Move the default_backing_dev_info out of readahead.c and into backing-dev.c

It really makes no sense to have it in readahead.c, so move it where
it belongs.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

mm/backing-dev.c

@@ -2,11 +2,24 @@
 #include <linux/wait.h>
 #include <linux/backing-dev.h>
 #include <linux/fs.h>
+#include <linux/pagemap.h>
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/writeback.h>
 #include <linux/device.h>
 
+void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
+{
+}
+EXPORT_SYMBOL(default_unplug_io_fn);
+
+struct backing_dev_info default_backing_dev_info = {
+	.ra_pages	= VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
+	.state		= 0,
+	.capabilities	= BDI_CAP_MAP_COPY,
+	.unplug_io_fn	= default_unplug_io_fn,
+};
+EXPORT_SYMBOL_GPL(default_backing_dev_info);
 
 static struct class *bdi_class;
 
@@ -166,9 +179,20 @@ static __init int bdi_class_init(void)
 	bdi_debug_init();
 	return 0;
 }
-
 postcore_initcall(bdi_class_init);
 
+static int __init default_bdi_init(void)
+{
+	int err;
+
+	err = bdi_init(&default_backing_dev_info);
+	if (!err)
+		bdi_register(&default_backing_dev_info, NULL, "default");
+
+	return err;
+}
+subsys_initcall(default_bdi_init);
+
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 		const char *fmt, ...)
 {

mm/readahead.c

@@ -17,19 +17,6 @@
 #include <linux/pagevec.h>
 #include <linux/pagemap.h>
 
-void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
-{
-}
-EXPORT_SYMBOL(default_unplug_io_fn);
-
-struct backing_dev_info default_backing_dev_info = {
-	.ra_pages	= VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
-	.state		= 0,
-	.capabilities	= BDI_CAP_MAP_COPY,
-	.unplug_io_fn	= default_unplug_io_fn,
-};
-EXPORT_SYMBOL_GPL(default_backing_dev_info);
-
 /*
  * Initialise a struct file's readahead state.  Assumes that the caller has
  * memset *ra to zero.
@@ -233,18 +220,6 @@ unsigned long max_sane_readahead(unsigned long nr)
 		+ node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2);
 }
 
-static int __init readahead_init(void)
-{
-	int err;
-
-	err = bdi_init(&default_backing_dev_info);
-	if (!err)
-		bdi_register(&default_backing_dev_info, NULL, "default");
-
-	return err;
-}
-subsys_initcall(readahead_init);
-
 /*
  * Submit IO for the read-ahead request in file_ra_state.
  */