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