parisc: Switch from DISCONTIGMEM to SPARSEMEM

The commit 1c30844d2dfe ("mm: reclaim small amounts of memory when an
external fragmentation event occurs") breaks memory management on a
parisc c8000 workstation with this memory layout:

	0) Start 0x0000000000000000 End 0x000000003fffffff Size   1024 MB
	1) Start 0x0000000100000000 End 0x00000001bfdfffff Size   3070 MB
	2) Start 0x0000004040000000 End 0x00000040ffffffff Size   3072 MB

With the patch 1c30844d2dfe, the kernel will incorrectly reclaim the
first zone when it fills up, ignoring the fact that there are two
completely free zones. Basiscally, it limits cache size to 1GiB.

The parisc kernel is currently using the DISCONTIGMEM implementation,
but isn't NUMA. Avoid this issue or strange work-arounds by switching to
the more commonly used SPARSEMEM implementation.

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
Signed-off-by: Helge Deller <deller@gmx.de>

3 files changed, 17 insertions, 59 deletions

diff --git a/arch/parisc/include/asm/mmzone.h b/arch/parisc/include/asm/mmzone.h
index fafa3893fd70..8d390406d862 100644
--- a/arch/parisc/include/asm/mmzone.h
+++ b/arch/parisc/include/asm/mmzone.h
@@ -2,62 +2,6 @@
 #ifndef _PARISC_MMZONE_H
 #define _PARISC_MMZONE_H
 
-#define MAX_PHYSMEM_RANGES 8 /* Fix the size for now (current known max is 3) */
+#define MAX_PHYSMEM_RANGES 4 /* Fix the size for now (current known max is 3) */
 
-#ifdef CONFIG_DISCONTIGMEM
-
-extern int npmem_ranges;
-
-struct node_map_data {
-    pg_data_t pg_data;
-};
-
-extern struct node_map_data node_data[];
-
-#define NODE_DATA(nid)          (&node_data[nid].pg_data)
-
-/* We have these possible memory map layouts:
- * Astro: 0-3.75, 67.75-68, 4-64
- * zx1: 0-1, 257-260, 4-256
- * Stretch (N-class): 0-2, 4-32, 34-xxx
- */
-
-/* Since each 1GB can only belong to one region (node), we can create
- * an index table for pfn to nid lookup; each entry in pfnnid_map 
- * represents 1GB, and contains the node that the memory belongs to. */
-
-#define PFNNID_SHIFT (30 - PAGE_SHIFT)
-#define PFNNID_MAP_MAX  512     /* support 512GB */
-extern signed char pfnnid_map[PFNNID_MAP_MAX];
-
-#ifndef CONFIG_64BIT
-#define pfn_is_io(pfn) ((pfn & (0xf0000000UL >> PAGE_SHIFT)) == (0xf0000000UL >> PAGE_SHIFT))
-#else
-/* io can be 0xf0f0f0f0f0xxxxxx or 0xfffffffff0000000 */
-#define pfn_is_io(pfn) ((pfn & (0xf000000000000000UL >> PAGE_SHIFT)) == (0xf000000000000000UL >> PAGE_SHIFT))
-#endif
-
-static inline int pfn_to_nid(unsigned long pfn)
-{
-	unsigned int i;
-
-	if (unlikely(pfn_is_io(pfn)))
-		return 0;
-
-	i = pfn >> PFNNID_SHIFT;
-	BUG_ON(i >= ARRAY_SIZE(pfnnid_map));
-
-	return pfnnid_map[i];
-}
-
-static inline int pfn_valid(int pfn)
-{
-	int nid = pfn_to_nid(pfn);
-
-	if (nid >= 0)
-		return (pfn < node_end_pfn(nid));
-	return 0;
-}
-
-#endif
 #endif /* _PARISC_MMZONE_H */
diff --git a/arch/parisc/include/asm/page.h b/arch/parisc/include/asm/page.h
index b77f49ce6220..93caf17ac5e2 100644
--- a/arch/parisc/include/asm/page.h
+++ b/arch/parisc/include/asm/page.h
@@ -147,9 +147,9 @@ extern int npmem_ranges;
 #define __pa(x)			((unsigned long)(x)-PAGE_OFFSET)
 #define __va(x)			((void *)((unsigned long)(x)+PAGE_OFFSET))
 
-#ifndef CONFIG_DISCONTIGMEM
+#ifndef CONFIG_SPARSEMEM
 #define pfn_valid(pfn)		((pfn) < max_mapnr)
-#endif /* CONFIG_DISCONTIGMEM */
+#endif
 
 #ifdef CONFIG_HUGETLB_PAGE
 #define HPAGE_SHIFT		PMD_SHIFT /* fixed for transparent huge pages */
diff --git a/arch/parisc/include/asm/sparsemem.h b/arch/parisc/include/asm/sparsemem.h
new file mode 100644
index 000000000000..b5c3a79045b4
--- /dev/null
+++ b/arch/parisc/include/asm/sparsemem.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ASM_PARISC_SPARSEMEM_H
+#define ASM_PARISC_SPARSEMEM_H
+
+/* We have these possible memory map layouts:
+ * Astro: 0-3.75, 67.75-68, 4-64
+ * zx1: 0-1, 257-260, 4-256
+ * Stretch (N-class): 0-2, 4-32, 34-xxx
+ */
+
+#define MAX_PHYSMEM_BITS	39	/* 512 GB */
+#define SECTION_SIZE_BITS	27	/* 128 MB */
+
+#endif