[PATCH] change gen_pool allocator to not touch managed memory

Modify the gen_pool allocator (lib/genalloc.c) to utilize a bitmap scheme
instead of the buddy scheme.  The purpose of this change is to eliminate
the touching of the actual memory being allocated.

Since the change modifies the interface, a change to the uncached allocator
(arch/ia64/kernel/uncached.c) is also required.

Both Andrey Volkov and Jes Sorenson have expressed a desire that the
gen_pool allocator not write to the memory being managed. See the
following:

  http://marc.theaimsgroup.com/?l=linux-kernel&m=113518602713125&w=2
  http://marc.theaimsgroup.com/?l=linux-kernel&m=113533568827916&w=2

Signed-off-by: Dean Nelson <dcn@sgi.com>
Cc: Andrey Volkov <avolkov@varma-el.com>
Acked-by: Jes Sorensen <jes@trained-monkey.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ia64/sn/kernel/sn2/cache.c

@@ -3,11 +3,12 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  * 
- * Copyright (C) 2001-2003 Silicon Graphics, Inc. All rights reserved.
+ * Copyright (C) 2001-2003, 2006 Silicon Graphics, Inc. All rights reserved.
  *
  */
 #include <linux/module.h>
 #include <asm/pgalloc.h>
+#include <asm/sn/arch.h>
 
 /**
  * sn_flush_all_caches - flush a range of address from all caches (incl. L4)
@@ -17,18 +18,24 @@
  * Flush a range of addresses from all caches including L4. 
  * All addresses fully or partially contained within 
  * @flush_addr to @flush_addr + @bytes are flushed
- * from the all caches.
+ * from all caches.
  */
 void
 sn_flush_all_caches(long flush_addr, long bytes)
 {
-	flush_icache_range(flush_addr, flush_addr+bytes);
+	unsigned long addr = flush_addr;
+
+	/* SHub1 requires a cached address */
+	if (is_shub1() && (addr & RGN_BITS) == RGN_BASE(RGN_UNCACHED))
+		addr = (addr - RGN_BASE(RGN_UNCACHED)) + RGN_BASE(RGN_KERNEL);
+
+	flush_icache_range(addr, addr + bytes);
 	/*
 	 * The last call may have returned before the caches
 	 * were actually flushed, so we call it again to make
 	 * sure.
 	 */
-	flush_icache_range(flush_addr, flush_addr+bytes);
+	flush_icache_range(addr, addr + bytes);
 	mb();
 }
 EXPORT_SYMBOL(sn_flush_all_caches);