patch-2.3.23 linux/mm/highmem.c

• Lines: 82
• Date: Tue Oct 19 10:22:19 1999
• Orig file: v2.3.22/linux/mm/highmem.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.22/linux/mm/highmem.c linux/mm/highmem.c
@@ -0,0 +1,81 @@
+/*
+ * High memory handling common code and variables.
+ *
+ * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
+ *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
+ *
+ * Redesigned the x86 32-bit VM architecture to deal with
+ * 64-bit physical space. With current x86 CPUs this
+ * means up to 64 Gigabytes physical RAM.
+ *
+ * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+
+unsigned long highmem_mapnr;
+unsigned long nr_free_highpages = 0;
+
+struct page * prepare_highmem_swapout(struct page * page)
+{
+	unsigned long regular_page;
+	unsigned long vaddr;
+	/*
+	 * If this is a highmem page so it can't be swapped out directly
+	 * otherwise the b_data buffer addresses will break
+	 * the lowlevel device drivers.
+	 */
+	if (!PageHighMem(page))
+		return page;
+
+	regular_page = __get_free_page(GFP_ATOMIC);
+	if (!regular_page)
+		return NULL;
+
+	vaddr = kmap(page, KM_READ);
+	copy_page((void *)regular_page, (void *)vaddr);
+	kunmap(vaddr, KM_READ);
+
+	/*
+	 * ok, we can just forget about our highmem page since 
+	 * we stored its data into the new regular_page.
+	 */
+	__free_page(page);
+
+	return mem_map + MAP_NR(regular_page);
+}
+
+struct page * replace_with_highmem(struct page * page)
+{
+	struct page *highpage;
+	unsigned long vaddr;
+
+	if (PageHighMem(page) || !nr_free_highpages)
+		return page;
+
+	highpage = get_free_highpage(GFP_ATOMIC|__GFP_HIGHMEM);
+	if (!highpage)
+		return page;
+	if (!PageHighMem(highpage)) {
+		__free_page(highpage);
+		return page;
+	}
+
+	vaddr = kmap(highpage, KM_WRITE);
+	copy_page((void *)vaddr, (void *)page_address(page));
+	kunmap(vaddr, KM_WRITE);
+
+	/* Preserve the caching of the swap_entry. */
+	highpage->offset = page->offset;
+	highpage->inode = page->inode;
+
+	/*
+	 * We can just forget the old page since 
+	 * we stored its data into the new highmem-page.
+	 */
+	__free_page(page);
+
+	return highpage;
+}