Wrapper for lower-level revalidate_disk routines.

This is a wrapper for the lower-level revalidate_disk call-backs such
as sd_revalidate_disk(). It allows us to perform pre and post
operations when calling them.

We will use this wrapper in a later patch to adjust block device sizes
after an online resize (a _post_ operation).

Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index c3fa19b..4eeb69a 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -852,6 +852,27 @@
 
 EXPORT_SYMBOL(open_by_devnum);
 
+/**
+ * revalidate_disk - wrapper for lower-level driver's revalidate_disk
+ *                   call-back
+ *
+ * @disk: struct gendisk to be revalidated
+ *
+ * This routine is a wrapper for lower-level driver's revalidate_disk
+ * call-backs.  It is used to do common pre and post operations needed
+ * for all revalidate_disk operations.
+ */
+int revalidate_disk(struct gendisk *disk)
+{
+	int ret = 0;
+
+	if (disk->fops->revalidate_disk)
+		ret = disk->fops->revalidate_disk(disk);
+
+	return ret;
+}
+EXPORT_SYMBOL(revalidate_disk);
+
 /*
  * This routine checks whether a removable media has been changed,
  * and invalidates all buffer-cache-entries in that case. This