Commit | Line | Data |
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5dc8bf81 DL |
1 | /* |
2 | * fs/anon_inodes.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * | |
6 | * Thanks to Arnd Bergmann for code review and suggestions. | |
7 | * More changes for Thomas Gleixner suggestions. | |
8 | * | |
9 | */ | |
10 | ||
a99bbaf5 | 11 | #include <linux/cred.h> |
5dc8bf81 DL |
12 | #include <linux/file.h> |
13 | #include <linux/poll.h> | |
a99bbaf5 | 14 | #include <linux/sched.h> |
5dc8bf81 DL |
15 | #include <linux/init.h> |
16 | #include <linux/fs.h> | |
17 | #include <linux/mount.h> | |
18 | #include <linux/module.h> | |
19 | #include <linux/kernel.h> | |
20 | #include <linux/magic.h> | |
21 | #include <linux/anon_inodes.h> | |
22 | ||
23 | #include <asm/uaccess.h> | |
24 | ||
25 | static struct vfsmount *anon_inode_mnt __read_mostly; | |
26 | static struct inode *anon_inode_inode; | |
5dc8bf81 | 27 | |
b9aff027 NP |
28 | /* |
29 | * anon_inodefs_dname() is called from d_path(). | |
30 | */ | |
31 | static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen) | |
32 | { | |
33 | return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s", | |
34 | dentry->d_name.name); | |
35 | } | |
36 | ||
c74a1cbb AV |
37 | static const struct dentry_operations anon_inodefs_dentry_operations = { |
38 | .d_dname = anon_inodefs_dname, | |
39 | }; | |
40 | ||
ca7068c4 AV |
41 | static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type, |
42 | int flags, const char *dev_name, void *data) | |
43 | { | |
44 | struct dentry *root; | |
45 | root = mount_pseudo(fs_type, "anon_inode:", NULL, | |
46 | &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC); | |
47 | if (!IS_ERR(root)) { | |
48 | struct super_block *s = root->d_sb; | |
6987843f | 49 | anon_inode_inode = alloc_anon_inode(s); |
ca7068c4 AV |
50 | if (IS_ERR(anon_inode_inode)) { |
51 | dput(root); | |
52 | deactivate_locked_super(s); | |
53 | root = ERR_CAST(anon_inode_inode); | |
54 | } | |
55 | } | |
56 | return root; | |
57 | } | |
58 | ||
59 | static struct file_system_type anon_inode_fs_type = { | |
60 | .name = "anon_inodefs", | |
61 | .mount = anon_inodefs_mount, | |
62 | .kill_sb = kill_anon_super, | |
63 | }; | |
64 | ||
5dc8bf81 | 65 | /** |
c0d8768a NK |
66 | * anon_inode_getfile - creates a new file instance by hooking it up to an |
67 | * anonymous inode, and a dentry that describe the "class" | |
68 | * of the file | |
5dc8bf81 | 69 | * |
5dc8bf81 | 70 | * @name: [in] name of the "class" of the new file |
7d9dbca3 UD |
71 | * @fops: [in] file operations for the new file |
72 | * @priv: [in] private data for the new file (will be file's private_data) | |
73 | * @flags: [in] flags | |
5dc8bf81 DL |
74 | * |
75 | * Creates a new file by hooking it on a single inode. This is useful for files | |
76 | * that do not need to have a full-fledged inode in order to operate correctly. | |
562787a5 | 77 | * All the files created with anon_inode_getfile() will share a single inode, |
5dc8bf81 | 78 | * hence saving memory and avoiding code duplication for the file/inode/dentry |
562787a5 | 79 | * setup. Returns the newly created file* or an error pointer. |
5dc8bf81 | 80 | */ |
562787a5 DL |
81 | struct file *anon_inode_getfile(const char *name, |
82 | const struct file_operations *fops, | |
83 | void *priv, int flags) | |
5dc8bf81 DL |
84 | { |
85 | struct qstr this; | |
2c48b9c4 | 86 | struct path path; |
5dc8bf81 | 87 | struct file *file; |
5dc8bf81 DL |
88 | |
89 | if (IS_ERR(anon_inode_inode)) | |
562787a5 | 90 | return ERR_PTR(-ENODEV); |
5dc8bf81 | 91 | |
e3a2a0d4 | 92 | if (fops->owner && !try_module_get(fops->owner)) |
562787a5 | 93 | return ERR_PTR(-ENOENT); |
5dc8bf81 DL |
94 | |
95 | /* | |
96 | * Link the inode to a directory entry by creating a unique name | |
97 | * using the inode sequence number. | |
98 | */ | |
39b65252 | 99 | file = ERR_PTR(-ENOMEM); |
5dc8bf81 DL |
100 | this.name = name; |
101 | this.len = strlen(name); | |
102 | this.hash = 0; | |
4b936885 | 103 | path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this); |
2c48b9c4 | 104 | if (!path.dentry) |
562787a5 | 105 | goto err_module; |
96fdc72d | 106 | |
2c48b9c4 | 107 | path.mnt = mntget(anon_inode_mnt); |
96fdc72d DL |
108 | /* |
109 | * We know the anon_inode inode count is always greater than zero, | |
7de9c6ee | 110 | * so ihold() is safe. |
96fdc72d | 111 | */ |
7de9c6ee | 112 | ihold(anon_inode_inode); |
96fdc72d | 113 | |
2c48b9c4 | 114 | d_instantiate(path.dentry, anon_inode_inode); |
5dc8bf81 | 115 | |
5300990c | 116 | file = alloc_file(&path, OPEN_FMODE(flags), fops); |
39b65252 | 117 | if (IS_ERR(file)) |
430e285e | 118 | goto err_dput; |
96fdc72d | 119 | file->f_mapping = anon_inode_inode->i_mapping; |
5dc8bf81 | 120 | |
628ff7c1 | 121 | file->f_flags = flags & (O_ACCMODE | O_NONBLOCK); |
5dc8bf81 DL |
122 | file->private_data = priv; |
123 | ||
562787a5 DL |
124 | return file; |
125 | ||
126 | err_dput: | |
2c48b9c4 | 127 | path_put(&path); |
562787a5 DL |
128 | err_module: |
129 | module_put(fops->owner); | |
39b65252 | 130 | return file; |
562787a5 DL |
131 | } |
132 | EXPORT_SYMBOL_GPL(anon_inode_getfile); | |
133 | ||
134 | /** | |
135 | * anon_inode_getfd - creates a new file instance by hooking it up to an | |
136 | * anonymous inode, and a dentry that describe the "class" | |
137 | * of the file | |
138 | * | |
139 | * @name: [in] name of the "class" of the new file | |
140 | * @fops: [in] file operations for the new file | |
141 | * @priv: [in] private data for the new file (will be file's private_data) | |
142 | * @flags: [in] flags | |
143 | * | |
144 | * Creates a new file by hooking it on a single inode. This is useful for files | |
145 | * that do not need to have a full-fledged inode in order to operate correctly. | |
146 | * All the files created with anon_inode_getfd() will share a single inode, | |
147 | * hence saving memory and avoiding code duplication for the file/inode/dentry | |
148 | * setup. Returns new descriptor or an error code. | |
149 | */ | |
150 | int anon_inode_getfd(const char *name, const struct file_operations *fops, | |
151 | void *priv, int flags) | |
152 | { | |
153 | int error, fd; | |
154 | struct file *file; | |
155 | ||
156 | error = get_unused_fd_flags(flags); | |
157 | if (error < 0) | |
158 | return error; | |
159 | fd = error; | |
160 | ||
161 | file = anon_inode_getfile(name, fops, priv, flags); | |
162 | if (IS_ERR(file)) { | |
163 | error = PTR_ERR(file); | |
164 | goto err_put_unused_fd; | |
165 | } | |
5dc8bf81 DL |
166 | fd_install(fd, file); |
167 | ||
2030a42c | 168 | return fd; |
5dc8bf81 DL |
169 | |
170 | err_put_unused_fd: | |
171 | put_unused_fd(fd); | |
5dc8bf81 DL |
172 | return error; |
173 | } | |
d6d28168 | 174 | EXPORT_SYMBOL_GPL(anon_inode_getfd); |
5dc8bf81 | 175 | |
5dc8bf81 DL |
176 | static int __init anon_inode_init(void) |
177 | { | |
178 | int error; | |
179 | ||
180 | error = register_filesystem(&anon_inode_fs_type); | |
181 | if (error) | |
182 | goto err_exit; | |
183 | anon_inode_mnt = kern_mount(&anon_inode_fs_type); | |
184 | if (IS_ERR(anon_inode_mnt)) { | |
185 | error = PTR_ERR(anon_inode_mnt); | |
186 | goto err_unregister_filesystem; | |
187 | } | |
5dc8bf81 DL |
188 | return 0; |
189 | ||
5dc8bf81 DL |
190 | err_unregister_filesystem: |
191 | unregister_filesystem(&anon_inode_fs_type); | |
192 | err_exit: | |
193 | panic(KERN_ERR "anon_inode_init() failed (%d)\n", error); | |
194 | } | |
195 | ||
196 | fs_initcall(anon_inode_init); | |
197 |