1 files changed, 236 insertions, 0 deletions
diff --git a/fs/filesystems.c b/fs/filesystems.c
new file mode 100644
index 00000000000..44082bfdfec
--- /dev/null
+++ b/fs/filesystems.c
@@ -0,0 +1,236 @@
+/*
+ *  linux/fs/filesystems.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  table of configured filesystems
+ */
+
+#include <linux/syscalls.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/kmod.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+/*
+ * Handling of filesystem drivers list.
+ * Rules:
+ *	Inclusion to/removals from/scanning of list are protected by spinlock.
+ *	During the unload module must call unregister_filesystem().
+ *	We can access the fields of list element if:
+ *		1) spinlock is held or
+ *		2) we hold the reference to the module.
+ *	The latter can be guaranteed by call of try_module_get(); if it
+ *	returned 0 we must skip the element, otherwise we got the reference.
+ *	Once the reference is obtained we can drop the spinlock.
+ */
+
+static struct file_system_type *file_systems;
+static DEFINE_RWLOCK(file_systems_lock);
+
+/* WARNING: This can be used only if we _already_ own a reference */
+void get_filesystem(struct file_system_type *fs)
+{
+	__module_get(fs->owner);
+}
+
+void put_filesystem(struct file_system_type *fs)
+{
+	module_put(fs->owner);
+}
+
+static struct file_system_type **find_filesystem(const char *name)
+{
+	struct file_system_type **p;
+	for (p=&file_systems; *p; p=&(*p)->next)
+		if (strcmp((*p)->name,name) == 0)
+			break;
+	return p;
+}
+
+/**
+ *	register_filesystem - register a new filesystem
+ *	@fs: the file system structure
+ *
+ *	Adds the file system passed to the list of file systems the kernel
+ *	is aware of for mount and other syscalls. Returns 0 on success,
+ *	or a negative errno code on an error.
+ *
+ *	The &struct file_system_type that is passed is linked into the kernel 
+ *	structures and must not be freed until the file system has been
+ *	unregistered.
+ */
+ 
+int register_filesystem(struct file_system_type * fs)
+{
+	int res = 0;
+	struct file_system_type ** p;
+
+	if (!fs)
+		return -EINVAL;
+	if (fs->next)
+		return -EBUSY;
+	INIT_LIST_HEAD(&fs->fs_supers);
+	write_lock(&file_systems_lock);
+	p = find_filesystem(fs->name);
+	if (*p)
+		res = -EBUSY;
+	else
+		*p = fs;
+	write_unlock(&file_systems_lock);
+	return res;
+}
+
+EXPORT_SYMBOL(register_filesystem);
+
+/**
+ *	unregister_filesystem - unregister a file system
+ *	@fs: filesystem to unregister
+ *
+ *	Remove a file system that was previously successfully registered
+ *	with the kernel. An error is returned if the file system is not found.
+ *	Zero is returned on a success.
+ *	
+ *	Once this function has returned the &struct file_system_type structure
+ *	may be freed or reused.
+ */
+ 
+int unregister_filesystem(struct file_system_type * fs)
+{
+	struct file_system_type ** tmp;
+
+	write_lock(&file_systems_lock);
+	tmp = &file_systems;
+	while (*tmp) {
+		if (fs == *tmp) {
+			*tmp = fs->next;
+			fs->next = NULL;
+			write_unlock(&file_systems_lock);
+			return 0;
+		}
+		tmp = &(*tmp)->next;
+	}
+	write_unlock(&file_systems_lock);
+	return -EINVAL;
+}
+
+EXPORT_SYMBOL(unregister_filesystem);
+
+static int fs_index(const char __user * __name)
+{
+	struct file_system_type * tmp;
+	char * name;
+	int err, index;
+
+	name = getname(__name);
+	err = PTR_ERR(name);
+	if (IS_ERR(name))
+		return err;
+
+	err = -EINVAL;
+	read_lock(&file_systems_lock);
+	for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
+		if (strcmp(tmp->name,name) == 0) {
+			err = index;
+			break;
+		}
+	}
+	read_unlock(&file_systems_lock);
+	putname(name);
+	return err;
+}
+
+static int fs_name(unsigned int index, char __user * buf)
+{
+	struct file_system_type * tmp;
+	int len, res;
+
+	read_lock(&file_systems_lock);
+	for (tmp = file_systems; tmp; tmp = tmp->next, index--)
+		if (index <= 0 && try_module_get(tmp->owner))
+			break;
+	read_unlock(&file_systems_lock);
+	if (!tmp)
+		return -EINVAL;
+
+	/* OK, we got the reference, so we can safely block */
+	len = strlen(tmp->name) + 1;
+	res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
+	put_filesystem(tmp);
+	return res;
+}
+
+static int fs_maxindex(void)
+{
+	struct file_system_type * tmp;
+	int index;
+
+	read_lock(&file_systems_lock);
+	for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
+		;
+	read_unlock(&file_systems_lock);
+	return index;
+}
+
+/*
+ * Whee.. Weird sysv syscall. 
+ */
+asmlinkage long sys_sysfs(int option, unsigned long arg1, unsigned long arg2)
+{
+	int retval = -EINVAL;
+
+	switch (option) {
+		case 1:
+			retval = fs_index((const char __user *) arg1);
+			break;
+
+		case 2:
+			retval = fs_name(arg1, (char __user *) arg2);
+			break;
+
+		case 3:
+			retval = fs_maxindex();
+			break;
+	}
+	return retval;
+}
+
+int get_filesystem_list(char * buf)
+{
+	int len = 0;
+	struct file_system_type * tmp;
+
+	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;
+	}
+	read_unlock(&file_systems_lock);
+	return len;
+}
+
+struct file_system_type *get_fs_type(const char *name)
+{
+	struct file_system_type *fs;
+
+	read_lock(&file_systems_lock);
+	fs = *(find_filesystem(name));
+	if (fs && !try_module_get(fs->owner))
+		fs = NULL;
+	read_unlock(&file_systems_lock);
+	if (!fs && (request_module("%s", name) == 0)) {
+		read_lock(&file_systems_lock);
+		fs = *(find_filesystem(name));
+		if (fs && !try_module_get(fs->owner))
+			fs = NULL;
+		read_unlock(&file_systems_lock);
+	}
+	return fs;
+}
+
+EXPORT_SYMBOL(get_fs_type);