diff options
Diffstat (limited to 'arch/arm26/mm/small_page.c')
| -rw-r--r-- | arch/arm26/mm/small_page.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/arch/arm26/mm/small_page.c b/arch/arm26/mm/small_page.c new file mode 100644 index 00000000000..77be86cca78 --- /dev/null +++ b/arch/arm26/mm/small_page.c @@ -0,0 +1,194 @@ +/* + * linux/arch/arm26/mm/small_page.c + * + * Copyright (C) 1996 Russell King + * Copyright (C) 2003 Ian Molton + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * Changelog: + * 26/01/1996 RMK Cleaned up various areas to make little more generic + * 07/02/1999 RMK Support added for 16K and 32K page sizes + * containing 8K blocks + * 23/05/2004 IM Fixed to use struct page->lru (thanks wli) + * + */ +#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/ptrace.h> +#include <linux/mman.h> +#include <linux/mm.h> +#include <linux/swap.h> +#include <linux/smp.h> +#include <linux/bitops.h> + +#include <asm/pgtable.h> + +#define PEDANTIC + +/* + * Requirement: + * We need to be able to allocate naturally aligned memory of finer + * granularity than the page size. This is typically used for the + * second level page tables on 32-bit ARMs. + * + * FIXME - this comment is *out of date* + * Theory: + * We "misuse" the Linux memory management system. We use alloc_page + * to allocate a page and then mark it as reserved. The Linux memory + * management system will then ignore the "offset", "next_hash" and + * "pprev_hash" entries in the mem_map for this page. + * + * We then use a bitstring in the "offset" field to mark which segments + * of the page are in use, and manipulate this as required during the + * allocation and freeing of these small pages. + * + * We also maintain a queue of pages being used for this purpose using + * the "next_hash" and "pprev_hash" entries of mem_map; + */ + +struct order { + struct list_head queue; + unsigned int mask; /* (1 << shift) - 1 */ + unsigned int shift; /* (1 << shift) size of page */ + unsigned int block_mask; /* nr_blocks - 1 */ + unsigned int all_used; /* (1 << nr_blocks) - 1 */ +}; + + +static struct order orders[] = { +#if PAGE_SIZE == 32768 + { LIST_HEAD_INIT(orders[0].queue), 2047, 11, 15, 0x0000ffff }, + { LIST_HEAD_INIT(orders[1].queue), 8191, 13, 3, 0x0000000f } +#else +#error unsupported page size (ARGH!) +#endif +}; + +#define USED_MAP(pg) ((pg)->index) +#define TEST_AND_CLEAR_USED(pg,off) (test_and_clear_bit(off, &USED_MAP(pg))) +#define SET_USED(pg,off) (set_bit(off, &USED_MAP(pg))) + +static DEFINE_SPINLOCK(small_page_lock); + +static unsigned long __get_small_page(int priority, struct order *order) +{ + unsigned long flags; + struct page *page; + int offset; + + do { + spin_lock_irqsave(&small_page_lock, flags); + + if (list_empty(&order->queue)) + goto need_new_page; + + page = list_entry(order->queue.next, struct page, lru); +again: +#ifdef PEDANTIC + if (USED_MAP(page) & ~order->all_used) + PAGE_BUG(page); +#endif + offset = ffz(USED_MAP(page)); + SET_USED(page, offset); + if (USED_MAP(page) == order->all_used) + list_del_init(&page->lru); + spin_unlock_irqrestore(&small_page_lock, flags); + + return (unsigned long) page_address(page) + (offset << order->shift); + +need_new_page: + spin_unlock_irqrestore(&small_page_lock, flags); + page = alloc_page(priority); + spin_lock_irqsave(&small_page_lock, flags); + + if (list_empty(&order->queue)) { + if (!page) + goto no_page; + SetPageReserved(page); + USED_MAP(page) = 0; + list_add(&page->lru, &order->queue); + goto again; + } + + spin_unlock_irqrestore(&small_page_lock, flags); + __free_page(page); + } while (1); + +no_page: + spin_unlock_irqrestore(&small_page_lock, flags); + return 0; +} + +static void __free_small_page(unsigned long spage, struct order *order) +{ + unsigned long flags; + struct page *page; + + if (virt_addr_valid(spage)) { + page = virt_to_page(spage); + + /* + * The container-page must be marked Reserved + */ + if (!PageReserved(page) || spage & order->mask) + goto non_small; + +#ifdef PEDANTIC + if (USED_MAP(page) & ~order->all_used) + PAGE_BUG(page); +#endif + + spage = spage >> order->shift; + spage &= order->block_mask; + + /* + * the following must be atomic wrt get_page + */ + spin_lock_irqsave(&small_page_lock, flags); + + if (USED_MAP(page) == order->all_used) + list_add(&page->lru, &order->queue); + + if (!TEST_AND_CLEAR_USED(page, spage)) + goto already_free; + + if (USED_MAP(page) == 0) + goto free_page; + + spin_unlock_irqrestore(&small_page_lock, flags); + } + return; + +free_page: + /* + * unlink the page from the small page queue and free it + */ + list_del_init(&page->lru); + spin_unlock_irqrestore(&small_page_lock, flags); + ClearPageReserved(page); + __free_page(page); + return; + +non_small: + printk("Trying to free non-small page from %p\n", __builtin_return_address(0)); + return; +already_free: + printk("Trying to free free small page from %p\n", __builtin_return_address(0)); +} + +unsigned long get_page_8k(int priority) +{ + return __get_small_page(priority, orders+1); +} + +void free_page_8k(unsigned long spage) +{ + __free_small_page(spage, orders+1); +} |