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 000000000000..77be86cca789
--- /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+ * FIXME - this comment is *out of date*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);
+}