autofs: use inode permission method for write access

Patch series "autofs: misc patches".

This series contains several patches that resulted mostly from comments
made by Al Viro (quite a long time ago now).


This patch (of 5):

Eliminate some code duplication from mkdir/rmdir/symlink/unlink methods by
using the inode operation .permission().

Link: https://lkml.kernel.org/r/165724445154.30914.10970894936827635879.stgit@donald.themaw.net
Link: https://lkml.kernel.org/r/165724458096.30914.13499431569758625806.stgit@donald.themaw.net


Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>