mm: consolidate pmd_index() and pmd_offset() definitions

All architectures define pmd_index() as

	(address >> PMD_SHIFT) & (PTRS_PER_PMD - 1)

and all architectures that have at least three-level page tables define
pmd_offset() as an entry in the array of PMDs indexed by the pmd_index().

For the most architectures the pmd_offset() implementation relies on the
availability of pud_page_vaddr() that converts a PMD entry value to the
virtual address of the page containing PMD array.

Let's use such implementation as a generic and drop most of the
definitions of pmd_index() and pmd_offset() in <asm/pgtable.h> files.

The architectures that didn't provide pud_page_vaddr() are updated to have
that defined.

The generic implementation can be overridden by an architecture and this
ability is currently in use by there architectures:
* alpha has special requirements for memory access ordering
* arm has custom definition of folded 2-level page tables
* s390 has custom definitions of all page table accessors

Link: http://lkml.kernel.org/r/20200514170327.31389-11-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Guo Ren <guoren@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

2 files changed, 27 insertions, 3 deletions

diff --git a/include/asm-generic/pgtable-nopmd.h b/include/asm-generic/pgtable-nopmd.h
index 0d9b28cba16d..3e13acd019ae 100644
--- a/include/asm-generic/pgtable-nopmd.h
+++ b/include/asm-generic/pgtable-nopmd.h
@@ -45,6 +45,7 @@ static inline pmd_t * pmd_offset(pud_t * pud, unsigned long address)
 {
 	return (pmd_t *)pud;
 }
+#define pmd_offset pmd_offset
 
 #define pmd_val(x)				(pud_val((x).pud))
 #define __pmd(x)				((pmd_t) { __pud(x) } )
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 3465116b88e5..a83e1166f080 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -29,16 +29,30 @@
 #endif
 
 /*
- * the pte page can be thought of an array like this: pte_t[PTRS_PER_PTE]
+ * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
  *
- * this function returns the index of the entry in the pte page which would
- * control the given virtual address
+ * The pXx_index() functions return the index of the entry in the page
+ * table page which would control the given virtual address
+ *
+ * As these functions may be used by the same code for different levels of
+ * the page table folding, they are always available, regardless of
+ * CONFIG_PGTABLE_LEVELS value. For the folded levels they simply return 0
+ * because in such cases PTRS_PER_PxD equals 1.
  */
+
 static inline unsigned long pte_index(unsigned long address)
 {
 	return (address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 }
 
+#ifndef pmd_index
+static inline unsigned long pmd_index(unsigned long address)
+{
+	return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1);
+}
+#define pmd_index pmd_index
+#endif
+
 #ifndef pte_offset_kernel
 static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address)
 {
@@ -57,6 +71,15 @@ static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address)
 #define pte_unmap(pte) ((void)(pte))	/* NOP */
 #endif
 
+/* Find an entry in the second-level page table.. */
+#ifndef pmd_offset
+static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
+{
+	return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);
+}
+#define pmd_offset pmd_offset
+#endif
+
 /*
  * In many cases it is known that a virtual address is mapped at PMD or PTE
  * level, so instead of traversing all the page table levels, we can get a