[PATCH] add poison.h and patch primary users

Localize poison values into one header file for better documentation and
easier/quicker debugging and so that the same values won't be used for
multiple purposes.

Use these constants in core arch., mm, driver, and fs code.

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Matt Mackall <mpm@selenic.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/jbd/journal.c

@@ -34,6 +34,7 @@
 #include <linux/suspend.h>
 #include <linux/pagemap.h>
 #include <linux/kthread.h>
+#include <linux/poison.h>
 #include <linux/proc_fs.h>
 
 #include <asm/uaccess.h>
@@ -1675,7 +1676,7 @@ static void journal_free_journal_head(struct journal_head *jh)
 {
 #ifdef CONFIG_JBD_DEBUG
 	atomic_dec(&nr_journal_heads);
-	memset(jh, 0x5b, sizeof(*jh));
+	memset(jh, JBD_POISON_FREE, sizeof(*jh));
 #endif
 	kmem_cache_free(journal_head_cache, jh);
 }