mm: move PMD_ORDER to pgtable.h

Patch series "Change calling convention for ->huge_fault", v2.

There are two unrelated changes to the calling convention for
->huge_fault.  I've bundled them together to help people notice the
change.  The first is to improve scalability of DAX page faults by
allowing them to be handled under the VMA lock.  The second is to remove
enum page_entry_size since it's really unnecessary.  The changelogs and
documentation updates hopefully work to that end.


This patch (of 3):

Allow this to be used in generic code.  Also add PUD_ORDER.

Link: https://lkml.kernel.org/r/20230818202335.2739663-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230818202335.2739663-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Matthew Wilcox (Oracle)

fs/dax.c

@@ -49,9 +49,6 @@ static inline unsigned int pe_order(enum page_entry_size pe_size)
 #define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
 #define PG_PMD_NR	(PMD_SIZE >> PAGE_SHIFT)
 
-/* The order of a PMD entry */
-#define PMD_ORDER	(PMD_SHIFT - PAGE_SHIFT)
-
 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)

include/linux/pgtable.h

@@ -5,6 +5,9 @@
 #include <linux/pfn.h>
 #include <asm/pgtable.h>
 
+#define PMD_ORDER	(PMD_SHIFT - PAGE_SHIFT)
+#define PUD_ORDER	(PUD_SHIFT - PAGE_SHIFT)
+
 #ifndef __ASSEMBLY__
 #ifdef CONFIG_MMU