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/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
24 static struct file_system_type tmpfs_fs_type = {
25 .name = "tmpfs",
26 .get_sb = ramfs_get_sb,
27 .kill_sb = kill_litter_super,
28 };
29
30 static struct vfsmount *shm_mnt;
31
32 static int __init init_tmpfs(void)
33 {
34 BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
35
36 #ifdef CONFIG_TMPFS
37 devfs_mk_dir("shm");
38 #endif
39 shm_mnt = kern_mount(&tmpfs_fs_type);
40 BUG_ON(IS_ERR(shm_mnt));
41
42 return 0;
43 }
44 module_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 */
53 struct 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_nlink = 0; /* It is unlinked */
85
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
92 /* notify everyone as to the change of file size */
93 error = do_truncate(dentry, size, 0, file);
94 if (error < 0)
95 goto close_file;
96
97 return file;
98
99 close_file:
100 put_filp(file);
101 put_dentry:
102 dput(dentry);
103 put_memory:
104 return ERR_PTR(error);
105 }
106
107 /*
108 * shmem_zero_setup - setup a shared anonymous mapping
109 *
110 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
111 */
112 int shmem_zero_setup(struct vm_area_struct *vma)
113 {
114 struct file *file;
115 loff_t size = vma->vm_end - vma->vm_start;
116
117 file = shmem_file_setup("dev/zero", size, vma->vm_flags);
118 if (IS_ERR(file))
119 return PTR_ERR(file);
120
121 if (vma->vm_file)
122 fput(vma->vm_file);
123 vma->vm_file = file;
124 vma->vm_ops = &generic_file_vm_ops;
125 return 0;
126 }
127
128 int shmem_unuse(swp_entry_t entry, struct page *page)
129 {
130 return 0;
131 }
132
133 int shmem_mmap(struct file *file, struct vm_area_struct *vma)
134 {
135 file_accessed(file);
136 #ifndef CONFIG_MMU
137 return ramfs_nommu_mmap(file, vma);
138 #else
139 return 0;
140 #endif
141 }
142
143 #ifndef CONFIG_MMU
144 unsigned long shmem_get_unmapped_area(struct file *file,
145 unsigned long addr,
146 unsigned long len,
147 unsigned long pgoff,
148 unsigned long flags)
149 {
150 return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
151 }
152 #endif
153
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