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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/arm26/mm/small_page.c
downloadlinux-stericsson-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/arm26/mm/small_page.c')
-rw-r--r--arch/arm26/mm/small_page.c194
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
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+++ b/arch/arm26/mm/small_page.c
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+/*
+ * 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+ * FIXME - this comment is *out of date*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);
+}