list debugging: use WARN() instead of BUG()

Arjan noted that the list_head debugging is BUG'ing when it detects
corruption.  By causing the box to panic immediately, we're possibly
losing some bug reports.  Changing this to a WARN() should mean we at the
least start seeing reports collected at kerneloops.org

Signed-off-by: Dave Jones <davej@redhat.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/list_debug.c

@@ -20,18 +20,14 @@ void __list_add(struct list_head *new,
 			      struct list_head *prev,
 			      struct list_head *next)
 {
-	if (unlikely(next->prev != prev)) {
-		printk(KERN_ERR "list_add corruption. next->prev should be "
-			"prev (%p), but was %p. (next=%p).\n",
-			prev, next->prev, next);
-		BUG();
-	}
-	if (unlikely(prev->next != next)) {
-		printk(KERN_ERR "list_add corruption. prev->next should be "
-			"next (%p), but was %p. (prev=%p).\n",
-			next, prev->next, prev);
-		BUG();
-	}
+	WARN(next->prev != prev,
+		"list_add corruption. next->prev should be "
+		"prev (%p), but was %p. (next=%p).\n",
+		prev, next->prev, next);
+	WARN(prev->next != next,
+		"list_add corruption. prev->next should be "
+		"next (%p), but was %p. (prev=%p).\n",
+		next, prev->next, prev);
 	next->prev = new;
 	new->next = next;
 	new->prev = prev;
@@ -47,16 +43,12 @@ EXPORT_SYMBOL(__list_add);
  */
 void list_del(struct list_head *entry)
 {
-	if (unlikely(entry->prev->next != entry)) {
-		printk(KERN_ERR "list_del corruption. prev->next should be %p, "
-				"but was %p\n", entry, entry->prev->next);
-		BUG();
-	}
-	if (unlikely(entry->next->prev != entry)) {
-		printk(KERN_ERR "list_del corruption. next->prev should be %p, "
-				"but was %p\n", entry, entry->next->prev);
-		BUG();
-	}
+	WARN(entry->prev->next != entry,
+		"list_del corruption. prev->next should be %p, "
+		"but was %p\n", entry, entry->prev->next);
+	WARN(entry->next->prev != entry,
+		"list_del corruption. next->prev should be %p, "
+		"but was %p\n", entry, entry->next->prev);
 	__list_del(entry->prev, entry->next);
 	entry->next = LIST_POISON1;
 	entry->prev = LIST_POISON2;