llist: make llist_add_batch() a static inline

The function is small enough that it should be, and it's a (very) hot path
for io_uring.  Doing this actually reduces my vmlinux text size for my
standard build/test box.

Before:
axboe@r7625 ~/g/linux (test)> size vmlinux
   text	   data	    bss	    dec	    hex		filename
19892174 5938310 2470432 28300916 1afd674	vmlinux

After:
axboe@r7625 ~/g/linux (test)> size vmlinux
   text	   data	    bss	    dec	    hex		filename
19891878 5938310 2470436 28300624 1afd550	vmlinux

Link: https://lkml.kernel.org/r/f1d104c6-7ac8-457a-a53d-6bb741421b2f@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: axboe

include/linux/llist.h

@@ -223,9 +223,26 @@ static inline struct llist_node *llist_next(struct llist_node *node)
 	return node->next;
 }
 
-extern bool llist_add_batch(struct llist_node *new_first,
-			    struct llist_node *new_last,
-			    struct llist_head *head);
+/**
+ * llist_add_batch - add several linked entries in batch
+ * @new_first:	first entry in batch to be added
+ * @new_last:	last entry in batch to be added
+ * @head:	the head for your lock-less list
+ *
+ * Return whether list is empty before adding.
+ */
+static inline bool llist_add_batch(struct llist_node *new_first,
+				   struct llist_node *new_last,
+				   struct llist_head *head)
+{
+	struct llist_node *first = READ_ONCE(head->first);
+
+	do {
+		new_last->next = first;
+	} while (!try_cmpxchg(&head->first, &first, new_first));
+
+	return !first;
+}
 
 static inline bool __llist_add_batch(struct llist_node *new_first,
 				     struct llist_node *new_last,

lib/llist.c

@@ -14,28 +14,6 @@
 #include <linux/export.h>
 #include <linux/llist.h>
 
-
-/**
- * llist_add_batch - add several linked entries in batch
- * @new_first:	first entry in batch to be added
- * @new_last:	last entry in batch to be added
- * @head:	the head for your lock-less list
- *
- * Return whether list is empty before adding.
- */
-bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
-		     struct llist_head *head)
-{
-	struct llist_node *first = READ_ONCE(head->first);
-
-	do {
-		new_last->next = first;
-	} while (!try_cmpxchg(&head->first, &first, new_first));
-
-	return !first;
-}
-EXPORT_SYMBOL_GPL(llist_add_batch);
-
 /**
  * llist_del_first - delete the first entry of lock-less list
  * @head:	the head for your lock-less list