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/slab.h> |
16 | #include <linux/init.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/mount.h> | |
19 | #include <linux/module.h> | |
20 | #include <linux/kernel.h> | |
21 | #include <linux/magic.h> | |
22 | #include <linux/anon_inodes.h> | |
23 | ||
24 | #include <asm/uaccess.h> | |
25 | ||
26 | static struct vfsmount *anon_inode_mnt __read_mostly; | |
27 | static struct inode *anon_inode_inode; | |
28 | static const struct file_operations anon_inode_fops; | |
29 | ||
30 | static int anon_inodefs_get_sb(struct file_system_type *fs_type, int flags, | |
31 | const char *dev_name, void *data, | |
32 | struct vfsmount *mnt) | |
33 | { | |
34 | return get_sb_pseudo(fs_type, "anon_inode:", NULL, ANON_INODE_FS_MAGIC, | |
35 | mnt); | |
36 | } | |
37 | ||
b9aff027 NP |
38 | /* |
39 | * anon_inodefs_dname() is called from d_path(). | |
40 | */ | |
41 | static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen) | |
42 | { | |
43 | return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s", | |
44 | dentry->d_name.name); | |
45 | } | |
46 | ||
5dc8bf81 DL |
47 | static struct file_system_type anon_inode_fs_type = { |
48 | .name = "anon_inodefs", | |
49 | .get_sb = anon_inodefs_get_sb, | |
50 | .kill_sb = kill_anon_super, | |
51 | }; | |
3ba13d17 | 52 | static const struct dentry_operations anon_inodefs_dentry_operations = { |
b9aff027 | 53 | .d_dname = anon_inodefs_dname, |
5dc8bf81 DL |
54 | }; |
55 | ||
d3a9262e PZ |
56 | /* |
57 | * nop .set_page_dirty method so that people can use .page_mkwrite on | |
58 | * anon inodes. | |
59 | */ | |
60 | static int anon_set_page_dirty(struct page *page) | |
61 | { | |
62 | return 0; | |
63 | }; | |
64 | ||
65 | static const struct address_space_operations anon_aops = { | |
66 | .set_page_dirty = anon_set_page_dirty, | |
67 | }; | |
68 | ||
5dc8bf81 | 69 | /** |
4b4e5a14 | 70 | * anon_inode_getfd - creates a new file instance by hooking it up to an |
5dc8bf81 DL |
71 | * anonymous inode, and a dentry that describe the "class" |
72 | * of the file | |
73 | * | |
5dc8bf81 | 74 | * @name: [in] name of the "class" of the new file |
7d9dbca3 UD |
75 | * @fops: [in] file operations for the new file |
76 | * @priv: [in] private data for the new file (will be file's private_data) | |
77 | * @flags: [in] flags | |
5dc8bf81 DL |
78 | * |
79 | * Creates a new file by hooking it on a single inode. This is useful for files | |
80 | * that do not need to have a full-fledged inode in order to operate correctly. | |
562787a5 | 81 | * All the files created with anon_inode_getfile() will share a single inode, |
5dc8bf81 | 82 | * hence saving memory and avoiding code duplication for the file/inode/dentry |
562787a5 | 83 | * setup. Returns the newly created file* or an error pointer. |
5dc8bf81 | 84 | */ |
562787a5 DL |
85 | struct file *anon_inode_getfile(const char *name, |
86 | const struct file_operations *fops, | |
87 | void *priv, int flags) | |
5dc8bf81 DL |
88 | { |
89 | struct qstr this; | |
2c48b9c4 | 90 | struct path path; |
5dc8bf81 | 91 | struct file *file; |
562787a5 | 92 | int error; |
5dc8bf81 DL |
93 | |
94 | if (IS_ERR(anon_inode_inode)) | |
562787a5 | 95 | return ERR_PTR(-ENODEV); |
5dc8bf81 | 96 | |
e3a2a0d4 | 97 | if (fops->owner && !try_module_get(fops->owner)) |
562787a5 | 98 | return ERR_PTR(-ENOENT); |
5dc8bf81 DL |
99 | |
100 | /* | |
101 | * Link the inode to a directory entry by creating a unique name | |
102 | * using the inode sequence number. | |
103 | */ | |
104 | error = -ENOMEM; | |
105 | this.name = name; | |
106 | this.len = strlen(name); | |
107 | this.hash = 0; | |
2c48b9c4 AV |
108 | path.dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this); |
109 | if (!path.dentry) | |
562787a5 | 110 | goto err_module; |
96fdc72d | 111 | |
2c48b9c4 | 112 | path.mnt = mntget(anon_inode_mnt); |
96fdc72d DL |
113 | /* |
114 | * We know the anon_inode inode count is always greater than zero, | |
115 | * so we can avoid doing an igrab() and we can use an open-coded | |
116 | * atomic_inc(). | |
117 | */ | |
118 | atomic_inc(&anon_inode_inode->i_count); | |
119 | ||
2c48b9c4 | 120 | path.dentry->d_op = &anon_inodefs_dentry_operations; |
2c48b9c4 | 121 | d_instantiate(path.dentry, anon_inode_inode); |
5dc8bf81 | 122 | |
430e285e | 123 | error = -ENFILE; |
2c48b9c4 | 124 | file = alloc_file(&path, FMODE_READ | FMODE_WRITE, fops); |
430e285e DH |
125 | if (!file) |
126 | goto err_dput; | |
96fdc72d | 127 | file->f_mapping = anon_inode_inode->i_mapping; |
5dc8bf81 DL |
128 | |
129 | file->f_pos = 0; | |
99829b83 | 130 | file->f_flags = O_RDWR | (flags & O_NONBLOCK); |
5dc8bf81 DL |
131 | file->f_version = 0; |
132 | file->private_data = priv; | |
133 | ||
562787a5 DL |
134 | return file; |
135 | ||
136 | err_dput: | |
2c48b9c4 | 137 | path_put(&path); |
562787a5 DL |
138 | err_module: |
139 | module_put(fops->owner); | |
140 | return ERR_PTR(error); | |
141 | } | |
142 | EXPORT_SYMBOL_GPL(anon_inode_getfile); | |
143 | ||
144 | /** | |
145 | * anon_inode_getfd - creates a new file instance by hooking it up to an | |
146 | * anonymous inode, and a dentry that describe the "class" | |
147 | * of the file | |
148 | * | |
149 | * @name: [in] name of the "class" of the new file | |
150 | * @fops: [in] file operations for the new file | |
151 | * @priv: [in] private data for the new file (will be file's private_data) | |
152 | * @flags: [in] flags | |
153 | * | |
154 | * Creates a new file by hooking it on a single inode. This is useful for files | |
155 | * that do not need to have a full-fledged inode in order to operate correctly. | |
156 | * All the files created with anon_inode_getfd() will share a single inode, | |
157 | * hence saving memory and avoiding code duplication for the file/inode/dentry | |
158 | * setup. Returns new descriptor or an error code. | |
159 | */ | |
160 | int anon_inode_getfd(const char *name, const struct file_operations *fops, | |
161 | void *priv, int flags) | |
162 | { | |
163 | int error, fd; | |
164 | struct file *file; | |
165 | ||
166 | error = get_unused_fd_flags(flags); | |
167 | if (error < 0) | |
168 | return error; | |
169 | fd = error; | |
170 | ||
171 | file = anon_inode_getfile(name, fops, priv, flags); | |
172 | if (IS_ERR(file)) { | |
173 | error = PTR_ERR(file); | |
174 | goto err_put_unused_fd; | |
175 | } | |
5dc8bf81 DL |
176 | fd_install(fd, file); |
177 | ||
2030a42c | 178 | return fd; |
5dc8bf81 DL |
179 | |
180 | err_put_unused_fd: | |
181 | put_unused_fd(fd); | |
5dc8bf81 DL |
182 | return error; |
183 | } | |
d6d28168 | 184 | EXPORT_SYMBOL_GPL(anon_inode_getfd); |
5dc8bf81 DL |
185 | |
186 | /* | |
4b4e5a14 BF |
187 | * A single inode exists for all anon_inode files. Contrary to pipes, |
188 | * anon_inode inodes have no associated per-instance data, so we need | |
189 | * only allocate one of them. | |
5dc8bf81 DL |
190 | */ |
191 | static struct inode *anon_inode_mkinode(void) | |
192 | { | |
193 | struct inode *inode = new_inode(anon_inode_mnt->mnt_sb); | |
194 | ||
195 | if (!inode) | |
196 | return ERR_PTR(-ENOMEM); | |
197 | ||
198 | inode->i_fop = &anon_inode_fops; | |
199 | ||
d3a9262e PZ |
200 | inode->i_mapping->a_ops = &anon_aops; |
201 | ||
5dc8bf81 DL |
202 | /* |
203 | * Mark the inode dirty from the very beginning, | |
204 | * that way it will never be moved to the dirty | |
205 | * list because mark_inode_dirty() will think | |
206 | * that it already _is_ on the dirty list. | |
207 | */ | |
208 | inode->i_state = I_DIRTY; | |
209 | inode->i_mode = S_IRUSR | S_IWUSR; | |
da9592ed DH |
210 | inode->i_uid = current_fsuid(); |
211 | inode->i_gid = current_fsgid(); | |
5dc8bf81 DL |
212 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
213 | return inode; | |
214 | } | |
215 | ||
216 | static int __init anon_inode_init(void) | |
217 | { | |
218 | int error; | |
219 | ||
220 | error = register_filesystem(&anon_inode_fs_type); | |
221 | if (error) | |
222 | goto err_exit; | |
223 | anon_inode_mnt = kern_mount(&anon_inode_fs_type); | |
224 | if (IS_ERR(anon_inode_mnt)) { | |
225 | error = PTR_ERR(anon_inode_mnt); | |
226 | goto err_unregister_filesystem; | |
227 | } | |
228 | anon_inode_inode = anon_inode_mkinode(); | |
229 | if (IS_ERR(anon_inode_inode)) { | |
230 | error = PTR_ERR(anon_inode_inode); | |
231 | goto err_mntput; | |
232 | } | |
233 | ||
234 | return 0; | |
235 | ||
236 | err_mntput: | |
237 | mntput(anon_inode_mnt); | |
238 | err_unregister_filesystem: | |
239 | unregister_filesystem(&anon_inode_fs_type); | |
240 | err_exit: | |
241 | panic(KERN_ERR "anon_inode_init() failed (%d)\n", error); | |
242 | } | |
243 | ||
244 | fs_initcall(anon_inode_init); | |
245 |