autofs: remove left-over autofs4 stubs

There's no need to retain the fs/autofs4 directory for backward
compatibility.

Adding an AUTOFS4_FS fragment to the autofs Kconfig and a module alias
for autofs4 is sufficient for almost all cases. Not keeping fs/autofs4
remnants will prevent "insmod <path>/autofs4/autofs4.ko" from working
but this shouldn't be used in automation scripts rather than
modprobe(8).

There were some comments about things to look out for with the module
rename in the fs/autofs4/Kconfig that is removed by this patch, see the
commit patch if you are interested.

One potential problem with this change is that when the
fs/autofs/Kconfig fragment for AUTOFS4_FS is removed any AUTOFS4_FS
entries will be removed from the kernel config, resulting in no autofs
file system being built if there is no AUTOFS_FS entry also.

This would have also happened if the fs/autofs4 remnants had remained
and is most likely to be a problem with automated builds.

Please check your build configurations before the removal which will
occur after the next couple of kernel releases.

Acked-by: Ian Kent <raven@themaw.net>
[ With edits and commit message from Ian Kent ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/Kconfig

@@ -110,7 +110,6 @@ source "fs/notify/Kconfig"
 source "fs/quota/Kconfig"
 
 source "fs/autofs/Kconfig"
-source "fs/autofs4/Kconfig"
 source "fs/fuse/Kconfig"
 source "fs/overlayfs/Kconfig"
 

fs/Makefile

@@ -103,7 +103,6 @@ obj-$(CONFIG_ROMFS_FS)		+= romfs/
 obj-$(CONFIG_QNX4FS_FS)		+= qnx4/
 obj-$(CONFIG_QNX6FS_FS)		+= qnx6/
 obj-$(CONFIG_AUTOFS_FS)		+= autofs/
-obj-$(CONFIG_AUTOFS4_FS)	+= autofs4/
 obj-$(CONFIG_ADFS_FS)		+= adfs/
 obj-$(CONFIG_FUSE_FS)		+= fuse/
 obj-$(CONFIG_OVERLAY_FS)	+= overlayfs/

fs/autofs/Kconfig

@@ -1,3 +1,14 @@
+config AUTOFS4_FS
+	tristate "Old Kconfig name for Kernel automounter support"
+	select AUTOFS_FS
+	help
+	   This name exists for people to just automatically pick up the
+	   new name of the autofs Kconfig option. All it does is select
+	   thenew new option name.
+
+	   It will go away in a release or two as people have
+	   transitioned to just plain AUTOFS_FS.
+
 config AUTOFS_FS
 	tristate "Kernel automounter support (supports v3, v4 and v5)"
 	default n

fs/autofs/init.c

@@ -23,6 +23,7 @@ static struct file_system_type autofs_fs_type = {
 	.kill_sb	= autofs_kill_sb,
 };
 MODULE_ALIAS_FS("autofs");
+MODULE_ALIAS("autofs4");
 
 static int __init init_autofs_fs(void)
 {