Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm...
[linux-2.6.git] / fs / anon_inodes.c
blob24084732b1d0b264b5c3262796f1ec3dd5fc505f
1 /*
2 * fs/anon_inodes.c
4 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 * Thanks to Arnd Bergmann for code review and suggestions.
7 * More changes for Thomas Gleixner suggestions.
9 */
11 #include <linux/cred.h>
12 #include <linux/file.h>
13 #include <linux/poll.h>
14 #include <linux/sched.h>
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>
23 #include <asm/uaccess.h>
25 static struct vfsmount *anon_inode_mnt __read_mostly;
26 static struct inode *anon_inode_inode;
29 * anon_inodefs_dname() is called from d_path().
31 static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
33 return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
34 dentry->d_name.name);
37 static const struct dentry_operations anon_inodefs_dentry_operations = {
38 .d_dname = anon_inodefs_dname,
41 static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
42 int flags, const char *dev_name, void *data)
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;
49 anon_inode_inode = alloc_anon_inode(s);
50 if (IS_ERR(anon_inode_inode)) {
51 dput(root);
52 deactivate_locked_super(s);
53 root = ERR_CAST(anon_inode_inode);
56 return root;
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,
65 /**
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
70 * @name: [in] name of the "class" of the new file
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
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.
77 * All the files created with anon_inode_getfile() will share a single inode,
78 * hence saving memory and avoiding code duplication for the file/inode/dentry
79 * setup. Returns the newly created file* or an error pointer.
81 struct file *anon_inode_getfile(const char *name,
82 const struct file_operations *fops,
83 void *priv, int flags)
85 struct qstr this;
86 struct path path;
87 struct file *file;
89 if (IS_ERR(anon_inode_inode))
90 return ERR_PTR(-ENODEV);
92 if (fops->owner && !try_module_get(fops->owner))
93 return ERR_PTR(-ENOENT);
96 * Link the inode to a directory entry by creating a unique name
97 * using the inode sequence number.
99 file = ERR_PTR(-ENOMEM);
100 this.name = name;
101 this.len = strlen(name);
102 this.hash = 0;
103 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
104 if (!path.dentry)
105 goto err_module;
107 path.mnt = mntget(anon_inode_mnt);
109 * We know the anon_inode inode count is always greater than zero,
110 * so ihold() is safe.
112 ihold(anon_inode_inode);
114 d_instantiate(path.dentry, anon_inode_inode);
116 file = alloc_file(&path, OPEN_FMODE(flags), fops);
117 if (IS_ERR(file))
118 goto err_dput;
119 file->f_mapping = anon_inode_inode->i_mapping;
121 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
122 file->private_data = priv;
124 return file;
126 err_dput:
127 path_put(&path);
128 err_module:
129 module_put(fops->owner);
130 return file;
132 EXPORT_SYMBOL_GPL(anon_inode_getfile);
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
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
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.
150 int anon_inode_getfd(const char *name, const struct file_operations *fops,
151 void *priv, int flags)
153 int error, fd;
154 struct file *file;
156 error = get_unused_fd_flags(flags);
157 if (error < 0)
158 return error;
159 fd = error;
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;
166 fd_install(fd, file);
168 return fd;
170 err_put_unused_fd:
171 put_unused_fd(fd);
172 return error;
174 EXPORT_SYMBOL_GPL(anon_inode_getfd);
176 static int __init anon_inode_init(void)
178 int error;
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;
188 return 0;
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);
196 fs_initcall(anon_inode_init);