/* * 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 <asm/uaccess.h> #include "internal.h" #define RAMFS_DEFAULT_MODE 0755 static const struct super_operations ramfs_ops; static const struct inode_operations ramfs_dir_inode_operations; static struct backing_dev_info ramfs_backing_dev_info = { .name = "ramfs", .ra_pages = 0, /* No readahead */ .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY | BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP, }; 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(inode, dir, mode); inode->i_mapping->a_ops = &ramfs_aops; inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info; 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; 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; break; } } return inode; } /* * File creation. Allocate an inode, and we're done.. */ /* SMP-safe */ static int ramfs_mknod(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; } return error; } static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode) { int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0); if (!retval) inc_nlink(dir); return retval; } static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl) { return ramfs_mknod(dir, dentry, mode | S_IFREG, 0); } static int ramfs_symlink(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; } else iput(inode); } return error; } 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, }; static const struct super_operations ramfs_ops = { .statfs = simple_statfs, .drop_inode = generic_delete_inode, .show_options = generic_show_options, }; struct ramfs_mount_opts { umode_t mode; }; enum { Opt_mode, Opt_err }; static const match_table_t tokens = { {Opt_mode, "mode=%o"}, {Opt_err, NULL} }; struct ramfs_fs_info { struct ramfs_mount_opts mount_opts; }; static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts) { substring_t args[MAX_OPT_ARGS]; int option; int token; char *p; opts->mode = RAMFS_DEFAULT_MODE; while ((p = strsep(&data, ",")) != NULL) { if (!*p) continue; token = match_token(p, tokens, args); switch (token) { case Opt_mode: if (match_octal(&args[0], &option)) return -EINVAL; opts->mode = option & S_IALLUGO; break; /* * 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. */ } } return 0; } int ramfs_fill_super(struct super_block *sb, void *data, int silent) { struct ramfs_fs_info *fsi; struct inode *inode; int err; save_mount_options(sb, data); fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL); sb->s_fs_info = fsi; if (!fsi) return -ENOMEM; err = ramfs_parse_options(data, &fsi->mount_opts); if (err) return err; sb->s_maxbytes = MAX_LFS_FILESIZE; sb->s_blocksize = PAGE_CACHE_SIZE; sb->s_blocksize_bits = PAGE_CACHE_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; } struct dentry *ramfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { return mount_nodev(fs_type, flags, data, ramfs_fill_super); } static struct dentry *rootfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); } 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", .mount = ramfs_mount, .kill_sb = ramfs_kill_sb, .fs_flags = FS_USERNS_MOUNT, }; static struct file_system_type rootfs_fs_type = { .name = "rootfs", .mount = rootfs_mount, .kill_sb = kill_litter_super, }; static int __init init_ramfs_fs(void) { return register_filesystem(&ramfs_fs_type); } module_init(init_ramfs_fs) int __init init_rootfs(void) { int err; err = bdi_init(&ramfs_backing_dev_info); if (err) return err; err = register_filesystem(&rootfs_fs_type); if (err) bdi_destroy(&ramfs_backing_dev_info); return err; }