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Davide Libenzi5dc8bf82007-05-10 22:23:11 -07001/*
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
Alexey Dobriyana99bbaf2009-10-04 16:11:37 +040011#include <linux/cred.h>
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070012#include <linux/file.h>
13#include <linux/poll.h>
Alexey Dobriyana99bbaf2009-10-04 16:11:37 +040014#include <linux/sched.h>
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070015#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
Linus Torvalds7c0f6ba2016-12-24 11:46:01 -080023#include <linux/uaccess.h>
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070024
25static struct vfsmount *anon_inode_mnt __read_mostly;
26static struct inode *anon_inode_inode;
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070027
Nick Pigginb9aff022009-11-20 14:28:35 -080028/*
29 * anon_inodefs_dname() is called from d_path().
30 */
31static 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
Al Viroc74a1cb2011-01-12 16:59:34 -050037static const struct dentry_operations anon_inodefs_dentry_operations = {
38 .d_dname = anon_inodefs_dname,
39};
40
Al Viroca7068c2012-03-17 02:52:29 -040041static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
42 int flags, const char *dev_name, void *data)
43{
Jan Kara75c5a522014-03-26 06:20:14 +010044 return mount_pseudo(fs_type, "anon_inode:", NULL,
Al Viroca7068c2012-03-17 02:52:29 -040045 &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
Al Viroca7068c2012-03-17 02:52:29 -040046}
47
48static 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
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070054/**
Namhyung Kimc0d87682010-12-10 12:11:50 +090055 * 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
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070058 *
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070059 * @name: [in] name of the "class" of the new file
Ulrich Drepper7d9dbca2008-07-23 21:29:22 -070060 * @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
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070063 *
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.
Davide Libenzi562787a2009-09-22 16:43:57 -070066 * All the files created with anon_inode_getfile() will share a single inode,
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070067 * hence saving memory and avoiding code duplication for the file/inode/dentry
Davide Libenzi562787a2009-09-22 16:43:57 -070068 * setup. Returns the newly created file* or an error pointer.
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070069 */
Davide Libenzi562787a2009-09-22 16:43:57 -070070struct file *anon_inode_getfile(const char *name,
71 const struct file_operations *fops,
72 void *priv, int flags)
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070073{
74 struct qstr this;
Al Viro2c48b9c2009-08-09 00:52:35 +040075 struct path path;
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070076 struct file *file;
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070077
78 if (IS_ERR(anon_inode_inode))
Davide Libenzi562787a2009-09-22 16:43:57 -070079 return ERR_PTR(-ENODEV);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070080
Christian Borntraegere3a2a0d2008-12-02 11:16:03 +010081 if (fops->owner && !try_module_get(fops->owner))
Davide Libenzi562787a2009-09-22 16:43:57 -070082 return ERR_PTR(-ENOENT);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070083
84 /*
85 * Link the inode to a directory entry by creating a unique name
86 * using the inode sequence number.
87 */
Anatol Pomozov39b65252012-09-12 20:11:55 -070088 file = ERR_PTR(-ENOMEM);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -070089 this.name = name;
90 this.len = strlen(name);
91 this.hash = 0;
Nick Piggin4b936882011-01-07 17:50:07 +110092 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
Al Viro2c48b9c2009-08-09 00:52:35 +040093 if (!path.dentry)
Davide Libenzi562787a2009-09-22 16:43:57 -070094 goto err_module;
Davide Libenzi96fdc722007-10-16 23:30:19 -070095
Al Viro2c48b9c2009-08-09 00:52:35 +040096 path.mnt = mntget(anon_inode_mnt);
Davide Libenzi96fdc722007-10-16 23:30:19 -070097 /*
98 * We know the anon_inode inode count is always greater than zero,
Al Viro7de9c6ee2010-10-23 11:11:40 -040099 * so ihold() is safe.
Davide Libenzi96fdc722007-10-16 23:30:19 -0700100 */
Al Viro7de9c6ee2010-10-23 11:11:40 -0400101 ihold(anon_inode_inode);
Davide Libenzi96fdc722007-10-16 23:30:19 -0700102
Al Viro2c48b9c2009-08-09 00:52:35 +0400103 d_instantiate(path.dentry, anon_inode_inode);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700104
Al Viro53009902009-12-19 10:15:07 -0500105 file = alloc_file(&path, OPEN_FMODE(flags), fops);
Anatol Pomozov39b65252012-09-12 20:11:55 -0700106 if (IS_ERR(file))
Dave Hansen430e2852008-02-15 14:37:26 -0800107 goto err_dput;
Davide Libenzi96fdc722007-10-16 23:30:19 -0700108 file->f_mapping = anon_inode_inode->i_mapping;
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700109
Roland Dreier628ff7c2009-12-18 09:41:24 -0800110 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700111 file->private_data = priv;
112
Davide Libenzi562787a2009-09-22 16:43:57 -0700113 return file;
114
115err_dput:
Al Viro2c48b9c2009-08-09 00:52:35 +0400116 path_put(&path);
Davide Libenzi562787a2009-09-22 16:43:57 -0700117err_module:
118 module_put(fops->owner);
Anatol Pomozov39b65252012-09-12 20:11:55 -0700119 return file;
Davide Libenzi562787a2009-09-22 16:43:57 -0700120}
121EXPORT_SYMBOL_GPL(anon_inode_getfile);
122
123/**
124 * anon_inode_getfd - creates a new file instance by hooking it up to an
125 * anonymous inode, and a dentry that describe the "class"
126 * of the file
127 *
128 * @name: [in] name of the "class" of the new file
129 * @fops: [in] file operations for the new file
130 * @priv: [in] private data for the new file (will be file's private_data)
131 * @flags: [in] flags
132 *
133 * Creates a new file by hooking it on a single inode. This is useful for files
134 * that do not need to have a full-fledged inode in order to operate correctly.
135 * All the files created with anon_inode_getfd() will share a single inode,
136 * hence saving memory and avoiding code duplication for the file/inode/dentry
137 * setup. Returns new descriptor or an error code.
138 */
139int anon_inode_getfd(const char *name, const struct file_operations *fops,
140 void *priv, int flags)
141{
142 int error, fd;
143 struct file *file;
144
145 error = get_unused_fd_flags(flags);
146 if (error < 0)
147 return error;
148 fd = error;
149
150 file = anon_inode_getfile(name, fops, priv, flags);
151 if (IS_ERR(file)) {
152 error = PTR_ERR(file);
153 goto err_put_unused_fd;
154 }
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700155 fd_install(fd, file);
156
Al Viro2030a422008-02-23 06:46:49 -0500157 return fd;
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700158
159err_put_unused_fd:
160 put_unused_fd(fd);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700161 return error;
162}
Avi Kivityd6d28162007-06-28 08:38:16 -0400163EXPORT_SYMBOL_GPL(anon_inode_getfd);
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700164
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700165static int __init anon_inode_init(void)
166{
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700167 anon_inode_mnt = kern_mount(&anon_inode_fs_type);
Jan Kara75c5a522014-03-26 06:20:14 +0100168 if (IS_ERR(anon_inode_mnt))
169 panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt));
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700170
Jan Kara75c5a522014-03-26 06:20:14 +0100171 anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
172 if (IS_ERR(anon_inode_inode))
173 panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode));
174
175 return 0;
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700176}
177
178fs_initcall(anon_inode_init);
179