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![Jeff Layton](/assets/img/avatar_default.png)
In later patches, we're going to change how the inode's ctime field is used. Switch to using accessor functions instead of raw accesses of inode->i_ctime. Signed-off-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Message-Id: <20230705190309.579783-69-jlayton@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
299 lines
7.1 KiB
C
299 lines
7.1 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 <linux/fs_context.h>
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#include <linux/fs_parser.h>
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#include <linux/seq_file.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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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(&nop_mnt_idmap, inode, dir, mode);
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inode->i_mapping->a_ops = &ram_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_set_ctime_current(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 mnt_idmap *idmap, struct inode *dir,
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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 = inode_set_ctime_current(dir);
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}
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return error;
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}
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static int ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
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struct dentry *dentry, umode_t mode)
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{
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int retval = ramfs_mknod(&nop_mnt_idmap, 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 mnt_idmap *idmap, struct inode *dir,
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struct dentry *dentry, umode_t mode, bool excl)
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{
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return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
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}
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static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
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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 = inode_set_ctime_current(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 int ramfs_tmpfile(struct mnt_idmap *idmap,
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struct inode *dir, struct file *file, umode_t mode)
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{
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struct inode *inode;
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inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
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if (!inode)
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return -ENOSPC;
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d_tmpfile(file, inode);
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return finish_open_simple(file, 0);
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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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.tmpfile = ramfs_tmpfile,
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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 ramfs_param {
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Opt_mode,
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};
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const struct fs_parameter_spec ramfs_fs_parameters[] = {
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fsparam_u32oct("mode", Opt_mode),
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{}
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};
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static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
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{
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struct fs_parse_result result;
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struct ramfs_fs_info *fsi = fc->s_fs_info;
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int opt;
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opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
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if (opt == -ENOPARAM) {
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opt = vfs_parse_fs_param_source(fc, param);
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if (opt != -ENOPARAM)
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return opt;
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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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return 0;
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}
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if (opt < 0)
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return opt;
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switch (opt) {
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case Opt_mode:
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fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
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break;
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}
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return 0;
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}
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static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
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{
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struct ramfs_fs_info *fsi = sb->s_fs_info;
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struct inode *inode;
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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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static int ramfs_get_tree(struct fs_context *fc)
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{
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return get_tree_nodev(fc, ramfs_fill_super);
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}
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static void ramfs_free_fc(struct fs_context *fc)
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{
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kfree(fc->s_fs_info);
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}
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static const struct fs_context_operations ramfs_context_ops = {
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.free = ramfs_free_fc,
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.parse_param = ramfs_parse_param,
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.get_tree = ramfs_get_tree,
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};
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int ramfs_init_fs_context(struct fs_context *fc)
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{
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struct ramfs_fs_info *fsi;
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fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
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if (!fsi)
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return -ENOMEM;
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fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
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fc->s_fs_info = fsi;
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fc->ops = &ramfs_context_ops;
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return 0;
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}
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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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.init_fs_context = ramfs_init_fs_context,
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.parameters = ramfs_fs_parameters,
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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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static int __init init_ramfs_fs(void)
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{
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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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