From 16203a7a9422315bc929461503e3a046459ea5ff Mon Sep 17 00:00:00 2001
From: Rob Landley
Date: Wed, 11 Sep 2013 14:26:12 -0700
Subject: initmpfs: make rootfs use tmpfs when CONFIG_TMPFS enabled

Conditionally call the appropriate fs_init function and fill_super
functions.  Add a use once guard to shmem_init() to simply succeed on a
second call.

(Note that IS_ENABLED() is a compile time constant so dead code
elimination removes unused function calls when CONFIG_TMPFS is disabled.)

Signed-off-by: Rob Landley <rob@landley.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jim Cromie <jim.cromie@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 init/do_mounts.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'init/do_mounts.c')

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 5d8d48fd0ee4..e27908b949d4 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -27,6 +27,7 @@
 #include <linux/fs_struct.h>
 #include <linux/slab.h>
 #include <linux/ramfs.h>
+#include <linux/shmem_fs.h>
 
 #include <linux/nfs_fs.h>
 #include <linux/nfs_fs_sb.h>
@@ -598,7 +599,8 @@ static struct dentry *rootfs_mount(struct file_system_type *fs_type,
 	if (test_and_set_bit(0, &once))
 		return ERR_PTR(-ENODEV);
 
-	return mount_nodev(fs_type, flags, data, ramfs_fill_super);
+	return mount_nodev(fs_type, flags, data,
+		IS_ENABLED(CONFIG_TMPFS) ? shmem_fill_super : ramfs_fill_super);
 }
 
 static struct file_system_type rootfs_fs_type = {
@@ -614,7 +616,11 @@ int __init init_rootfs(void)
 	if (err)
 		return err;
 
-	err = init_ramfs_fs();
+	if (IS_ENABLED(CONFIG_TMPFS))
+		err = shmem_init();
+	else
+		err = init_ramfs_fs();
+
 	if (err)
 		unregister_filesystem(&rootfs_fs_type);
 
-- 
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