Merge branch 'work.init' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull root filesystem type handling updates from Al Viro:
 "Teach init/do_mounts.c to handle non-block filesystems, hopefully
  preventing even more special-cased kludges (such as root=/dev/nfs,
  etc)"

* 'work.init' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: simplify get_filesystem_list / get_all_fs_names
  init: allow mounting arbitrary non-blockdevice filesystems as root
  init: split get_fs_names

fs/filesystems.c

@@ -209,21 +209,28 @@ SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
 }
 #endif
 
-int __init get_filesystem_list(char *buf)
+int __init list_bdev_fs_names(char *buf, size_t size)
 {
-	int len = 0;
-	struct file_system_type * tmp;
+	struct file_system_type *p;
+	size_t len;
+	int count = 0;
 
 	read_lock(&file_systems_lock);
-	tmp = file_systems;
-	while (tmp && len < PAGE_SIZE - 80) {
-		len += sprintf(buf+len, "%s\t%s\n",
-			(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
-			tmp->name);
-		tmp = tmp->next;
+	for (p = file_systems; p; p = p->next) {
+		if (!(p->fs_flags & FS_REQUIRES_DEV))
+			continue;
+		len = strlen(p->name) + 1;
+		if (len > size) {
+			pr_warn("%s: truncating file system list\n", __func__);
+			break;
+		}
+		memcpy(buf, p->name, len);
+		buf += len;
+		size -= len;
+		count++;
 	}
 	read_unlock(&file_systems_lock);
-	return len;
+	return count;
 }
 
 #ifdef CONFIG_PROC_FS

include/linux/fs.h

@@ -3592,7 +3592,7 @@ int proc_nr_dentry(struct ctl_table *table, int write,
 		  void *buffer, size_t *lenp, loff_t *ppos);
 int proc_nr_inodes(struct ctl_table *table, int write,
 		   void *buffer, size_t *lenp, loff_t *ppos);
-int __init get_filesystem_list(char *buf);
+int __init list_bdev_fs_names(char *buf, size_t size);
 
 #define __FMODE_EXEC		((__force int) FMODE_EXEC)
 #define __FMODE_NONOTIFY	((__force int) FMODE_NONOTIFY)

init/do_mounts.c

@@ -338,31 +338,22 @@ __setup("rootflags=", root_data_setup);
 __setup("rootfstype=", fs_names_setup);
 __setup("rootdelay=", root_delay_setup);
 
-static void __init get_fs_names(char *page)
+static int __init split_fs_names(char *page, char *names)
 {
-	char *s = page;
+	int count = 0;
+	char *p = page;
 
-	if (root_fs_names) {
-		strcpy(page, root_fs_names);
-		while (*s++) {
-			if (s[-1] == ',')
-				s[-1] = '\0';
+	strcpy(p, root_fs_names);
+	while (*p++) {
+		if (p[-1] == ',')
+			p[-1] = '\0';
 	}
-	} else {
-		int len = get_filesystem_list(page);
-		char *p, *next;
+	*p = '\0';
 
-		page[len] = '\0';
-		for (p = page-1; p; p = next) {
-			next = strchr(++p, '\n');
-			if (*p++ != '\t')
-				continue;
-			while ((*s++ = *p++) != '\n')
-				;
-			s[-1] = '\0';
-		}
-	}
-	*s = '\0';
+	for (p = page; *p; p += strlen(p)+1)
+		count++;
+
+	return count;
 }
 
 static int __init do_mount_root(const char *name, const char *fs,
@@ -408,12 +399,16 @@ void __init mount_block_root(char *name, int flags)
 	char *fs_names = page_address(page);
 	char *p;
 	char b[BDEVNAME_SIZE];
+	int num_fs, i;
 
 	scnprintf(b, BDEVNAME_SIZE, "unknown-block(%u,%u)",
 		  MAJOR(ROOT_DEV), MINOR(ROOT_DEV));
-	get_fs_names(fs_names);
+	if (root_fs_names)
+		num_fs = split_fs_names(fs_names, root_fs_names);
+	else
+		num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE);
 retry:
-	for (p = fs_names; *p; p += strlen(p)+1) {
+	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1) {
 		int err = do_mount_root(name, p, flags, root_mount_data);
 		switch (err) {
 			case 0:
@@ -442,7 +437,7 @@ void __init mount_block_root(char *name, int flags)
 	printk("List of all partitions:\n");
 	printk_all_partitions();
 	printk("No filesystem could mount root, tried: ");
-	for (p = fs_names; *p; p += strlen(p)+1)
+	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1)
 		printk(" %s", p);
 	printk("\n");
 	panic("VFS: Unable to mount root fs on %s", b);
@@ -526,6 +521,47 @@ static int __init mount_cifs_root(void)
 }
 #endif
 
+static bool __init fs_is_nodev(char *fstype)
+{
+	struct file_system_type *fs = get_fs_type(fstype);
+	bool ret = false;
+
+	if (fs) {
+		ret = !(fs->fs_flags & FS_REQUIRES_DEV);
+		put_filesystem(fs);
+	}
+
+	return ret;
+}
+
+static int __init mount_nodev_root(void)
+{
+	char *fs_names, *fstype;
+	int err = -EINVAL;
+	int num_fs, i;
+
+	fs_names = (void *)__get_free_page(GFP_KERNEL);
+	if (!fs_names)
+		return -EINVAL;
+	num_fs = split_fs_names(fs_names, root_fs_names);
+
+	for (i = 0, fstype = fs_names; i < num_fs;
+	     i++, fstype += strlen(fstype) + 1) {
+		if (!fs_is_nodev(fstype))
+			continue;
+		err = do_mount_root(root_device_name, fstype, root_mountflags,
+				    root_mount_data);
+		if (!err)
+			break;
+		if (err != -EACCES && err != -EINVAL)
+			panic("VFS: Unable to mount root \"%s\" (%s), err=%d\n",
+			      root_device_name, fstype, err);
+	}
+
+	free_page((unsigned long)fs_names);
+	return err;
+}
+
 void __init mount_root(void)
 {
 #ifdef CONFIG_ROOT_NFS
@@ -542,6 +578,10 @@ void __init mount_root(void)
 		return;
 	}
 #endif
+	if (ROOT_DEV == 0 && root_device_name && root_fs_names) {
+		if (mount_nodev_root() == 0)
+			return;
+	}
 #ifdef CONFIG_BLOCK
 	{
 		int err = create_dev("/dev/root", ROOT_DEV);