1 files changed, 236 insertions, 0 deletions

diff --git a/fs/filesystems.c b/fs/filesystems.c
new file mode 100644
index 000000000000..44082bfdfec9
--- /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);