Some callers, namely iommu/io-pgtable-arm-v7s, expect the physical
address returned by kmem_cache_alloc with GFP_DMA parameter to be
a 32-bit address.

Instead of adding a separate SLAB_CACHE_DMA32 (and then audit
all the calls to check if they require memory from DMA or DMA32
zone), we simply allocate SLAB_CACHE_DMA cache in DMA32 region,
if CONFIG_ZONE_DMA32 is set.

Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
Signed-off-by: Nicolas Boichat <redacted>
---
 include/linux/slab.h | 13 ++++++++++++-
 mm/slab.c            |  2 +-
 mm/slub.c            |  2 +-
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 918f374e7156f4..390afe90c5dec0 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h

@@ -30,7 +30,7 @@
 #define SLAB_POISON		((slab_flags_t __force)0x00000800U)
 /* Align objs on cache lines */
 #define SLAB_HWCACHE_ALIGN	((slab_flags_t __force)0x00002000U)
-/* Use GFP_DMA memory */
+/* Use GFP_DMA or GFP_DMA32 memory */
 #define SLAB_CACHE_DMA		((slab_flags_t __force)0x00004000U)
 /* DEBUG: Store the last owner for bug hunting */
 #define SLAB_STORE_USER		((slab_flags_t __force)0x00010000U)

@@ -126,6 +126,17 @@
 #define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \
 				(unsigned long)ZERO_SIZE_PTR)
 
+/*
+ * When ZONE_DMA32 is defined, have SLAB_CACHE_DMA allocate memory with
+ * GFP_DMA32 instead of GFP_DMA, as this is what some of the callers
+ * require (instead of duplicating cache for DMA and DMA32 zones).
+ */
+#ifdef CONFIG_ZONE_DMA32
+#define SLAB_CACHE_DMA_GFP GFP_DMA32
+#else
+#define SLAB_CACHE_DMA_GFP GFP_DMA
+#endif