linux_kernel/arch/powerpc/mm/init-common.c

/*
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
 *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
 *    Copyright (C) 1996 Paul Mackerras
 *
 *  Derived from "arch/i386/mm/init.c"
 *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Dave Engebretsen <engebret@us.ibm.com>
 *      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/string.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>

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);
	if (!new)
		panic("Could not allocate pgtable cache for order %d", shift);

	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_CACHE_INDEX && !PGT_CACHE(PMD_CACHE_INDEX))
		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);
}