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.
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>
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",
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)
45 root = mount_pseudo(fs_type, "anon_inode:", NULL,
46 &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
48 struct super_block *s = root->d_sb;
49 anon_inode_inode = alloc_anon_inode(s);
50 if (IS_ERR(anon_inode_inode)) {
52 deactivate_locked_super(s);
53 root = ERR_CAST(anon_inode_inode);
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,
66 * anon_inode_getfile_private - creates a new file instance by hooking it up to an
67 * anonymous inode, and a dentry that describe the "class"
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)
76 * Similar to anon_inode_getfile, but each file holds a single inode.
79 struct file *anon_inode_getfile_private(const char *name,
80 const struct file_operations *fops,
81 void *priv, int flags)
88 if (fops->owner && !try_module_get(fops->owner))
89 return ERR_PTR(-ENOENT);
91 inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
93 file = ERR_PTR(-ENOMEM);
98 * Link the inode to a directory entry by creating a unique name
99 * using the inode sequence number.
101 file = ERR_PTR(-ENOMEM);
103 this.len = strlen(name);
105 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
109 path.mnt = mntget(anon_inode_mnt);
111 d_instantiate(path.dentry, inode);
113 file = alloc_file(&path, OPEN_FMODE(flags), fops);
117 file->f_mapping = inode->i_mapping;
118 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
119 file->private_data = priv;
126 module_put(fops->owner);
129 EXPORT_SYMBOL_GPL(anon_inode_getfile_private);
132 * anon_inode_getfile - creates a new file instance by hooking it up to an
133 * anonymous inode, and a dentry that describe the "class"
136 * @name: [in] name of the "class" of the new file
137 * @fops: [in] file operations for the new file
138 * @priv: [in] private data for the new file (will be file's private_data)
141 * Creates a new file by hooking it on a single inode. This is useful for files
142 * that do not need to have a full-fledged inode in order to operate correctly.
143 * All the files created with anon_inode_getfile() will share a single inode,
144 * hence saving memory and avoiding code duplication for the file/inode/dentry
145 * setup. Returns the newly created file* or an error pointer.
147 struct file *anon_inode_getfile(const char *name,
148 const struct file_operations *fops,
149 void *priv, int flags)
155 if (IS_ERR(anon_inode_inode))
156 return ERR_PTR(-ENODEV);
158 if (fops->owner && !try_module_get(fops->owner))
159 return ERR_PTR(-ENOENT);
162 * Link the inode to a directory entry by creating a unique name
163 * using the inode sequence number.
165 file = ERR_PTR(-ENOMEM);
167 this.len = strlen(name);
169 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
173 path.mnt = mntget(anon_inode_mnt);
175 * We know the anon_inode inode count is always greater than zero,
176 * so ihold() is safe.
178 ihold(anon_inode_inode);
180 d_instantiate(path.dentry, anon_inode_inode);
182 file = alloc_file(&path, OPEN_FMODE(flags), fops);
185 file->f_mapping = anon_inode_inode->i_mapping;
187 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
188 file->private_data = priv;
195 module_put(fops->owner);
198 EXPORT_SYMBOL_GPL(anon_inode_getfile);
201 * anon_inode_getfd - creates a new file instance by hooking it up to an
202 * anonymous inode, and a dentry that describe the "class"
205 * @name: [in] name of the "class" of the new file
206 * @fops: [in] file operations for the new file
207 * @priv: [in] private data for the new file (will be file's private_data)
210 * Creates a new file by hooking it on a single inode. This is useful for files
211 * that do not need to have a full-fledged inode in order to operate correctly.
212 * All the files created with anon_inode_getfd() will share a single inode,
213 * hence saving memory and avoiding code duplication for the file/inode/dentry
214 * setup. Returns new descriptor or an error code.
216 int anon_inode_getfd(const char *name, const struct file_operations *fops,
217 void *priv, int flags)
222 error = get_unused_fd_flags(flags);
227 file = anon_inode_getfile(name, fops, priv, flags);
229 error = PTR_ERR(file);
230 goto err_put_unused_fd;
232 fd_install(fd, file);
240 EXPORT_SYMBOL_GPL(anon_inode_getfd);
242 static int __init anon_inode_init(void)
246 error = register_filesystem(&anon_inode_fs_type);
249 anon_inode_mnt = kern_mount(&anon_inode_fs_type);
250 if (IS_ERR(anon_inode_mnt)) {
251 error = PTR_ERR(anon_inode_mnt);
252 goto err_unregister_filesystem;
256 err_unregister_filesystem:
257 unregister_filesystem(&anon_inode_fs_type);
259 panic(KERN_ERR "anon_inode_init() failed (%d)\n", error);
262 fs_initcall(anon_inode_init);