[Suspend2][] [Suspend2] Dynamically allocated pageflags

[Nigel Cunningham]

Add support for dynamically allocated pageflags - bitmaps consisting of
single pages merged together into per zone bitmaps that can then be used as
temporary page flags.

Signed-off-by: Nigel Cunningham <nigel@xxxxxxxxxxxx>

 include/linux/dyn_pageflags.h |   66 ++++++++
 lib/Kconfig                   |    3 
 lib/Makefile                  |    2 
 lib/dyn_pageflags.c           |  330 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 401 insertions(+), 0 deletions(-)

diff --git a/include/linux/dyn_pageflags.h b/include/linux/dyn_pageflags.h
new file mode 100644
index 0000000..1a7b5d8
--- /dev/null
+++ b/include/linux/dyn_pageflags.h
@@ -0,0 +1,66 @@
+/*
+ * include/linux/dyn_pageflags.h
+ *
+ * Copyright (C) 2004-2006 Nigel Cunningham <nigel@xxxxxxxxxxxx>
+ *
+ * This file is released under the GPLv2.
+ *
+ * It implements support for dynamically allocated bitmaps that are
+ * used for temporary or infrequently used pageflags, in lieu of
+ * bits in the struct page flags entry.
+ */
+
+#ifndef DYN_PAGEFLAGS_H
+#define DYN_PAGEFLAGS_H
+
+#include <linux/mm.h>
+
+typedef unsigned long *** dyn_pageflags_t;
+
+#define BITNUMBER(page) (page_to_pfn(page))
+
+#if BITS_PER_LONG == 32
+#define UL_SHIFT 5
+#else 
+#if BITS_PER_LONG == 64
+#define UL_SHIFT 6
+#else
+#error Bits per long not 32 or 64?
+#endif
+#endif
+
+#define BIT_NUM_MASK (sizeof(unsigned long) * 8 - 1)
+#define PAGE_NUM_MASK (~((1 << (PAGE_SHIFT + 3)) - 1))
+#define UL_NUM_MASK (~(BIT_NUM_MASK | PAGE_NUM_MASK))
+
+#define BITS_PER_PAGE (PAGE_SIZE << 3)
+#define PAGENUMBER(zone_offset) (zone_offset >> (PAGE_SHIFT + 3))
+#define PAGEINDEX(zone_offset) ((zone_offset & UL_NUM_MASK) >> UL_SHIFT)
+#define PAGEBIT(zone_offset) (zone_offset & BIT_NUM_MASK)
+
+#define PAGE_UL_PTR(bitmap, zone_num, zone_pfn) \
+       ((bitmap[zone_num][PAGENUMBER(zone_pfn)])+PAGEINDEX(zone_pfn))
+
+/* With the above macros defined, you can do...
+
+#define PagePageset1(page) (test_dynpageflag(&pageset1_map, page))
+#define SetPagePageset1(page) (set_dynpageflag(&pageset1_map, page))
+#define ClearPagePageset1(page) (clear_dynpageflag(&pageset1_map, page))
+*/
+
+#define BITMAP_FOR_EACH_SET(bitmap, counter) \
+	for (counter = get_next_bit_on(bitmap, -1); counter > -1; \
+		counter = get_next_bit_on(bitmap, counter))
+
+extern void clear_dyn_pageflags(dyn_pageflags_t pagemap);
+extern int allocate_dyn_pageflags(dyn_pageflags_t *pagemap);
+extern void free_dyn_pageflags(dyn_pageflags_t *pagemap);
+extern int dyn_pageflags_pages_per_bitmap(void);
+extern int get_next_bit_on(dyn_pageflags_t bitmap, int counter);
+extern unsigned long *dyn_pageflags_ul_ptr(dyn_pageflags_t *bitmap,
+		struct page *pg);
+
+extern int test_dynpageflag(dyn_pageflags_t *bitmap, struct page *page);
+extern void set_dynpageflag(dyn_pageflags_t *bitmap, struct page *page);
+extern void clear_dynpageflag(dyn_pageflags_t *bitmap, struct page *page);
+#endif
diff --git a/lib/Kconfig b/lib/Kconfig
index 3de9335..5596bd8 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -38,6 +38,9 @@ config LIBCRC32C
 	  require M here.  See Castagnoli93.
 	  Module will be libcrc32c.
 
+config DYN_PAGEFLAGS
+	bool
+
 #
 # compression support is select'ed if needed
 #
diff --git a/lib/Makefile b/lib/Makefile
index b830c9a..8290e9b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -31,6 +31,8 @@ ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
   lib-y += dec_and_lock.o
 endif
 
+obj-$(CONFIG_DYN_PAGEFLAGS) += dyn_pageflags.o
+
 obj-$(CONFIG_CRC_CCITT)	+= crc-ccitt.o
 obj-$(CONFIG_CRC16)	+= crc16.o
 obj-$(CONFIG_CRC32)	+= crc32.o
diff --git a/lib/dyn_pageflags.c b/lib/dyn_pageflags.c
new file mode 100644
index 0000000..4da52f5
--- /dev/null
+++ b/lib/dyn_pageflags.c
@@ -0,0 +1,330 @@
+/*
+ * lib/dyn_pageflags.c
+ *
+ * Copyright (C) 2004-2006 Nigel Cunningham <nigel@xxxxxxxxxxxx>
+ * 
+ * This file is released under the GPLv2.
+ *
+ * Routines for dynamically allocating and releasing bitmaps
+ * used as pseudo-pageflags.
+ *
+ * Arrays are not contiguous. The first sizeof(void *) bytes are
+ * the pointer to the next page in the bitmap. This allows us to
+ * work under low memory conditions where order 0 might be all
+ * that's available. In their original use (suspend2), it also
+ * lets us save the pages at suspend time, reload and relocate them
+ * as necessary at resume time without much effort.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/dyn_pageflags.h>
+#include <linux/bootmem.h>
+
+#define page_to_zone_offset(pg) (page_to_pfn(pg) - page_zone(pg)->zone_start_pfn)
+
+/* 
+ * num_zones
+ * 
+ * How many zones are there?
+ *
+ */
+
+static int num_zones(void)
+{
+	int result = 0;
+	struct zone *zone;
+
+	for_each_zone(zone)
+		result++;
+
+	return result;
+}
+
+/* 
+ * pages_for_zone(struct zone *zone)
+ * 
+ * How many pages do we need for a bitmap for this zone?
+ *
+ */
+
+static int pages_for_zone(struct zone *zone)
+{
+	return (zone->spanned_pages + (PAGE_SIZE << 3) - 1) >>
+			(PAGE_SHIFT + 3);
+}
+
+/*
+ * page_zone_number(struct page *page)
+ *
+ * Which zone index does the page match?
+ *
+ */
+
+static int page_zone_number(struct page *page)
+{
+	struct zone *zone, *zone_sought = page_zone(page);
+	int zone_num = 0;
+
+	for_each_zone(zone)
+		if (zone == zone_sought)
+			return zone_num;
+		else
+			zone_num++;
+
+	printk("Was looking for a zone for page %p.\n", page);
+	BUG_ON(1);
+
+	return 0;
+}
+
+/*
+ * dyn_pageflags_pages_per_bitmap
+ *
+ * Number of pages needed for a bitmap covering all zones.
+ *
+ */
+int dyn_pageflags_pages_per_bitmap(void)
+{
+	int total = 0;
+	struct zone *zone;
+
+	for_each_zone(zone)
+		total += pages_for_zone(zone);
+
+	return total;
+}
+
+/* 
+ * clear_dyn_pageflags(dyn_pageflags_t pagemap)
+ *
+ * Clear an array used to store local page flags.
+ *
+ */
+
+void clear_dyn_pageflags(dyn_pageflags_t pagemap)
+{
+	int i = 0, zone_num = 0;
+	struct zone *zone;
+	
+	BUG_ON(!pagemap);
+
+	for_each_zone(zone) {
+		for (i = 0; i < pages_for_zone(zone); i++)
+			memset((pagemap[zone_num][i]), 0, PAGE_SIZE);
+		zone_num++;
+	}
+}
+
+/* 
+ * allocate_dyn_pageflags(dyn_pageflags_t *pagemap)
+ *
+ * Allocate a bitmap for dynamic page flags.
+ *
+ */
+int allocate_dyn_pageflags(dyn_pageflags_t *pagemap)
+{
+	int i, zone_num = 0;
+	struct zone *zone;
+
+	BUG_ON(*pagemap);
+
+	*pagemap = kmalloc(sizeof(void *) * num_zones(), GFP_ATOMIC);
+
+	if (!*pagemap)
+		return -ENOMEM;
+
+	for_each_zone(zone) {
+		int zone_pages = pages_for_zone(zone);
+		(*pagemap)[zone_num] = kmalloc(sizeof(void *) * zone_pages,
+					       GFP_ATOMIC);
+
+		if (!(*pagemap)[zone_num]) {
+			kfree (*pagemap);
+			return -ENOMEM;
+		}
+
+		for (i = 0; i < zone_pages; i++) {
+			unsigned long address = get_zeroed_page(GFP_ATOMIC);
+			(*pagemap)[zone_num][i] = (unsigned long *) address;
+			if (!(*pagemap)[zone_num][i]) {
+				printk("Error. Unable to allocate memory for "
+					"dynamic pageflags.");
+				free_dyn_pageflags(pagemap);
+				return -ENOMEM;
+			}
+		}
+		zone_num++;
+	}
+
+	return 0;
+}
+
+/* 
+ * free_dyn_pageflags(dyn_pageflags_t *pagemap)
+ *
+ * Free a dynamically allocated pageflags bitmap. For Suspend2 usage, we
+ * support data being relocated from slab to pages that don't conflict
+ * with the image that will be copied back. This is the reason for the
+ * PageSlab tests below.
+ *
+ */
+void free_dyn_pageflags(dyn_pageflags_t *pagemap)
+{
+	int i = 0, zone_num = 0;
+	struct zone *zone;
+
+	if (!*pagemap)
+		return;
+	
+	for_each_zone(zone) {
+		int zone_pages = pages_for_zone(zone);
+
+		if (!((*pagemap)[zone_num]))
+			continue;
+		for (i = 0; i < zone_pages; i++)
+			if ((*pagemap)[zone_num][i])
+				free_page((unsigned long) (*pagemap)[zone_num][i]);
+	
+		if (PageSlab(virt_to_page((*pagemap)[zone_num])))
+			kfree((*pagemap)[zone_num]);
+		else
+			free_page((unsigned long) (*pagemap)[zone_num]);
+
+		zone_num++;
+	}
+
+	if (PageSlab(virt_to_page((*pagemap))))
+		kfree(*pagemap);
+	else
+		free_page((unsigned long) (*pagemap));
+
+	*pagemap = NULL;
+	return;
+}
+
+/*
+ * dyn_pageflags_ul_ptr(dyn_pageflags_t *bitmap, struct page *pg)
+ *
+ * Get a pointer to the unsigned long containing the flag in the bitmap
+ * for the given page.
+ *
+ */
+
+unsigned long *dyn_pageflags_ul_ptr(dyn_pageflags_t *bitmap, struct page *pg)
+{
+	int zone_pfn = page_to_zone_offset(pg);
+	int zone_num = page_zone_number(pg);
+	int pagenum = PAGENUMBER(zone_pfn);
+	int page_offset = PAGEINDEX(zone_pfn);
+	return ((*bitmap)[zone_num][pagenum]) + page_offset;
+}
+
+/*
+ * test_dynpageflag(dyn_pageflags_t *bitmap, struct page *page)
+ *
+ * Is the page flagged in the given bitmap?
+ *
+ */
+
+int test_dynpageflag(dyn_pageflags_t *bitmap, struct page *page)
+{
+	unsigned long *ul = dyn_pageflags_ul_ptr(bitmap, page);
+	int zone_offset = page_to_zone_offset(page);
+	int bit = PAGEBIT(zone_offset);
+	
+	return test_bit(bit, ul);
+}
+
+/*
+ * set_dynpageflag(dyn_pageflags_t *bitmap, struct page *page)
+ *
+ * Set the flag for the page in the given bitmap.
+ *
+ */
+
+void set_dynpageflag(dyn_pageflags_t *bitmap, struct page *page)
+{
+	unsigned long *ul = dyn_pageflags_ul_ptr(bitmap, page);
+	int zone_offset = page_to_zone_offset(page);
+	int bit = PAGEBIT(zone_offset);
+	set_bit(bit, ul);
+}
+
+/*
+ * clear_dynpageflags(dyn_pageflags_t *bitmap, struct page *page)
+ *
+ * Clear the flag for the page in the given bitmap.
+ *
+ */
+
+void clear_dynpageflag(dyn_pageflags_t *bitmap, struct page *page)
+{
+	unsigned long *ul = dyn_pageflags_ul_ptr(bitmap, page);
+	int zone_offset = page_to_zone_offset(page);
+	int bit = PAGEBIT(zone_offset);
+	clear_bit(bit, ul);
+}
+
+/*
+ * get_next_bit_on(dyn_pageflags_t bitmap, int counter)
+ *
+ * Given a pfn (possibly -1), find the next pfn in the bitmap that
+ * is set. If there are no more flags set, return -1.
+ *
+ */
+
+int get_next_bit_on(dyn_pageflags_t bitmap, int counter)
+{
+	struct page *page;
+	struct zone *zone;
+	unsigned long *ul = NULL;
+	int zone_offset, pagebit, zone_num, first;
+
+	first = (counter == -1);
+	
+	if (first)
+		counter = first_online_pgdat()->node_zones->zone_start_pfn;
+
+	page = pfn_to_page(counter);
+	zone = page_zone(page);
+	zone_num = page_zone_number(page);
+	zone_offset = counter - zone->zone_start_pfn;
+
+	if (first) {
+		counter--;
+		zone_offset--;
+	} else
+		ul = (bitmap[zone_num][PAGENUMBER(zone_offset)]) + PAGEINDEX(zone_offset);
+
+	do {
+		counter++;
+		zone_offset++;
+	
+		if (zone_offset >= zone->spanned_pages) {
+			do {
+				zone = next_zone(zone);
+				if (!zone)
+					return -1;
+				zone_num++;
+			} while(!zone->spanned_pages);
+
+			counter = zone->zone_start_pfn;
+			zone_offset = 0;
+		}
+		
+		/*
+		 * This could be optimised, but there are more
+		 * important things and the code is simple at
+		 * the moment 
+		 */
+		pagebit = PAGEBIT(zone_offset);
+
+		if (!pagebit)
+			ul = (bitmap[zone_num][PAGENUMBER(zone_offset)]) + PAGEINDEX(zone_offset);
+
+	} while(!test_bit(pagebit, ul));
+
+	return counter;
+}
+

--
Nigel Cunningham		nigel at suspend2 dot net
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