include/linux/page-flags-layout.h: cleanups

Tidy things up and delete comments stating the obvious with typos or
making no sense.

Link: https://lkml.kernel.org/r/20210303071609.797782-2-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/page-flags-layout.h

@@ -21,16 +21,17 @@
 #elif MAX_NR_ZONES <= 8
 #define ZONES_SHIFT 3
 #else
-#error ZONES_SHIFT -- too many zones configured adjust calculation
+#error ZONES_SHIFT "Too many zones configured"
 #endif
 
+#define ZONES_WIDTH		ZONES_SHIFT
+
 #ifdef CONFIG_SPARSEMEM
 #include <asm/sparsemem.h>
-
-/* SECTION_SHIFT	#bits space required to store a section # */
 #define SECTIONS_SHIFT	(MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
-
-#endif /* CONFIG_SPARSEMEM */
+#else
+#define SECTIONS_SHIFT	0
+#endif
 
 #ifndef BUILD_VDSO32_64
 /*
@@ -54,17 +55,28 @@
 #define SECTIONS_WIDTH		0
 #endif
 
-#define ZONES_WIDTH		ZONES_SHIFT
-
-#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
+#if ZONES_WIDTH + SECTIONS_WIDTH + NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
 #define NODES_WIDTH		NODES_SHIFT
-#else
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
+#elif defined(CONFIG_SPARSEMEM_VMEMMAP)
 #error "Vmemmap: No space for nodes field in page flags"
-#endif
+#else
 #define NODES_WIDTH		0
 #endif
 
+/*
+ * Note that this #define MUST have a value so that it can be tested with
+ * the IS_ENABLED() macro.
+ */
+#if NODES_SHIFT != 0 && NODES_WIDTH == 0
+#define NODE_NOT_IN_PAGE_FLAGS	1
+#endif
+
+#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
+#define KASAN_TAG_WIDTH 8
+#else
+#define KASAN_TAG_WIDTH 0
+#endif
+
 #ifdef CONFIG_NUMA_BALANCING
 #define LAST__PID_SHIFT 8
 #define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
@@ -77,37 +89,21 @@
 #define LAST_CPUPID_SHIFT 0
 #endif
 
-#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
-#define KASAN_TAG_WIDTH 8
-#else
-#define KASAN_TAG_WIDTH 0
-#endif
-
-#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_WIDTH+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \
+#if ZONES_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + KASAN_TAG_WIDTH + LAST_CPUPID_SHIFT \
 	<= BITS_PER_LONG - NR_PAGEFLAGS
 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
 #else
 #define LAST_CPUPID_WIDTH 0
 #endif
 
-#if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \
+#if LAST_CPUPID_SHIFT != 0 && LAST_CPUPID_WIDTH == 0
+#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
+#endif
+
+#if ZONES_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + KASAN_TAG_WIDTH + LAST_CPUPID_WIDTH \
 	> BITS_PER_LONG - NR_PAGEFLAGS
 #error "Not enough bits in page flags"
 #endif
 
-/*
- * We are going to use the flags for the page to node mapping if its in
- * there.  This includes the case where there is no node, so it is implicit.
- * Note that this #define MUST have a value so that it can be tested with
- * the IS_ENABLED() macro.
- */
-#if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
-#define NODE_NOT_IN_PAGE_FLAGS 1
-#endif
-
-#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
-#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
-#endif
-
 #endif
 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */

mm/mm_init.c

@@ -19,10 +19,6 @@
 #ifdef CONFIG_DEBUG_MEMORY_INIT
 int __meminitdata mminit_loglevel;
 
-#ifndef SECTIONS_SHIFT
-#define SECTIONS_SHIFT	0
-#endif
-
 /* The zonelists are simply reported, validation is manual. */
 void __init mminit_verify_zonelist(void)
 {