swsusp cleanups

Index: linux-2.6.18-rc1/kernel/power/snapshot.c
===================================================================
@@ -156,7 +156,7 @@ static inline int save_highmem(void) {re
 static inline int restore_highmem(void) {return 0;}
 #endif
 
-static int pfn_is_nosave(unsigned long pfn)
+static inline int pfn_is_nosave(unsigned long pfn)
 {
 	unsigned long nosave_begin_pfn = __pa(&__nosave_begin) >> PAGE_SHIFT;
 	unsigned long nosave_end_pfn = PAGE_ALIGN(__pa(&__nosave_end)) >> PAGE_SHIFT;

@@ -167,43 +167,43 @@ static int pfn_is_nosave(unsigned long p
  *	saveable - Determine whether a page should be cloned or not.
  *	@pfn:	The page PFN
  *
- *	We save a page if it's Reserved, and not in the range of pages
- *	statically defined as 'unsaveable', or if it isn't reserved, and
- *	isn't part of a free chunk of pages.
+ *	We save a page if it isn't Nosave, and is not in the range of pages
+ *	statically defined as 'unsaveable', and it
+ *	isn't a part of a free chunk of pages.
  */
 
-static int saveable(struct zone *zone, unsigned long *zone_pfn)
+static struct page *saveable_page(unsigned long pfn)
 {
-	unsigned long pfn = *zone_pfn + zone->zone_start_pfn;
 	struct page *page;
 
 	if (!pfn_valid(pfn))
-		return 0;
+		return NULL;
 
 	page = pfn_to_page(pfn);
-	BUG_ON(PageReserved(page) && PageNosave(page));
+
 	if (PageNosave(page))
-		return 0;
+		return NULL;
 	if (PageReserved(page) && pfn_is_nosave(pfn))
-		return 0;
+		return NULL;
 	if (PageNosaveFree(page))
-		return 0;
+		return NULL;
 
-	return 1;
+	return page;
 }
 
 unsigned int count_data_pages(void)
 {
 	struct zone *zone;
-	unsigned long zone_pfn;
+	unsigned long pfn, max_zone_pfn;
 	unsigned int n = 0;
 
 	for_each_zone (zone) {
 		if (is_highmem(zone))
 			continue;
 		mark_free_pages(zone);
-		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
-			n += saveable(zone, &zone_pfn);
+		max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
+			n += !!saveable_page(pfn);
 	}
 	return n;
 }

@@ -211,7 +211,7 @@ unsigned int count_data_pages(void)
 static void copy_data_pages(struct pbe *pblist)
 {
 	struct zone *zone;
-	unsigned long zone_pfn;
+	unsigned long pfn, max_zone_pfn;
 	struct pbe *pbe, *p;
 
 	pbe = pblist;

@@ -224,13 +224,14 @@ static void copy_data_pages(struct pbe *
 			SetPageNosaveFree(virt_to_page(p));
 		for_each_pbe (p, pblist)
 			SetPageNosaveFree(virt_to_page(p->address));
-		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
-			if (saveable(zone, &zone_pfn)) {
-				struct page *page;
+		max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
+			struct page *page = saveable_page(pfn);
+
+			if (page) {
 				long *src, *dst;
 				int n;
 
-				page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
 				BUG_ON(!pbe);
 				pbe->orig_address = (unsigned long)page_address(page);
 				/* copy_page and memcpy are not usable for copying task structs. */

@@ -383,13 +384,14 @@ static struct pbe *alloc_pagedir(unsigne
 void swsusp_free(void)
 {
 	struct zone *zone;
-	unsigned long zone_pfn;
+	unsigned long pfn, max_zone_pfn;
 
 	for_each_zone(zone) {
-		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
-			if (pfn_valid(zone_pfn + zone->zone_start_pfn)) {
-				struct page *page;
-				page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
+		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) && PageNosaveFree(page)) {
 					ClearPageNosave(page);
 					ClearPageNosaveFree(page);

@@ -598,7 +600,7 @@ int snapshot_read_next(struct snapshot_h
 static int mark_unsafe_pages(struct pbe *pblist)
 {
 	struct zone *zone;
-	unsigned long zone_pfn;
+	unsigned long pfn, max_zone_pfn;
 	struct pbe *p;
 
 	if (!pblist) /* a sanity check */

@@ -606,10 +608,10 @@ static int mark_unsafe_pages(struct pbe 
 
 	/* Clear page flags */
 	for_each_zone (zone) {
-		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
-			if (pfn_valid(zone_pfn + zone->zone_start_pfn))
-				ClearPageNosaveFree(pfn_to_page(zone_pfn +
-					zone->zone_start_pfn));
+		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));
 	}
 
 	/* Mark orig addresses */

Index: linux-2.6.18-rc1-mm1/kernel/power/power.h
===================================================================
@@ -50,17 +50,65 @@ extern asmlinkage int swsusp_arch_resume
 
 extern unsigned int count_data_pages(void);
 
+/**
+ *	Auxiliary structure used for reading the snapshot image data and
+ *	metadata from and writing them to the list of page backup entries
+ *	(PBEs) which is the main data structure of swsusp.
+ *
+ *	Using struct snapshot_handle we can transfer the image, including its
+ *	metadata, as a continuous sequence of bytes with the help of
+ *	snapshot_read_next() and snapshot_write_next().
+ *
+ *	The code that writes the image to a storage or transfers it to
+ *	the user land is required to use snapshot_read_next() for this
+ *	purpose and it should not make any assumptions regarding the internal
+ *	structure of the image.  Similarly, the code that reads the image from
+ *	a storage or transfers it from the user land is required to use
+ *	snapshot_write_next().
+ *
+ *	This may allow us to change the internal structure of the image
+ *	in the future with considerably less effort.
+ */
+
 struct snapshot_handle {
-	loff_t		offset;
-	unsigned int	page;
-	unsigned int	page_offset;
-	unsigned int	prev;
-	struct pbe	*pbe, *last_pbe;
-	void		*buffer;
-	unsigned int	buf_offset;
-	int		sync_read;
+	loff_t		offset;	/* number of the last byte ready for reading
+				 * or writing in the sequence
+				 */
+	unsigned int	cur;	/* number of the block of PAGE_SIZE bytes the
+				 * next operation will refer to (ie. current)
+				 */
+	unsigned int	cur_offset;	/* offset with respect to the current
+					 * block (for the next operation)
+					 */
+	unsigned int	prev;	/* number of the block of PAGE_SIZE bytes that
+				 * was the current one previously
+				 */
+	struct pbe	*pbe;	/* PBE that corresponds to 'buffer' */
+	struct pbe	*last_pbe;	/* When the image is restored (eg. read
+					 * from disk) we can store some image
+					 * data directly in the page frames
+					 * in which they were before suspend.
+					 * In such a case the PBEs that
+					 * correspond to them will be unused.
+					 * This is the last PBE, so far, that
+					 * does not correspond to such data.
+					 */
+	void		*buffer;	/* address of the block to read from
+					 * or write to
+					 */
+	unsigned int	buf_offset;	/* location to read from or write to,
+					 * given as a displacement from 'buffer'
+					 */
+	int		sync_read;	/* Set to one to notify the caller of
+					 * snapshot_write_next() that it may
+					 * need to call wait_on_bio_chain()
+					 */
 };
 
+/* This macro returns the address from/to which the caller of
+ * snapshot_read_next()/snapshot_write_next() is allowed to
+ * read/write data after the function returns
+ */
 #define data_of(handle)	((handle).buffer + (handle).buf_offset)
 
 extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);

Index: linux-2.6.18-rc1-mm1/kernel/power/snapshot.c
===================================================================
@@ -555,7 +555,7 @@ static inline struct pbe *pack_orig_addr
 
 int snapshot_read_next(struct snapshot_handle *handle, size_t count)
 {
-	if (handle->page > nr_meta_pages + nr_copy_pages)
+	if (handle->cur > nr_meta_pages + nr_copy_pages)
 		return 0;
 	if (!buffer) {
 		/* This makes the buffer be freed by swsusp_free() */

@@ -568,8 +568,8 @@ int snapshot_read_next(struct snapshot_h
 		handle->buffer = buffer;
 		handle->pbe = pagedir_nosave;
 	}
-	if (handle->prev < handle->page) {
-		if (handle->page <= nr_meta_pages) {
+	if (handle->prev < handle->cur) {
+		if (handle->cur <= nr_meta_pages) {
 			handle->pbe = pack_orig_addresses(buffer, handle->pbe);
 			if (!handle->pbe)
 				handle->pbe = pagedir_nosave;

@@ -577,15 +577,15 @@ int snapshot_read_next(struct snapshot_h
 			handle->buffer = (void *)handle->pbe->address;
 			handle->pbe = handle->pbe->next;
 		}
-		handle->prev = handle->page;
+		handle->prev = handle->cur;
 	}
-	handle->buf_offset = handle->page_offset;
-	if (handle->page_offset + count >= PAGE_SIZE) {
-		count = PAGE_SIZE - handle->page_offset;
-		handle->page_offset = 0;
-		handle->page++;
+	handle->buf_offset = handle->cur_offset;
+	if (handle->cur_offset + count >= PAGE_SIZE) {
+		count = PAGE_SIZE - handle->cur_offset;
+		handle->cur_offset = 0;
+		handle->cur++;
 	} else {
-		handle->page_offset += count;
+		handle->cur_offset += count;
 	}
 	handle->offset += count;
 	return count;

@@ -820,7 +820,7 @@ int snapshot_write_next(struct snapshot_
 {
 	int error = 0;
 
-	if (handle->prev && handle->page > nr_meta_pages + nr_copy_pages)
+	if (handle->prev && handle->cur > nr_meta_pages + nr_copy_pages)
 		return 0;
 	if (!buffer) {
 		/* This makes the buffer be freed by swsusp_free() */

@@ -831,7 +831,7 @@ int snapshot_write_next(struct snapshot_
 	if (!handle->offset)
 		handle->buffer = buffer;
 	handle->sync_read = 1;
-	if (handle->prev < handle->page) {
+	if (handle->prev < handle->cur) {
 		if (!handle->prev) {
 			error = load_header(handle,
 					(struct swsusp_info *)buffer);

@@ -854,15 +854,15 @@ int snapshot_write_next(struct snapshot_
 			handle->buffer = get_buffer(handle);
 			handle->sync_read = 0;
 		}
-		handle->prev = handle->page;
+		handle->prev = handle->cur;
 	}
-	handle->buf_offset = handle->page_offset;
-	if (handle->page_offset + count >= PAGE_SIZE) {
-		count = PAGE_SIZE - handle->page_offset;
-		handle->page_offset = 0;
-		handle->page++;
+	handle->buf_offset = handle->cur_offset;
+	if (handle->cur_offset + count >= PAGE_SIZE) {
+		count = PAGE_SIZE - handle->cur_offset;
+		handle->cur_offset = 0;
+		handle->cur++;
 	} else {
-		handle->page_offset += count;
+		handle->cur_offset += count;
 	}
 	handle->offset += count;
 	return count;

@@ -871,5 +871,5 @@ int snapshot_write_next(struct snapshot_
 int snapshot_image_loaded(struct snapshot_handle *handle)
 {
 	return !(!handle->pbe || handle->pbe->next || !nr_copy_pages ||
-		handle->page <= nr_meta_pages + nr_copy_pages);
+		handle->cur <= nr_meta_pages + nr_copy_pages);
 }