[PATCH -mm] swsusp: support creating bigger images (rev. 2)

[Rafael J. Wysocki]

On Tuesday 09 May 2006 12:19, Rafael J. Wysocki wrote:
> On Tuesday 09 May 2006 09:33, you wrote:
> > "Rafael J. Wysocki" <rjw@xxxxxxx> wrote:
}-- snip --{
> 
> Thanks for the comments.  I'll do my best to fix all of the issues in the next
> version.

Corrected patch follows.

---
Currently swsusp is only capable of creating suspend images that are not
bigger than 1/2 of the normal zone, because it needs to create a copy of every
page which should be included in the image.  This may hurt the system
responsiveness after resume, especially on systems with less that 1 GB of RAM.

To allow swsusp to create bigger images we can use the observation that
if some pages don't change after the snapshot image of the system has been
created and before the image is entirely saved, they can be included in the
image without copying.  Now if the mapped pages that are not mapped by the
current task are considered, it turns out that they would change only if they
were reclaimed by try_to_free_pages().  Thus if we take them out of reach
of try_to_free_pages(), for example by (temporarily) moving them out of their
respective LRU lists after creating the image, we will be able to include them
in the image without copying.

If these pages are included in the image without copying, the amount of free
memory needed by swsusp is usually much less than otherwise, so the size
of the image may be bigger.  This also makes swsusp use less memory during
suspend and saves us quite a lot of memory allocations and copyings.

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
 include/linux/rmap.h    |    6 +
 include/linux/swap.h    |    4 
 kernel/power/power.h    |   14 ++
 kernel/power/snapshot.c |  230 +++++++++++++++++++++++++++++++++---------------
 kernel/power/swsusp.c   |   16 +--
 kernel/power/user.c     |    2 
 mm/rmap.c               |   44 +++++++++
 mm/vmscan.c             |   68 +++++++++++++-
 8 files changed, 306 insertions(+), 78 deletions(-)

Index: linux-2.6.17-rc3-mm1/mm/rmap.c
===================================================================
--- linux-2.6.17-rc3-mm1.orig/mm/rmap.c	2006-05-01 14:11:50.000000000 +0200
+++ linux-2.6.17-rc3-mm1/mm/rmap.c	2006-05-09 22:44:05.000000000 +0200
@@ -857,3 +857,47 @@ int try_to_unmap(struct page *page, int 
 	return ret;
 }
 
+#ifdef CONFIG_SOFTWARE_SUSPEND
+static int page_mapped_by_task(struct page *page, struct task_struct *task)
+{
+	struct vm_area_struct *vma;
+	int ret = 0;
+
+	if (!task)
+		return 0;
+
+	spin_lock(&task->mm->page_table_lock);
+
+	for (vma = task->mm->mmap; vma; vma = vma->vm_next)
+		if (page_address_in_vma(page, vma) != -EFAULT) {
+			ret = 1;
+			break;
+		}
+
+	spin_unlock(&task->mm->page_table_lock);
+
+	return ret;
+}
+
+/**
+ *	suspend_safe_page - determine if a page can be included in the
+ *	suspend image without copying (returns true if so).
+ *
+ *	It is safe to include the page in the suspend image without
+ *	copying if (a) it's on the LRU and (b) it's mapped by a frozen task
+ *	(all tasks except for the current task should be frozen when it's
+ *	called).  Otherwise the page should be copied for this purpose
+ *	(compound pages are avoided for simplicity).
+ */
+
+int suspend_safe_page(struct page *page)
+{
+	if (!PageLRU(page) || PageCompound(page))
+		return 0;
+
+	if (page_mapped(page))
+		return !page_mapped_by_task(page, current);
+
+	return 0;
+}
+#endif /* CONFIG_SOFTWARE_SUSPEND */
Index: linux-2.6.17-rc3-mm1/include/linux/rmap.h
===================================================================
--- linux-2.6.17-rc3-mm1.orig/include/linux/rmap.h	2006-05-01 14:11:47.000000000 +0200
+++ linux-2.6.17-rc3-mm1/include/linux/rmap.h	2006-05-09 22:43:40.000000000 +0200
@@ -104,6 +104,12 @@ pte_t *page_check_address(struct page *,
  */
 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 
+/*
+ * Used to determine if the page can be included in the suspend image without
+ * copying
+ */
+int suspend_safe_page(struct page *);
+
 #else	/* !CONFIG_MMU */
 
 #define anon_vma_init()		do {} while (0)
Index: linux-2.6.17-rc3-mm1/kernel/power/snapshot.c
===================================================================
--- linux-2.6.17-rc3-mm1.orig/kernel/power/snapshot.c	2006-05-01 14:11:47.000000000 +0200
+++ linux-2.6.17-rc3-mm1/kernel/power/snapshot.c	2006-05-09 23:19:15.000000000 +0200
@@ -13,6 +13,7 @@
 #include <linux/version.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/rmap.h>
 #include <linux/suspend.h>
 #include <linux/smp_lock.h>
 #include <linux/delay.h>
@@ -261,6 +262,14 @@ int restore_special_mem(void)
 	return ret;
 }
 
+/* Represents a stacked allocated page to be used in the future */
+struct res_page {
+	struct res_page *next;
+	char padding[PAGE_SIZE - sizeof(void *)];
+};
+
+static struct res_page *page_list;
+
 static int pfn_is_nosave(unsigned long pfn)
 {
 	unsigned long nosave_begin_pfn = __pa(&__nosave_begin) >> PAGE_SHIFT;
@@ -269,7 +278,7 @@ static int pfn_is_nosave(unsigned long p
 }
 
 /**
- *	saveable - Determine whether a page should be cloned or not.
+ *	saveable - Determine whether a page should be saved or not.
  *	@pfn:	The page
  *
  *	We save a page if it's Reserved, and not in the range of pages
@@ -277,9 +286,8 @@ static int pfn_is_nosave(unsigned long p
  *	isn't part of a free chunk of pages.
  */
 
-static int saveable(struct zone *zone, unsigned long *zone_pfn)
+static int saveable(unsigned long pfn)
 {
-	unsigned long pfn = *zone_pfn + zone->zone_start_pfn;
 	struct page *page;
 
 	if (!pfn_valid(pfn))
@@ -296,46 +304,103 @@ static int saveable(struct zone *zone, u
 	return 1;
 }
 
-unsigned int count_data_pages(void)
+/**
+ *	count_data_pages - returns the number of pages that need to be copied
+ *	in order to be included in the suspend snapshot image.  If @total is
+ *	not null, the total number of pages that should be included in the
+ *	snapshot image is stored in the location pointed to by it.
+ */
+
+unsigned int count_data_pages(unsigned int *total)
 {
 	struct zone *zone;
 	unsigned long zone_pfn;
-	unsigned int n = 0;
+	unsigned int data_pages = 0;
+	unsigned int safe_pages = 0;
 
-	for_each_zone (zone) {
+	for_each_zone(zone) {
 		if (is_highmem(zone))
 			continue;
 		mark_free_pages(zone);
-		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
-			n += saveable(zone, &zone_pfn);
+		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
+			unsigned long pfn = zone_pfn + zone->zone_start_pfn;
+
+			if (saveable(pfn)) {
+				data_pages++;
+				if (suspend_safe_page(pfn_to_page(pfn)))
+					safe_pages++;
+			}
+		}
 	}
-	return n;
+	if (total)
+		*total = data_pages;
+
+	return data_pages - safe_pages;
 }
 
+/**
+ *	copy_data_pages - populates the page backup list @pblist with
+ *	the addresses of the pages that should be included in the
+ *	suspend snapshot image.  The pages that cannot be included in the
+ *	image without copying are copied into empty page frames allocated
+ *	earlier and available from the list page_list (the addresses of
+ *	these page frames are also stored in the page backup list).
+ *
+ *	This function is only called from the critical section, ie. when
+ *	processes are frozen, there's only one CPU online and local IRQs
+ *	are disabled on it.
+ */
+
 static void copy_data_pages(struct pbe *pblist)
 {
 	struct zone *zone;
 	unsigned long zone_pfn;
 	struct pbe *pbe, *p;
+	struct res_page *ptr;
 
 	pbe = pblist;
 	for_each_zone (zone) {
 		if (is_highmem(zone))
 			continue;
+
 		mark_free_pages(zone);
-		/* This is necessary for swsusp_free() */
+		/* This is necessary for free_image() */
 		for_each_pb_page (p, pblist)
 			SetPageNosaveFree(virt_to_page(p));
+
 		for_each_pbe (p, pblist)
-			SetPageNosaveFree(virt_to_page(p->address));
+			if (p->address && p->orig_address != p->address)
+				SetPageNosaveFree(virt_to_page(p->address));
+
+		ptr = page_list;
+		while (ptr) {
+			SetPageNosaveFree(virt_to_page(ptr));
+			ptr = ptr->next;
+		}
+
 		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
-			if (saveable(zone, &zone_pfn)) {
+			unsigned long pfn = zone_pfn + zone->zone_start_pfn;
+
+			if (saveable(pfn)) {
 				struct page *page;
-				page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
+
 				BUG_ON(!pbe);
+				page = pfn_to_page(pfn);
 				pbe->orig_address = (unsigned long)page_address(page);
-				/* copy_page is not usable for copying task structs. */
-				memcpy((void *)pbe->address, (void *)pbe->orig_address, PAGE_SIZE);
+				if (suspend_safe_page(page)) {
+					pbe->address = pbe->orig_address;
+				} else {
+					BUG_ON(!page_list);
+					pbe->address = (unsigned long)page_list;
+					page_list = page_list->next;
+					/*
+					 * copy_page is not usable for copying
+					 * task structs.
+					 */
+					memcpy((void *)pbe->address,
+						(void *)pbe->orig_address,
+						PAGE_SIZE);
+				}
 				pbe = pbe->next;
 			}
 		}
@@ -419,7 +484,7 @@ static inline void *alloc_image_page(gfp
 	res = (void *)get_zeroed_page(gfp_mask);
 	if (safe_needed)
 		while (res && PageNosaveFree(virt_to_page(res))) {
-			/* The page is unsafe, mark it for swsusp_free() */
+			/* The page is unsafe, mark it for free_image() */
 			SetPageNosave(virt_to_page(res));
 			unsafe_pages++;
 			res = (void *)get_zeroed_page(gfp_mask);
@@ -474,11 +539,32 @@ static struct pbe *alloc_pagedir(unsigne
 }
 
 /**
+ *	protect_data_pages - move data pages that need to be protected from
+ *	being reclaimed (ie. those included in the suspend image without
+ *	copying) out of their respective LRU lists.  This is done after the
+ *	image has been created so the LRU lists only have to be restored if
+ *	the suspend fails.
+ *
+ *	This function is only called from the critical section, ie. when
+ *	processes are frozen, there's only one CPU online and local IRQs
+ *	are disabled on it.
+ */
+
+static void protect_data_pages(struct pbe *pblist)
+{
+	struct pbe *p;
+
+	for_each_pbe(p, pblist)
+		if (p->address == p->orig_address)
+			move_out_of_lru(virt_to_page(p->address));
+}
+
+/**
  * Free pages we allocated for suspend. Suspend pages are alocated
  * before atomic copy, so we need to free them after resume.
  */
 
-void swsusp_free(void)
+void free_image(void)
 {
 	struct zone *zone;
 	unsigned long zone_pfn;
@@ -501,6 +587,11 @@ void swsusp_free(void)
 	buffer = NULL;
 }
 
+void swsusp_free(void)
+{
+	free_image();
+	restore_active_inactive_lists();
+}
 
 /**
  *	enough_free_mem - Make sure we enough free memory to snapshot.
@@ -509,32 +600,33 @@ void swsusp_free(void)
  *	free pages.
  */
 
-static int enough_free_mem(unsigned int nr_pages)
+static int enough_free_mem(unsigned int nr_pages, unsigned int copy_pages)
 {
 	struct zone *zone;
-	unsigned int n = 0;
-
-	for_each_zone (zone)
-		if (!is_highmem(zone))
-			n += zone->free_pages;
-	pr_debug("swsusp: available memory: %u pages\n", n);
-	return n > (nr_pages + PAGES_FOR_IO +
-		(nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
-}
+	long avail_pages = 0;
 
-static int alloc_data_pages(struct pbe *pblist, gfp_t gfp_mask, int safe_needed)
-{
-	struct pbe *p;
+	pr_debug("swsusp: pages needed: %u + %lu + %lu\n",
+		 copy_pages,
+		 DIV_ROUND_UP(nr_pages, PBES_PER_PAGE),
+		 SUSPEND_EXTRA_PAGES);
+
+	for_each_zone(zone)
+		if (!is_highmem(zone) && populated_zone(zone)) {
+			avail_pages += zone->free_pages;
+			/*
+			 * We're going to use atomic allocations, so we
+			 * shouldn't count the lowmem reserves in the lower
+			 * zones as available to us
+			 */
+			avail_pages -= zone->lowmem_reserve[ZONE_NORMAL];
+		}
 
-	for_each_pbe (p, pblist) {
-		p->address = (unsigned long)alloc_image_page(gfp_mask, safe_needed);
-		if (!p->address)
-			return -ENOMEM;
-	}
-	return 0;
+	pr_debug("swsusp: available memory: %ld pages\n", avail_pages);
+	return avail_pages > (long)(copy_pages + SUSPEND_EXTRA_PAGES +
+		DIV_ROUND_UP(nr_pages, PBES_PER_PAGE));
 }
 
-static struct pbe *swsusp_alloc(unsigned int nr_pages)
+static struct pbe *swsusp_alloc(unsigned int nr_pages, unsigned int copy_pages)
 {
 	struct pbe *pblist;
 
@@ -543,10 +635,19 @@ static struct pbe *swsusp_alloc(unsigned
 		return NULL;
 	}
 
-	if (alloc_data_pages(pblist, GFP_ATOMIC | __GFP_COLD, 0)) {
-		printk(KERN_ERR "suspend: Allocating image pages failed.\n");
-		swsusp_free();
-		return NULL;
+	page_list = NULL;
+	while (copy_pages--) {
+		struct res_page *ptr;
+
+		ptr = alloc_image_page(GFP_ATOMIC | __GFP_COLD, 0);
+		if (!ptr) {
+			printk(KERN_ERR
+				"suspend: Allocating image pages failed.\n");
+			free_image();
+			return NULL;
+		}
+		ptr->next = page_list;
+		page_list = ptr;
 	}
 
 	return pblist;
@@ -555,24 +656,21 @@ static struct pbe *swsusp_alloc(unsigned
 asmlinkage int swsusp_save(void)
 {
 	unsigned int nr_pages;
+	unsigned int copy_pages;
 
 	pr_debug("swsusp: critical section: \n");
 
 	drain_local_pages();
-	nr_pages = count_data_pages();
-	printk("swsusp: Need to copy %u pages\n", nr_pages);
+	copy_pages = count_data_pages(&nr_pages);
+	printk("swsusp: Need to save %u pages\n", nr_pages);
+	printk("swsusp: %u pages to copy\n", copy_pages);
 
-	pr_debug("swsusp: pages needed: %u + %lu + %u, free: %u\n",
-		 nr_pages,
-		 (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE,
-		 PAGES_FOR_IO, nr_free_pages());
-
-	if (!enough_free_mem(nr_pages)) {
+	if (!enough_free_mem(nr_pages, copy_pages)) {
 		printk(KERN_ERR "swsusp: Not enough free memory\n");
 		return -ENOMEM;
 	}
 
-	pagedir_nosave = swsusp_alloc(nr_pages);
+	pagedir_nosave = swsusp_alloc(nr_pages, copy_pages);
 	if (!pagedir_nosave)
 		return -ENOMEM;
 
@@ -582,6 +680,9 @@ asmlinkage int swsusp_save(void)
 	drain_local_pages();
 	copy_data_pages(pagedir_nosave);
 
+	/* Make sure the pages that we have not copied won't be reclaimed */
+	protect_data_pages(pagedir_nosave);
+
 	/*
 	 * End of critical section. From now on, we can write to memory,
 	 * but we should not touch disk. This specially means we must _not_
@@ -591,7 +692,7 @@ asmlinkage int swsusp_save(void)
 	nr_copy_pages = nr_pages;
 	nr_meta_pages = (nr_pages * sizeof(long) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 
-	printk("swsusp: critical section/: done (%d pages copied)\n", nr_pages);
+	printk("swsusp: critical section/: done (%d pages)\n", nr_pages);
 	return 0;
 }
 
@@ -654,7 +755,7 @@ int snapshot_read_next(struct snapshot_h
 	if (handle->page > nr_meta_pages + nr_copy_pages)
 		return 0;
 	if (!buffer) {
-		/* This makes the buffer be freed by swsusp_free() */
+		/* This makes the buffer be freed by free_image() */
 		buffer = alloc_image_page(GFP_ATOMIC, 0);
 		if (!buffer)
 			return -ENOMEM;
@@ -810,13 +911,6 @@ static inline struct pbe *unpack_orig_ad
  *	of "safe" which will be used later
  */
 
-struct safe_page {
-	struct safe_page *next;
-	char padding[PAGE_SIZE - sizeof(void *)];
-};
-
-static struct safe_page *safe_pages;
-
 static int prepare_image(struct snapshot_handle *handle)
 {
 	int error = 0;
@@ -833,21 +927,21 @@ static int prepare_image(struct snapshot
 		if (!pblist)
 			error = -ENOMEM;
 	}
-	safe_pages = NULL;
+	page_list = NULL;
 	if (!error && nr_pages > unsafe_pages) {
 		nr_pages -= unsafe_pages;
 		while (nr_pages--) {
-			struct safe_page *ptr;
+			struct res_page *ptr;
 
-			ptr = (struct safe_page *)get_zeroed_page(GFP_ATOMIC);
+			ptr = (struct res_page *)get_zeroed_page(GFP_ATOMIC);
 			if (!ptr) {
 				error = -ENOMEM;
 				break;
 			}
 			if (!PageNosaveFree(virt_to_page(ptr))) {
 				/* The page is "safe", add it to the list */
-				ptr->next = safe_pages;
-				safe_pages = ptr;
+				ptr->next = page_list;
+				page_list = ptr;
 			}
 			/* Mark the page as allocated */
 			SetPageNosave(virt_to_page(ptr));
@@ -858,7 +952,7 @@ static int prepare_image(struct snapshot
 		pagedir_nosave = pblist;
 	} else {
 		handle->pbe = NULL;
-		swsusp_free();
+		free_image();
 	}
 	return error;
 }
@@ -882,8 +976,8 @@ static void *get_buffer(struct snapshot_
 	 * The "original" page frame has not been allocated and we have to
 	 * use a "safe" page frame to store the read page
 	 */
-	pbe->address = (unsigned long)safe_pages;
-	safe_pages = safe_pages->next;
+	pbe->address = (unsigned long)page_list;
+	page_list = page_list->next;
 	if (last)
 		last->next = pbe;
 	handle->last_pbe = pbe;
@@ -919,7 +1013,7 @@ int snapshot_write_next(struct snapshot_
 	if (handle->prev && handle->page > nr_meta_pages + nr_copy_pages)
 		return 0;
 	if (!buffer) {
-		/* This makes the buffer be freed by swsusp_free() */
+		/* This makes the buffer be freed by free_image() */
 		buffer = alloc_image_page(GFP_ATOMIC, 0);
 		if (!buffer)
 			return -ENOMEM;
Index: linux-2.6.17-rc3-mm1/kernel/power/power.h
===================================================================
--- linux-2.6.17-rc3-mm1.orig/kernel/power/power.h	2006-05-01 14:11:47.000000000 +0200
+++ linux-2.6.17-rc3-mm1/kernel/power/power.h	2006-05-09 23:03:35.000000000 +0200
@@ -48,7 +48,18 @@ extern dev_t swsusp_resume_device;
 extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);
 
-extern unsigned int count_data_pages(void);
+/*
+ * If the userland suspend is used, some extra space will be needed during
+ * resume for the initrd, the resume binary and its data
+ */
+#if (defined(CONFIG_BLK_DEV_INITRD) && defined(CONFIG_BLK_DEV_RAM))
+#define SUSPEND_EXTRA_PAGES	(PAGES_FOR_IO + \
+				(2 * CONFIG_BLK_DEV_RAM_SIZE * 1024) / PAGE_SIZE)
+#else
+#define SUSPEND_EXTRA_PAGES	PAGES_FOR_IO
+#endif
+
+extern unsigned int count_data_pages(unsigned int *total);
 
 struct snapshot_handle {
 	loff_t		offset;
@@ -111,6 +122,7 @@ extern int restore_special_mem(void);
 
 extern int swsusp_check(void);
 extern int swsusp_shrink_memory(void);
+extern void free_image(void);
 extern void swsusp_free(void);
 extern int swsusp_suspend(void);
 extern int swsusp_resume(void);
Index: linux-2.6.17-rc3-mm1/kernel/power/swsusp.c
===================================================================
--- linux-2.6.17-rc3-mm1.orig/kernel/power/swsusp.c	2006-05-01 14:11:47.000000000 +0200
+++ linux-2.6.17-rc3-mm1/kernel/power/swsusp.c	2006-05-09 23:17:32.000000000 +0200
@@ -177,28 +177,30 @@ int swsusp_shrink_memory(void)
 	long size, tmp;
 	struct zone *zone;
 	unsigned long pages = 0;
-	unsigned int i = 0;
+	unsigned int pages_to_save;
+	unsigned int i = 0; /* for the progress meter */
 	char *p = "-\\|/";
 
 	printk("Shrinking memory...  ");
 	do {
 		size = 2 * count_special_pages();
-		size += size / 50 + count_data_pages();
-		size += (size + PBES_PER_PAGE - 1) / PBES_PER_PAGE +
-			PAGES_FOR_IO;
+		size += size / 50 + count_data_pages(&pages_to_save);
+		size += DIV_ROUND_UP(pages_to_save, PBES_PER_PAGE) +
+			SUSPEND_EXTRA_PAGES;
 		tmp = size;
 		for_each_zone (zone)
 			if (!is_highmem(zone) && populated_zone(zone)) {
 				tmp -= zone->free_pages;
 				tmp += zone->lowmem_reserve[ZONE_NORMAL];
 			}
+		size = pages_to_save * (PAGE_SIZE + sizeof(long));
 		if (tmp > 0) {
 			tmp = __shrink_memory(tmp);
 			if (!tmp)
 				return -ENOMEM;
 			pages += tmp;
-		} else if (size > image_size / PAGE_SIZE) {
-			tmp = __shrink_memory(size - (image_size / PAGE_SIZE));
+		} else if (size > image_size) {
+			tmp = __shrink_memory(size - image_size);
 			pages += tmp;
 		}
 		printk("\b%c", p[i++%4]);
@@ -261,7 +263,7 @@ int swsusp_resume(void)
 	 * very tight, so we have to free it as soon as we can to avoid
 	 * subsequent failures
 	 */
-	swsusp_free();
+	free_image();
 	restore_processor_state();
 	restore_special_mem();
 	touch_softlockup_watchdog();
Index: linux-2.6.17-rc3-mm1/kernel/power/user.c
===================================================================
--- linux-2.6.17-rc3-mm1.orig/kernel/power/user.c	2006-05-01 14:11:21.000000000 +0200
+++ linux-2.6.17-rc3-mm1/kernel/power/user.c	2006-05-01 16:00:00.000000000 +0200
@@ -153,6 +153,8 @@ static int snapshot_ioctl(struct inode *
 	case SNAPSHOT_UNFREEZE:
 		if (!data->frozen)
 			break;
+		if (data->ready)
+			swsusp_free();
 		down(&pm_sem);
 		thaw_processes();
 		enable_nonboot_cpus();
Index: linux-2.6.17-rc3-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.17-rc3-mm1.orig/mm/vmscan.c	2006-05-01 14:11:50.000000000 +0200
+++ linux-2.6.17-rc3-mm1/mm/vmscan.c	2006-05-09 23:26:24.000000000 +0200
@@ -1437,7 +1437,73 @@ out:
 
 	return ret;
 }
-#endif
+
+#ifdef CONFIG_SOFTWARE_SUSPEND
+static LIST_HEAD(saved_active_pages);
+static LIST_HEAD(saved_inactive_pages);
+
+/**
+ *	move_out_of_lru - software suspend includes some pages in the
+ *	suspend snapshot image without copying and these pages should be
+ *	procected from being reclaimed, which can be done by (temporarily)
+ *	moving them out of their respective LRU lists
+ *
+ *	It is to be called with local IRQs disabled.
+ */
+
+void move_out_of_lru(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+
+	spin_lock(&zone->lru_lock);
+	if (likely(PageLRU(page))) {
+		if (PageActive(page)) {
+			del_page_from_active_list(zone, page);
+			list_add(&page->lru, &saved_active_pages);
+		} else {
+			del_page_from_inactive_list(zone, page);
+			list_add(&page->lru, &saved_inactive_pages);
+		}
+		ClearPageLRU(page);
+	}
+	spin_unlock(&zone->lru_lock);
+}
+
+
+/**
+ *	restore_active_inactive_lists - used by the software suspend to move
+ *	the pages taken out of the LRU by take_page_out_of_lru() back to
+ *	their respective active/inactive lists (if the suspend fails)
+ */
+
+void restore_active_inactive_lists(void)
+{
+	struct page *page;
+	struct zone *zone;
+
+	while (!list_empty(&saved_active_pages)) {
+		page = lru_to_page(&saved_active_pages);
+		zone = page_zone(page);
+		list_del(&page->lru);
+		spin_lock_irq(&zone->lru_lock);
+		SetPageLRU(page);
+		add_page_to_active_list(zone, page);
+		spin_unlock_irq(&zone->lru_lock);
+	}
+
+	while (!list_empty(&saved_inactive_pages)) {
+		page = lru_to_page(&saved_inactive_pages);
+		zone = page_zone(page);
+		list_del(&page->lru);
+		spin_lock_irq(&zone->lru_lock);
+		SetPageLRU(page);
+		add_page_to_inactive_list(zone, page);
+		spin_unlock_irq(&zone->lru_lock);
+	}
+}
+#endif /* CONFIG_SOFTWARE_SUSPEND */
+
+#endif /* CONFIG_PM */
 
 #ifdef CONFIG_HOTPLUG_CPU
 /* It's optimal to keep kswapds on the same CPUs as their memory, but
Index: linux-2.6.17-rc3-mm1/include/linux/swap.h
===================================================================
--- linux-2.6.17-rc3-mm1.orig/include/linux/swap.h	2006-05-01 14:11:47.000000000 +0200
+++ linux-2.6.17-rc3-mm1/include/linux/swap.h	2006-05-07 14:17:36.000000000 +0200
@@ -184,7 +184,9 @@ extern void swap_setup(void);
 
 /* linux/mm/vmscan.c */
 extern unsigned long try_to_free_pages(struct zone **, gfp_t);
-extern unsigned long shrink_all_memory(unsigned long nr_pages);
+extern unsigned long shrink_all_memory(unsigned long);
+extern void move_out_of_lru(struct page *);
+extern void restore_active_inactive_lists(void);
 extern int vm_swappiness;
 extern int remove_mapping(struct address_space *mapping, struct page *page);
 
-
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