[RFC][PATCH 0/3] swsusp: Stop using page flags

[RFC][PATCH 0/3] swsusp: Stop using page flags

[Rafael J. Wysocki]

Hi,

The following three patches make swsusp use its own data structures for memory
management instead of special page flags.  Thus the page flags used so far by
swsusp (PG_nosave, PG_nosave_free) can be used for other purposes and I believe
there are some urgend needs of them. :-)

Last week I sent these patches to the linux-pm and linux-mm lists and there
were no negative comments.  Also I've been testing them on my x86_64 boxes for
a few days and apparently they don't break anything.  I think they can go into
-mm for testing.

Comments are welcome.

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

[RFC][PATCH 1/3] swsusp: Use inline functions for changing page flags

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Replace direct invocations of SetPageNosave(), SetPageNosaveFree() etc. with
calls to inline functions that can be changed in subsequent patches without
modifying the code calling them.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 include/linux/suspend.h |   33 +++++++++++++++++++++++++++++++++
 kernel/power/snapshot.c |   48 +++++++++++++++++++++++++-----------------------
 mm/page_alloc.c         |    6 +++---
 3 files changed, 61 insertions(+), 26 deletions(-)

Index: linux-2.6.21-rc2/include/linux/suspend.h
===================================================================
--- linux-2.6.21-rc2.orig/include/linux/suspend.h	2007-03-02 09:05:53.000000000 +0100
+++ linux-2.6.21-rc2/include/linux/suspend.h	2007-03-02 09:24:02.000000000 +0100
@@ -8,6 +8,7 @@
 #include <linux/notifier.h>
 #include <linux/init.h>
 #include <linux/pm.h>
+#include <linux/mm.h>
 
 /* struct pbe is used for creating lists of pages that should be restored
  * atomically during the resume from disk, because the page frames they have
@@ -49,6 +50,38 @@ void __save_processor_state(struct saved
 void __restore_processor_state(struct saved_context *ctxt);
 unsigned long get_safe_page(gfp_t gfp_mask);
 
+/* Page management functions for the software suspend (swsusp) */
+
+static inline void swsusp_set_page_forbidden(struct page *page)
+{
+	SetPageNosave(page);
+}
+
+static inline int swsusp_page_is_forbidden(struct page *page)
+{
+	return PageNosave(page);
+}
+
+static inline void swsusp_unset_page_forbidden(struct page *page)
+{
+	ClearPageNosave(page);
+}
+
+static inline void swsusp_set_page_free(struct page *page)
+{
+	SetPageNosaveFree(page);
+}
+
+static inline int swsusp_page_is_free(struct page *page)
+{
+	return PageNosaveFree(page);
+}
+
+static inline void swsusp_unset_page_free(struct page *page)
+{
+	ClearPageNosaveFree(page);
+}
+
 /*
  * XXX: We try to keep some more pages free so that I/O operations succeed
  * without paging. Might this be more?
Index: linux-2.6.21-rc2/kernel/power/snapshot.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/snapshot.c	2007-03-02 09:05:53.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/snapshot.c	2007-03-02 09:27:06.000000000 +0100
@@ -67,15 +67,15 @@ static void *get_image_page(gfp_t gfp_ma
 
 	res = (void *)get_zeroed_page(gfp_mask);
 	if (safe_needed)
-		while (res && PageNosaveFree(virt_to_page(res))) {
+		while (res && swsusp_page_is_free(virt_to_page(res))) {
 			/* The page is unsafe, mark it for swsusp_free() */
-			SetPageNosave(virt_to_page(res));
+			swsusp_set_page_forbidden(virt_to_page(res));
 			allocated_unsafe_pages++;
 			res = (void *)get_zeroed_page(gfp_mask);
 		}
 	if (res) {
-		SetPageNosave(virt_to_page(res));
-		SetPageNosaveFree(virt_to_page(res));
+		swsusp_set_page_forbidden(virt_to_page(res));
+		swsusp_set_page_free(virt_to_page(res));
 	}
 	return res;
 }
@@ -91,8 +91,8 @@ static struct page *alloc_image_page(gfp
 
 	page = alloc_page(gfp_mask);
 	if (page) {
-		SetPageNosave(page);
-		SetPageNosaveFree(page);
+		swsusp_set_page_forbidden(page);
+		swsusp_set_page_free(page);
 	}
 	return page;
 }
@@ -110,9 +110,9 @@ static inline void free_image_page(void 
 
 	page = virt_to_page(addr);
 
-	ClearPageNosave(page);
+	swsusp_unset_page_forbidden(page);
 	if (clear_nosave_free)
-		ClearPageNosaveFree(page);
+		swsusp_unset_page_free(page);
 
 	__free_page(page);
 }
@@ -615,7 +615,8 @@ static struct page *saveable_highmem_pag
 
 	BUG_ON(!PageHighMem(page));
 
-	if (PageNosave(page) || PageReserved(page) || PageNosaveFree(page))
+	if (swsusp_page_is_forbidden(page) ||  swsusp_page_is_free(page) ||
+	    PageReserved(page))
 		return NULL;
 
 	return page;
@@ -681,7 +682,7 @@ static struct page *saveable_page(unsign
 
 	BUG_ON(PageHighMem(page));
 
-	if (PageNosave(page) || PageNosaveFree(page))
+	if (swsusp_page_is_forbidden(page) || swsusp_page_is_free(page))
 		return NULL;
 
 	if (PageReserved(page) && pfn_is_nosave(pfn))
@@ -821,9 +822,10 @@ void swsusp_free(void)
 			if (pfn_valid(pfn)) {
 				struct page *page = pfn_to_page(pfn);
 
-				if (PageNosave(page) && PageNosaveFree(page)) {
-					ClearPageNosave(page);
-					ClearPageNosaveFree(page);
+				if (swsusp_page_is_forbidden(page) &&
+				    swsusp_page_is_free(page)) {
+					swsusp_unset_page_forbidden(page);
+					swsusp_unset_page_free(page);
 					__free_page(page);
 				}
 			}
@@ -1146,7 +1148,7 @@ static int mark_unsafe_pages(struct memo
 		max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
 			if (pfn_valid(pfn))
-				ClearPageNosaveFree(pfn_to_page(pfn));
+				swsusp_unset_page_free(pfn_to_page(pfn));
 	}
 
 	/* Mark pages that correspond to the "original" pfns as "unsafe" */
@@ -1155,7 +1157,7 @@ static int mark_unsafe_pages(struct memo
 		pfn = memory_bm_next_pfn(bm);
 		if (likely(pfn != BM_END_OF_MAP)) {
 			if (likely(pfn_valid(pfn)))
-				SetPageNosaveFree(pfn_to_page(pfn));
+				swsusp_set_page_free(pfn_to_page(pfn));
 			else
 				return -EFAULT;
 		}
@@ -1321,14 +1323,14 @@ prepare_highmem_image(struct memory_bitm
 		struct page *page;
 
 		page = alloc_page(__GFP_HIGHMEM);
-		if (!PageNosaveFree(page)) {
+		if (!swsusp_page_is_free(page)) {
 			/* The page is "safe", set its bit the bitmap */
 			memory_bm_set_bit(bm, page_to_pfn(page));
 			safe_highmem_pages++;
 		}
 		/* Mark the page as allocated */
-		SetPageNosave(page);
-		SetPageNosaveFree(page);
+		swsusp_set_page_forbidden(page);
+		swsusp_set_page_free(page);
 	}
 	memory_bm_position_reset(bm);
 	safe_highmem_bm = bm;
@@ -1360,7 +1362,7 @@ get_highmem_page_buffer(struct page *pag
 	struct highmem_pbe *pbe;
 	void *kaddr;
 
-	if (PageNosave(page) && PageNosaveFree(page)) {
+	if (swsusp_page_is_forbidden(page) && swsusp_page_is_free(page)) {
 		/* We have allocated the "original" page frame and we can
 		 * use it directly to store the loaded page.
 		 */
@@ -1522,14 +1524,14 @@ prepare_image(struct memory_bitmap *new_
 			error = -ENOMEM;
 			goto Free;
 		}
-		if (!PageNosaveFree(virt_to_page(lp))) {
+		if (!swsusp_page_is_free(virt_to_page(lp))) {
 			/* The page is "safe", add it to the list */
 			lp->next = safe_pages_list;
 			safe_pages_list = lp;
 		}
 		/* Mark the page as allocated */
-		SetPageNosave(virt_to_page(lp));
-		SetPageNosaveFree(virt_to_page(lp));
+		swsusp_set_page_forbidden(virt_to_page(lp));
+		swsusp_set_page_free(virt_to_page(lp));
 		nr_pages--;
 	}
 	/* Free the reserved safe pages so that chain_alloc() can use them */
@@ -1558,7 +1560,7 @@ static void *get_buffer(struct memory_bi
 	if (PageHighMem(page))
 		return get_highmem_page_buffer(page, ca);
 
-	if (PageNosave(page) && PageNosaveFree(page))
+	if (swsusp_page_is_forbidden(page) && swsusp_page_is_free(page))
 		/* We have allocated the "original" page frame and we can
 		 * use it directly to store the loaded page.
 		 */
Index: linux-2.6.21-rc2/mm/page_alloc.c
===================================================================
--- linux-2.6.21-rc2.orig/mm/page_alloc.c	2007-03-02 09:03:43.000000000 +0100
+++ linux-2.6.21-rc2/mm/page_alloc.c	2007-03-02 09:11:54.000000000 +0100
@@ -770,8 +770,8 @@ void mark_free_pages(struct zone *zone)
 		if (pfn_valid(pfn)) {
 			struct page *page = pfn_to_page(pfn);
 
-			if (!PageNosave(page))
-				ClearPageNosaveFree(page);
+			if (!swsusp_page_is_forbidden(page))
+				swsusp_unset_page_free(page);
 		}
 
 	for (order = MAX_ORDER - 1; order >= 0; --order)
@@ -780,7 +780,7 @@ void mark_free_pages(struct zone *zone)
 
 			pfn = page_to_pfn(list_entry(curr, struct page, lru));
 			for (i = 0; i < (1UL << order); i++)
-				SetPageNosaveFree(pfn_to_page(pfn + i));
+				swsusp_set_page_free(pfn_to_page(pfn + i));
 		}
 
 	spin_unlock_irqrestore(&zone->lock, flags);

Re: [RFC][PATCH 1/3] swsusp: Use inline functions for changing page flags

[Pavel Machek]

Hi!

> Replace direct invocations of SetPageNosave(), SetPageNosaveFree() etc. with
> calls to inline functions that can be changed in subsequent patches without
> modifying the code calling them.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

ACK.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Make swsusp use memory bitmaps instead of page flags for marking 'nosave' and
free pages.  This allows us to 'recycle' two page flags that can be used for other
purposes.  Also, the memory needed to store the bitmaps is allocated when
necessary (ie. before the suspend) and freed after the resume which is more
reasonable.

The patch is designed to minimize the amount of changes and there are some nice
simplifications and optimizations possible on top of it.  I am going to
implement them separately in the future.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 arch/x86_64/kernel/e820.c |   26 +---
 include/linux/suspend.h   |   58 +++-------
 kernel/power/disk.c       |   23 +++-
 kernel/power/power.h      |    2 
 kernel/power/snapshot.c   |  250 +++++++++++++++++++++++++++++++++++++++++++---
 kernel/power/user.c       |    4 
 6 files changed, 281 insertions(+), 82 deletions(-)

Index: linux-2.6.21-rc3/include/linux/suspend.h
===================================================================
--- linux-2.6.21-rc3.orig/include/linux/suspend.h
+++ linux-2.6.21-rc3/include/linux/suspend.h
@@ -24,63 +24,41 @@ struct pbe {
 extern void drain_local_pages(void);
 extern void mark_free_pages(struct zone *zone);
 
-#ifdef CONFIG_PM
-/* kernel/power/swsusp.c */
-extern int software_suspend(void);
-
-#if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
+#if defined(CONFIG_PM) && defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
 extern int pm_prepare_console(void);
 extern void pm_restore_console(void);
 #else
 static inline int pm_prepare_console(void) { return 0; }
 static inline void pm_restore_console(void) {}
-#endif /* defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE) */
+#endif
+
+#if defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND)
+/* kernel/power/swsusp.c */
+extern int software_suspend(void);
+/* kernel/power/snapshot.c */
+extern void __init register_nosave_region(unsigned long, unsigned long);
+extern int swsusp_page_is_forbidden(struct page *);
+extern void swsusp_set_page_free(struct page *);
+extern void swsusp_unset_page_free(struct page *);
+extern unsigned long get_safe_page(gfp_t gfp_mask);
 #else
 static inline int software_suspend(void)
 {
 	printk("Warning: fake suspend called\n");
 	return -ENOSYS;
 }
-#endif /* CONFIG_PM */
+
+static inline void register_nosave_region(unsigned long b, unsigned long e) {}
+static inline int swsusp_page_is_forbidden(struct page *p) { return 0; }
+static inline void swsusp_set_page_free(struct page *p) {}
+static inline void swsusp_unset_page_free(struct page *p) {}
+#endif /* defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND) */
 
 void save_processor_state(void);
 void restore_processor_state(void);
 struct saved_context;
 void __save_processor_state(struct saved_context *ctxt);
 void __restore_processor_state(struct saved_context *ctxt);
-unsigned long get_safe_page(gfp_t gfp_mask);
-
-/* Page management functions for the software suspend (swsusp) */
-
-static inline void swsusp_set_page_forbidden(struct page *page)
-{
-	SetPageNosave(page);
-}
-
-static inline int swsusp_page_is_forbidden(struct page *page)
-{
-	return PageNosave(page);
-}
-
-static inline void swsusp_unset_page_forbidden(struct page *page)
-{
-	ClearPageNosave(page);
-}
-
-static inline void swsusp_set_page_free(struct page *page)
-{
-	SetPageNosaveFree(page);
-}
-
-static inline int swsusp_page_is_free(struct page *page)
-{
-	return PageNosaveFree(page);
-}
-
-static inline void swsusp_unset_page_free(struct page *page)
-{
-	ClearPageNosaveFree(page);
-}
 
 /*
  * XXX: We try to keep some more pages free so that I/O operations succeed
Index: linux-2.6.21-rc3/kernel/power/snapshot.c
===================================================================
--- linux-2.6.21-rc3.orig/kernel/power/snapshot.c
+++ linux-2.6.21-rc3/kernel/power/snapshot.c
@@ -21,6 +21,7 @@
 #include <linux/kernel.h>
 #include <linux/pm.h>
 #include <linux/device.h>
+#include <linux/init.h>
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/console.h>
@@ -34,6 +35,10 @@
 
 #include "power.h"
 
+static int swsusp_page_is_free(struct page *);
+static void swsusp_set_page_forbidden(struct page *);
+static void swsusp_unset_page_forbidden(struct page *);
+
 /* List of PBEs needed for restoring the pages that were allocated before
  * the suspend and included in the suspend image, but have also been
  * allocated by the "resume" kernel, so their contents cannot be written
@@ -224,11 +229,6 @@ static void chain_free(struct chain_allo
  *	of type unsigned long each).  It also contains the pfns that
  *	correspond to the start and end of the represented memory area and
  *	the number of bit chunks in the block.
- *
- *	NOTE: Memory bitmaps are used for two types of operations only:
- *	"set a bit" and "find the next bit set".  Moreover, the searching
- *	is always carried out after all of the "set a bit" operations
- *	on given bitmap.
  */
 
 #define BM_END_OF_MAP	(~0UL)
@@ -443,15 +443,13 @@ static void memory_bm_free(struct memory
 }
 
 /**
- *	memory_bm_set_bit - set the bit in the bitmap @bm that corresponds
+ *	memory_bm_find_bit - find the bit in the bitmap @bm that corresponds
  *	to given pfn.  The cur_zone_bm member of @bm and the cur_block member
  *	of @bm->cur_zone_bm are updated.
- *
- *	If the bit cannot be set, the function returns -EINVAL .
  */
 
-static int
-memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
+static void memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn,
+				void **addr, unsigned int *bit_nr)
 {
 	struct zone_bitmap *zone_bm;
 	struct bm_block *bb;
@@ -463,8 +461,8 @@ memory_bm_set_bit(struct memory_bitmap *
 		/* We don't assume that the zones are sorted by pfns */
 		while (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
 			zone_bm = zone_bm->next;
-			if (unlikely(!zone_bm))
-				return -EINVAL;
+
+			BUG_ON(!zone_bm);
 		}
 		bm->cur.zone_bm = zone_bm;
 	}
@@ -475,13 +473,40 @@ memory_bm_set_bit(struct memory_bitmap *
 
 	while (pfn >= bb->end_pfn) {
 		bb = bb->next;
-		if (unlikely(!bb))
-			return -EINVAL;
+
+		BUG_ON(!bb);
 	}
 	zone_bm->cur_block = bb;
 	pfn -= bb->start_pfn;
-	set_bit(pfn % BM_BITS_PER_CHUNK, bb->data + pfn / BM_BITS_PER_CHUNK);
-	return 0;
+	*bit_nr = pfn % BM_BITS_PER_CHUNK;
+	*addr = bb->data + pfn / BM_BITS_PER_CHUNK;
+}
+
+static void memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	set_bit(bit, addr);
+}
+
+static void memory_bm_clear_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	clear_bit(bit, addr);
+}
+
+static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	return test_bit(bit, addr);
 }
 
 /* Two auxiliary functions for memory_bm_next_pfn */
@@ -564,6 +589,199 @@ static unsigned long memory_bm_next_pfn(
 }
 
 /**
+ *	This structure represents a range of page frames the contents of which
+ *	should not be saved during the suspend.
+ */
+
+struct nosave_region {
+	struct list_head list;
+	unsigned long start_pfn;
+	unsigned long end_pfn;
+};
+
+static LIST_HEAD(nosave_regions);
+
+/**
+ *	register_nosave_region - register a range of page frames the contents
+ *	of which should not be saved during the suspend (to be used in the early
+ *	initializatoion code)
+ */
+
+void __init
+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
+{
+	struct nosave_region *region;
+
+	if (start_pfn >= end_pfn)
+		return;
+
+	if (!list_empty(&nosave_regions)) {
+		/* Try to extend the previous region (they should be sorted) */
+		region = list_entry(nosave_regions.prev,
+					struct nosave_region, list);
+		if (region->end_pfn == start_pfn) {
+			region->end_pfn = end_pfn;
+			goto Report;
+		}
+	}
+	/* This allocation cannot fail */
+	region = alloc_bootmem_low(sizeof(struct nosave_region));
+	region->start_pfn = start_pfn;
+	region->end_pfn = end_pfn;
+	list_add_tail(&region->list, &nosave_regions);
+ Report:
+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
+}
+
+/*
+ * Set bits in this map correspond to the page frames the contents of which
+ * should not be saved during the suspend.
+ */
+static struct memory_bitmap *forbidden_pages_map;
+
+/* Set bits in this map correspond to free page frames. */
+static struct memory_bitmap *free_pages_map;
+
+/*
+ * Each page frame allocated for creating the image is marked by setting the
+ * corresponding bits in forbidden_pages_map and free_pages_map simultaneously
+ */
+
+void swsusp_set_page_free(struct page *page)
+{
+	if (free_pages_map)
+		memory_bm_set_bit(free_pages_map, page_to_pfn(page));
+}
+
+static int swsusp_page_is_free(struct page *page)
+{
+	return free_pages_map ?
+		memory_bm_test_bit(free_pages_map, page_to_pfn(page)) : 0;
+}
+
+void swsusp_unset_page_free(struct page *page)
+{
+	if (free_pages_map)
+		memory_bm_clear_bit(free_pages_map, page_to_pfn(page));
+}
+
+static void swsusp_set_page_forbidden(struct page *page)
+{
+	if (forbidden_pages_map)
+		memory_bm_set_bit(forbidden_pages_map, page_to_pfn(page));
+}
+
+int swsusp_page_is_forbidden(struct page *page)
+{
+	return forbidden_pages_map ?
+		memory_bm_test_bit(forbidden_pages_map, page_to_pfn(page)) : 0;
+}
+
+static void swsusp_unset_page_forbidden(struct page *page)
+{
+	if (forbidden_pages_map)
+		memory_bm_clear_bit(forbidden_pages_map, page_to_pfn(page));
+}
+
+/**
+ *	mark_nosave_pages - set bits corresponding to the page frames the
+ *	contents of which should not be saved in a given bitmap.
+ */
+
+static void mark_nosave_pages(struct memory_bitmap *bm)
+{
+	struct nosave_region *region;
+
+	if (list_empty(&nosave_regions))
+		return;
+
+	list_for_each_entry(region, &nosave_regions, list) {
+		unsigned long pfn;
+
+		printk("swsusp: Marking nosave pages: %016lx - %016lx\n",
+				region->start_pfn << PAGE_SHIFT,
+				region->end_pfn << PAGE_SHIFT);
+
+		for (pfn = region->start_pfn; pfn < region->end_pfn; pfn++)
+			memory_bm_set_bit(bm, pfn);
+	}
+}
+
+/**
+ *	create_basic_memory_bitmaps - create bitmaps needed for marking page
+ *	frames that should not be saved and free page frames.  The pointers
+ *	forbidden_pages_map and free_pages_map are only modified if everything
+ *	goes well, because we don't want the bits to be used before both bitmaps
+ *	are set up.
+ */
+
+int create_basic_memory_bitmaps(void)
+{
+	struct memory_bitmap *bm1, *bm2;
+	int error = 0;
+
+	BUG_ON(forbidden_pages_map || free_pages_map);
+
+	bm1 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
+	if (!bm1)
+		return -ENOMEM;
+
+	error = memory_bm_create(bm1, GFP_ATOMIC | __GFP_COLD, PG_ANY);
+	if (error)
+		goto Free_first_object;
+
+	bm2 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
+	if (!bm2)
+		goto Free_first_bitmap;
+
+	error = memory_bm_create(bm2, GFP_ATOMIC | __GFP_COLD, PG_ANY);
+	if (error)
+		goto Free_second_object;
+
+	forbidden_pages_map = bm1;
+	free_pages_map = bm2;
+	mark_nosave_pages(forbidden_pages_map);
+
+	printk("swsusp: Basic memory bitmaps created\n");
+
+	return 0;
+
+ Free_second_object:
+	kfree(bm2);
+ Free_first_bitmap:
+ 	memory_bm_free(bm1, PG_UNSAFE_CLEAR);
+ Free_first_object:
+	kfree(bm1);
+	return -ENOMEM;
+}
+
+/**
+ *	free_basic_memory_bitmaps - free memory bitmaps allocated by
+ *	create_basic_memory_bitmaps().  The auxiliary pointers are necessary
+ *	so that the bitmaps themselves are not referred to while they are being
+ *	freed.
+ */
+
+void free_basic_memory_bitmaps(void)
+{
+	struct memory_bitmap *bm1, *bm2;
+
+	BUG_ON(!(forbidden_pages_map && free_pages_map));
+
+	bm1 = forbidden_pages_map;
+	bm2 = free_pages_map;
+	forbidden_pages_map = NULL;
+	free_pages_map = NULL;
+	memory_bm_free(bm1, PG_UNSAFE_CLEAR);
+	kfree(bm1);
+	memory_bm_free(bm2, PG_UNSAFE_CLEAR);
+	kfree(bm2);
+
+	printk("swsusp: Basic memory bitmaps freed\n");
+}
+
+/**
  *	snapshot_additional_pages - estimate the number of additional pages
  *	be needed for setting up the suspend image data structures for given
  *	zone (usually the returned value is greater than the exact number)
Index: linux-2.6.21-rc3/arch/x86_64/kernel/e820.c
===================================================================
--- linux-2.6.21-rc3.orig/arch/x86_64/kernel/e820.c
+++ linux-2.6.21-rc3/arch/x86_64/kernel/e820.c
@@ -17,6 +17,8 @@
 #include <linux/kexec.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/suspend.h>
+#include <linux/pfn.h>
 
 #include <asm/pgtable.h>
 #include <asm/page.h>
@@ -255,22 +257,6 @@ void __init e820_reserve_resources(void)
 	}
 }
 
-/* Mark pages corresponding to given address range as nosave */
-static void __init
-e820_mark_nosave_range(unsigned long start, unsigned long end)
-{
-	unsigned long pfn, max_pfn;
-
-	if (start >= end)
-		return;
-
-	printk("Nosave address range: %016lx - %016lx\n", start, end);
-	max_pfn = end >> PAGE_SHIFT;
-	for (pfn = start >> PAGE_SHIFT; pfn < max_pfn; pfn++)
-		if (pfn_valid(pfn))
-			SetPageNosave(pfn_to_page(pfn));
-}
-
 /*
  * Find the ranges of physical addresses that do not correspond to
  * e820 RAM areas and mark the corresponding pages as nosave for software
@@ -289,13 +275,13 @@ void __init e820_mark_nosave_regions(voi
 		struct e820entry *ei = &e820.map[i];
 
 		if (paddr < ei->addr)
-			e820_mark_nosave_range(paddr,
-					round_up(ei->addr, PAGE_SIZE));
+			register_nosave_region(PFN_DOWN(paddr),
+						PFN_UP(ei->addr));
 
 		paddr = round_down(ei->addr + ei->size, PAGE_SIZE);
 		if (ei->type != E820_RAM)
-			e820_mark_nosave_range(round_up(ei->addr, PAGE_SIZE),
-					paddr);
+			register_nosave_region(PFN_UP(ei->addr),
+						PFN_DOWN(paddr));
 
 		if (paddr >= (end_pfn << PAGE_SHIFT))
 			break;
Index: linux-2.6.21-rc3/kernel/power/power.h
===================================================================
--- linux-2.6.21-rc3.orig/kernel/power/power.h
+++ linux-2.6.21-rc3/kernel/power/power.h
@@ -49,6 +49,8 @@ extern sector_t swsusp_resume_block;
 extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);
 
+extern int create_basic_memory_bitmaps(void);
+extern void free_basic_memory_bitmaps(void);
 extern unsigned int count_data_pages(void);
 
 /**
Index: linux-2.6.21-rc3/kernel/power/user.c
===================================================================
--- linux-2.6.21-rc3.orig/kernel/power/user.c
+++ linux-2.6.21-rc3/kernel/power/user.c
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *i
 	if ((filp->f_flags & O_ACCMODE) == O_RDWR)
 		return -ENOSYS;
 
+	if(create_basic_memory_bitmaps())
+		return -ENOMEM;
+
 	nonseekable_open(inode, filp);
 	data = &snapshot_state;
 	filp->private_data = data;
@@ -77,6 +80,7 @@ static int snapshot_release(struct inode
 	struct snapshot_data *data;
 
 	swsusp_free();
+	free_basic_memory_bitmaps();
 	data = filp->private_data;
 	free_all_swap_pages(data->swap, data->bitmap);
 	free_bitmap(data->bitmap);
Index: linux-2.6.21-rc3/kernel/power/disk.c
===================================================================
--- linux-2.6.21-rc3.orig/kernel/power/disk.c
+++ linux-2.6.21-rc3/kernel/power/disk.c
@@ -127,14 +127,19 @@ int pm_suspend_disk(void)
 		mdelay(5000);
 		goto Thaw;
 	}
+	/* Allocate memory management structures */
+	error = create_basic_memory_bitmaps();
+	if (error)
+		goto Thaw;
+
 	/* Free memory before shutting down devices. */
 	error = swsusp_shrink_memory();
 	if (error)
-		goto Thaw;
+		goto Finish;
 
 	error = platform_prepare();
 	if (error)
-		goto Thaw;
+		goto Finish;
 
 	suspend_console();
 	error = device_suspend(PMSG_FREEZE);
@@ -169,7 +174,7 @@ int pm_suspend_disk(void)
 			power_down(pm_disk_mode);
 		else {
 			swsusp_free();
-			goto Thaw;
+			goto Finish;
 		}
 	} else {
 		pr_debug("PM: Image restored successfully.\n");
@@ -182,6 +187,8 @@ int pm_suspend_disk(void)
 	platform_finish();
 	device_resume();
 	resume_console();
+ Finish:
+	free_basic_memory_bitmaps();
  Thaw:
 	unprepare_processes();
 	return error;
@@ -227,13 +234,15 @@ static int software_resume(void)
 	}
 
 	pr_debug("PM: Checking swsusp image.\n");
-
 	error = swsusp_check();
 	if (error)
-		goto Done;
+		goto Unlock;
 
-	pr_debug("PM: Preparing processes for restore.\n");
+	error = create_basic_memory_bitmaps();
+	if (error)
+		goto Unlock;
 
+	pr_debug("PM: Preparing processes for restore.\n");
 	error = prepare_processes();
 	if (error) {
 		swsusp_close();
@@ -275,7 +284,9 @@ static int software_resume(void)
 	printk(KERN_ERR "PM: Restore failed, recovering.\n");
 	unprepare_processes();
  Done:
+	free_basic_memory_bitmaps();
 	/* For success case, the suspend path will release the lock */
+ Unlock:
 	mutex_unlock(&pm_mutex);
 	pr_debug("PM: Resume from disk failed.\n");
 	return 0;

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Pavel Machek]

Hi!

> Make swsusp use memory bitmaps instead of page flags for marking 'nosave' and
> free pages.  This allows us to 'recycle' two page flags that can be used for other
> purposes.  Also, the memory needed to store the bitmaps is allocated when
> necessary (ie. before the suspend) and freed after the resume which is more
> reasonable.
> 
> The patch is designed to minimize the amount of changes and there are some nice
> simplifications and optimizations possible on top of it.  I am going to
> implement them separately in the future.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Looks ok, but needs to stay in -mm for a while. ACK.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[RFC][PATCH 3/3] mm: Remove unused page flags

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Remove the two page flags that were previously used by swsusp and are no longer
needed.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 include/linux/page-flags.h |   12 ------------
 1 file changed, 12 deletions(-)

Index: linux-2.6.21-rc3/include/linux/page-flags.h
===================================================================
--- linux-2.6.21-rc3.orig/include/linux/page-flags.h
+++ linux-2.6.21-rc3/include/linux/page-flags.h
@@ -82,13 +82,11 @@
 #define PG_private		11	/* If pagecache, has fs-private data */
 
 #define PG_writeback		12	/* Page is under writeback */
-#define PG_nosave		13	/* Used for system suspend/resume */
 #define PG_compound		14	/* Part of a compound page */
 #define PG_swapcache		15	/* Swap page: swp_entry_t in private */
 
 #define PG_mappedtodisk		16	/* Has blocks allocated on-disk */
 #define PG_reclaim		17	/* To be reclaimed asap */
-#define PG_nosave_free		18	/* Used for system suspend/resume */
 #define PG_buddy		19	/* Page is free, on buddy lists */
 
 /* PG_owner_priv_1 users should have descriptive aliases */
@@ -214,16 +212,6 @@ static inline void SetPageUptodate(struc
 		ret;							\
 	})
 
-#define PageNosave(page)	test_bit(PG_nosave, &(page)->flags)
-#define SetPageNosave(page)	set_bit(PG_nosave, &(page)->flags)
-#define TestSetPageNosave(page)	test_and_set_bit(PG_nosave, &(page)->flags)
-#define ClearPageNosave(page)		clear_bit(PG_nosave, &(page)->flags)
-#define TestClearPageNosave(page)	test_and_clear_bit(PG_nosave, &(page)->flags)
-
-#define PageNosaveFree(page)	test_bit(PG_nosave_free, &(page)->flags)
-#define SetPageNosaveFree(page)	set_bit(PG_nosave_free, &(page)->flags)
-#define ClearPageNosaveFree(page)		clear_bit(PG_nosave_free, &(page)->flags)
-
 #define PageBuddy(page)		test_bit(PG_buddy, &(page)->flags)
 #define __SetPageBuddy(page)	__set_bit(PG_buddy, &(page)->flags)
 #define __ClearPageBuddy(page)	__clear_bit(PG_buddy, &(page)->flags)

Re: [RFC][PATCH 3/3] mm: Remove unused page flags

[Pavel Machek]

On Sun 2007-03-11 11:34:53, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@sisk.pl>
> 
> Remove the two page flags that were previously used by swsusp and are no longer
> needed.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

ACK.
								Pavel

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [RFC][PATCH 0/3] swsusp: Stop using page flags

[Peter Zijlstra]

On Sun, 2007-03-11 at 11:17 +0100, Rafael J. Wysocki wrote:
> Hi,
> 
> The following three patches make swsusp use its own data structures for memory
> management instead of special page flags.  Thus the page flags used so far by
> swsusp (PG_nosave, PG_nosave_free) can be used for other purposes and I believe
> there are some urgend needs of them. :-)
> 
> Last week I sent these patches to the linux-pm and linux-mm lists and there
> were no negative comments.  Also I've been testing them on my x86_64 boxes for
> a few days and apparently they don't break anything.  I think they can go into
> -mm for testing.
> 
> Comments are welcome.

These patches have my blessing, they look good to me, but I'm not much
involved with the swsusp code, so I won't ACK them.

Again, thanks a bunch for freeing up 2 page flags :-)

Peter

Remove page flags for software suspend

[Christoph Lameter]

I think we can just move the flags completely into the kernel/power 
directory? This centralizes all your handling of pageflags into snapshot.c 
so that you need no external definitions anymore.


Index: linux-2.6.20-mm1/include/linux/mmzone.h
===================================================================
--- linux-2.6.20-mm1.orig/include/linux/mmzone.h	2007-02-16 01:11:46.000000000 -0800
+++ linux-2.6.20-mm1/include/linux/mmzone.h	2007-02-16 01:12:23.000000000 -0800
@@ -295,6 +295,7 @@ struct zone {
 	unsigned long		spanned_pages;	/* total size, including holes */
 	unsigned long		present_pages;	/* amount of memory (excluding holes) */
 
+	unsigned long		*suspend_flags;
 	/*
 	 * rarely used fields:
 	 */
Index: linux-2.6.20-mm1/include/linux/page-flags.h
===================================================================
--- linux-2.6.20-mm1.orig/include/linux/page-flags.h	2007-02-16 01:05:26.000000000 -0800
+++ linux-2.6.20-mm1/include/linux/page-flags.h	2007-02-16 01:16:45.000000000 -0800
@@ -82,13 +82,11 @@
 #define PG_private		11	/* If pagecache, has fs-private data */
 
 #define PG_writeback		12	/* Page is under writeback */
-#define PG_nosave		13	/* Used for system suspend/resume */
 #define PG_compound		14	/* Part of a compound page */
 #define PG_swapcache		15	/* Swap page: swp_entry_t in private */
 
 #define PG_mappedtodisk		16	/* Has blocks allocated on-disk */
 #define PG_reclaim		17	/* To be reclaimed asap */
-#define PG_nosave_free		18	/* Used for system suspend/resume */
 #define PG_buddy		19	/* Page is free, on buddy lists */
 
 #define PG_mlocked		20	/* Page is mlocked */
@@ -192,16 +190,6 @@ static inline void SetPageUptodate(struc
 #define TestClearPageWriteback(page) test_and_clear_bit(PG_writeback,	\
 							&(page)->flags)
 
-#define PageNosave(page)	test_bit(PG_nosave, &(page)->flags)
-#define SetPageNosave(page)	set_bit(PG_nosave, &(page)->flags)
-#define TestSetPageNosave(page)	test_and_set_bit(PG_nosave, &(page)->flags)
-#define ClearPageNosave(page)		clear_bit(PG_nosave, &(page)->flags)
-#define TestClearPageNosave(page)	test_and_clear_bit(PG_nosave, &(page)->flags)
-
-#define PageNosaveFree(page)	test_bit(PG_nosave_free, &(page)->flags)
-#define SetPageNosaveFree(page)	set_bit(PG_nosave_free, &(page)->flags)
-#define ClearPageNosaveFree(page)		clear_bit(PG_nosave_free, &(page)->flags)
-
 #define PageBuddy(page)		test_bit(PG_buddy, &(page)->flags)
 #define __SetPageBuddy(page)	__set_bit(PG_buddy, &(page)->flags)
 #define __ClearPageBuddy(page)	__clear_bit(PG_buddy, &(page)->flags)
Index: linux-2.6.20-mm1/include/linux/suspend.h
===================================================================
--- linux-2.6.20-mm1.orig/include/linux/suspend.h	2007-02-16 01:15:30.000000000 -0800
+++ linux-2.6.20-mm1/include/linux/suspend.h	2007-02-16 01:57:51.000000000 -0800
@@ -21,7 +22,6 @@ struct pbe {
 
 /* mm/page_alloc.c */
 extern void drain_local_pages(void);
-extern void mark_free_pages(struct zone *zone);
 
 #ifdef CONFIG_PM
 /* kernel/power/swsusp.c */
@@ -42,6 +42,18 @@ static inline int software_suspend(void)
 }
 #endif /* CONFIG_PM */
 
+#ifdef CONFIG_SOFTWARE_SUSPEND
+int suspend_flags_init(struct zone *zone, unsigned long zone_size_pages);
+void mark_free_pages(struct zone *zone);
+#else
+static inline int suspend_flags_init(struct zone *zone, unsigned long zone_size_pages)
+{
+	return 0;
+}
+
+static inline void mark_free_pages(struct zone *zone) {}
+#endif
+
 void save_processor_state(void);
 void restore_processor_state(void);
 struct saved_context;
Index: linux-2.6.20-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.20-mm1.orig/mm/page_alloc.c	2007-02-16 01:22:09.000000000 -0800
+++ linux-2.6.20-mm1/mm/page_alloc.c	2007-02-16 01:40:39.000000000 -0800
@@ -767,40 +767,6 @@ static void __drain_pages(unsigned int c
 }
 
 #ifdef CONFIG_PM
-
-void mark_free_pages(struct zone *zone)
-{
-	unsigned long pfn, max_zone_pfn;
-	unsigned long flags;
-	int order;
-	struct list_head *curr;
-
-	if (!zone->spanned_pages)
-		return;
-
-	spin_lock_irqsave(&zone->lock, flags);
-
-	max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
-	for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
-		if (pfn_valid(pfn)) {
-			struct page *page = pfn_to_page(pfn);
-
-			if (!PageNosave(page))
-				ClearPageNosaveFree(page);
-		}
-
-	for (order = MAX_ORDER - 1; order >= 0; --order)
-		list_for_each(curr, &zone->free_area[order].free_list) {
-			unsigned long i;
-
-			pfn = page_to_pfn(list_entry(curr, struct page, lru));
-			for (i = 0; i < (1UL << order); i++)
-				SetPageNosaveFree(pfn_to_page(pfn + i));
-		}
-
-	spin_unlock_irqrestore(&zone->lock, flags);
-}
-
 /*
  * Spill all of this CPU's per-cpu pages back into the buddy allocator.
  */
@@ -2354,6 +2320,9 @@ __meminit int init_currently_empty_zone(
 	ret = zone_wait_table_init(zone, size);
 	if (ret)
 		return ret;
+	ret = suspend_flags_init(zone, size);
+	if (ret)
+		return ret;
 	pgdat->nr_zones = zone_idx(zone) + 1;
 
 	zone->zone_start_pfn = zone_start_pfn;
Index: linux-2.6.20-mm1/kernel/power/snapshot.c
===================================================================
--- linux-2.6.20-mm1.orig/kernel/power/snapshot.c	2007-02-16 01:46:02.000000000 -0800
+++ linux-2.6.20-mm1/kernel/power/snapshot.c	2007-02-16 01:59:24.000000000 -0800
@@ -34,6 +34,126 @@
 
 #include "power.h"
 
+static inline int PageNosave(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	return test_bit(offset * 2, zone->suspend_flags);
+}
+
+static inline void SetPageNosave(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	set_bit(offset * 2, zone->suspend_flags);
+}
+
+static inline int TestSetPageNosave(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	return test_and_set_bit(offset * 2, zone->suspend_flags);
+}
+
+static inline void ClearPageNosave(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	clear_bit(offset * 2, zone->suspend_flags);
+}
+
+static inline int TestClearPageNosave(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	return test_and_clear_bit(offset * 2, zone->suspend_flags);
+}
+
+
+static inline int PageNosaveFree(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	return test_bit(offset * 2 + 1, zone->suspend_flags);
+}
+
+static inline void SetPageNosaveFree(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	set_bit(offset * 2 + 1, zone->suspend_flags);
+}
+
+static inline void ClearPageNosaveFree(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long offset = page_to_pfn(page) - zone->zone_start_pfn;
+
+	clear_bit(offset * 2 + 1, zone->suspend_flags);
+}
+
+int suspend_flags_init(struct zone *zone, unsigned long zone_size_pages)
+{
+	struct pglist_data *pgdat = zone->zone_pgdat;
+	size_t alloc_size;
+
+	/*
+	 * We need two bits per page in the zone. One for PageNosave and the other
+	 * for PageNosaveFree.
+	 */
+	alloc_size = BITS_TO_LONGS(zone_size_pages * 2);
+ 	if (system_state == SYSTEM_BOOTING) {
+		zone->suspend_flags = (unsigned long *)
+			alloc_bootmem_node(pgdat, alloc_size);
+	} else
+		zone->suspend_flags = (unsigned long *)vmalloc(alloc_size);
+	if (!zone->suspend_flags)
+		return -ENOMEM;
+
+	bitmap_zero(zone->suspend_flags, 2 * zone_size_pages);
+	return 0;
+}
+
+void mark_free_pages(struct zone *zone)
+{
+	unsigned long pfn, max_zone_pfn;
+	unsigned long flags;
+	int order;
+	struct list_head *curr;
+
+	if (!zone->spanned_pages)
+		return;
+
+	spin_lock_irqsave(&zone->lock, flags);
+
+	max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+	for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
+		if (pfn_valid(pfn)) {
+			struct page *page = pfn_to_page(pfn);
+
+			if (!PageNosave(page))
+				ClearPageNosaveFree(page);
+		}
+
+	for (order = MAX_ORDER - 1; order >= 0; --order)
+		list_for_each(curr, &zone->free_area[order].free_list) {
+			unsigned long i;
+
+			pfn = page_to_pfn(list_entry(curr, struct page, lru));
+			for (i = 0; i < (1UL << order); i++)
+				SetPageNosaveFree(pfn_to_page(pfn + i));
+		}
+
+	spin_unlock_irqrestore(&zone->lock, flags);
+}
+
 /* List of PBEs needed for restoring the pages that were allocated before
  * the suspend and included in the suspend image, but have also been
  * allocated by the "resume" kernel, so their contents cannot be written

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Re: Remove page flags for software suspend

[Rafael J. Wysocki]

On Thursday, 1 March 2007 16:18, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Wednesday, 28 February 2007 16:25, Christoph Lameter wrote:
> > 
> >>On Wed, 28 Feb 2007, Pavel Machek wrote:
> >>
> >>
> >>>I... actually do not like that patch. It adds code... at little or no
> >>>benefit.
> >>
> >>We are looking into saving page flags since we are running out. The two 
> >>page flags used by software suspend are rarely needed and should be taken 
> >>out of the flags. If you can do it a different way then please do.
> > 
> > 
> > As I have already said for a couple of times, I think we can and I'm going to
> > do it, but right now I'm a bit busy with other things that I consider as more
> > urgent.
> 
> I need one bit for lockless pagecache ;)
> 
> Anyway, I guess if you want something done you have to do it yourself.
> 
> This patch still needs work (and I don't know if it even works, because
> I can't make swsusp resume even on a vanilla kernel). But this is my
> WIP for removing swsusp page flags.
> 
> This patch adds a simple extent based nosave region tracker, and
> rearranges some of the snapshot code to be a bit simpler and more
> amenable to having dynamically allocated flags (they aren't actually
> dynamically allocated in this patch, however).

Thanks for the patch.

Probably I'd like to do some things in a different way, I'll think about that
later today.

I hope I'll have a working patch that removes the "offending" page flags after
the weekend.

Greetings,
Rafael

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[RFC][PATCH 0/3] swsusp: Do not use page flags (was: Re: Remove page flags for software suspend)

[Rafael J. Wysocki]

On Thursday, 1 March 2007 16:33, Rafael J. Wysocki wrote:
> On Thursday, 1 March 2007 16:18, Nick Piggin wrote:
> > Rafael J. Wysocki wrote:
> > > On Wednesday, 28 February 2007 16:25, Christoph Lameter wrote:
> > > 
> > >>On Wed, 28 Feb 2007, Pavel Machek wrote:
> > >>
> > >>
> > >>>I... actually do not like that patch. It adds code... at little or no
> > >>>benefit.
> > >>
> > >>We are looking into saving page flags since we are running out. The two 
> > >>page flags used by software suspend are rarely needed and should be taken 
> > >>out of the flags. If you can do it a different way then please do.
> > > 
> > > 
> > > As I have already said for a couple of times, I think we can and I'm going to
> > > do it, but right now I'm a bit busy with other things that I consider as more
> > > urgent.
> > 
> > I need one bit for lockless pagecache ;)
> > 
> > Anyway, I guess if you want something done you have to do it yourself.
> > 
> > This patch still needs work (and I don't know if it even works, because
> > I can't make swsusp resume even on a vanilla kernel). But this is my
> > WIP for removing swsusp page flags.
> > 
> > This patch adds a simple extent based nosave region tracker, and
> > rearranges some of the snapshot code to be a bit simpler and more
> > amenable to having dynamically allocated flags (they aren't actually
> > dynamically allocated in this patch, however).
> 
> Thanks for the patch.
> 
> Probably I'd like to do some things in a different way, I'll think about that
> later today.
> 
> I hope I'll have a working patch that removes the "offending" page flags after
> the weekend.

Okay, the next three messages contain patches that should do the trick.

They have been tested on x86_64, but not very thoroughly.

Greetings,
Rafael

[RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

Make swsusp use memory bitmaps instead of page flags for marking 'nosave' and
free pages.  This allows us to 'recycle' two page flags that can be used for other
purposes.  Also, the memory needed to store the bitmaps is allocated when
necessary (ie. before the suspend) and freed after the resume which is more
reasonable.

The patch is designed to minimize the amount of changes and there are some nice
simplifications and optimizations possible on top of it.  I am going to post
them as separate patches in the future.

---
 arch/x86_64/kernel/e820.c |   26 +---
 include/linux/suspend.h   |   58 +++-------
 kernel/power/disk.c       |   23 +++-
 kernel/power/power.h      |    2 
 kernel/power/snapshot.c   |  250 +++++++++++++++++++++++++++++++++++++++++++---
 kernel/power/user.c       |    4 
 6 files changed, 281 insertions(+), 82 deletions(-)

Index: linux-2.6.21-rc2/include/linux/suspend.h
===================================================================
--- linux-2.6.21-rc2.orig/include/linux/suspend.h	2007-03-04 11:52:46.000000000 +0100
+++ linux-2.6.21-rc2/include/linux/suspend.h	2007-03-04 11:52:46.000000000 +0100
@@ -24,63 +24,41 @@ struct pbe {
 extern void drain_local_pages(void);
 extern void mark_free_pages(struct zone *zone);
 
-#ifdef CONFIG_PM
-/* kernel/power/swsusp.c */
-extern int software_suspend(void);
-
-#if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
+#if defined(CONFIG_PM) && defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
 extern int pm_prepare_console(void);
 extern void pm_restore_console(void);
 #else
 static inline int pm_prepare_console(void) { return 0; }
 static inline void pm_restore_console(void) {}
-#endif /* defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE) */
+#endif
+
+#if defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND)
+/* kernel/power/swsusp.c */
+extern int software_suspend(void);
+/* kernel/power/snapshot.c */
+extern void __init register_nosave_region(unsigned long, unsigned long);
+extern int swsusp_page_is_forbidden(struct page *);
+extern void swsusp_set_page_free(struct page *);
+extern void swsusp_unset_page_free(struct page *);
+extern unsigned long get_safe_page(gfp_t gfp_mask);
 #else
 static inline int software_suspend(void)
 {
 	printk("Warning: fake suspend called\n");
 	return -ENOSYS;
 }
-#endif /* CONFIG_PM */
+
+static inline void register_nosave_region(unsigned long b, unsigned long e) {}
+static inline int swsusp_page_is_forbidden(struct page *p) { return 0; }
+static inline void swsusp_set_page_free(struct page *p) {}
+static inline void swsusp_unset_page_free(struct page *p) {}
+#endif /* defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND) */
 
 void save_processor_state(void);
 void restore_processor_state(void);
 struct saved_context;
 void __save_processor_state(struct saved_context *ctxt);
 void __restore_processor_state(struct saved_context *ctxt);
-unsigned long get_safe_page(gfp_t gfp_mask);
-
-/* Page management functions for the software suspend (swsusp) */
-
-static inline void swsusp_set_page_forbidden(struct page *page)
-{
-	SetPageNosave(page);
-}
-
-static inline int swsusp_page_is_forbidden(struct page *page)
-{
-	return PageNosave(page);
-}
-
-static inline void swsusp_unset_page_forbidden(struct page *page)
-{
-	ClearPageNosave(page);
-}
-
-static inline void swsusp_set_page_free(struct page *page)
-{
-	SetPageNosaveFree(page);
-}
-
-static inline int swsusp_page_is_free(struct page *page)
-{
-	return PageNosaveFree(page);
-}
-
-static inline void swsusp_unset_page_free(struct page *page)
-{
-	ClearPageNosaveFree(page);
-}
 
 /*
  * XXX: We try to keep some more pages free so that I/O operations succeed
Index: linux-2.6.21-rc2/kernel/power/snapshot.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/snapshot.c	2007-03-04 11:52:46.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/snapshot.c	2007-03-04 15:06:13.000000000 +0100
@@ -21,6 +21,7 @@
 #include <linux/kernel.h>
 #include <linux/pm.h>
 #include <linux/device.h>
+#include <linux/init.h>
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/console.h>
@@ -34,6 +35,10 @@
 
 #include "power.h"
 
+static int swsusp_page_is_free(struct page *);
+static void swsusp_set_page_forbidden(struct page *);
+static void swsusp_unset_page_forbidden(struct page *);
+
 /* List of PBEs needed for restoring the pages that were allocated before
  * the suspend and included in the suspend image, but have also been
  * allocated by the "resume" kernel, so their contents cannot be written
@@ -224,11 +229,6 @@ static void chain_free(struct chain_allo
  *	of type unsigned long each).  It also contains the pfns that
  *	correspond to the start and end of the represented memory area and
  *	the number of bit chunks in the block.
- *
- *	NOTE: Memory bitmaps are used for two types of operations only:
- *	"set a bit" and "find the next bit set".  Moreover, the searching
- *	is always carried out after all of the "set a bit" operations
- *	on given bitmap.
  */
 
 #define BM_END_OF_MAP	(~0UL)
@@ -443,15 +443,13 @@ static void memory_bm_free(struct memory
 }
 
 /**
- *	memory_bm_set_bit - set the bit in the bitmap @bm that corresponds
+ *	memory_bm_find_bit - find the bit in the bitmap @bm that corresponds
  *	to given pfn.  The cur_zone_bm member of @bm and the cur_block member
  *	of @bm->cur_zone_bm are updated.
- *
- *	If the bit cannot be set, the function returns -EINVAL .
  */
 
-static int
-memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
+static void memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn,
+				void **addr, unsigned int *bit_nr)
 {
 	struct zone_bitmap *zone_bm;
 	struct bm_block *bb;
@@ -463,8 +461,8 @@ memory_bm_set_bit(struct memory_bitmap *
 		/* We don't assume that the zones are sorted by pfns */
 		while (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
 			zone_bm = zone_bm->next;
-			if (unlikely(!zone_bm))
-				return -EINVAL;
+
+			BUG_ON(!zone_bm);
 		}
 		bm->cur.zone_bm = zone_bm;
 	}
@@ -475,13 +473,40 @@ memory_bm_set_bit(struct memory_bitmap *
 
 	while (pfn >= bb->end_pfn) {
 		bb = bb->next;
-		if (unlikely(!bb))
-			return -EINVAL;
+
+		BUG_ON(!bb);
 	}
 	zone_bm->cur_block = bb;
 	pfn -= bb->start_pfn;
-	set_bit(pfn % BM_BITS_PER_CHUNK, bb->data + pfn / BM_BITS_PER_CHUNK);
-	return 0;
+	*bit_nr = pfn % BM_BITS_PER_CHUNK;
+	*addr = bb->data + pfn / BM_BITS_PER_CHUNK;
+}
+
+static void memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	set_bit(bit, addr);
+}
+
+static void memory_bm_clear_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	clear_bit(bit, addr);
+}
+
+static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	return test_bit(bit, addr);
 }
 
 /* Two auxiliary functions for memory_bm_next_pfn */
@@ -564,6 +589,199 @@ static unsigned long memory_bm_next_pfn(
 }
 
 /**
+ *	This structure represents a range of page frames the contents of which
+ *	should not be saved during the suspend.
+ */
+
+struct nosave_region {
+	struct list_head list;
+	unsigned long start_pfn;
+	unsigned long end_pfn;
+};
+
+static LIST_HEAD(nosave_regions);
+
+/**
+ *	register_nosave_region - register a range of page frames the contents
+ *	of which should not be saved during the suspend (to be used in the early
+ *	initializatoion code)
+ */
+
+void __init
+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
+{
+	struct nosave_region *region;
+
+	if (start_pfn >= end_pfn)
+		return;
+
+	if (!list_empty(&nosave_regions)) {
+		/* Try to extend the previous region (they should be sorted) */
+		region = list_entry(nosave_regions.prev,
+					struct nosave_region, list);
+		if (region->end_pfn == start_pfn) {
+			region->end_pfn = end_pfn;
+			goto Report;
+		}
+	}
+	/* This allocation cannot fail */
+	region = alloc_bootmem_low(sizeof(struct nosave_region));
+	region->start_pfn = start_pfn;
+	region->end_pfn = end_pfn;
+	list_add_tail(&region->list, &nosave_regions);
+ Report:
+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
+}
+
+/*
+ * Set bits in this map correspond to the page frames the contents of which
+ * should not be saved during the suspend.
+ */
+static struct memory_bitmap *forbidden_pages_map;
+
+/* Set bits in this map correspond to free page frames. */
+static struct memory_bitmap *free_pages_map;
+
+/*
+ * Each page frame allocated for creating the image is marked by setting the
+ * corresponding bits in forbidden_pages_map and free_pages_map simultaneously
+ */
+
+void swsusp_set_page_free(struct page *page)
+{
+	if (free_pages_map)
+		memory_bm_set_bit(free_pages_map, page_to_pfn(page));
+}
+
+static int swsusp_page_is_free(struct page *page)
+{
+	return free_pages_map ?
+		memory_bm_test_bit(free_pages_map, page_to_pfn(page)) : 0;
+}
+
+void swsusp_unset_page_free(struct page *page)
+{
+	if (free_pages_map)
+		memory_bm_clear_bit(free_pages_map, page_to_pfn(page));
+}
+
+static void swsusp_set_page_forbidden(struct page *page)
+{
+	if (forbidden_pages_map)
+		memory_bm_set_bit(forbidden_pages_map, page_to_pfn(page));
+}
+
+int swsusp_page_is_forbidden(struct page *page)
+{
+	return forbidden_pages_map ?
+		memory_bm_test_bit(forbidden_pages_map, page_to_pfn(page)) : 0;
+}
+
+static void swsusp_unset_page_forbidden(struct page *page)
+{
+	if (forbidden_pages_map)
+		memory_bm_clear_bit(forbidden_pages_map, page_to_pfn(page));
+}
+
+/**
+ *	mark_nosave_pages - set bits corresponding to the page frames the
+ *	contents of which should not be saved in a given bitmap.
+ */
+
+static void mark_nosave_pages(struct memory_bitmap *bm)
+{
+	struct nosave_region *region;
+
+	if (list_empty(&nosave_regions))
+		return;
+
+	list_for_each_entry(region, &nosave_regions, list) {
+		unsigned long pfn;
+
+		printk("swsusp: Marking nosave pages: %016lx - %016lx\n",
+				region->start_pfn << PAGE_SHIFT,
+				region->end_pfn << PAGE_SHIFT);
+
+		for (pfn = region->start_pfn; pfn < region->end_pfn; pfn++)
+			memory_bm_set_bit(bm, pfn);
+	}
+}
+
+/**
+ *	create_basic_memory_bitmaps - create bitmaps needed for marking page
+ *	frames that should not be saved and free page frames.  The pointers
+ *	forbidden_pages_map and free_pages_map are only modified if everything
+ *	goes well, because we don't want the bits to be used before both bitmaps
+ *	are set up.
+ */
+
+int create_basic_memory_bitmaps(void)
+{
+	struct memory_bitmap *bm1, *bm2;
+	int error = 0;
+
+	BUG_ON(forbidden_pages_map || free_pages_map);
+
+	bm1 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
+	if (!bm1)
+		return -ENOMEM;
+
+	error = memory_bm_create(bm1, GFP_ATOMIC | __GFP_COLD, PG_ANY);
+	if (error)
+		goto Free_first_object;
+
+	bm2 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
+	if (!bm2)
+		goto Free_first_bitmap;
+
+	error = memory_bm_create(bm2, GFP_ATOMIC | __GFP_COLD, PG_ANY);
+	if (error)
+		goto Free_second_object;
+
+	forbidden_pages_map = bm1;
+	free_pages_map = bm2;
+	mark_nosave_pages(forbidden_pages_map);
+
+	printk("swsusp: Basic memory bitmaps created\n");
+
+	return 0;
+
+ Free_second_object:
+	kfree(bm2);
+ Free_first_bitmap:
+ 	memory_bm_free(bm1, PG_UNSAFE_CLEAR);
+ Free_first_object:
+	kfree(bm1);
+	return -ENOMEM;
+}
+
+/**
+ *	free_basic_memory_bitmaps - free memory bitmaps allocated by
+ *	create_basic_memory_bitmaps().  The auxiliary pointers are necessary
+ *	so that the bitmaps themselves are not referred to while they are being
+ *	freed.
+ */
+
+void free_basic_memory_bitmaps(void)
+{
+	struct memory_bitmap *bm1, *bm2;
+
+	BUG_ON(!(forbidden_pages_map && free_pages_map));
+
+	bm1 = forbidden_pages_map;
+	bm2 = free_pages_map;
+	forbidden_pages_map = NULL;
+	free_pages_map = NULL;
+	memory_bm_free(bm1, PG_UNSAFE_CLEAR);
+	kfree(bm1);
+	memory_bm_free(bm2, PG_UNSAFE_CLEAR);
+	kfree(bm2);
+
+	printk("swsusp: Basic memory bitmaps freed\n");
+}
+
+/**
  *	snapshot_additional_pages - estimate the number of additional pages
  *	be needed for setting up the suspend image data structures for given
  *	zone (usually the returned value is greater than the exact number)
Index: linux-2.6.21-rc2/arch/x86_64/kernel/e820.c
===================================================================
--- linux-2.6.21-rc2.orig/arch/x86_64/kernel/e820.c	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/arch/x86_64/kernel/e820.c	2007-03-04 13:25:20.000000000 +0100
@@ -17,6 +17,8 @@
 #include <linux/kexec.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/suspend.h>
+#include <linux/pfn.h>
 
 #include <asm/pgtable.h>
 #include <asm/page.h>
@@ -255,22 +257,6 @@ void __init e820_reserve_resources(void)
 	}
 }
 
-/* Mark pages corresponding to given address range as nosave */
-static void __init
-e820_mark_nosave_range(unsigned long start, unsigned long end)
-{
-	unsigned long pfn, max_pfn;
-
-	if (start >= end)
-		return;
-
-	printk("Nosave address range: %016lx - %016lx\n", start, end);
-	max_pfn = end >> PAGE_SHIFT;
-	for (pfn = start >> PAGE_SHIFT; pfn < max_pfn; pfn++)
-		if (pfn_valid(pfn))
-			SetPageNosave(pfn_to_page(pfn));
-}
-
 /*
  * Find the ranges of physical addresses that do not correspond to
  * e820 RAM areas and mark the corresponding pages as nosave for software
@@ -289,13 +275,13 @@ void __init e820_mark_nosave_regions(voi
 		struct e820entry *ei = &e820.map[i];
 
 		if (paddr < ei->addr)
-			e820_mark_nosave_range(paddr,
-					round_up(ei->addr, PAGE_SIZE));
+			register_nosave_region(PFN_DOWN(paddr),
+						PFN_UP(ei->addr));
 
 		paddr = round_down(ei->addr + ei->size, PAGE_SIZE);
 		if (ei->type != E820_RAM)
-			e820_mark_nosave_range(round_up(ei->addr, PAGE_SIZE),
-					paddr);
+			register_nosave_region(PFN_UP(ei->addr),
+						PFN_DOWN(paddr));
 
 		if (paddr >= (end_pfn << PAGE_SHIFT))
 			break;
Index: linux-2.6.21-rc2/kernel/power/power.h
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/power.h	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/power.h	2007-03-04 11:52:46.000000000 +0100
@@ -49,6 +49,8 @@ extern sector_t swsusp_resume_block;
 extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);
 
+extern int create_basic_memory_bitmaps(void);
+extern void free_basic_memory_bitmaps(void);
 extern unsigned int count_data_pages(void);
 
 /**
Index: linux-2.6.21-rc2/kernel/power/user.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/user.c	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/user.c	2007-03-04 14:02:19.000000000 +0100
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *i
 	if ((filp->f_flags & O_ACCMODE) == O_RDWR)
 		return -ENOSYS;
 
+	if(create_basic_memory_bitmaps())
+		return -ENOMEM;
+
 	nonseekable_open(inode, filp);
 	data = &snapshot_state;
 	filp->private_data = data;
@@ -77,6 +80,7 @@ static int snapshot_release(struct inode
 	struct snapshot_data *data;
 
 	swsusp_free();
+	free_basic_memory_bitmaps();
 	data = filp->private_data;
 	free_all_swap_pages(data->swap, data->bitmap);
 	free_bitmap(data->bitmap);
Index: linux-2.6.21-rc2/kernel/power/disk.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/disk.c	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/disk.c	2007-03-04 11:52:46.000000000 +0100
@@ -127,14 +127,19 @@ int pm_suspend_disk(void)
 		mdelay(5000);
 		goto Thaw;
 	}
+	/* Allocate memory management structures */
+	error = create_basic_memory_bitmaps();
+	if (error)
+		goto Thaw;
+
 	/* Free memory before shutting down devices. */
 	error = swsusp_shrink_memory();
 	if (error)
-		goto Thaw;
+		goto Finish;
 
 	error = platform_prepare();
 	if (error)
-		goto Thaw;
+		goto Finish;
 
 	suspend_console();
 	error = device_suspend(PMSG_FREEZE);
@@ -169,7 +174,7 @@ int pm_suspend_disk(void)
 			power_down(pm_disk_mode);
 		else {
 			swsusp_free();
-			goto Thaw;
+			goto Finish;
 		}
 	} else {
 		pr_debug("PM: Image restored successfully.\n");
@@ -182,6 +187,8 @@ int pm_suspend_disk(void)
 	platform_finish();
 	device_resume();
 	resume_console();
+ Finish:
+	free_basic_memory_bitmaps();
  Thaw:
 	unprepare_processes();
 	return error;
@@ -227,13 +234,15 @@ static int software_resume(void)
 	}
 
 	pr_debug("PM: Checking swsusp image.\n");
-
 	error = swsusp_check();
 	if (error)
-		goto Done;
+		goto Unlock;
 
-	pr_debug("PM: Preparing processes for restore.\n");
+	error = create_basic_memory_bitmaps();
+	if (error)
+		goto Unlock;
 
+	pr_debug("PM: Preparing processes for restore.\n");
 	error = prepare_processes();
 	if (error) {
 		swsusp_close();
@@ -275,7 +284,9 @@ static int software_resume(void)
 	printk(KERN_ERR "PM: Restore failed, recovering.\n");
 	unprepare_processes();
  Done:
+	free_basic_memory_bitmaps();
 	/* For success case, the suspend path will release the lock */
+ Unlock:
 	mutex_unlock(&pm_mutex);
 	pr_debug("PM: Resume from disk failed.\n");
 	return 0;

[RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

Make swsusp use memory bitmaps instead of page flags for marking 'nosave' and
free pages.  This allows us to 'recycle' two page flags that can be used for other
purposes.  Also, the memory needed to store the bitmaps is allocated when
necessary (ie. before the suspend) and freed after the resume which is more
reasonable.

The patch is designed to minimize the amount of changes and there are some nice
simplifications and optimizations possible on top of it.  I am going to post
them as separate patches in the future.

---
 arch/x86_64/kernel/e820.c |   26 +---
 include/linux/suspend.h   |   58 +++-------
 kernel/power/disk.c       |   23 +++-
 kernel/power/power.h      |    2 
 kernel/power/snapshot.c   |  250 +++++++++++++++++++++++++++++++++++++++++++---
 kernel/power/user.c       |    4 
 6 files changed, 281 insertions(+), 82 deletions(-)

Index: linux-2.6.21-rc2/include/linux/suspend.h
===================================================================
--- linux-2.6.21-rc2.orig/include/linux/suspend.h	2007-03-04 11:52:46.000000000 +0100
+++ linux-2.6.21-rc2/include/linux/suspend.h	2007-03-04 11:52:46.000000000 +0100
@@ -24,63 +24,41 @@ struct pbe {
 extern void drain_local_pages(void);
 extern void mark_free_pages(struct zone *zone);
 
-#ifdef CONFIG_PM
-/* kernel/power/swsusp.c */
-extern int software_suspend(void);
-
-#if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
+#if defined(CONFIG_PM) && defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
 extern int pm_prepare_console(void);
 extern void pm_restore_console(void);
 #else
 static inline int pm_prepare_console(void) { return 0; }
 static inline void pm_restore_console(void) {}
-#endif /* defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE) */
+#endif
+
+#if defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND)
+/* kernel/power/swsusp.c */
+extern int software_suspend(void);
+/* kernel/power/snapshot.c */
+extern void __init register_nosave_region(unsigned long, unsigned long);
+extern int swsusp_page_is_forbidden(struct page *);
+extern void swsusp_set_page_free(struct page *);
+extern void swsusp_unset_page_free(struct page *);
+extern unsigned long get_safe_page(gfp_t gfp_mask);
 #else
 static inline int software_suspend(void)
 {
 	printk("Warning: fake suspend called\n");
 	return -ENOSYS;
 }
-#endif /* CONFIG_PM */
+
+static inline void register_nosave_region(unsigned long b, unsigned long e) {}
+static inline int swsusp_page_is_forbidden(struct page *p) { return 0; }
+static inline void swsusp_set_page_free(struct page *p) {}
+static inline void swsusp_unset_page_free(struct page *p) {}
+#endif /* defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND) */
 
 void save_processor_state(void);
 void restore_processor_state(void);
 struct saved_context;
 void __save_processor_state(struct saved_context *ctxt);
 void __restore_processor_state(struct saved_context *ctxt);
-unsigned long get_safe_page(gfp_t gfp_mask);
-
-/* Page management functions for the software suspend (swsusp) */
-
-static inline void swsusp_set_page_forbidden(struct page *page)
-{
-	SetPageNosave(page);
-}
-
-static inline int swsusp_page_is_forbidden(struct page *page)
-{
-	return PageNosave(page);
-}
-
-static inline void swsusp_unset_page_forbidden(struct page *page)
-{
-	ClearPageNosave(page);
-}
-
-static inline void swsusp_set_page_free(struct page *page)
-{
-	SetPageNosaveFree(page);
-}
-
-static inline int swsusp_page_is_free(struct page *page)
-{
-	return PageNosaveFree(page);
-}
-
-static inline void swsusp_unset_page_free(struct page *page)
-{
-	ClearPageNosaveFree(page);
-}
 
 /*
  * XXX: We try to keep some more pages free so that I/O operations succeed
Index: linux-2.6.21-rc2/kernel/power/snapshot.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/snapshot.c	2007-03-04 11:52:46.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/snapshot.c	2007-03-04 15:06:13.000000000 +0100
@@ -21,6 +21,7 @@
 #include <linux/kernel.h>
 #include <linux/pm.h>
 #include <linux/device.h>
+#include <linux/init.h>
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/console.h>
@@ -34,6 +35,10 @@
 
 #include "power.h"
 
+static int swsusp_page_is_free(struct page *);
+static void swsusp_set_page_forbidden(struct page *);
+static void swsusp_unset_page_forbidden(struct page *);
+
 /* List of PBEs needed for restoring the pages that were allocated before
  * the suspend and included in the suspend image, but have also been
  * allocated by the "resume" kernel, so their contents cannot be written
@@ -224,11 +229,6 @@ static void chain_free(struct chain_allo
  *	of type unsigned long each).  It also contains the pfns that
  *	correspond to the start and end of the represented memory area and
  *	the number of bit chunks in the block.
- *
- *	NOTE: Memory bitmaps are used for two types of operations only:
- *	"set a bit" and "find the next bit set".  Moreover, the searching
- *	is always carried out after all of the "set a bit" operations
- *	on given bitmap.
  */
 
 #define BM_END_OF_MAP	(~0UL)
@@ -443,15 +443,13 @@ static void memory_bm_free(struct memory
 }
 
 /**
- *	memory_bm_set_bit - set the bit in the bitmap @bm that corresponds
+ *	memory_bm_find_bit - find the bit in the bitmap @bm that corresponds
  *	to given pfn.  The cur_zone_bm member of @bm and the cur_block member
  *	of @bm->cur_zone_bm are updated.
- *
- *	If the bit cannot be set, the function returns -EINVAL .
  */
 
-static int
-memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
+static void memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn,
+				void **addr, unsigned int *bit_nr)
 {
 	struct zone_bitmap *zone_bm;
 	struct bm_block *bb;
@@ -463,8 +461,8 @@ memory_bm_set_bit(struct memory_bitmap *
 		/* We don't assume that the zones are sorted by pfns */
 		while (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
 			zone_bm = zone_bm->next;
-			if (unlikely(!zone_bm))
-				return -EINVAL;
+
+			BUG_ON(!zone_bm);
 		}
 		bm->cur.zone_bm = zone_bm;
 	}
@@ -475,13 +473,40 @@ memory_bm_set_bit(struct memory_bitmap *
 
 	while (pfn >= bb->end_pfn) {
 		bb = bb->next;
-		if (unlikely(!bb))
-			return -EINVAL;
+
+		BUG_ON(!bb);
 	}
 	zone_bm->cur_block = bb;
 	pfn -= bb->start_pfn;
-	set_bit(pfn % BM_BITS_PER_CHUNK, bb->data + pfn / BM_BITS_PER_CHUNK);
-	return 0;
+	*bit_nr = pfn % BM_BITS_PER_CHUNK;
+	*addr = bb->data + pfn / BM_BITS_PER_CHUNK;
+}
+
+static void memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	set_bit(bit, addr);
+}
+
+static void memory_bm_clear_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	clear_bit(bit, addr);
+}
+
+static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
+{
+	void *addr;
+	unsigned int bit;
+
+	memory_bm_find_bit(bm, pfn, &addr, &bit);
+	return test_bit(bit, addr);
 }
 
 /* Two auxiliary functions for memory_bm_next_pfn */
@@ -564,6 +589,199 @@ static unsigned long memory_bm_next_pfn(
 }
 
 /**
+ *	This structure represents a range of page frames the contents of which
+ *	should not be saved during the suspend.
+ */
+
+struct nosave_region {
+	struct list_head list;
+	unsigned long start_pfn;
+	unsigned long end_pfn;
+};
+
+static LIST_HEAD(nosave_regions);
+
+/**
+ *	register_nosave_region - register a range of page frames the contents
+ *	of which should not be saved during the suspend (to be used in the early
+ *	initializatoion code)
+ */
+
+void __init
+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
+{
+	struct nosave_region *region;
+
+	if (start_pfn >= end_pfn)
+		return;
+
+	if (!list_empty(&nosave_regions)) {
+		/* Try to extend the previous region (they should be sorted) */
+		region = list_entry(nosave_regions.prev,
+					struct nosave_region, list);
+		if (region->end_pfn == start_pfn) {
+			region->end_pfn = end_pfn;
+			goto Report;
+		}
+	}
+	/* This allocation cannot fail */
+	region = alloc_bootmem_low(sizeof(struct nosave_region));
+	region->start_pfn = start_pfn;
+	region->end_pfn = end_pfn;
+	list_add_tail(&region->list, &nosave_regions);
+ Report:
+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
+}
+
+/*
+ * Set bits in this map correspond to the page frames the contents of which
+ * should not be saved during the suspend.
+ */
+static struct memory_bitmap *forbidden_pages_map;
+
+/* Set bits in this map correspond to free page frames. */
+static struct memory_bitmap *free_pages_map;
+
+/*
+ * Each page frame allocated for creating the image is marked by setting the
+ * corresponding bits in forbidden_pages_map and free_pages_map simultaneously
+ */
+
+void swsusp_set_page_free(struct page *page)
+{
+	if (free_pages_map)
+		memory_bm_set_bit(free_pages_map, page_to_pfn(page));
+}
+
+static int swsusp_page_is_free(struct page *page)
+{
+	return free_pages_map ?
+		memory_bm_test_bit(free_pages_map, page_to_pfn(page)) : 0;
+}
+
+void swsusp_unset_page_free(struct page *page)
+{
+	if (free_pages_map)
+		memory_bm_clear_bit(free_pages_map, page_to_pfn(page));
+}
+
+static void swsusp_set_page_forbidden(struct page *page)
+{
+	if (forbidden_pages_map)
+		memory_bm_set_bit(forbidden_pages_map, page_to_pfn(page));
+}
+
+int swsusp_page_is_forbidden(struct page *page)
+{
+	return forbidden_pages_map ?
+		memory_bm_test_bit(forbidden_pages_map, page_to_pfn(page)) : 0;
+}
+
+static void swsusp_unset_page_forbidden(struct page *page)
+{
+	if (forbidden_pages_map)
+		memory_bm_clear_bit(forbidden_pages_map, page_to_pfn(page));
+}
+
+/**
+ *	mark_nosave_pages - set bits corresponding to the page frames the
+ *	contents of which should not be saved in a given bitmap.
+ */
+
+static void mark_nosave_pages(struct memory_bitmap *bm)
+{
+	struct nosave_region *region;
+
+	if (list_empty(&nosave_regions))
+		return;
+
+	list_for_each_entry(region, &nosave_regions, list) {
+		unsigned long pfn;
+
+		printk("swsusp: Marking nosave pages: %016lx - %016lx\n",
+				region->start_pfn << PAGE_SHIFT,
+				region->end_pfn << PAGE_SHIFT);
+
+		for (pfn = region->start_pfn; pfn < region->end_pfn; pfn++)
+			memory_bm_set_bit(bm, pfn);
+	}
+}
+
+/**
+ *	create_basic_memory_bitmaps - create bitmaps needed for marking page
+ *	frames that should not be saved and free page frames.  The pointers
+ *	forbidden_pages_map and free_pages_map are only modified if everything
+ *	goes well, because we don't want the bits to be used before both bitmaps
+ *	are set up.
+ */
+
+int create_basic_memory_bitmaps(void)
+{
+	struct memory_bitmap *bm1, *bm2;
+	int error = 0;
+
+	BUG_ON(forbidden_pages_map || free_pages_map);
+
+	bm1 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
+	if (!bm1)
+		return -ENOMEM;
+
+	error = memory_bm_create(bm1, GFP_ATOMIC | __GFP_COLD, PG_ANY);
+	if (error)
+		goto Free_first_object;
+
+	bm2 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
+	if (!bm2)
+		goto Free_first_bitmap;
+
+	error = memory_bm_create(bm2, GFP_ATOMIC | __GFP_COLD, PG_ANY);
+	if (error)
+		goto Free_second_object;
+
+	forbidden_pages_map = bm1;
+	free_pages_map = bm2;
+	mark_nosave_pages(forbidden_pages_map);
+
+	printk("swsusp: Basic memory bitmaps created\n");
+
+	return 0;
+
+ Free_second_object:
+	kfree(bm2);
+ Free_first_bitmap:
+ 	memory_bm_free(bm1, PG_UNSAFE_CLEAR);
+ Free_first_object:
+	kfree(bm1);
+	return -ENOMEM;
+}
+
+/**
+ *	free_basic_memory_bitmaps - free memory bitmaps allocated by
+ *	create_basic_memory_bitmaps().  The auxiliary pointers are necessary
+ *	so that the bitmaps themselves are not referred to while they are being
+ *	freed.
+ */
+
+void free_basic_memory_bitmaps(void)
+{
+	struct memory_bitmap *bm1, *bm2;
+
+	BUG_ON(!(forbidden_pages_map && free_pages_map));
+
+	bm1 = forbidden_pages_map;
+	bm2 = free_pages_map;
+	forbidden_pages_map = NULL;
+	free_pages_map = NULL;
+	memory_bm_free(bm1, PG_UNSAFE_CLEAR);
+	kfree(bm1);
+	memory_bm_free(bm2, PG_UNSAFE_CLEAR);
+	kfree(bm2);
+
+	printk("swsusp: Basic memory bitmaps freed\n");
+}
+
+/**
  *	snapshot_additional_pages - estimate the number of additional pages
  *	be needed for setting up the suspend image data structures for given
  *	zone (usually the returned value is greater than the exact number)
Index: linux-2.6.21-rc2/arch/x86_64/kernel/e820.c
===================================================================
--- linux-2.6.21-rc2.orig/arch/x86_64/kernel/e820.c	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/arch/x86_64/kernel/e820.c	2007-03-04 13:25:20.000000000 +0100
@@ -17,6 +17,8 @@
 #include <linux/kexec.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/suspend.h>
+#include <linux/pfn.h>
 
 #include <asm/pgtable.h>
 #include <asm/page.h>
@@ -255,22 +257,6 @@ void __init e820_reserve_resources(void)
 	}
 }
 
-/* Mark pages corresponding to given address range as nosave */
-static void __init
-e820_mark_nosave_range(unsigned long start, unsigned long end)
-{
-	unsigned long pfn, max_pfn;
-
-	if (start >= end)
-		return;
-
-	printk("Nosave address range: %016lx - %016lx\n", start, end);
-	max_pfn = end >> PAGE_SHIFT;
-	for (pfn = start >> PAGE_SHIFT; pfn < max_pfn; pfn++)
-		if (pfn_valid(pfn))
-			SetPageNosave(pfn_to_page(pfn));
-}
-
 /*
  * Find the ranges of physical addresses that do not correspond to
  * e820 RAM areas and mark the corresponding pages as nosave for software
@@ -289,13 +275,13 @@ void __init e820_mark_nosave_regions(voi
 		struct e820entry *ei = &e820.map[i];
 
 		if (paddr < ei->addr)
-			e820_mark_nosave_range(paddr,
-					round_up(ei->addr, PAGE_SIZE));
+			register_nosave_region(PFN_DOWN(paddr),
+						PFN_UP(ei->addr));
 
 		paddr = round_down(ei->addr + ei->size, PAGE_SIZE);
 		if (ei->type != E820_RAM)
-			e820_mark_nosave_range(round_up(ei->addr, PAGE_SIZE),
-					paddr);
+			register_nosave_region(PFN_UP(ei->addr),
+						PFN_DOWN(paddr));
 
 		if (paddr >= (end_pfn << PAGE_SHIFT))
 			break;
Index: linux-2.6.21-rc2/kernel/power/power.h
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/power.h	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/power.h	2007-03-04 11:52:46.000000000 +0100
@@ -49,6 +49,8 @@ extern sector_t swsusp_resume_block;
 extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);
 
+extern int create_basic_memory_bitmaps(void);
+extern void free_basic_memory_bitmaps(void);
 extern unsigned int count_data_pages(void);
 
 /**
Index: linux-2.6.21-rc2/kernel/power/user.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/user.c	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/user.c	2007-03-04 14:02:19.000000000 +0100
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *i
 	if ((filp->f_flags & O_ACCMODE) == O_RDWR)
 		return -ENOSYS;
 
+	if(create_basic_memory_bitmaps())
+		return -ENOMEM;
+
 	nonseekable_open(inode, filp);
 	data = &snapshot_state;
 	filp->private_data = data;
@@ -77,6 +80,7 @@ static int snapshot_release(struct inode
 	struct snapshot_data *data;
 
 	swsusp_free();
+	free_basic_memory_bitmaps();
 	data = filp->private_data;
 	free_all_swap_pages(data->swap, data->bitmap);
 	free_bitmap(data->bitmap);
Index: linux-2.6.21-rc2/kernel/power/disk.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/power/disk.c	2007-03-04 11:30:18.000000000 +0100
+++ linux-2.6.21-rc2/kernel/power/disk.c	2007-03-04 11:52:46.000000000 +0100
@@ -127,14 +127,19 @@ int pm_suspend_disk(void)
 		mdelay(5000);
 		goto Thaw;
 	}
+	/* Allocate memory management structures */
+	error = create_basic_memory_bitmaps();
+	if (error)
+		goto Thaw;
+
 	/* Free memory before shutting down devices. */
 	error = swsusp_shrink_memory();
 	if (error)
-		goto Thaw;
+		goto Finish;
 
 	error = platform_prepare();
 	if (error)
-		goto Thaw;
+		goto Finish;
 
 	suspend_console();
 	error = device_suspend(PMSG_FREEZE);
@@ -169,7 +174,7 @@ int pm_suspend_disk(void)
 			power_down(pm_disk_mode);
 		else {
 			swsusp_free();
-			goto Thaw;
+			goto Finish;
 		}
 	} else {
 		pr_debug("PM: Image restored successfully.\n");
@@ -182,6 +187,8 @@ int pm_suspend_disk(void)
 	platform_finish();
 	device_resume();
 	resume_console();
+ Finish:
+	free_basic_memory_bitmaps();
  Thaw:
 	unprepare_processes();
 	return error;
@@ -227,13 +234,15 @@ static int software_resume(void)
 	}
 
 	pr_debug("PM: Checking swsusp image.\n");
-
 	error = swsusp_check();
 	if (error)
-		goto Done;
+		goto Unlock;
 
-	pr_debug("PM: Preparing processes for restore.\n");
+	error = create_basic_memory_bitmaps();
+	if (error)
+		goto Unlock;
 
+	pr_debug("PM: Preparing processes for restore.\n");
 	error = prepare_processes();
 	if (error) {
 		swsusp_close();
@@ -275,7 +284,9 @@ static int software_resume(void)
 	printk(KERN_ERR "PM: Restore failed, recovering.\n");
 	unprepare_processes();
  Done:
+	free_basic_memory_bitmaps();
 	/* For success case, the suspend path will release the lock */
+ Unlock:
 	mutex_unlock(&pm_mutex);
 	pr_debug("PM: Resume from disk failed.\n");
 	return 0;

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:

>  }
>  
>  /**
> + *	This structure represents a range of page frames the contents of which
> + *	should not be saved during the suspend.
> + */
> +
> +struct nosave_region {
> +	struct list_head list;
> +	unsigned long start_pfn;
> +	unsigned long end_pfn;
> +};
> +
> +static LIST_HEAD(nosave_regions);
> +
> +/**
> + *	register_nosave_region - register a range of page frames the contents
> + *	of which should not be saved during the suspend (to be used in the early
> + *	initializatoion code)
> + */
> +
> +void __init
> +register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
> +{
> +	struct nosave_region *region;
> +
> +	if (start_pfn >= end_pfn)
> +		return;
> +
> +	if (!list_empty(&nosave_regions)) {
> +		/* Try to extend the previous region (they should be sorted) */
> +		region = list_entry(nosave_regions.prev,
> +					struct nosave_region, list);
> +		if (region->end_pfn == start_pfn) {
> +			region->end_pfn = end_pfn;
> +			goto Report;
> +		}
> +	}
> +	/* This allocation cannot fail */
> +	region = alloc_bootmem_low(sizeof(struct nosave_region));
> +	region->start_pfn = start_pfn;
> +	region->end_pfn = end_pfn;
> +	list_add_tail(&region->list, &nosave_regions);
> + Report:
> +	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
> +		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
> +}


I wonder why you reimplemented this and put it in snapshot.c, rather than
use my version which was nicely in its own file, had appropriate locking,
etc.?

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:

>  }
>  
>  /**
> + *	This structure represents a range of page frames the contents of which
> + *	should not be saved during the suspend.
> + */
> +
> +struct nosave_region {
> +	struct list_head list;
> +	unsigned long start_pfn;
> +	unsigned long end_pfn;
> +};
> +
> +static LIST_HEAD(nosave_regions);
> +
> +/**
> + *	register_nosave_region - register a range of page frames the contents
> + *	of which should not be saved during the suspend (to be used in the early
> + *	initializatoion code)
> + */
> +
> +void __init
> +register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
> +{
> +	struct nosave_region *region;
> +
> +	if (start_pfn >= end_pfn)
> +		return;
> +
> +	if (!list_empty(&nosave_regions)) {
> +		/* Try to extend the previous region (they should be sorted) */
> +		region = list_entry(nosave_regions.prev,
> +					struct nosave_region, list);
> +		if (region->end_pfn == start_pfn) {
> +			region->end_pfn = end_pfn;
> +			goto Report;
> +		}
> +	}
> +	/* This allocation cannot fail */
> +	region = alloc_bootmem_low(sizeof(struct nosave_region));
> +	region->start_pfn = start_pfn;
> +	region->end_pfn = end_pfn;
> +	list_add_tail(&region->list, &nosave_regions);
> + Report:
> +	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
> +		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
> +}


I wonder why you reimplemented this and put it in snapshot.c, rather than
use my version which was nicely in its own file, had appropriate locking,
etc.?

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Tuesday, 13 March 2007 05:47, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> 
> >  }
> >  
> >  /**
> > + *	This structure represents a range of page frames the contents of which
> > + *	should not be saved during the suspend.
> > + */
> > +
> > +struct nosave_region {
> > +	struct list_head list;
> > +	unsigned long start_pfn;
> > +	unsigned long end_pfn;
> > +};
> > +
> > +static LIST_HEAD(nosave_regions);
> > +
> > +/**
> > + *	register_nosave_region - register a range of page frames the contents
> > + *	of which should not be saved during the suspend (to be used in the early
> > + *	initializatoion code)
> > + */
> > +
> > +void __init
> > +register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
> > +{
> > +	struct nosave_region *region;
> > +
> > +	if (start_pfn >= end_pfn)
> > +		return;
> > +
> > +	if (!list_empty(&nosave_regions)) {
> > +		/* Try to extend the previous region (they should be sorted) */
> > +		region = list_entry(nosave_regions.prev,
> > +					struct nosave_region, list);
> > +		if (region->end_pfn == start_pfn) {
> > +			region->end_pfn = end_pfn;
> > +			goto Report;
> > +		}
> > +	}
> > +	/* This allocation cannot fail */
> > +	region = alloc_bootmem_low(sizeof(struct nosave_region));
> > +	region->start_pfn = start_pfn;
> > +	region->end_pfn = end_pfn;
> > +	list_add_tail(&region->list, &nosave_regions);
> > + Report:
> > +	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
> > +		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
> > +}
> 
> 
> I wonder why you reimplemented this and put it in snapshot.c, rather than
> use my version which was nicely in its own file, had appropriate locking,
> etc.?

Well, the locking is not necessary and we only need a list for that.  Also,
mark_nosave_pages() refers to a function that's invisible outside snapshot.c
and I didn't think it was a good idea to separate mark_nosave_pages()
from register_nosave_region().

Greetings,
Rafael

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Tuesday, 13 March 2007 05:47, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> 
> >  }
> >  
> >  /**
> > + *	This structure represents a range of page frames the contents of which
> > + *	should not be saved during the suspend.
> > + */
> > +
> > +struct nosave_region {
> > +	struct list_head list;
> > +	unsigned long start_pfn;
> > +	unsigned long end_pfn;
> > +};
> > +
> > +static LIST_HEAD(nosave_regions);
> > +
> > +/**
> > + *	register_nosave_region - register a range of page frames the contents
> > + *	of which should not be saved during the suspend (to be used in the early
> > + *	initializatoion code)
> > + */
> > +
> > +void __init
> > +register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
> > +{
> > +	struct nosave_region *region;
> > +
> > +	if (start_pfn >= end_pfn)
> > +		return;
> > +
> > +	if (!list_empty(&nosave_regions)) {
> > +		/* Try to extend the previous region (they should be sorted) */
> > +		region = list_entry(nosave_regions.prev,
> > +					struct nosave_region, list);
> > +		if (region->end_pfn == start_pfn) {
> > +			region->end_pfn = end_pfn;
> > +			goto Report;
> > +		}
> > +	}
> > +	/* This allocation cannot fail */
> > +	region = alloc_bootmem_low(sizeof(struct nosave_region));
> > +	region->start_pfn = start_pfn;
> > +	region->end_pfn = end_pfn;
> > +	list_add_tail(&region->list, &nosave_regions);
> > + Report:
> > +	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
> > +		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
> > +}
> 
> 
> I wonder why you reimplemented this and put it in snapshot.c, rather than
> use my version which was nicely in its own file, had appropriate locking,
> etc.?

Well, the locking is not necessary and we only need a list for that.  Also,
mark_nosave_pages() refers to a function that's invisible outside snapshot.c
and I didn't think it was a good idea to separate mark_nosave_pages()
from register_nosave_region().

Greetings,
Rafael

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 05:47, Nick Piggin wrote:
> 
>>Rafael J. Wysocki wrote:
>>
>>
>>> }
>>> 
>>> /**
>>>+ *	This structure represents a range of page frames the contents of which
>>>+ *	should not be saved during the suspend.
>>>+ */
>>>+
>>>+struct nosave_region {
>>>+	struct list_head list;
>>>+	unsigned long start_pfn;
>>>+	unsigned long end_pfn;
>>>+};
>>>+
>>>+static LIST_HEAD(nosave_regions);
>>>+
>>>+/**
>>>+ *	register_nosave_region - register a range of page frames the contents
>>>+ *	of which should not be saved during the suspend (to be used in the early
>>>+ *	initializatoion code)
>>>+ */
>>>+
>>>+void __init
>>>+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
>>>+{
>>>+	struct nosave_region *region;
>>>+
>>>+	if (start_pfn >= end_pfn)
>>>+		return;
>>>+
>>>+	if (!list_empty(&nosave_regions)) {
>>>+		/* Try to extend the previous region (they should be sorted) */
>>>+		region = list_entry(nosave_regions.prev,
>>>+					struct nosave_region, list);
>>>+		if (region->end_pfn == start_pfn) {
>>>+			region->end_pfn = end_pfn;
>>>+			goto Report;
>>>+		}
>>>+	}
>>>+	/* This allocation cannot fail */
>>>+	region = alloc_bootmem_low(sizeof(struct nosave_region));
>>>+	region->start_pfn = start_pfn;
>>>+	region->end_pfn = end_pfn;
>>>+	list_add_tail(&region->list, &nosave_regions);
>>>+ Report:
>>>+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
>>>+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
>>>+}
>>
>>
>>I wonder why you reimplemented this and put it in snapshot.c, rather than
>>use my version which was nicely in its own file, had appropriate locking,
>>etc.?
> 
> 
> Well, the locking is not necessary and we only need a list for that.  Also,

I wouldn't say that. You're creating an interface here that is going to be
used outside swsusp. Users of that interface may not need locking now, but
that could cause problems down the line.

Sure you don't _need_ an rbtree, but our implementation makes it so simple
that there isn't much downside.

> mark_nosave_pages() refers to a function that's invisible outside snapshot.c
> and I didn't think it was a good idea to separate mark_nosave_pages()
> from register_nosave_region().

But that's because you even use mark_nosave_pages in your implementation.
Mine uses the nosave regions directly.

-- 
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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 05:47, Nick Piggin wrote:
> 
>>Rafael J. Wysocki wrote:
>>
>>
>>> }
>>> 
>>> /**
>>>+ *	This structure represents a range of page frames the contents of which
>>>+ *	should not be saved during the suspend.
>>>+ */
>>>+
>>>+struct nosave_region {
>>>+	struct list_head list;
>>>+	unsigned long start_pfn;
>>>+	unsigned long end_pfn;
>>>+};
>>>+
>>>+static LIST_HEAD(nosave_regions);
>>>+
>>>+/**
>>>+ *	register_nosave_region - register a range of page frames the contents
>>>+ *	of which should not be saved during the suspend (to be used in the early
>>>+ *	initializatoion code)
>>>+ */
>>>+
>>>+void __init
>>>+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
>>>+{
>>>+	struct nosave_region *region;
>>>+
>>>+	if (start_pfn >= end_pfn)
>>>+		return;
>>>+
>>>+	if (!list_empty(&nosave_regions)) {
>>>+		/* Try to extend the previous region (they should be sorted) */
>>>+		region = list_entry(nosave_regions.prev,
>>>+					struct nosave_region, list);
>>>+		if (region->end_pfn == start_pfn) {
>>>+			region->end_pfn = end_pfn;
>>>+			goto Report;
>>>+		}
>>>+	}
>>>+	/* This allocation cannot fail */
>>>+	region = alloc_bootmem_low(sizeof(struct nosave_region));
>>>+	region->start_pfn = start_pfn;
>>>+	region->end_pfn = end_pfn;
>>>+	list_add_tail(&region->list, &nosave_regions);
>>>+ Report:
>>>+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
>>>+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
>>>+}
>>
>>
>>I wonder why you reimplemented this and put it in snapshot.c, rather than
>>use my version which was nicely in its own file, had appropriate locking,
>>etc.?
> 
> 
> Well, the locking is not necessary and we only need a list for that.  Also,

I wouldn't say that. You're creating an interface here that is going to be
used outside swsusp. Users of that interface may not need locking now, but
that could cause problems down the line.

Sure you don't _need_ an rbtree, but our implementation makes it so simple
that there isn't much downside.

> mark_nosave_pages() refers to a function that's invisible outside snapshot.c
> and I didn't think it was a good idea to separate mark_nosave_pages()
> from register_nosave_region().

But that's because you even use mark_nosave_pages in your implementation.
Mine uses the nosave regions directly.

-- 
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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 13 March 2007 05:47, Nick Piggin wrote:
> > 
> >>Rafael J. Wysocki wrote:
> >>
> >>
> >>> }
> >>> 
> >>> /**
> >>>+ *	This structure represents a range of page frames the contents of which
> >>>+ *	should not be saved during the suspend.
> >>>+ */
> >>>+
> >>>+struct nosave_region {
> >>>+	struct list_head list;
> >>>+	unsigned long start_pfn;
> >>>+	unsigned long end_pfn;
> >>>+};
> >>>+
> >>>+static LIST_HEAD(nosave_regions);
> >>>+
> >>>+/**
> >>>+ *	register_nosave_region - register a range of page frames the contents
> >>>+ *	of which should not be saved during the suspend (to be used in the early
> >>>+ *	initializatoion code)
> >>>+ */
> >>>+
> >>>+void __init
> >>>+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
> >>>+{
> >>>+	struct nosave_region *region;
> >>>+
> >>>+	if (start_pfn >= end_pfn)
> >>>+		return;
> >>>+
> >>>+	if (!list_empty(&nosave_regions)) {
> >>>+		/* Try to extend the previous region (they should be sorted) */
> >>>+		region = list_entry(nosave_regions.prev,
> >>>+					struct nosave_region, list);
> >>>+		if (region->end_pfn == start_pfn) {
> >>>+			region->end_pfn = end_pfn;
> >>>+			goto Report;
> >>>+		}
> >>>+	}
> >>>+	/* This allocation cannot fail */
> >>>+	region = alloc_bootmem_low(sizeof(struct nosave_region));
> >>>+	region->start_pfn = start_pfn;
> >>>+	region->end_pfn = end_pfn;
> >>>+	list_add_tail(&region->list, &nosave_regions);
> >>>+ Report:
> >>>+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
> >>>+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
> >>>+}
> >>
> >>
> >>I wonder why you reimplemented this and put it in snapshot.c, rather than
> >>use my version which was nicely in its own file, had appropriate locking,
> >>etc.?
> > 
> > 
> > Well, the locking is not necessary and we only need a list for that.  Also,
> 
> I wouldn't say that. You're creating an interface here that is going to be
> used outside swsusp. Users of that interface may not need locking now, but
> that could cause problems down the line.

I think we can add the locking when it's necessary.  For now, IMHO, it could be
confusing to someone who doesn't know the locking is not needed.

> Sure you don't _need_ an rbtree, but our implementation makes it so simple
> that there isn't much downside.

Not much, but the code is more complicated.

> > mark_nosave_pages() refers to a function that's invisible outside snapshot.c
> > and I didn't think it was a good idea to separate mark_nosave_pages()
> > from register_nosave_region().
> 
> But that's because you even use mark_nosave_pages in your implementation.
> Mine uses the nosave regions directly.

Well, I think we need two bits per page anyway, to mark free pages and
pages allocated by swsusp, so using the nosave regions directly won't save us
much.

Still, for now the bits are not optimally used, but I'm going to change that.
I just wanted to avoid making too many changes at a time in this particular
patch series.

Greetings,
Rafael

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 13 March 2007 05:47, Nick Piggin wrote:
> > 
> >>Rafael J. Wysocki wrote:
> >>
> >>
> >>> }
> >>> 
> >>> /**
> >>>+ *	This structure represents a range of page frames the contents of which
> >>>+ *	should not be saved during the suspend.
> >>>+ */
> >>>+
> >>>+struct nosave_region {
> >>>+	struct list_head list;
> >>>+	unsigned long start_pfn;
> >>>+	unsigned long end_pfn;
> >>>+};
> >>>+
> >>>+static LIST_HEAD(nosave_regions);
> >>>+
> >>>+/**
> >>>+ *	register_nosave_region - register a range of page frames the contents
> >>>+ *	of which should not be saved during the suspend (to be used in the early
> >>>+ *	initializatoion code)
> >>>+ */
> >>>+
> >>>+void __init
> >>>+register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
> >>>+{
> >>>+	struct nosave_region *region;
> >>>+
> >>>+	if (start_pfn >= end_pfn)
> >>>+		return;
> >>>+
> >>>+	if (!list_empty(&nosave_regions)) {
> >>>+		/* Try to extend the previous region (they should be sorted) */
> >>>+		region = list_entry(nosave_regions.prev,
> >>>+					struct nosave_region, list);
> >>>+		if (region->end_pfn == start_pfn) {
> >>>+			region->end_pfn = end_pfn;
> >>>+			goto Report;
> >>>+		}
> >>>+	}
> >>>+	/* This allocation cannot fail */
> >>>+	region = alloc_bootmem_low(sizeof(struct nosave_region));
> >>>+	region->start_pfn = start_pfn;
> >>>+	region->end_pfn = end_pfn;
> >>>+	list_add_tail(&region->list, &nosave_regions);
> >>>+ Report:
> >>>+	printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
> >>>+		start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
> >>>+}
> >>
> >>
> >>I wonder why you reimplemented this and put it in snapshot.c, rather than
> >>use my version which was nicely in its own file, had appropriate locking,
> >>etc.?
> > 
> > 
> > Well, the locking is not necessary and we only need a list for that.  Also,
> 
> I wouldn't say that. You're creating an interface here that is going to be
> used outside swsusp. Users of that interface may not need locking now, but
> that could cause problems down the line.

I think we can add the locking when it's necessary.  For now, IMHO, it could be
confusing to someone who doesn't know the locking is not needed.

> Sure you don't _need_ an rbtree, but our implementation makes it so simple
> that there isn't much downside.

Not much, but the code is more complicated.

> > mark_nosave_pages() refers to a function that's invisible outside snapshot.c
> > and I didn't think it was a good idea to separate mark_nosave_pages()
> > from register_nosave_region().
> 
> But that's because you even use mark_nosave_pages in your implementation.
> Mine uses the nosave regions directly.

Well, I think we need two bits per page anyway, to mark free pages and
pages allocated by swsusp, so using the nosave regions directly won't save us
much.

Still, for now the bits are not optimally used, but I'm going to change that.
I just wanted to avoid making too many changes at a time in this particular
patch series.

Greetings,
Rafael

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> 

>>I wouldn't say that. You're creating an interface here that is going to be
>>used outside swsusp. Users of that interface may not need locking now, but
>>that could cause problems down the line.
> 
> 
> I think we can add the locking when it's necessary.  For now, IMHO, it could be
> confusing to someone who doesn't know the locking is not needed.

I don't know why it would confuse them. We just define the API to
guarantee the correct locking, and that means the locking _is_ needed.

You don't have to care what the callers are doing. That's the beauty
of a sane API.


>>Sure you don't _need_ an rbtree, but our implementation makes it so simple
>>that there isn't much downside.
> 
> 
> Not much, but the code is more complicated.

But it's in its own file and has a contained API, so it is very easy
to review, test and verify.


>>>mark_nosave_pages() refers to a function that's invisible outside snapshot.c
>>>and I didn't think it was a good idea to separate mark_nosave_pages()
>>>from register_nosave_region().
>>
>>But that's because you even use mark_nosave_pages in your implementation.
>>Mine uses the nosave regions directly.
> 
> 
> Well, I think we need two bits per page anyway, to mark free pages and
> pages allocated by swsusp, so using the nosave regions directly won't save us
> much.

Well I think it is a cleaner though.

-- 
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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> 

>>I wouldn't say that. You're creating an interface here that is going to be
>>used outside swsusp. Users of that interface may not need locking now, but
>>that could cause problems down the line.
> 
> 
> I think we can add the locking when it's necessary.  For now, IMHO, it could be
> confusing to someone who doesn't know the locking is not needed.

I don't know why it would confuse them. We just define the API to
guarantee the correct locking, and that means the locking _is_ needed.

You don't have to care what the callers are doing. That's the beauty
of a sane API.


>>Sure you don't _need_ an rbtree, but our implementation makes it so simple
>>that there isn't much downside.
> 
> 
> Not much, but the code is more complicated.

But it's in its own file and has a contained API, so it is very easy
to review, test and verify.


>>>mark_nosave_pages() refers to a function that's invisible outside snapshot.c
>>>and I didn't think it was a good idea to separate mark_nosave_pages()
>>>from register_nosave_region().
>>
>>But that's because you even use mark_nosave_pages in your implementation.
>>Mine uses the nosave regions directly.
> 
> 
> Well, I think we need two bits per page anyway, to mark free pages and
> pages allocated by swsusp, so using the nosave regions directly won't save us
> much.

Well I think it is a cleaner though.

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Tuesday, 13 March 2007 11:31, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> > 
> 
> >>I wouldn't say that. You're creating an interface here that is going to be
> >>used outside swsusp. Users of that interface may not need locking now, but
> >>that could cause problems down the line.
> > 
> > 
> > I think we can add the locking when it's necessary.  For now, IMHO, it could be
> > confusing to someone who doesn't know the locking is not needed.
> 
> I don't know why it would confuse them. We just define the API to
> guarantee the correct locking, and that means the locking _is_ needed.

Even if there are no users that actually need the locking and probably never
will be?

For now, register_nosave_region() is to be called by architecture
initialization code _only_ and there's no reason whatsoever why any
architecture would need to call it concurrently from many places.

> You don't have to care what the callers are doing. That's the beauty
> of a sane API.

Well, I don't think adding unneded infrastructure is a good thing.

> >>Sure you don't _need_ an rbtree, but our implementation makes it so simple
> >>that there isn't much downside.
> > 
> > 
> > Not much, but the code is more complicated.
> 
> But it's in its own file and has a contained API, so it is very easy
> to review, test and verify.

I'm still thinking that register_nosave_region() in its current form is simpler
and easier to review than the code using rbtrees.  Still, of course this only
is my personal opinion. :-)

> >>>mark_nosave_pages() refers to a function that's invisible outside snapshot.c
> >>>and I didn't think it was a good idea to separate mark_nosave_pages()
> >>>from register_nosave_region().
> >>
> >>But that's because you even use mark_nosave_pages in your implementation.
> >>Mine uses the nosave regions directly.
> > 
> > 
> > Well, I think we need two bits per page anyway, to mark free pages and
> > pages allocated by swsusp, so using the nosave regions directly won't save us
> > much.
> 
> Well I think it is a cleaner though.

This is a matter of opinion, too ...

Greetings,
Rafael

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Tuesday, 13 March 2007 11:31, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> > 
> 
> >>I wouldn't say that. You're creating an interface here that is going to be
> >>used outside swsusp. Users of that interface may not need locking now, but
> >>that could cause problems down the line.
> > 
> > 
> > I think we can add the locking when it's necessary.  For now, IMHO, it could be
> > confusing to someone who doesn't know the locking is not needed.
> 
> I don't know why it would confuse them. We just define the API to
> guarantee the correct locking, and that means the locking _is_ needed.

Even if there are no users that actually need the locking and probably never
will be?

For now, register_nosave_region() is to be called by architecture
initialization code _only_ and there's no reason whatsoever why any
architecture would need to call it concurrently from many places.

> You don't have to care what the callers are doing. That's the beauty
> of a sane API.

Well, I don't think adding unneded infrastructure is a good thing.

> >>Sure you don't _need_ an rbtree, but our implementation makes it so simple
> >>that there isn't much downside.
> > 
> > 
> > Not much, but the code is more complicated.
> 
> But it's in its own file and has a contained API, so it is very easy
> to review, test and verify.

I'm still thinking that register_nosave_region() in its current form is simpler
and easier to review than the code using rbtrees.  Still, of course this only
is my personal opinion. :-)

> >>>mark_nosave_pages() refers to a function that's invisible outside snapshot.c
> >>>and I didn't think it was a good idea to separate mark_nosave_pages()
> >>>from register_nosave_region().
> >>
> >>But that's because you even use mark_nosave_pages in your implementation.
> >>Mine uses the nosave regions directly.
> > 
> > 
> > Well, I think we need two bits per page anyway, to mark free pages and
> > pages allocated by swsusp, so using the nosave regions directly won't save us
> > much.
> 
> Well I think it is a cleaner though.

This is a matter of opinion, too ...

Greetings,
Rafael

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 11:31, Nick Piggin wrote:
> 
>>Rafael J. Wysocki wrote:
>>
>>>On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
>>>
>>
>>>>I wouldn't say that. You're creating an interface here that is going to be
>>>>used outside swsusp. Users of that interface may not need locking now, but
>>>>that could cause problems down the line.
>>>
>>>
>>>I think we can add the locking when it's necessary.  For now, IMHO, it could be
>>>confusing to someone who doesn't know the locking is not needed.
>>
>>I don't know why it would confuse them. We just define the API to
>>guarantee the correct locking, and that means the locking _is_ needed.
> 
> 
> Even if there are no users that actually need the locking and probably never
> will be?

Probably is the keyword.

Why would you *not* make this a sane API? Surely performance isn't the
reason? Nor complexity.

> For now, register_nosave_region() is to be called by architecture
> initialization code _only_ and there's no reason whatsoever why any
> architecture would need to call it concurrently from many places.
> 
> 
>>You don't have to care what the callers are doing. That's the beauty
>>of a sane API.
> 
> 
> Well, I don't think adding unneded infrastructure is a good thing.


But defining good APIs is a very good thing. And with my good API, the
lock is not unneeded.

>>>>But that's because you even use mark_nosave_pages in your implementation.
>>>>Mine uses the nosave regions directly.
>>>
>>>
>>>Well, I think we need two bits per page anyway, to mark free pages and
>>>pages allocated by swsusp, so using the nosave regions directly won't save us
>>>much.
>>
>>Well I think it is a cleaner though.
> 
> 
> This is a matter of opinion, too ...


Well, as I'm not volunteering to maintain swsusp, if your opinion is that
your way is cleaner, I can't argue ;) So long as it stops wasting those page
flags then I'm happy.

However the register_nosave API really should use locking, I think. There
is absolutely no downside, AFAIKS.

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Nick Piggin]

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 11:31, Nick Piggin wrote:
> 
>>Rafael J. Wysocki wrote:
>>
>>>On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
>>>
>>
>>>>I wouldn't say that. You're creating an interface here that is going to be
>>>>used outside swsusp. Users of that interface may not need locking now, but
>>>>that could cause problems down the line.
>>>
>>>
>>>I think we can add the locking when it's necessary.  For now, IMHO, it could be
>>>confusing to someone who doesn't know the locking is not needed.
>>
>>I don't know why it would confuse them. We just define the API to
>>guarantee the correct locking, and that means the locking _is_ needed.
> 
> 
> Even if there are no users that actually need the locking and probably never
> will be?

Probably is the keyword.

Why would you *not* make this a sane API? Surely performance isn't the
reason? Nor complexity.

> For now, register_nosave_region() is to be called by architecture
> initialization code _only_ and there's no reason whatsoever why any
> architecture would need to call it concurrently from many places.
> 
> 
>>You don't have to care what the callers are doing. That's the beauty
>>of a sane API.
> 
> 
> Well, I don't think adding unneded infrastructure is a good thing.


But defining good APIs is a very good thing. And with my good API, the
lock is not unneeded.

>>>>But that's because you even use mark_nosave_pages in your implementation.
>>>>Mine uses the nosave regions directly.
>>>
>>>
>>>Well, I think we need two bits per page anyway, to mark free pages and
>>>pages allocated by swsusp, so using the nosave regions directly won't save us
>>>much.
>>
>>Well I think it is a cleaner though.
> 
> 
> This is a matter of opinion, too ...


Well, as I'm not volunteering to maintain swsusp, if your opinion is that
your way is cleaner, I can't argue ;) So long as it stops wasting those page
flags then I'm happy.

However the register_nosave API really should use locking, I think. There
is absolutely no downside, AFAIKS.

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 

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Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Wednesday, 14 March 2007 04:17, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 13 March 2007 11:31, Nick Piggin wrote:
> > 
> >>Rafael J. Wysocki wrote:
> >>
> >>>On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> >>>
> >>
> >>>>I wouldn't say that. You're creating an interface here that is going to be
> >>>>used outside swsusp. Users of that interface may not need locking now, but
> >>>>that could cause problems down the line.
> >>>
> >>>
> >>>I think we can add the locking when it's necessary.  For now, IMHO, it could be
> >>>confusing to someone who doesn't know the locking is not needed.
> >>
> >>I don't know why it would confuse them. We just define the API to
> >>guarantee the correct locking, and that means the locking _is_ needed.
> > 
> > 
> > Even if there are no users that actually need the locking and probably never
> > will be?
> 
> Probably is the keyword.
> 
> Why would you *not* make this a sane API? Surely performance isn't the
> reason? Nor complexity.
> 
> > For now, register_nosave_region() is to be called by architecture
> > initialization code _only_ and there's no reason whatsoever why any
> > architecture would need to call it concurrently from many places.
> > 
> > 
> >>You don't have to care what the callers are doing. That's the beauty
> >>of a sane API.
> > 
> > 
> > Well, I don't think adding unneded infrastructure is a good thing.
> 
> 
> But defining good APIs is a very good thing. And with my good API, the
> lock is not unneeded.
> 
> >>>>But that's because you even use mark_nosave_pages in your implementation.
> >>>>Mine uses the nosave regions directly.
> >>>
> >>>
> >>>Well, I think we need two bits per page anyway, to mark free pages and
> >>>pages allocated by swsusp, so using the nosave regions directly won't save us
> >>>much.
> >>
> >>Well I think it is a cleaner though.
> > 
> > 
> > This is a matter of opinion, too ...
> 
> 
> Well, as I'm not volunteering to maintain swsusp, if your opinion is that
> your way is cleaner, I can't argue ;) So long as it stops wasting those page
> flags then I'm happy.
> 
> However the register_nosave API really should use locking, I think. There
> is absolutely no downside, AFAIKS.

Hm, I can add the lock, but currently register_nosave_region() calls
alloc_bootmem_low() directly, which means it won't even work outside the
early initialization code which is single-threaded.  For this reason I think
that the locking can be added later, when register_nosave_region() is
extended so that it can be called from other contexts too.

Greetings,
Rafael

Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

[Rafael J. Wysocki]

On Wednesday, 14 March 2007 04:17, Nick Piggin wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 13 March 2007 11:31, Nick Piggin wrote:
> > 
> >>Rafael J. Wysocki wrote:
> >>
> >>>On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> >>>
> >>
> >>>>I wouldn't say that. You're creating an interface here that is going to be
> >>>>used outside swsusp. Users of that interface may not need locking now, but
> >>>>that could cause problems down the line.
> >>>
> >>>
> >>>I think we can add the locking when it's necessary.  For now, IMHO, it could be
> >>>confusing to someone who doesn't know the locking is not needed.
> >>
> >>I don't know why it would confuse them. We just define the API to
> >>guarantee the correct locking, and that means the locking _is_ needed.
> > 
> > 
> > Even if there are no users that actually need the locking and probably never
> > will be?
> 
> Probably is the keyword.
> 
> Why would you *not* make this a sane API? Surely performance isn't the
> reason? Nor complexity.
> 
> > For now, register_nosave_region() is to be called by architecture
> > initialization code _only_ and there's no reason whatsoever why any
> > architecture would need to call it concurrently from many places.
> > 
> > 
> >>You don't have to care what the callers are doing. That's the beauty
> >>of a sane API.
> > 
> > 
> > Well, I don't think adding unneded infrastructure is a good thing.
> 
> 
> But defining good APIs is a very good thing. And with my good API, the
> lock is not unneeded.
> 
> >>>>But that's because you even use mark_nosave_pages in your implementation.
> >>>>Mine uses the nosave regions directly.
> >>>
> >>>
> >>>Well, I think we need two bits per page anyway, to mark free pages and
> >>>pages allocated by swsusp, so using the nosave regions directly won't save us
> >>>much.
> >>
> >>Well I think it is a cleaner though.
> > 
> > 
> > This is a matter of opinion, too ...
> 
> 
> Well, as I'm not volunteering to maintain swsusp, if your opinion is that
> your way is cleaner, I can't argue ;) So long as it stops wasting those page
> flags then I'm happy.
> 
> However the register_nosave API really should use locking, I think. There
> is absolutely no downside, AFAIKS.

Hm, I can add the lock, but currently register_nosave_region() calls
alloc_bootmem_low() directly, which means it won't even work outside the
early initialization code which is single-threaded.  For this reason I think
that the locking can be added later, when register_nosave_region() is
extended so that it can be called from other contexts too.

Greetings,
Rafael

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