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 | ||
7c0f6ba6 | 23 | #include <linux/uaccess.h> |
5dc8bf81 DL |
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 | { | |
75c5a52d | 44 | return mount_pseudo(fs_type, "anon_inode:", NULL, |
ca7068c4 | 45 | &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC); |
ca7068c4 AV |
46 | } |
47 | ||
48 | static struct file_system_type anon_inode_fs_type = { | |
49 | .name = "anon_inodefs", | |
50 | .mount = anon_inodefs_mount, | |
51 | .kill_sb = kill_anon_super, | |
52 | }; | |
53 | ||
5dc8bf81 | 54 | /** |
c0d8768a NK |
55 | * anon_inode_getfile - creates a new file instance by hooking it up to an |
56 | * anonymous inode, and a dentry that describe the "class" | |
57 | * of the file | |
5dc8bf81 | 58 | * |
5dc8bf81 | 59 | * @name: [in] name of the "class" of the new file |
7d9dbca3 UD |
60 | * @fops: [in] file operations for the new file |
61 | * @priv: [in] private data for the new file (will be file's private_data) | |
62 | * @flags: [in] flags | |
5dc8bf81 DL |
63 | * |
64 | * Creates a new file by hooking it on a single inode. This is useful for files | |
65 | * that do not need to have a full-fledged inode in order to operate correctly. | |
562787a5 | 66 | * All the files created with anon_inode_getfile() will share a single inode, |
5dc8bf81 | 67 | * hence saving memory and avoiding code duplication for the file/inode/dentry |
562787a5 | 68 | * setup. Returns the newly created file* or an error pointer. |
5dc8bf81 | 69 | */ |
562787a5 DL |
70 | struct file *anon_inode_getfile(const char *name, |
71 | const struct file_operations *fops, | |
72 | void *priv, int flags) | |
5dc8bf81 DL |
73 | { |
74 | struct qstr this; | |
2c48b9c4 | 75 | struct path path; |
5dc8bf81 | 76 | struct file *file; |
5dc8bf81 DL |
77 | |
78 | if (IS_ERR(anon_inode_inode)) | |
562787a5 | 79 | return ERR_PTR(-ENODEV); |
5dc8bf81 | 80 | |
e3a2a0d4 | 81 | if (fops->owner && !try_module_get(fops->owner)) |
562787a5 | 82 | return ERR_PTR(-ENOENT); |
5dc8bf81 DL |
83 | |
84 | /* | |
85 | * Link the inode to a directory entry by creating a unique name | |
86 | * using the inode sequence number. | |
87 | */ | |
39b65252 | 88 | file = ERR_PTR(-ENOMEM); |
5dc8bf81 DL |
89 | this.name = name; |
90 | this.len = strlen(name); | |
91 | this.hash = 0; | |
4b936885 | 92 | path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this); |
2c48b9c4 | 93 | if (!path.dentry) |
562787a5 | 94 | goto err_module; |
96fdc72d | 95 | |
2c48b9c4 | 96 | path.mnt = mntget(anon_inode_mnt); |
96fdc72d DL |
97 | /* |
98 | * We know the anon_inode inode count is always greater than zero, | |
7de9c6ee | 99 | * so ihold() is safe. |
96fdc72d | 100 | */ |
7de9c6ee | 101 | ihold(anon_inode_inode); |
96fdc72d | 102 | |
2c48b9c4 | 103 | d_instantiate(path.dentry, anon_inode_inode); |
5dc8bf81 | 104 | |
c9c554f2 | 105 | file = alloc_file(&path, flags & (O_ACCMODE | O_NONBLOCK), fops); |
39b65252 | 106 | if (IS_ERR(file)) |
430e285e | 107 | goto err_dput; |
96fdc72d | 108 | file->f_mapping = anon_inode_inode->i_mapping; |
5dc8bf81 | 109 | |
5dc8bf81 DL |
110 | file->private_data = priv; |
111 | ||
562787a5 DL |
112 | return file; |
113 | ||
114 | err_dput: | |
2c48b9c4 | 115 | path_put(&path); |
562787a5 DL |
116 | err_module: |
117 | module_put(fops->owner); | |
39b65252 | 118 | return file; |
562787a5 DL |
119 | } |
120 | EXPORT_SYMBOL_GPL(anon_inode_getfile); | |
121 | ||
122 | /** | |
123 | * anon_inode_getfd - creates a new file instance by hooking it up to an | |
124 | * anonymous inode, and a dentry that describe the "class" | |
125 | * of the file | |
126 | * | |
127 | * @name: [in] name of the "class" of the new file | |
128 | * @fops: [in] file operations for the new file | |
129 | * @priv: [in] private data for the new file (will be file's private_data) | |
130 | * @flags: [in] flags | |
131 | * | |
132 | * Creates a new file by hooking it on a single inode. This is useful for files | |
133 | * that do not need to have a full-fledged inode in order to operate correctly. | |
134 | * All the files created with anon_inode_getfd() will share a single inode, | |
135 | * hence saving memory and avoiding code duplication for the file/inode/dentry | |
136 | * setup. Returns new descriptor or an error code. | |
137 | */ | |
138 | int anon_inode_getfd(const char *name, const struct file_operations *fops, | |
139 | void *priv, int flags) | |
140 | { | |
141 | int error, fd; | |
142 | struct file *file; | |
143 | ||
144 | error = get_unused_fd_flags(flags); | |
145 | if (error < 0) | |
146 | return error; | |
147 | fd = error; | |
148 | ||
149 | file = anon_inode_getfile(name, fops, priv, flags); | |
150 | if (IS_ERR(file)) { | |
151 | error = PTR_ERR(file); | |
152 | goto err_put_unused_fd; | |
153 | } | |
5dc8bf81 DL |
154 | fd_install(fd, file); |
155 | ||
2030a42c | 156 | return fd; |
5dc8bf81 DL |
157 | |
158 | err_put_unused_fd: | |
159 | put_unused_fd(fd); | |
5dc8bf81 DL |
160 | return error; |
161 | } | |
d6d28168 | 162 | EXPORT_SYMBOL_GPL(anon_inode_getfd); |
5dc8bf81 | 163 | |
5dc8bf81 DL |
164 | static int __init anon_inode_init(void) |
165 | { | |
5dc8bf81 | 166 | anon_inode_mnt = kern_mount(&anon_inode_fs_type); |
75c5a52d JK |
167 | if (IS_ERR(anon_inode_mnt)) |
168 | panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt)); | |
5dc8bf81 | 169 | |
75c5a52d JK |
170 | anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb); |
171 | if (IS_ERR(anon_inode_inode)) | |
172 | panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode)); | |
173 | ||
174 | return 0; | |
5dc8bf81 DL |
175 | } |
176 | ||
177 | fs_initcall(anon_inode_init); | |
178 |