1 << GFP_ZONES_SHIFT) - 1);
VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
return z;
}