1 files changed, 179 insertions, 0 deletions
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
new file mode 100644
index 000000000..80ef38c73
--- /dev/null
+++ b/fs/anon_inodes.c
@@ -0,0 +1,179 @@
+/*
+ *  fs/anon_inodes.c
+ *
+ *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
+ *
+ *  Thanks to Arnd Bergmann for code review and suggestions.
+ *  More changes for Thomas Gleixner suggestions.
+ *
+ */
+
+#include <linux/cred.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/magic.h>
+#include <linux/anon_inodes.h>
+
+#include <asm/uaccess.h>
+
+static struct vfsmount *anon_inode_mnt __read_mostly;
+static struct inode *anon_inode_inode;
+
+/*
+ * anon_inodefs_dname() is called from d_path().
+ */
+static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+	return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
+				dentry->d_name.name);
+}
+
+static const struct dentry_operations anon_inodefs_dentry_operations = {
+	.d_dname	= anon_inodefs_dname,
+};
+
+static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
+				int flags, const char *dev_name, void *data)
+{
+	return mount_pseudo(fs_type, "anon_inode:", NULL,
+			&anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
+}
+
+static struct file_system_type anon_inode_fs_type = {
+	.name		= "anon_inodefs",
+	.mount		= anon_inodefs_mount,
+	.kill_sb	= kill_anon_super,
+};
+
+/**
+ * anon_inode_getfile - creates a new file instance by hooking it up to an
+ *                      anonymous inode, and a dentry that describe the "class"
+ *                      of the file
+ *
+ * @name:    [in]    name of the "class" of the new file
+ * @fops:    [in]    file operations for the new file
+ * @priv:    [in]    private data for the new file (will be file's private_data)
+ * @flags:   [in]    flags
+ *
+ * Creates a new file by hooking it on a single inode. This is useful for files
+ * that do not need to have a full-fledged inode in order to operate correctly.
+ * All the files created with anon_inode_getfile() will share a single inode,
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup.  Returns the newly created file* or an error pointer.
+ */
+struct file *anon_inode_getfile(const char *name,
+				const struct file_operations *fops,
+				void *priv, int flags)
+{
+	struct qstr this;
+	struct path path;
+	struct file *file;
+
+	if (IS_ERR(anon_inode_inode))
+		return ERR_PTR(-ENODEV);
+
+	if (fops->owner && !try_module_get(fops->owner))
+		return ERR_PTR(-ENOENT);
+
+	/*
+	 * Link the inode to a directory entry by creating a unique name
+	 * using the inode sequence number.
+	 */
+	file = ERR_PTR(-ENOMEM);
+	this.name = name;
+	this.len = strlen(name);
+	this.hash = 0;
+	path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
+	if (!path.dentry)
+		goto err_module;
+
+	path.mnt = mntget(anon_inode_mnt);
+	/*
+	 * We know the anon_inode inode count is always greater than zero,
+	 * so ihold() is safe.
+	 */
+	ihold(anon_inode_inode);
+
+	d_instantiate(path.dentry, anon_inode_inode);
+
+	file = alloc_file(&path, OPEN_FMODE(flags), fops);
+	if (IS_ERR(file))
+		goto err_dput;
+	file->f_mapping = anon_inode_inode->i_mapping;
+
+	file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
+	file->private_data = priv;
+
+	return file;
+
+err_dput:
+	path_put(&path);
+err_module:
+	module_put(fops->owner);
+	return file;
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfile);
+
+/**
+ * anon_inode_getfd - creates a new file instance by hooking it up to an
+ *                    anonymous inode, and a dentry that describe the "class"
+ *                    of the file
+ *
+ * @name:    [in]    name of the "class" of the new file
+ * @fops:    [in]    file operations for the new file
+ * @priv:    [in]    private data for the new file (will be file's private_data)
+ * @flags:   [in]    flags
+ *
+ * Creates a new file by hooking it on a single inode. This is useful for files
+ * that do not need to have a full-fledged inode in order to operate correctly.
+ * All the files created with anon_inode_getfd() will share a single inode,
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup.  Returns new descriptor or an error code.
+ */
+int anon_inode_getfd(const char *name, const struct file_operations *fops,
+		     void *priv, int flags)
+{
+	int error, fd;
+	struct file *file;
+
+	error = get_unused_fd_flags(flags);
+	if (error < 0)
+		return error;
+	fd = error;
+
+	file = anon_inode_getfile(name, fops, priv, flags);
+	if (IS_ERR(file)) {
+		error = PTR_ERR(file);
+		goto err_put_unused_fd;
+	}
+	fd_install(fd, file);
+
+	return fd;
+
+err_put_unused_fd:
+	put_unused_fd(fd);
+	return error;
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfd);
+
+static int __init anon_inode_init(void)
+{
+	anon_inode_mnt = kern_mount(&anon_inode_fs_type);
+	if (IS_ERR(anon_inode_mnt))
+		panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt));
+
+	anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
+	if (IS_ERR(anon_inode_inode))
+		panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode));
+
+	return 0;
+}
+
+fs_initcall(anon_inode_init);
+