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[/] [test_project/] [trunk/] [linux_sd_driver/] [fs/] [filesystems.c] - Blame information for rev 62

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Line No. Rev Author Line
1 62 marcus.erl
/*
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 *  linux/fs/filesystems.c
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 *
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 *  Copyright (C) 1991, 1992  Linus Torvalds
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 *
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 *  table of configured filesystems
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 */
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#include <linux/syscalls.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/kmod.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <asm/uaccess.h>
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/*
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 * Handling of filesystem drivers list.
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 * Rules:
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 *      Inclusion to/removals from/scanning of list are protected by spinlock.
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 *      During the unload module must call unregister_filesystem().
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 *      We can access the fields of list element if:
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 *              1) spinlock is held or
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 *              2) we hold the reference to the module.
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 *      The latter can be guaranteed by call of try_module_get(); if it
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 *      returned 0 we must skip the element, otherwise we got the reference.
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 *      Once the reference is obtained we can drop the spinlock.
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 */
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static struct file_system_type *file_systems;
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static DEFINE_RWLOCK(file_systems_lock);
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/* WARNING: This can be used only if we _already_ own a reference */
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void get_filesystem(struct file_system_type *fs)
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{
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        __module_get(fs->owner);
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}
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void put_filesystem(struct file_system_type *fs)
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{
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        module_put(fs->owner);
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}
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static struct file_system_type **find_filesystem(const char *name, unsigned len)
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{
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        struct file_system_type **p;
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        for (p=&file_systems; *p; p=&(*p)->next)
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                if (strlen((*p)->name) == len &&
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                    strncmp((*p)->name, name, len) == 0)
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                        break;
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        return p;
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}
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/**
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 *      register_filesystem - register a new filesystem
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 *      @fs: the file system structure
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 *
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 *      Adds the file system passed to the list of file systems the kernel
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 *      is aware of for mount and other syscalls. Returns 0 on success,
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 *      or a negative errno code on an error.
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 *
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 *      The &struct file_system_type that is passed is linked into the kernel
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 *      structures and must not be freed until the file system has been
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 *      unregistered.
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 */
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int register_filesystem(struct file_system_type * fs)
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{
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        int res = 0;
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        struct file_system_type ** p;
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        BUG_ON(strchr(fs->name, '.'));
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        if (fs->next)
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                return -EBUSY;
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        INIT_LIST_HEAD(&fs->fs_supers);
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        write_lock(&file_systems_lock);
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        p = find_filesystem(fs->name, strlen(fs->name));
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        if (*p)
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                res = -EBUSY;
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        else
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                *p = fs;
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        write_unlock(&file_systems_lock);
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        return res;
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}
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EXPORT_SYMBOL(register_filesystem);
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/**
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 *      unregister_filesystem - unregister a file system
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 *      @fs: filesystem to unregister
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 *
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 *      Remove a file system that was previously successfully registered
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 *      with the kernel. An error is returned if the file system is not found.
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 *      Zero is returned on a success.
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 *
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 *      Once this function has returned the &struct file_system_type structure
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 *      may be freed or reused.
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 */
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int unregister_filesystem(struct file_system_type * fs)
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{
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        struct file_system_type ** tmp;
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        write_lock(&file_systems_lock);
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        tmp = &file_systems;
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        while (*tmp) {
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                if (fs == *tmp) {
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                        *tmp = fs->next;
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                        fs->next = NULL;
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                        write_unlock(&file_systems_lock);
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                        return 0;
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                }
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                tmp = &(*tmp)->next;
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        }
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        write_unlock(&file_systems_lock);
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        return -EINVAL;
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}
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EXPORT_SYMBOL(unregister_filesystem);
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static int fs_index(const char __user * __name)
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{
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        struct file_system_type * tmp;
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        char * name;
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        int err, index;
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        name = getname(__name);
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        err = PTR_ERR(name);
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        if (IS_ERR(name))
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                return err;
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        err = -EINVAL;
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        read_lock(&file_systems_lock);
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        for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
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                if (strcmp(tmp->name,name) == 0) {
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                        err = index;
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                        break;
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                }
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        }
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        read_unlock(&file_systems_lock);
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        putname(name);
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        return err;
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}
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static int fs_name(unsigned int index, char __user * buf)
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{
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        struct file_system_type * tmp;
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        int len, res;
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        read_lock(&file_systems_lock);
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        for (tmp = file_systems; tmp; tmp = tmp->next, index--)
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                if (index <= 0 && try_module_get(tmp->owner))
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                        break;
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        read_unlock(&file_systems_lock);
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        if (!tmp)
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                return -EINVAL;
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        /* OK, we got the reference, so we can safely block */
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        len = strlen(tmp->name) + 1;
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        res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
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        put_filesystem(tmp);
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        return res;
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}
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static int fs_maxindex(void)
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{
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        struct file_system_type * tmp;
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        int index;
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        read_lock(&file_systems_lock);
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        for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
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                ;
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        read_unlock(&file_systems_lock);
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        return index;
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}
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/*
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 * Whee.. Weird sysv syscall.
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 */
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asmlinkage long sys_sysfs(int option, unsigned long arg1, unsigned long arg2)
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{
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        int retval = -EINVAL;
183
 
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        switch (option) {
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                case 1:
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                        retval = fs_index((const char __user *) arg1);
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                        break;
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                case 2:
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                        retval = fs_name(arg1, (char __user *) arg2);
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                        break;
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                case 3:
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                        retval = fs_maxindex();
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                        break;
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        }
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        return retval;
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}
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int get_filesystem_list(char * buf)
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{
202
        int len = 0;
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        struct file_system_type * tmp;
204
 
205
        read_lock(&file_systems_lock);
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        tmp = file_systems;
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        while (tmp && len < PAGE_SIZE - 80) {
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                len += sprintf(buf+len, "%s\t%s\n",
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                        (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
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                        tmp->name);
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                tmp = tmp->next;
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        }
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        read_unlock(&file_systems_lock);
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        return len;
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}
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struct file_system_type *get_fs_type(const char *name)
218
{
219
        struct file_system_type *fs;
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        const char *dot = strchr(name, '.');
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        unsigned len = dot ? dot - name : strlen(name);
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223
        read_lock(&file_systems_lock);
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        fs = *(find_filesystem(name, len));
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        if (fs && !try_module_get(fs->owner))
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                fs = NULL;
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        read_unlock(&file_systems_lock);
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        if (!fs && (request_module("%.*s", len, name) == 0)) {
229
                read_lock(&file_systems_lock);
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                fs = *(find_filesystem(name, len));
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                if (fs && !try_module_get(fs->owner))
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                        fs = NULL;
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                read_unlock(&file_systems_lock);
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        }
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236
        if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
237
                put_filesystem(fs);
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                fs = NULL;
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        }
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        return fs;
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}
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EXPORT_SYMBOL(get_fs_type);

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