--- /dev/null
+/*
+ * 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);
Code Review / kvmfornfv.git / blobdiff