1/*
2 * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
3 *
4 * Matt Mackall <mpm@selenic.com> January, 2004
5 * derived from mm/shmem.c and fs/ramfs/inode.c
6 *
7 * This is intended for small system where the benefits of the full
8 * shmem code (swap-backed and resource-limited) are outweighed by
9 * their complexity. On systems without swap this code should be
10 * effectively equivalent, but much lighter weight.
11 */
12
13#include <linux/fs.h>
14#include <linux/init.h>
15#include <linux/vfs.h>
16#include <linux/mount.h>
17#include <linux/file.h>
18#include <linux/mm.h>
19#include <linux/module.h>
20#include <linux/swap.h>
21#include <linux/ramfs.h>
22
23static struct file_system_type tmpfs_fs_type = {
24	.name		= "tmpfs",
25	.get_sb		= ramfs_get_sb,
26	.kill_sb	= kill_litter_super,
27};
28
29static struct vfsmount *shm_mnt;
30
31static int __init init_tmpfs(void)
32{
33	BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
34
35	shm_mnt = kern_mount(&tmpfs_fs_type);
36	BUG_ON(IS_ERR(shm_mnt));
37
38	return 0;
39}
40module_init(init_tmpfs)
41
42/*
43 * shmem_file_setup - get an unlinked file living in tmpfs
44 *
45 * @name: name for dentry (to be seen in /proc/<pid>/maps
46 * @size: size to be set for the file
47 *
48 */
49struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
50{
51	int error;
52	struct file *file;
53	struct inode *inode;
54	struct dentry *dentry, *root;
55	struct qstr this;
56
57	if (IS_ERR(shm_mnt))
58		return (void *)shm_mnt;
59
60	error = -ENOMEM;
61	this.name = name;
62	this.len = strlen(name);
63	this.hash = 0; /* will go */
64	root = shm_mnt->mnt_root;
65	dentry = d_alloc(root, &this);
66	if (!dentry)
67		goto put_memory;
68
69	error = -ENFILE;
70	file = get_empty_filp();
71	if (!file)
72		goto put_dentry;
73
74	error = -ENOSPC;
75	inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
76	if (!inode)
77		goto close_file;
78
79	d_instantiate(dentry, inode);
80	inode->i_nlink = 0;	/* It is unlinked */
81
82	file->f_path.mnt = mntget(shm_mnt);
83	file->f_path.dentry = dentry;
84	file->f_mapping = inode->i_mapping;
85	file->f_op = &ramfs_file_operations;
86	file->f_mode = FMODE_WRITE | FMODE_READ;
87
88	/* notify everyone as to the change of file size */
89	error = do_truncate(dentry, size, 0, file);
90	if (error < 0)
91		goto close_file;
92
93	return file;
94
95close_file:
96	put_filp(file);
97put_dentry:
98	dput(dentry);
99put_memory:
100	return ERR_PTR(error);
101}
102
103/*
104 * shmem_zero_setup - setup a shared anonymous mapping
105 *
106 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
107 */
108int shmem_zero_setup(struct vm_area_struct *vma)
109{
110	struct file *file;
111	loff_t size = vma->vm_end - vma->vm_start;
112
113	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
114	if (IS_ERR(file))
115		return PTR_ERR(file);
116
117	if (vma->vm_file)
118		fput(vma->vm_file);
119	vma->vm_file = file;
120	vma->vm_ops = &generic_file_vm_ops;
121	return 0;
122}
123
124int shmem_unuse(swp_entry_t entry, struct page *page)
125{
126	return 0;
127}
128
129
130#ifndef CONFIG_MMU
131unsigned long shmem_get_unmapped_area(struct file *file,
132				      unsigned long addr,
133				      unsigned long len,
134				      unsigned long pgoff,
135				      unsigned long flags)
136{
137	return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
138}
139#endif
140