Hibernation: do not try to mark invalid PFNs as nosave

On some systems some PFNs reported by the early initialization code as
'nosave' may be invalid.  If we try to set the corresponding bits in the
hibernation bitmap, BUG_ON() in memory_bm_find_bit() will be triggered and
the system won't be able to boot (cf.
https://bugzilla.novell.com/show_bug.cgi?id=296242).

Prevent this from happening by verifying if the 'nosave' PFNs are valid in
mark_nosave_pages().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/power/snapshot.c

@@ -709,7 +709,8 @@ static void mark_nosave_pages(struct memory_bitmap *bm)
 				region->end_pfn << PAGE_SHIFT);
 
 		for (pfn = region->start_pfn; pfn < region->end_pfn; pfn++)
-			memory_bm_set_bit(bm, pfn);
+			if (pfn_valid(pfn))
+				memory_bm_set_bit(bm, pfn);
 	}
 }