swsusp: free more memory

Move the definition of PAGES_FOR_IO to kernel/power/power.h and introduce
SPARE_PAGES representing the number of pages that should be freed by the
swsusp's memory shrinker in addition to PAGES_FOR_IO so that device drivers
can allocate some memory (up to 1 MB total) in their .suspend() routines
without causing the suspend to fail.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/suspend.h

@@ -52,10 +52,4 @@ struct saved_context;
 void __save_processor_state(struct saved_context *ctxt);
 void __restore_processor_state(struct saved_context *ctxt);
 
-/*
- * XXX: We try to keep some more pages free so that I/O operations succeed
- * without paging. Might this be more?
- */
-#define PAGES_FOR_IO	1024
-
 #endif /* _LINUX_SWSUSP_H */

kernel/power/power.h

@@ -14,8 +14,18 @@ struct swsusp_info {
 
 
 #ifdef CONFIG_SOFTWARE_SUSPEND
-extern int pm_suspend_disk(void);
+/*
+ * Keep some memory free so that I/O operations can succeed without paging
+ * [Might this be more than 4 MB?]
+ */
+#define PAGES_FOR_IO	((4096 * 1024) >> PAGE_SHIFT)
+/*
+ * Keep 1 MB of memory free so that device drivers can allocate some pages in
+ * their .suspend() routines without breaking the suspend to disk.
+ */
+#define SPARE_PAGES	((1024 * 1024) >> PAGE_SHIFT)
 
+extern int pm_suspend_disk(void);
 #else
 static inline int pm_suspend_disk(void)
 {

kernel/power/swsusp.c

@@ -233,7 +233,7 @@ int swsusp_shrink_memory(void)
 		long size, highmem_size;
 
 		highmem_size = count_highmem_pages();
-		size = count_data_pages() + PAGES_FOR_IO;
+		size = count_data_pages() + PAGES_FOR_IO + SPARE_PAGES;
 		tmp = size;
 		size += highmem_size;
 		for_each_zone (zone)