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)
44 return mount_pseudo(fs_type, "anon_inode:", NULL,
45 &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
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,
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"
59 * @name: [in] name of the "class" of the new file
60 * @fops: [in] file operations for the new file
61 * @priv: [in] private data for the new file (will be file's private_data)
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.
66 * All the files created with anon_inode_getfile() will share a single inode,
67 * hence saving memory and avoiding code duplication for the file/inode/dentry
68 * setup. Returns the newly created file* or an error pointer.
70 struct file *anon_inode_getfile(const char *name,
71 const struct file_operations *fops,
72 void *priv, int flags)
78 if (IS_ERR(anon_inode_inode))
79 return ERR_PTR(-ENODEV);
81 if (fops->owner && !try_module_get(fops->owner))
82 return ERR_PTR(-ENOENT);
85 * Link the inode to a directory entry by creating a unique name
86 * using the inode sequence number.
88 file = ERR_PTR(-ENOMEM);
90 this.len = strlen(name);
92 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
96 path.mnt = mntget(anon_inode_mnt);
98 * We know the anon_inode inode count is always greater than zero,
101 ihold(anon_inode_inode);
103 d_instantiate(path.dentry, anon_inode_inode);
105 file = alloc_file(&path, OPEN_FMODE(flags), fops);
108 file->f_mapping = anon_inode_inode->i_mapping;
110 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
111 file->private_data = priv;
118 module_put(fops->owner);
121 EXPORT_SYMBOL_GPL(anon_inode_getfile);
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"
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)
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.
139 int anon_inode_getfd(const char *name, const struct file_operations *fops,
140 void *priv, int flags)
145 error = get_unused_fd_flags(flags);
150 file = anon_inode_getfile(name, fops, priv, flags);
152 error = PTR_ERR(file);
153 goto err_put_unused_fd;
155 fd_install(fd, file);
163 EXPORT_SYMBOL_GPL(anon_inode_getfd);
165 static int __init anon_inode_init(void)
167 anon_inode_mnt = kern_mount(&anon_inode_fs_type);
168 if (IS_ERR(anon_inode_mnt))
169 panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt));
171 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));
178 fs_initcall(anon_inode_init);