/* * 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);