kfifo: implement missing __kfifo_skip_r()

kfifo_skip() is currently broken, due to the missing of the internal
helper function.  Add it.

Signed-off-by: Andrea Righi <arighi@develer.com>
Cc: Greg KH <greg@kroah.com>
Acked-by: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kfifo.h

@@ -836,6 +836,8 @@ extern void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize);
 
 extern unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize);
 
+extern void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize);
+
 extern unsigned int __kfifo_out_peek_r(struct __kfifo *fifo,
 	void *buf, unsigned int len, size_t recsize);
 

kernel/kfifo.c

@@ -503,6 +503,15 @@ unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf,
 }
 EXPORT_SYMBOL(__kfifo_out_r);
 
+void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize)
+{
+	unsigned int n;
+
+	n = __kfifo_peek_n(fifo, recsize);
+	fifo->out += n + recsize;
+}
+EXPORT_SYMBOL(__kfifo_skip_r);
+
 int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from,
 	unsigned long len, unsigned int *copied, size_t recsize)
 {