summaryrefslogtreecommitdiff
path: root/mm/tiny-shmem.c
blob: 3e67d575ee6e64821c43ea2b7d181a3d36d9805d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
/*
 * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
 *
 * Matt Mackall <mpm@selenic.com> January, 2004
 * derived from mm/shmem.c and fs/ramfs/inode.c
 *
 * This is intended for small system where the benefits of the full
 * shmem code (swap-backed and resource-limited) are outweighed by
 * their complexity. On systems without swap this code should be
 * effectively equivalent, but much lighter weight.
 */

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/vfs.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/swap.h>
#include <linux/ramfs.h>

static struct file_system_type tmpfs_fs_type = {
	.name		= "tmpfs",
	.get_sb		= ramfs_get_sb,
	.kill_sb	= kill_litter_super,
};

static struct vfsmount *shm_mnt;

static int __init init_tmpfs(void)
{
	BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);

	shm_mnt = kern_mount(&tmpfs_fs_type);
	BUG_ON(IS_ERR(shm_mnt));

	return 0;
}
module_init(init_tmpfs)

/**
 * shmem_file_setup - get an unlinked file living in tmpfs
 * @name: name for dentry (to be seen in /proc/<pid>/maps
 * @size: size to be set for the file
 * @flags: vm_flags
 */
struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
{
	int error;
	struct file *file;
	struct inode *inode;
	struct dentry *dentry, *root;
	struct qstr this;

	if (IS_ERR(shm_mnt))
		return (void *)shm_mnt;

	error = -ENOMEM;
	this.name = name;
	this.len = strlen(name);
	this.hash = 0; /* will go */
	root = shm_mnt->mnt_root;
	dentry = d_alloc(root, &this);
	if (!dentry)
		goto put_memory;

	error = -ENFILE;
	file = get_empty_filp();
	if (!file)
		goto put_dentry;

	error = -ENOSPC;
	inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
	if (!inode)
		goto close_file;

	d_instantiate(dentry, inode);
	inode->i_size = size;
	inode->i_nlink = 0;	/* It is unlinked */
	init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
			&ramfs_file_operations);

#ifndef CONFIG_MMU
	error = ramfs_nommu_expand_for_mapping(inode, size);
	if (error)
		goto close_file;
#endif
	return file;

close_file:
	put_filp(file);
put_dentry:
	dput(dentry);
put_memory:
	return ERR_PTR(error);
}
EXPORT_SYMBOL_GPL(shmem_file_setup);

/**
 * shmem_zero_setup - setup a shared anonymous mapping
 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
 */
int shmem_zero_setup(struct vm_area_struct *vma)
{
	struct file *file;
	loff_t size = vma->vm_end - vma->vm_start;

	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
	if (IS_ERR(file))
		return PTR_ERR(file);

	if (vma->vm_file)
		fput(vma->vm_file);
	vma->vm_file = file;
	vma->vm_ops = &generic_file_vm_ops;
	return 0;
}

int shmem_unuse(swp_entry_t entry, struct page *page)
{
	return 0;
}

#ifndef CONFIG_MMU
unsigned long shmem_get_unmapped_area(struct file *file,
				      unsigned long addr,
				      unsigned long len,
				      unsigned long pgoff,
				      unsigned long flags)
{
	return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
}
#endif