blob: 9ebd17d7befb2f0162dab656c44bc319efaaadc8 [file] [log] [blame]
/*
* Resizable simple ram filesystem for Linux.
*
* Copyright (C) 2000 Linus Torvalds.
* 2000 Transmeta Corp.
*
* Usage limits added by David Gibson, Linuxcare Australia.
* This file is released under the GPL.
*/
/*
* NOTE! This filesystem is probably most useful
* not as a real filesystem, but as an example of
* how virtual filesystems can be written.
*
* It doesn't get much simpler than this. Consider
* that this file implements the full semantics of
* a POSIX-compliant read-write filesystem.
*
* Note in particular how the filesystem does not
* need to implement any data structures of its own
* to keep track of the virtual data: using the VFS
* caches is sufficient.
*/
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/ramfs.h>
#include <linux/sched.h>
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include "internal.h"
struct ramfs_mount_opts {
umode_t mode;
};
struct ramfs_fs_info {
struct ramfs_mount_opts mount_opts;
};
#define RAMFS_DEFAULT_MODE 0755
static const struct super_operations ramfs_ops;
static const struct inode_operations ramfs_dir_inode_operations;
static const struct address_space_operations ramfs_aops = {
.readpage = simple_readpage,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
.set_page_dirty = __set_page_dirty_no_writeback,
};
struct inode *ramfs_get_inode(struct super_block *sb,
const struct inode *dir, umode_t mode, dev_t dev)
{
struct inode * inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
inode_init_owner(&init_user_ns, inode, dir, mode);
inode->i_mapping->a_ops = &ramfs_aops;
mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
mapping_set_unevictable(inode->i_mapping);
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
switch (mode & S_IFMT) {
default:
init_special_inode(inode, mode, dev);
break;
case S_IFREG:
inode->i_op = &ramfs_file_inode_operations;
inode->i_fop = &ramfs_file_operations;
break;
case S_IFDIR:
inode->i_op = &ramfs_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
break;
case S_IFLNK:
inode->i_op = &page_symlink_inode_operations;
inode_nohighmem(inode);
break;
}
}
return inode;
}
/*
* File creation. Allocate an inode, and we're done..
*/
/* SMP-safe */
static int
ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, umode_t mode, dev_t dev)
{
struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
int error = -ENOSPC;
if (inode) {
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
error = 0;
dir->i_mtime = dir->i_ctime = current_time(dir);
}
return error;
}
static int ramfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, umode_t mode)
{
int retval = ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0);
if (!retval)
inc_nlink(dir);
return retval;
}
static int ramfs_create(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, umode_t mode, bool excl)
{
return ramfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
}
static int ramfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, const char *symname)
{
struct inode *inode;
int error = -ENOSPC;
inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
if (inode) {
int l = strlen(symname)+1;
error = page_symlink(inode, symname, l);
if (!error) {
d_instantiate(dentry, inode);
dget(dentry);
dir->i_mtime = dir->i_ctime = current_time(dir);
} else
iput(inode);
}
return error;
}
static int ramfs_tmpfile(struct user_namespace *mnt_userns,
struct inode *dir, struct dentry *dentry, umode_t mode)
{
struct inode *inode;
inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
if (!inode)
return -ENOSPC;
d_tmpfile(dentry, inode);
return 0;
}
static const struct inode_operations ramfs_dir_inode_operations = {
.create = ramfs_create,
.lookup = simple_lookup,
.link = simple_link,
.unlink = simple_unlink,
.symlink = ramfs_symlink,
.mkdir = ramfs_mkdir,
.rmdir = simple_rmdir,
.mknod = ramfs_mknod,
.rename = simple_rename,
.tmpfile = ramfs_tmpfile,
};
/*
* Display the mount options in /proc/mounts.
*/
static int ramfs_show_options(struct seq_file *m, struct dentry *root)
{
struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
return 0;
}
static const struct super_operations ramfs_ops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.show_options = ramfs_show_options,
};
enum ramfs_param {
Opt_mode,
};
const struct fs_parameter_spec ramfs_fs_parameters[] = {
fsparam_u32oct("mode", Opt_mode),
{}
};
static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct fs_parse_result result;
struct ramfs_fs_info *fsi = fc->s_fs_info;
int opt;
opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
if (opt < 0) {
/*
* We might like to report bad mount options here;
* but traditionally ramfs has ignored all mount options,
* and as it is used as a !CONFIG_SHMEM simple substitute
* for tmpfs, better continue to ignore other mount options.
*/
if (opt == -ENOPARAM)
opt = 0;
return opt;
}
switch (opt) {
case Opt_mode:
fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
break;
}
return 0;
}
static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct ramfs_fs_info *fsi = sb->s_fs_info;
struct inode *inode;
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = RAMFS_MAGIC;
sb->s_op = &ramfs_ops;
sb->s_time_gran = 1;
inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
sb->s_root = d_make_root(inode);
if (!sb->s_root)
return -ENOMEM;
return 0;
}
static int ramfs_get_tree(struct fs_context *fc)
{
return get_tree_nodev(fc, ramfs_fill_super);
}
static void ramfs_free_fc(struct fs_context *fc)
{
kfree(fc->s_fs_info);
}
static const struct fs_context_operations ramfs_context_ops = {
.free = ramfs_free_fc,
.parse_param = ramfs_parse_param,
.get_tree = ramfs_get_tree,
};
int ramfs_init_fs_context(struct fs_context *fc)
{
struct ramfs_fs_info *fsi;
fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
if (!fsi)
return -ENOMEM;
fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
fc->s_fs_info = fsi;
fc->ops = &ramfs_context_ops;
return 0;
}
static void ramfs_kill_sb(struct super_block *sb)
{
kfree(sb->s_fs_info);
kill_litter_super(sb);
}
static struct file_system_type ramfs_fs_type = {
.name = "ramfs",
.init_fs_context = ramfs_init_fs_context,
.parameters = ramfs_fs_parameters,
.kill_sb = ramfs_kill_sb,
.fs_flags = FS_USERNS_MOUNT,
};
static int __init init_ramfs_fs(void)
{
return register_filesystem(&ramfs_fs_type);
}
fs_initcall(init_ramfs_fs);