[PATCH] Documentation/filesystems: sharedsubtree: add section headings

[Randy Dunlap <rdunlap@infradead.org>]

Several of the sections are missing underlines. This makes the
generated contents have missing entries, so add the underlines.

Fixes: 16c01b20ae05 ("doc/filesystems: more mount cleanups")
Fixes: 9cfcceea8f7e ("[PATCH] Complete description of shared subtrees.")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Peng Tao <bergwolf@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 Documentation/filesystems/sharedsubtree.rst |    4 ++++
 1 file changed, 4 insertions(+)

diff -- a/Documentation/filesystems/sharedsubtree.rst b/Documentation/filesystems/sharedsubtree.rst
--- a/Documentation/filesystems/sharedsubtree.rst
+++ b/Documentation/filesystems/sharedsubtree.rst
@@ -147,6 +147,7 @@ replicas continue to be exactly same.
 
 
 3) Setting mount states
+-----------------------
 
 	The mount command (util-linux package) can be used to set mount
 	states::
@@ -612,6 +613,7 @@ replicas continue to be exactly same.
 
 
 6) Quiz
+-------
 
 	A. What is the result of the following command sequence?
 
@@ -673,6 +675,7 @@ replicas continue to be exactly same.
 		/mnt/1/test be?
 
 7) FAQ
+------
 
 	Q1. Why is bind mount needed? How is it different from symbolic links?
 		symbolic links can get stale if the destination mount gets
@@ -841,6 +844,7 @@ replicas continue to be exactly same.
 			     tmp  usr tmp usr tmp usr
 
 8) Implementation
+-----------------
 
 8A) Datastructure