Subject: Re: [PATCH v2 1/3] powerpc: port 64 bits pgtable_cache to 32 bits

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 19 Sep 2016 10:52:33 +0530

Christophe Leroy <[email-masked]> writes:

> Today powerpc64 uses a set of pgtable_caches while powerpc32 uses
> standard pages when using 4k pages and a single pgtable_cache
> if using other size pages.
>
> In preparation of implementing huge pages on the 8xx, this patch
> replaces the specific powerpc32 handling by the 64 bits approach.
>
> This is done by:
> * moving 64 bits pgtable_cache_add() and pgtable_cache_init()
> in a new file called init-common.c
> * modifying pgtable_cache_init() to also handle the case
> without PMD
> * removing the 32 bits version of pgtable_cache_add() and
> pgtable_cache_init()
> * copying related header contents from 64 bits into both the
> book3s/32 and nohash/32 header files
>
> On the 8xx, the following cache sizes will be used:
> * 4k pages mode:
> - PGT_CACHE(10) for PGD
> - PGT_CACHE(3) for 512k hugepage tables
> * 16k pages mode:
> - PGT_CACHE(6) for PGD
> - PGT_CACHE(7) for 512k hugepage tables
> - PGT_CACHE(3) for 8M hugepage tables
>
> Signed-off-by: Christophe Leroy <[email-masked]>
> ---
> v2: in v1, hugepte_cache was wrongly replaced by PGT_CACHE(1).
> This modification has been removed from v2.
>
>  arch/powerpc/include/asm/book3s/32/pgalloc.h |  44 ++++++--
>  arch/powerpc/include/asm/book3s/32/pgtable.h |  43 ++++----
>  arch/powerpc/include/asm/book3s/64/pgtable.h |   3 -
>  arch/powerpc/include/asm/nohash/32/pgalloc.h |  44 ++++++--
>  arch/powerpc/include/asm/nohash/32/pgtable.h |  45 ++++----
>  arch/powerpc/include/asm/nohash/64/pgtable.h |   2 -
>  arch/powerpc/include/asm/pgtable.h           |   2 +
>  arch/powerpc/mm/Makefile                     |   3 +-
>  arch/powerpc/mm/init-common.c                | 147 +++++++++++++++++++++++++++
>  arch/powerpc/mm/init_64.c                    |  77 --------------
>  arch/powerpc/mm/pgtable_32.c                 |  37 -------
>  11 files changed, 273 insertions(+), 174 deletions(-)
>  create mode 100644 arch/powerpc/mm/init-common.c
>
> diff --git a/arch/powerpc/include/asm/book3s/32/pgalloc.h b/arch/powerpc/include/asm/book3s/32/pgalloc.h
> index 8e21bb4..d310546 100644
> --- a/arch/powerpc/include/asm/book3s/32/pgalloc.h
> +++ b/arch/powerpc/include/asm/book3s/32/pgalloc.h
> @@ -2,14 +2,42 @@
>  #define _ASM_POWERPC_BOOK3S_32_PGALLOC_H
>  
>  #include <linux/threads.h>
> +#include <linux/slab.h>
>  
> -/* For 32-bit, all levels of page tables are just drawn from get_free_page() */
> -#define MAX_PGTABLE_INDEX_SIZE	0
> +/*
> + * Functions that deal with pagetables that could be at any level of
> + * the table need to be passed an "index_size" so they know how to
> + * handle allocation.  For PTE pages (which are linked to a struct
> + * page for now, and drawn from the main get_free_pages() pool), the
> + * allocation size will be (2^index_size * sizeof(pointer)) and
> + * allocations are drawn from the kmem_cache in PGT_CACHE(index_size).
> + *
> + * The maximum index size needs to be big enough to allow any
> + * pagetable sizes we need, but small enough to fit in the low bits of
> + * any page table pointer.  In other words all pagetables, even tiny
> + * ones, must be aligned to allow at least enough low 0 bits to
> + * contain this value.  This value is also used as a mask, so it must
> + * be one less than a power of two.
> + */
> +#define MAX_PGTABLE_INDEX_SIZE	0xf
>  
>  extern void __bad_pte(pmd_t *pmd);
>  
> -extern pgd_t *pgd_alloc(struct mm_struct *mm);
> -extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
> +extern struct kmem_cache *pgtable_cache[];
> +#define PGT_CACHE(shift) ({				\
> +			BUG_ON(!(shift));		\
> +			pgtable_cache[(shift) - 1];	\
> +		})
> +
> +static inline pgd_t *pgd_alloc(struct mm_struct *mm)
> +{
> +	return kmem_cache_alloc(PGT_CACHE(PGD_INDEX_SIZE), GFP_KERNEL);
> +}
> +
> +static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
> +{
> +	kmem_cache_free(PGT_CACHE(PGD_INDEX_SIZE), pgd);
> +}
>  
>  /*
>   * We don't have any real pmd's, and this code never triggers because
> @@ -68,8 +96,12 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t ptepage)
>  
>  static inline void pgtable_free(void *table, unsigned index_size)
>  {
> -	BUG_ON(index_size); /* 32-bit doesn't use this */
> -	free_page((unsigned long)table);
> +	if (!index_size) {
> +		free_page((unsigned long)table);
> +	} else {
> +		BUG_ON(index_size > MAX_PGTABLE_INDEX_SIZE);
> +		kmem_cache_free(PGT_CACHE(index_size), table);
> +	}
>  }
>  
>  #define check_pgt_cache()	do { } while (0)
> diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
> index 6b8b2d5..f887499 100644
> --- a/arch/powerpc/include/asm/book3s/32/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
> @@ -8,6 +8,26 @@
>  /* And here we include common definitions */
>  #include <asm/pte-common.h>
>  
> +#define PTE_INDEX_SIZE	PTE_SHIFT
> +#define PMD_INDEX_SIZE	0
> +#define PUD_INDEX_SIZE	0
> +#define PGD_INDEX_SIZE	(32 - PGDIR_SHIFT)
> +
> +#define PMD_CACHE_INDEX	PMD_INDEX_SIZE
> +
> +#ifndef __ASSEMBLY__
> +#define PTE_TABLE_SIZE	(sizeof(pte_t) << PTE_INDEX_SIZE)
> +#define PMD_TABLE_SIZE	(sizeof(pmd_t) << PTE_INDEX_SIZE)
> +#define PUD_TABLE_SIZE	(sizeof(pud_t) << PTE_INDEX_SIZE)
> +#define PGD_TABLE_SIZE	(sizeof(pgd_t) << PGD_INDEX_SIZE)
> +#endif	/* __ASSEMBLY__ */

Are these table size correct ? IIUC, We will have only PGD and PTE
tables right ?

> +
> +#define PTRS_PER_PTE	(1 << PTE_INDEX_SIZE)
> +#define PTRS_PER_PGD	(1 << PGD_INDEX_SIZE)
> +
> +/* With 4k base page size, hugepage PTEs go at the PMD level */
> +#define MIN_HUGEPTE_SHIFT	PMD_SHIFT
> +

What does that comment mean ? I guess that came from copy-paste from
other headers. I am not sure what it means there either other than the
64k hash config, where we place hugepage PTE at the PMD level. (ie, no hugepd).

>  /*
>   * The normal case is that PTEs are 32-bits and we have a 1-page
>   * 1024-entry pgdir pointing to 1-page 1024-entry PTE pages.  -- paulus
> @@ -19,14 +39,10 @@
>   * -Matt
>   */
>  /* PGDIR_SHIFT determines what a top-level page table entry can map */
> -#define PGDIR_SHIFT	(PAGE_SHIFT + PTE_SHIFT)
> +#define PGDIR_SHIFT	(PAGE_SHIFT + PTE_INDEX_SIZE)
>  #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
>  #define PGDIR_MASK	(~(PGDIR_SIZE-1))
>  
> -#define PTRS_PER_PTE	(1 << PTE_SHIFT)
> -#define PTRS_PER_PMD	1
> -#define PTRS_PER_PGD	(1 << (32 - PGDIR_SHIFT))
> -
>  #define USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)
>  /*
>   * This is the bottom of the PKMAP area with HIGHMEM or an arbitrary
> @@ -82,12 +98,8 @@
>  
>  extern unsigned long ioremap_bot;
>  
> -/*
> - * entries per page directory level: our page-table tree is two-level, so
> - * we don't really have any PMD directory.
> - */
> -#define PTE_TABLE_SIZE	(sizeof(pte_t) << PTE_SHIFT)
> -#define PGD_TABLE_SIZE	(sizeof(pgd_t) << (32 - PGDIR_SHIFT))
> +/* Bits to mask out from a PGD to get to the PUD page */
> +#define PGD_MASKED_BITS		0
>  
>  #define pte_ERROR(e) \
>  	pr_err("%s:%d: bad pte %llx.\n", __FILE__, __LINE__, \
> @@ -283,15 +295,6 @@ static inline void __ptep_set_access_flags(struct mm_struct *mm,
>  #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val(pte) >> 3 })
>  #define __swp_entry_to_pte(x)		((pte_t) { (x).val << 3 })
>  
> -#ifndef CONFIG_PPC_4K_PAGES
> -void pgtable_cache_init(void);
> -#else
> -/*
> - * No page table caches to initialise
> - */
> -#define pgtable_cache_init()	do { } while (0)
> -#endif
> -
>  extern int get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep,
>  		      pmd_t **pmdp);
>  
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index 9fd77f8..0a46a5f 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -789,9 +789,6 @@ extern struct page *pgd_page(pgd_t pgd);
>  #define pgd_ERROR(e) \
>  	pr_err("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))
>  
> -void pgtable_cache_add(unsigned shift, void (*ctor)(void *));
> -void pgtable_cache_init(void);
> -
>  static inline int map_kernel_page(unsigned long ea, unsigned long pa,
>  				  unsigned long flags)
>  {
> diff --git a/arch/powerpc/include/asm/nohash/32/pgalloc.h b/arch/powerpc/include/asm/nohash/32/pgalloc.h
> index 76d6b9e..6331392 100644
> --- a/arch/powerpc/include/asm/nohash/32/pgalloc.h
> +++ b/arch/powerpc/include/asm/nohash/32/pgalloc.h
> @@ -2,14 +2,42 @@
>  #define _ASM_POWERPC_PGALLOC_32_H
>  
>  #include <linux/threads.h>
> +#include <linux/slab.h>
>  
> -/* For 32-bit, all levels of page tables are just drawn from get_free_page() */
> -#define MAX_PGTABLE_INDEX_SIZE	0
> +/*
> + * Functions that deal with pagetables that could be at any level of
> + * the table need to be passed an "index_size" so they know how to
> + * handle allocation.  For PTE pages (which are linked to a struct
> + * page for now, and drawn from the main get_free_pages() pool), the
> + * allocation size will be (2^index_size * sizeof(pointer)) and
> + * allocations are drawn from the kmem_cache in PGT_CACHE(index_size).
> + *
> + * The maximum index size needs to be big enough to allow any
> + * pagetable sizes we need, but small enough to fit in the low bits of
> + * any page table pointer.  In other words all pagetables, even tiny
> + * ones, must be aligned to allow at least enough low 0 bits to
> + * contain this value.  This value is also used as a mask, so it must
> + * be one less than a power of two.
> + */
> +#define MAX_PGTABLE_INDEX_SIZE	0xf
>  
>  extern void __bad_pte(pmd_t *pmd);
>  
> -extern pgd_t *pgd_alloc(struct mm_struct *mm);
> -extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
> +extern struct kmem_cache *pgtable_cache[];
> +#define PGT_CACHE(shift) ({				\
> +			BUG_ON(!(shift));		\
> +			pgtable_cache[(shift) - 1];	\
> +		})
> +
> +static inline pgd_t *pgd_alloc(struct mm_struct *mm)
> +{
> +	return kmem_cache_alloc(PGT_CACHE(PGD_INDEX_SIZE), GFP_KERNEL);
> +}
> +
> +static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
> +{
> +	kmem_cache_free(PGT_CACHE(PGD_INDEX_SIZE), pgd);
> +}
>  
>  /*
>   * We don't have any real pmd's, and this code never triggers because
> @@ -68,8 +96,12 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t ptepage)
>  
>  static inline void pgtable_free(void *table, unsigned index_size)
>  {
> -	BUG_ON(index_size); /* 32-bit doesn't use this */
> -	free_page((unsigned long)table);
> +	if (!index_size) {
> +		free_page((unsigned long)table);
> +	} else {
> +		BUG_ON(index_size > MAX_PGTABLE_INDEX_SIZE);
> +		kmem_cache_free(PGT_CACHE(index_size), table);
> +	}
>  }
>  
>  #define check_pgt_cache()	do { } while (0)
> diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
> index c219ef7..8cbe222 100644
> --- a/arch/powerpc/include/asm/nohash/32/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
> @@ -16,6 +16,26 @@ extern int icache_44x_need_flush;
>  
>  #endif /* __ASSEMBLY__ */
>  
> +#define PTE_INDEX_SIZE	PTE_SHIFT
> +#define PMD_INDEX_SIZE	0
> +#define PUD_INDEX_SIZE	0
> +#define PGD_INDEX_SIZE	(32 - PGDIR_SHIFT)
> +
> +#define PMD_CACHE_INDEX	PMD_INDEX_SIZE
> +
> +#ifndef __ASSEMBLY__
> +#define PTE_TABLE_SIZE	(sizeof(pte_t) << PTE_INDEX_SIZE)
> +#define PMD_TABLE_SIZE	(sizeof(pmd_t) << PTE_INDEX_SIZE)
> +#define PUD_TABLE_SIZE	(sizeof(pud_t) << PTE_INDEX_SIZE)
> +#define PGD_TABLE_SIZE	(sizeof(pgd_t) << PGD_INDEX_SIZE)
> +#endif	/* __ASSEMBLY__ */
> +

Same, please comment on why those TABLE sizes ?

> +#define PTRS_PER_PTE	(1 << PTE_INDEX_SIZE)
> +#define PTRS_PER_PGD	(1 << PGD_INDEX_SIZE)
> +
> +/* With 4k base page size, hugepage PTEs go at the PMD level */
> +#define MIN_HUGEPTE_SHIFT	PMD_SHIFT
> +
>  /*
>   * The normal case is that PTEs are 32-bits and we have a 1-page
>   * 1024-entry pgdir pointing to 1-page 1024-entry PTE pages.  -- paulus
> @@ -27,22 +47,12 @@ extern int icache_44x_need_flush;
>   * -Matt
>   */
>  /* PGDIR_SHIFT determines what a top-level page table entry can map */
> -#define PGDIR_SHIFT	(PAGE_SHIFT + PTE_SHIFT)
> +#define PGDIR_SHIFT	(PAGE_SHIFT + PTE_INDEX_SIZE)
>  #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
>  #define PGDIR_MASK	(~(PGDIR_SIZE-1))
>  
> -/*
> - * entries per page directory level: our page-table tree is two-level, so
> - * we don't really have any PMD directory.
> - */
> -#ifndef __ASSEMBLY__
> -#define PTE_TABLE_SIZE	(sizeof(pte_t) << PTE_SHIFT)
> -#define PGD_TABLE_SIZE	(sizeof(pgd_t) << (32 - PGDIR_SHIFT))
> -#endif	/* __ASSEMBLY__ */
> -
> -#define PTRS_PER_PTE	(1 << PTE_SHIFT)
> -#define PTRS_PER_PMD	1
> -#define PTRS_PER_PGD	(1 << (32 - PGDIR_SHIFT))
> +/* Bits to mask out from a PGD to get to the PUD page */
> +#define PGD_MASKED_BITS		0
>  
>  #define USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)
>  #define FIRST_USER_ADDRESS	0UL
> @@ -328,15 +338,6 @@ static inline void __ptep_set_access_flags(struct mm_struct *mm,
>  #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val(pte) >> 3 })
>  #define __swp_entry_to_pte(x)		((pte_t) { (x).val << 3 })
>  
> -#ifndef CONFIG_PPC_4K_PAGES
> -void pgtable_cache_init(void);
> -#else
> -/*
> - * No page table caches to initialise
> - */
> -#define pgtable_cache_init()	do { } while (0)
> -#endif
> -
>  extern int get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep,
>  		      pmd_t **pmdp);
>  
> diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
> index 653a183..619018a 100644
> --- a/arch/powerpc/include/asm/nohash/64/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
> @@ -358,8 +358,6 @@ static inline void __ptep_set_access_flags(struct mm_struct *mm,
>  #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val((pte)) })
>  #define __swp_entry_to_pte(x)		__pte((x).val)
>  
> -void pgtable_cache_add(unsigned shift, void (*ctor)(void *));
> -void pgtable_cache_init(void);
>  extern int map_kernel_page(unsigned long ea, unsigned long pa,
>  			   unsigned long flags);
>  extern int __meminit vmemmap_create_mapping(unsigned long start,
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index 9bd87f2..dd01212 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -78,6 +78,8 @@ static inline pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
>  
>  unsigned long vmalloc_to_phys(void *vmalloc_addr);
>  
> +void pgtable_cache_add(unsigned shift, void (*ctor)(void *));
> +void pgtable_cache_init(void);
>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_POWERPC_PGTABLE_H */
> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
> index 1a4e570..e8a86d2 100644
> --- a/arch/powerpc/mm/Makefile
> +++ b/arch/powerpc/mm/Makefile
> @@ -7,7 +7,8 @@ subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
>  ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)
>  
>  obj-y				:= fault.o mem.o pgtable.o mmap.o \
> -				   init_$(BITS).o pgtable_$(BITS).o
> +				   init_$(BITS).o pgtable_$(BITS).o \
> +				   init-common.o
>  obj-$(CONFIG_PPC_MMU_NOHASH)	+= mmu_context_nohash.o tlb_nohash.o \
>  				   tlb_nohash_low.o
>  obj-$(CONFIG_PPC_BOOK3E)	+= tlb_low_$(BITS)e.o
> diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
> new file mode 100644
> index 0000000..ab2b947
> --- /dev/null
> +++ b/arch/powerpc/mm/init-common.c
> @@ -0,0 +1,147 @@
> +/*
> + *  PowerPC version
> + *    Copyright (C) 1995-1996 Gary Thomas ([email-masked])
> + *
> + *  Modifications by Paul Mackerras (PowerMac) ([email-masked])
> + *  and Cort Dougan (PReP) ([email-masked])
> + *    Copyright (C) 1996 Paul Mackerras
> + *
> + *  Derived from "arch/i386/mm/init.c"
> + *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
> + *
> + *  Dave Engebretsen <[email-masked]>
> + *      Rework for PPC64 port.
> + *
> + *  This program is free software; you can redistribute it and/or
> + *  modify it under the terms of the GNU General Public License
> + *  as published by the Free Software Foundation; either version
> + *  2 of the License, or (at your option) any later version.
> + *
> + */
> +
> +#undef DEBUG
> +
> +#include <linux/signal.h>
> +#include <linux/sched.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/types.h>
> +#include <linux/mman.h>
> +#include <linux/mm.h>
> +#include <linux/swap.h>
> +#include <linux/stddef.h>
> +#include <linux/vmalloc.h>
> +#include <linux/init.h>
> +#include <linux/delay.h>
> +#include <linux/highmem.h>
> +#include <linux/idr.h>
> +#include <linux/nodemask.h>
> +#include <linux/module.h>
> +#include <linux/poison.h>
> +#include <linux/memblock.h>
> +#include <linux/hugetlb.h>
> +#include <linux/slab.h>
> +
> +#include <asm/pgalloc.h>
> +#include <asm/page.h>
> +#include <asm/prom.h>
> +#include <asm/rtas.h>
> +#include <asm/io.h>
> +#include <asm/mmu_context.h>
> +#include <asm/pgtable.h>
> +#include <asm/mmu.h>
> +#include <asm/uaccess.h>
> +#include <asm/smp.h>
> +#include <asm/machdep.h>
> +#include <asm/tlb.h>
> +#include <asm/eeh.h>
> +#include <asm/processor.h>
> +#include <asm/mmzone.h>
> +#include <asm/cputable.h>
> +#include <asm/sections.h>
> +#include <asm/iommu.h>
> +#include <asm/vdso.h>
> +
> +#include "mmu_decl.h"

Do you need all these headers to get it compiled ?

> +
> +static void pgd_ctor(void *addr)
> +{
> +	memset(addr, 0, PGD_TABLE_SIZE);
> +}
> +
> +static void pud_ctor(void *addr)
> +{
> +	memset(addr, 0, PUD_TABLE_SIZE);
> +}
> +
> +static void pmd_ctor(void *addr)
> +{
> +	memset(addr, 0, PMD_TABLE_SIZE);
> +}
> +
> +struct kmem_cache *pgtable_cache[MAX_PGTABLE_INDEX_SIZE];
> +
> +/*
> + * Create a kmem_cache() for pagetables.  This is not used for PTE
> + * pages - they're linked to struct page, come from the normal free
> + * pages pool and have a different entry size (see real_pte_t) to
> + * everything else.  Caches created by this function are used for all
> + * the higher level pagetables, and for hugepage pagetables.
> + */
> +void pgtable_cache_add(unsigned shift, void (*ctor)(void *))
> +{
> +	char *name;
> +	unsigned long table_size = sizeof(void *) << shift;
> +	unsigned long align = table_size;
> +
> +	/* When batching pgtable pointers for RCU freeing, we store
> +	 * the index size in the low bits.  Table alignment must be
> +	 * big enough to fit it.
> +	 *
> +	 * Likewise, hugeapge pagetable pointers contain a (different)
> +	 * shift value in the low bits.  All tables must be aligned so
> +	 * as to leave enough 0 bits in the address to contain it. */
> +	unsigned long minalign = max(MAX_PGTABLE_INDEX_SIZE + 1,
> +				     HUGEPD_SHIFT_MASK + 1);
> +	struct kmem_cache *new;
> +
> +	/* It would be nice if this was a BUILD_BUG_ON(), but at the
> +	 * moment, gcc doesn't seem to recognize is_power_of_2 as a
> +	 * constant expression, so so much for that. */
> +	BUG_ON(!is_power_of_2(minalign));
> +	BUG_ON((shift < 1) || (shift > MAX_PGTABLE_INDEX_SIZE));
> +
> +	if (PGT_CACHE(shift))
> +		return; /* Already have a cache of this size */
> +
> +	align = max_t(unsigned long, align, minalign);
> +	name = kasprintf(GFP_KERNEL, "pgtable-2^%d", shift);
> +	new = kmem_cache_create(name, table_size, align, 0, ctor);
> +	kfree(name);
> +	pgtable_cache[shift - 1] = new;
> +	pr_debug("Allocated pgtable cache for order %d\n", shift);
> +}
> +
> +
> +void pgtable_cache_init(void)
> +{
> +	pgtable_cache_add(PGD_INDEX_SIZE, pgd_ctor);
> +
> +	if (PMD_INDEX_SIZE && !PGT_CACHE(PMD_INDEX_SIZE))
> +		pgtable_cache_add(PMD_CACHE_INDEX, pmd_ctor);
> +	/*
> +	 * In all current configs, when the PUD index exists it's the
> +	 * same size as either the pgd or pmd index except with THP enabled
> +	 * on book3s 64
> +	 */
> +	if (PUD_INDEX_SIZE && !PGT_CACHE(PUD_INDEX_SIZE))
> +		pgtable_cache_add(PUD_INDEX_SIZE, pud_ctor);
> +
> +	if (!PGT_CACHE(PGD_INDEX_SIZE))
> +		panic("Couldn't allocate pgd cache");
> +	if (PMD_INDEX_SIZE && !PGT_CACHE(PMD_INDEX_SIZE))
> +		panic("Couldn't allocate pmd pgtable caches");
> +	if (PUD_INDEX_SIZE && !PGT_CACHE(PUD_INDEX_SIZE))
> +		panic("Couldn't allocate pud pgtable caches");
> +}
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index 16ada1e..a000c35 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -80,83 +80,6 @@ EXPORT_SYMBOL_GPL(memstart_addr);
>  phys_addr_t kernstart_addr;
>  EXPORT_SYMBOL_GPL(kernstart_addr);
>  
> -static void pgd_ctor(void *addr)
> -{
> -	memset(addr, 0, PGD_TABLE_SIZE);
> -}
> -
> -static void pud_ctor(void *addr)
> -{
> -	memset(addr, 0, PUD_TABLE_SIZE);
> -}
> -
> -static void pmd_ctor(void *addr)
> -{
> -	memset(addr, 0, PMD_TABLE_SIZE);
> -}
> -
> -struct kmem_cache *pgtable_cache[MAX_PGTABLE_INDEX_SIZE];
> -
> -/*
> - * Create a kmem_cache() for pagetables.  This is not used for PTE
> - * pages - they're linked to struct page, come from the normal free
> - * pages pool and have a different entry size (see real_pte_t) to
> - * everything else.  Caches created by this function are used for all
> - * the higher level pagetables, and for hugepage pagetables.
> - */
> -void pgtable_cache_add(unsigned shift, void (*ctor)(void *))
> -{
> -	char *name;
> -	unsigned long table_size = sizeof(void *) << shift;
> -	unsigned long align = table_size;
> -
> -	/* When batching pgtable pointers for RCU freeing, we store
> -	 * the index size in the low bits.  Table alignment must be
> -	 * big enough to fit it.
> -	 *
> -	 * Likewise, hugeapge pagetable pointers contain a (different)
> -	 * shift value in the low bits.  All tables must be aligned so
> -	 * as to leave enough 0 bits in the address to contain it. */
> -	unsigned long minalign = max(MAX_PGTABLE_INDEX_SIZE + 1,
> -				     HUGEPD_SHIFT_MASK + 1);
> -	struct kmem_cache *new;
> -
> -	/* It would be nice if this was a BUILD_BUG_ON(), but at the
> -	 * moment, gcc doesn't seem to recognize is_power_of_2 as a
> -	 * constant expression, so so much for that. */
> -	BUG_ON(!is_power_of_2(minalign));
> -	BUG_ON((shift < 1) || (shift > MAX_PGTABLE_INDEX_SIZE));
> -
> -	if (PGT_CACHE(shift))
> -		return; /* Already have a cache of this size */
> -
> -	align = max_t(unsigned long, align, minalign);
> -	name = kasprintf(GFP_KERNEL, "pgtable-2^%d", shift);
> -	new = kmem_cache_create(name, table_size, align, 0, ctor);
> -	kfree(name);
> -	pgtable_cache[shift - 1] = new;
> -	pr_debug("Allocated pgtable cache for order %d\n", shift);
> -}
> -
> -
> -void pgtable_cache_init(void)
> -{
> -	pgtable_cache_add(PGD_INDEX_SIZE, pgd_ctor);
> -	pgtable_cache_add(PMD_CACHE_INDEX, pmd_ctor);
> -	/*
> -	 * In all current configs, when the PUD index exists it's the
> -	 * same size as either the pgd or pmd index except with THP enabled
> -	 * on book3s 64
> -	 */
> -	if (PUD_INDEX_SIZE && !PGT_CACHE(PUD_INDEX_SIZE))
> -		pgtable_cache_add(PUD_INDEX_SIZE, pud_ctor);
> -
> -	if (!PGT_CACHE(PGD_INDEX_SIZE) || !PGT_CACHE(PMD_CACHE_INDEX))
> -		panic("Couldn't allocate pgtable caches");
> -	if (PUD_INDEX_SIZE && !PGT_CACHE(PUD_INDEX_SIZE))
> -		panic("Couldn't allocate pud pgtable caches");
> -}
> -
>  #ifdef CONFIG_SPARSEMEM_VMEMMAP
>  /*
>   * Given an address within the vmemmap, determine the pfn of the page that
> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index 0ae0572..a65c0b4 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -42,43 +42,6 @@ EXPORT_SYMBOL(ioremap_bot);	/* aka VMALLOC_END */
>  
>  extern char etext[], _stext[], _sinittext[], _einittext[];
>  
> -#define PGDIR_ORDER	(32 + PGD_T_LOG2 - PGDIR_SHIFT)
> -
> -#ifndef CONFIG_PPC_4K_PAGES
> -static struct kmem_cache *pgtable_cache;
> -
> -void pgtable_cache_init(void)
> -{
> -	pgtable_cache = kmem_cache_create("PGDIR cache", 1 << PGDIR_ORDER,
> -					  1 << PGDIR_ORDER, 0, NULL);
> -	if (pgtable_cache == NULL)
> -		panic("Couldn't allocate pgtable caches");
> -}
> -#endif
> -
> -pgd_t *pgd_alloc(struct mm_struct *mm)
> -{
> -	pgd_t *ret;
> -
> -	/* pgdir take page or two with 4K pages and a page fraction otherwise */
> -#ifndef CONFIG_PPC_4K_PAGES
> -	ret = kmem_cache_alloc(pgtable_cache, GFP_KERNEL | __GFP_ZERO);
> -#else
> -	ret = (pgd_t *)__get_free_pages(GFP_KERNEL|__GFP_ZERO,
> -			PGDIR_ORDER - PAGE_SHIFT);
> -#endif
> -	return ret;
> -}
> -
> -void pgd_free(struct mm_struct *mm, pgd_t *pgd)
> -{
> -#ifndef CONFIG_PPC_4K_PAGES
> -	kmem_cache_free(pgtable_cache, (void *)pgd);
> -#else
> -	free_pages((unsigned long)pgd, PGDIR_ORDER - PAGE_SHIFT);
> -#endif
> -}
> -
>  __ref pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
>  {
>  	pte_t *pte;
> -- 
> 2.1.0