blob: b58abcf44ed658e0a44b129a216a16e5cfc6f2d7 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/devfs_fs_kernel.h>
16#include <linux/vfs.h>
17#include <linux/mount.h>
18#include <linux/file.h>
19#include <linux/mm.h>
20#include <linux/module.h>
21#include <linux/swap.h>
22#include <linux/ramfs.h>
23
24static struct file_system_type tmpfs_fs_type = {
25 .name = "tmpfs",
26 .get_sb = ramfs_get_sb,
27 .kill_sb = kill_litter_super,
28};
29
30static struct vfsmount *shm_mnt;
31
32static int __init init_tmpfs(void)
33{
Matt Mackall5d57bd32005-10-30 15:03:18 -080034 BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
35
Linus Torvalds1da177e2005-04-16 15:20:36 -070036#ifdef CONFIG_TMPFS
37 devfs_mk_dir("shm");
38#endif
39 shm_mnt = kern_mount(&tmpfs_fs_type);
Matt Mackall5d57bd32005-10-30 15:03:18 -080040 BUG_ON(IS_ERR(shm_mnt));
41
Linus Torvalds1da177e2005-04-16 15:20:36 -070042 return 0;
43}
44module_init(init_tmpfs)
45
46/*
47 * shmem_file_setup - get an unlinked file living in tmpfs
48 *
49 * @name: name for dentry (to be seen in /proc/<pid>/maps
50 * @size: size to be set for the file
51 *
52 */
53struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
54{
55 int error;
56 struct file *file;
57 struct inode *inode;
58 struct dentry *dentry, *root;
59 struct qstr this;
60
61 if (IS_ERR(shm_mnt))
62 return (void *)shm_mnt;
63
64 error = -ENOMEM;
65 this.name = name;
66 this.len = strlen(name);
67 this.hash = 0; /* will go */
68 root = shm_mnt->mnt_root;
69 dentry = d_alloc(root, &this);
70 if (!dentry)
71 goto put_memory;
72
73 error = -ENFILE;
74 file = get_empty_filp();
75 if (!file)
76 goto put_dentry;
77
78 error = -ENOSPC;
79 inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
80 if (!inode)
81 goto close_file;
82
83 d_instantiate(dentry, inode);
84 inode->i_size = size;
85 inode->i_nlink = 0; /* It is unlinked */
86 file->f_vfsmnt = mntget(shm_mnt);
87 file->f_dentry = dentry;
88 file->f_mapping = inode->i_mapping;
89 file->f_op = &ramfs_file_operations;
90 file->f_mode = FMODE_WRITE | FMODE_READ;
91 return file;
92
93close_file:
94 put_filp(file);
95put_dentry:
96 dput(dentry);
97put_memory:
98 return ERR_PTR(error);
99}
100
101/*
102 * shmem_zero_setup - setup a shared anonymous mapping
103 *
104 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
105 */
106int shmem_zero_setup(struct vm_area_struct *vma)
107{
108 struct file *file;
109 loff_t size = vma->vm_end - vma->vm_start;
110
111 file = shmem_file_setup("dev/zero", size, vma->vm_flags);
112 if (IS_ERR(file))
113 return PTR_ERR(file);
114
115 if (vma->vm_file)
116 fput(vma->vm_file);
117 vma->vm_file = file;
118 vma->vm_ops = &generic_file_vm_ops;
119 return 0;
120}
121
122int shmem_unuse(swp_entry_t entry, struct page *page)
123{
124 return 0;
125}