diff options
Diffstat (limited to 'kernel/fs/ramfs/inode.c')
| -rw-r--r-- | kernel/fs/ramfs/inode.c | 266 |
1 files changed, 266 insertions, 0 deletions
diff --git a/kernel/fs/ramfs/inode.c b/kernel/fs/ramfs/inode.c new file mode 100644 index 000000000..889d558b4 --- /dev/null +++ b/kernel/fs/ramfs/inode.c @@ -0,0 +1,266 @@ +/* + * 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 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(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; + 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 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, +}; + +int __init init_ramfs_fs(void) +{ + static unsigned long once; + + if (test_and_set_bit(0, &once)) + return 0; + return register_filesystem(&ramfs_fs_type); +} +fs_initcall(init_ramfs_fs); |