[PATCH 0/5] initmpfs: use tmpfs instead of ramfs for rootfs

[PATCH 0/5] initmpfs: use tmpfs instead of ramfs for rootfs

[Rob Landley]

Use tmpfs for rootfs when CONFIG_TMPFS=y and there's no root=.
Specify rootfstype=ramfs to get the old initramfs behavior.

The previous initramfs code provided a fairly crappy root filesystem:
didn't let you --bind mount directories out of it, reported zero
size/usage so it didn't show up in "df" and couldn't run things like
rpm that query available space before proceeding, would fill up all
available memory and panic the system if you wrote too much to it...

Using tmpfs instead provides a much better root filesystem.

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[PATCH 3/5] initmpfs: Move rootfs code from fs/ramfs/ to init/

[Rob Landley]

From: Rob Landley <rob@landley.net>

When the rootfs code was a wrapper around ramfs, having them in the same
file made sense. Now that it can wrap another filesystem type, move it
in with the init code instead.

This also allows a subsequent patch to access rootfstype= command line arg.

Signed-off-by: Rob Landley <rob@landley.net>
---

 fs/namespace.c        |    2 +-
 fs/ramfs/inode.c      |   34 +---------------------------------
 include/linux/init.h  |    1 +
 include/linux/ramfs.h |    2 +-
 init/do_mounts.c      |   34 ++++++++++++++++++++++++++++++++++
 5 files changed, 38 insertions(+), 35 deletions(-)

--- initold/fs/namespace.c	2013-06-28 15:09:19.389872904 -0500
+++ initold2/fs/namespace.c	2013-06-28 15:16:05.261889820 -0500
@@ -17,7 +17,7 @@
 #include <linux/security.h>
 #include <linux/idr.h>
 #include <linux/acct.h>		/* acct_auto_close_mnt */
-#include <linux/ramfs.h>	/* init_rootfs */
+#include <linux/init.h>		/* init_rootfs */
 #include <linux/fs_struct.h>	/* get_fs_root et.al. */
 #include <linux/fsnotify.h>	/* fsnotify_vfsmount_delete */
 #include <linux/uaccess.h>
--- initold/fs/ramfs/inode.c	2013-06-28 15:15:37.549888666 -0500
+++ initold2/fs/ramfs/inode.c	2013-06-28 15:16:05.273889820 -0500
@@ -244,19 +244,6 @@
 	return mount_nodev(fs_type, flags, data, ramfs_fill_super);
 }
 
-static struct dentry *rootfs_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
-{
-	static int once;
-
-	if (once)
-		return ERR_PTR(-ENODEV);
-	else
-		once++;
-
-	return mount_nodev(fs_type, flags, data, ramfs_fill_super);
-}
-
 static void ramfs_kill_sb(struct super_block *sb)
 {
 	kfree(sb->s_fs_info);
@@ -269,13 +256,8 @@
 	.kill_sb	= ramfs_kill_sb,
 	.fs_flags	= FS_USERNS_MOUNT,
 };
-static struct file_system_type rootfs_fs_type = {
-	.name		= "rootfs",
-	.mount		= rootfs_mount,
-	.kill_sb	= kill_litter_super,
-};
 
-static int __init init_ramfs_fs(void)
+int __init init_ramfs_fs(void)
 {
 	static int once;
 	int err;
@@ -296,17 +276,3 @@
 	return err;
 }
 module_init(init_ramfs_fs)
-
-int __init init_rootfs(void)
-{
-	int err = register_filesystem(&rootfs_fs_type);
-
-	if (err)
-		return err;
-
-	err = init_ramfs_fs();
-	if (err)
-		unregister_filesystem(&rootfs_fs_type);
-
-	return err;
-}
--- initold/include/linux/init.h	2013-06-28 15:09:19.517872909 -0500
+++ initold2/include/linux/init.h	2013-06-28 15:16:05.321889821 -0500
@@ -154,6 +154,7 @@
 void setup_arch(char **);
 void prepare_namespace(void);
 void __init load_default_modules(void);
+int __init init_rootfs(void);
 
 extern void (*late_time_init)(void);
 
--- initold/include/linux/ramfs.h	2013-06-28 15:09:19.537872910 -0500
+++ initold2/include/linux/ramfs.h	2013-06-28 15:16:05.513889832 -0500
@@ -25,7 +25,7 @@
 
 extern const struct file_operations ramfs_file_operations;
 extern const struct vm_operations_struct generic_file_vm_ops;
-extern int __init init_rootfs(void);
+extern int __init init_ramfs_fs(void);
 
 int ramfs_fill_super(struct super_block *sb, void *data, int silent);
 
--- initold/init/do_mounts.c	2013-06-28 15:09:19.585872913 -0500
+++ initold2/init/do_mounts.c	2013-06-28 15:16:05.561889831 -0500
@@ -26,6 +26,7 @@
 #include <linux/async.h>
 #include <linux/fs_struct.h>
 #include <linux/slab.h>
+#include <linux/ramfs.h>
 
 #include <linux/nfs_fs.h>
 #include <linux/nfs_fs_sb.h>
@@ -588,3 +589,36 @@
 	sys_mount(".", "/", NULL, MS_MOVE, NULL);
 	sys_chroot(".");
 }
+
+static struct dentry *rootfs_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
+{
+	static int once;
+
+	if (once)
+		return ERR_PTR(-ENODEV);
+	else
+		once++;
+
+	return mount_nodev(fs_type, flags, data, ramfs_fill_super);
+}
+
+static struct file_system_type rootfs_fs_type = {
+	.name		= "rootfs",
+	.mount		= rootfs_mount,
+	.kill_sb	= kill_litter_super,
+};
+
+int __init init_rootfs(void)
+{
+	int err = register_filesystem(&rootfs_fs_type);
+
+	if (err)
+		return err;
+
+	err = init_ramfs_fs();
+	if (err)
+		unregister_filesystem(&rootfs_fs_type);
+
+	return err;
+}
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index c24f1e1..3b9f114 100644