nfs: new subdir Documentation/filesystems/nfs

We're adding enough nfs documentation that it may as well have its own
subdirectory.

Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 197c7db..e9e1759 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -6,7 +6,7 @@
  * and for mapping back from file handles to dentries.
  *
  * For details on why we do all the strange and hairy things in here
- * take a look at Documentation/filesystems/Exporting.
+ * take a look at Documentation/filesystems/nfs/Exporting.
  */
 #include <linux/exportfs.h>
 #include <linux/fs.h>