swsusp: use GFP_KERNEL for creating basic data structures

Make swsusp call create_basic_memory_bitmaps() before processes are frozen, so
that GFP_KERNEL allocations can be made in it.  Additionally, ensure that the
swsusp's userland interface won't be used while either pm_suspend_disk() or
software_resume() is being executed.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 1f8052b..a64d3f2 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -140,6 +140,9 @@
 #define PMOPS_ENTER	2
 #define PMOPS_FINISH	3
 
+/* If unset, the snapshot device cannot be open. */
+extern atomic_t snapshot_device_available;
+
 /**
  *	The bitmap is used for tracing allocated swap pages
  *