Commit | Line | Data |
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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
5dc8bf81 DL |
2 | /* |
3 | * fs/anon_inodes.c | |
4 | * | |
5 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
6 | * | |
7 | * Thanks to Arnd Bergmann for code review and suggestions. | |
8 | * More changes for Thomas Gleixner suggestions. | |
9 | * | |
10 | */ | |
11 | ||
a99bbaf5 | 12 | #include <linux/cred.h> |
5dc8bf81 DL |
13 | #include <linux/file.h> |
14 | #include <linux/poll.h> | |
a99bbaf5 | 15 | #include <linux/sched.h> |
5dc8bf81 DL |
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 | ||
7c0f6ba6 | 24 | #include <linux/uaccess.h> |
5dc8bf81 DL |
25 | |
26 | static struct vfsmount *anon_inode_mnt __read_mostly; | |
27 | static struct inode *anon_inode_inode; | |
5dc8bf81 | 28 | |
b9aff027 NP |
29 | /* |
30 | * anon_inodefs_dname() is called from d_path(). | |
31 | */ | |
32 | static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen) | |
33 | { | |
34 | return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s", | |
35 | dentry->d_name.name); | |
36 | } | |
37 | ||
c74a1cbb AV |
38 | static const struct dentry_operations anon_inodefs_dentry_operations = { |
39 | .d_dname = anon_inodefs_dname, | |
40 | }; | |
41 | ||
ca7068c4 AV |
42 | static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type, |
43 | int flags, const char *dev_name, void *data) | |
44 | { | |
75c5a52d | 45 | return mount_pseudo(fs_type, "anon_inode:", NULL, |
ca7068c4 | 46 | &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC); |
ca7068c4 AV |
47 | } |
48 | ||
49 | static struct file_system_type anon_inode_fs_type = { | |
50 | .name = "anon_inodefs", | |
51 | .mount = anon_inodefs_mount, | |
52 | .kill_sb = kill_anon_super, | |
53 | }; | |
54 | ||
5dc8bf81 | 55 | /** |
c0d8768a NK |
56 | * anon_inode_getfile - creates a new file instance by hooking it up to an |
57 | * anonymous inode, and a dentry that describe the "class" | |
58 | * of the file | |
5dc8bf81 | 59 | * |
5dc8bf81 | 60 | * @name: [in] name of the "class" of the new file |
7d9dbca3 UD |
61 | * @fops: [in] file operations for the new file |
62 | * @priv: [in] private data for the new file (will be file's private_data) | |
63 | * @flags: [in] flags | |
5dc8bf81 DL |
64 | * |
65 | * Creates a new file by hooking it on a single inode. This is useful for files | |
66 | * that do not need to have a full-fledged inode in order to operate correctly. | |
562787a5 | 67 | * All the files created with anon_inode_getfile() will share a single inode, |
5dc8bf81 | 68 | * hence saving memory and avoiding code duplication for the file/inode/dentry |
562787a5 | 69 | * setup. Returns the newly created file* or an error pointer. |
5dc8bf81 | 70 | */ |
562787a5 DL |
71 | struct file *anon_inode_getfile(const char *name, |
72 | const struct file_operations *fops, | |
73 | void *priv, int flags) | |
5dc8bf81 | 74 | { |
5dc8bf81 | 75 | struct file *file; |
5dc8bf81 DL |
76 | |
77 | if (IS_ERR(anon_inode_inode)) | |
562787a5 | 78 | return ERR_PTR(-ENODEV); |
5dc8bf81 | 79 | |
e3a2a0d4 | 80 | if (fops->owner && !try_module_get(fops->owner)) |
562787a5 | 81 | return ERR_PTR(-ENOENT); |
5dc8bf81 | 82 | |
96fdc72d DL |
83 | /* |
84 | * We know the anon_inode inode count is always greater than zero, | |
7de9c6ee | 85 | * so ihold() is safe. |
96fdc72d | 86 | */ |
7de9c6ee | 87 | ihold(anon_inode_inode); |
52c91f8b AV |
88 | file = alloc_file_pseudo(anon_inode_inode, anon_inode_mnt, name, |
89 | flags & (O_ACCMODE | O_NONBLOCK), fops); | |
39b65252 | 90 | if (IS_ERR(file)) |
52c91f8b AV |
91 | goto err; |
92 | ||
96fdc72d | 93 | file->f_mapping = anon_inode_inode->i_mapping; |
5dc8bf81 | 94 | |
5dc8bf81 DL |
95 | file->private_data = priv; |
96 | ||
562787a5 DL |
97 | return file; |
98 | ||
52c91f8b AV |
99 | err: |
100 | iput(anon_inode_inode); | |
562787a5 | 101 | module_put(fops->owner); |
39b65252 | 102 | return file; |
562787a5 DL |
103 | } |
104 | EXPORT_SYMBOL_GPL(anon_inode_getfile); | |
105 | ||
106 | /** | |
107 | * anon_inode_getfd - creates a new file instance by hooking it up to an | |
108 | * anonymous inode, and a dentry that describe the "class" | |
109 | * of the file | |
110 | * | |
111 | * @name: [in] name of the "class" of the new file | |
112 | * @fops: [in] file operations for the new file | |
113 | * @priv: [in] private data for the new file (will be file's private_data) | |
114 | * @flags: [in] flags | |
115 | * | |
116 | * Creates a new file by hooking it on a single inode. This is useful for files | |
117 | * that do not need to have a full-fledged inode in order to operate correctly. | |
118 | * All the files created with anon_inode_getfd() will share a single inode, | |
119 | * hence saving memory and avoiding code duplication for the file/inode/dentry | |
120 | * setup. Returns new descriptor or an error code. | |
121 | */ | |
122 | int anon_inode_getfd(const char *name, const struct file_operations *fops, | |
123 | void *priv, int flags) | |
124 | { | |
125 | int error, fd; | |
126 | struct file *file; | |
127 | ||
128 | error = get_unused_fd_flags(flags); | |
129 | if (error < 0) | |
130 | return error; | |
131 | fd = error; | |
132 | ||
133 | file = anon_inode_getfile(name, fops, priv, flags); | |
134 | if (IS_ERR(file)) { | |
135 | error = PTR_ERR(file); | |
136 | goto err_put_unused_fd; | |
137 | } | |
5dc8bf81 DL |
138 | fd_install(fd, file); |
139 | ||
2030a42c | 140 | return fd; |
5dc8bf81 DL |
141 | |
142 | err_put_unused_fd: | |
143 | put_unused_fd(fd); | |
5dc8bf81 DL |
144 | return error; |
145 | } | |
d6d28168 | 146 | EXPORT_SYMBOL_GPL(anon_inode_getfd); |
5dc8bf81 | 147 | |
5dc8bf81 DL |
148 | static int __init anon_inode_init(void) |
149 | { | |
5dc8bf81 | 150 | anon_inode_mnt = kern_mount(&anon_inode_fs_type); |
75c5a52d JK |
151 | if (IS_ERR(anon_inode_mnt)) |
152 | panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt)); | |
5dc8bf81 | 153 | |
75c5a52d JK |
154 | anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb); |
155 | if (IS_ERR(anon_inode_inode)) | |
156 | panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode)); | |
157 | ||
158 | return 0; | |
5dc8bf81 DL |
159 | } |
160 | ||
161 | fs_initcall(anon_inode_init); | |
162 |